https://sprg.ssl.berkeley.edu/~tohban/wiki/index.php?title=DIY_spectroscopy:_Analyzing_AIA_diffraction_patterns&feed=atom&action=historyDIY spectroscopy: Analyzing AIA diffraction patterns - Revision history2024-03-28T20:55:25ZRevision history for this page on the wikiMediaWiki 1.16.0https://sprg.ssl.berkeley.edu/~tohban/wiki/index.php?title=DIY_spectroscopy:_Analyzing_AIA_diffraction_patterns&diff=10695&oldid=prevSchriste at 16:49, 22 August 20182018-08-22T16:49:06Z<p></p>
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<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>|second_author = S. Krucker</div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>|second_author = S. Krucker</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>|publish_date = 30 May 2011</div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>|publish_date = 30 May 2011</div></td></tr>
<tr><td class='diff-marker'>-</td><td style="background: #ffa; color:black; font-size: smaller;"><div>|next_nugget = [[<del class="diffchange diffchange-inline">Acceleration without Heating</del>]]</div></td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div>|next_nugget=<ins class="diffchange diffchange-inline">{{#ask: </ins>[[<ins class="diffchange diffchange-inline">Category:Nugget</ins>]] <ins class="diffchange diffchange-inline">[[RHESSI Nugget Index::153]]}}</ins></div></td></tr>
<tr><td class='diff-marker'>-</td><td style="background: #ffa; color:black; font-size: smaller;"><div>|previous_nugget = [<del class="diffchange diffchange-inline">http</del>:<del class="diffchange diffchange-inline">//sprg.ssl.berkeley.edu/~tohban/wiki/index.php/EVE/ESP_and_the_Neupert_Effect EVE/ESP_and_the_Neupert_Effect</del>]</div></td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div>|previous_nugget=<ins class="diffchange diffchange-inline">{{#ask: </ins>[<ins class="diffchange diffchange-inline">[Category</ins>:<ins class="diffchange diffchange-inline">Nugget]] [[RHESSI Nugget Index::151]</ins>]<ins class="diffchange diffchange-inline">}}</ins></div></td></tr>
<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>}}</div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>}}</div></td></tr>
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</table>Schristehttps://sprg.ssl.berkeley.edu/~tohban/wiki/index.php?title=DIY_spectroscopy:_Analyzing_AIA_diffraction_patterns&diff=8791&oldid=prevHhudson at 21:14, 30 December 20152015-12-30T21:14:27Z<p></p>
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<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>|second_author = S. Krucker</div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>|second_author = S. Krucker</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>|publish_date = 30 May 2011</div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>|publish_date = 30 May 2011</div></td></tr>
<tr><td class='diff-marker'>-</td><td style="background: #ffa; color:black; font-size: smaller;"><div>|next_nugget = <del class="diffchange diffchange-inline">TBD</del></div></td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div>|next_nugget = <ins class="diffchange diffchange-inline">[[Acceleration without Heating]]</ins></div></td></tr>
<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>|previous_nugget = [http://sprg.ssl.berkeley.edu/~tohban/wiki/index.php/EVE/ESP_and_the_Neupert_Effect EVE/ESP_and_the_Neupert_Effect]</div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>|previous_nugget = [http://sprg.ssl.berkeley.edu/~tohban/wiki/index.php/EVE/ESP_and_the_Neupert_Effect EVE/ESP_and_the_Neupert_Effect]</div></td></tr>
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</table>Hhudsonhttps://sprg.ssl.berkeley.edu/~tohban/wiki/index.php?title=DIY_spectroscopy:_Analyzing_AIA_diffraction_patterns&diff=4466&oldid=prevClaireRaftery at 21:02, 31 May 20112011-05-31T21:02:11Z<p></p>
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<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>|number = 152</div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>|number = 152</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>|first_author = C. L. Raftery</div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>|first_author = C. L. Raftery</div></td></tr>
<tr><td class='diff-marker'>-</td><td style="background: #ffa; color:black; font-size: smaller;"><div>|second_author = </div></td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div>|second_author = <ins class="diffchange diffchange-inline">S. Krucker</ins></div></td></tr>
<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>|publish_date = 30 May 2011</div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>|publish_date = 30 May 2011</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>|next_nugget = TBD</div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>|next_nugget = TBD</div></td></tr>
</table>ClaireRafteryhttps://sprg.ssl.berkeley.edu/~tohban/wiki/index.php?title=DIY_spectroscopy:_Analyzing_AIA_diffraction_patterns&diff=4465&oldid=prevHhudson: few more links2011-05-30T20:30:16Z<p>few more links</p>
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<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>The EUV portion of the spectrum reflects the physics of the solar</div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>The EUV portion of the spectrum reflects the physics of the solar</div></td></tr>
<tr><td class='diff-marker'>-</td><td style="background: #ffa; color:black; font-size: smaller;"><div>[http://en.wikipedia.org/wiki/Chromosphere chromosphere] and [http://solarscience.msfc.nasa.gov/t_region.shtml transition region] <del class="diffchange diffchange-inline">and in </del>this Nugget we show</div></td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div>[http://en.wikipedia.org/wiki/Chromosphere chromosphere] and [http://solarscience.msfc.nasa.gov/t_region.shtml transition region]</div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins class="diffchange diffchange-inline">In </ins>this Nugget we show</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>how an unheralded design feature of the </div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>how an unheralded design feature of the </div></td></tr>
<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>[http://sdo.gsfc.nasa.gov/ SDO]/[http://aia.lmsal.com/ AIA] instrument</div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>[http://sdo.gsfc.nasa.gov/ SDO]/[http://aia.lmsal.com/ AIA] instrument</div></td></tr>
<tr><td class='diff-marker'>-</td><td style="background: #ffa; color:black; font-size: smaller;"><div>allows us to study flare spectra pixel by pixel. <del class="diffchange diffchange-inline"> </del></div></td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div>allows us to study <ins class="diffchange diffchange-inline">EUV </ins>flare spectra pixel<ins class="diffchange diffchange-inline">-</ins>by<ins class="diffchange diffchange-inline">-</ins>pixel.</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>With the typical approach to EUV </div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>With the typical approach to EUV </div></td></tr>
<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>[http://en.wikipedia.org/wiki/Spectroscopy spectroscopy] - a scanning slit - </div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>[http://en.wikipedia.org/wiki/Spectroscopy spectroscopy] - a scanning slit - </div></td></tr>
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<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>[http://en.wikipedia.org/wiki/Wikipedia:TLAs_from_AAA_to_DZZ DIY] </div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>[http://en.wikipedia.org/wiki/Wikipedia:TLAs_from_AAA_to_DZZ DIY] </div></td></tr>
<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>spectroscopy: we are using the artifacts of</div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>spectroscopy: we are using the artifacts of</div></td></tr>
<tr><td class='diff-marker'>-</td><td style="background: #ffa; color:black; font-size: smaller;"><div>diffraction and dispersion to deconvolve the spectrum observed by</div></td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins class="diffchange diffchange-inline">[http://en.wikipedia.org/wiki/Diffraction </ins>diffraction<ins class="diffchange diffchange-inline">] </ins>and dispersion to deconvolve the spectrum observed by</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>AIA from its original single-flux-per-pixel value into the original</div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>AIA from its original single-flux-per-pixel value into the original</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>spectral line components.</div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>spectral line components.</div></td></tr>
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<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>== Technique ==</div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>== Technique ==</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"></td></tr>
<tr><td class='diff-marker'>-</td><td style="background: #ffa; color:black; font-size: smaller;"><div>Diffraction patterns can frequently be seen in AIA images, such as in Figure 1. These are caused by the <del class="diffchange diffchange-inline">front filter grid support </del>mesh <del class="diffchange diffchange-inline">behaving </del>as a pair of perpendicular diffraction gratings, forming a pair of orthogonal diffraction patterns. Since each telescope houses two front grids, we observe eight diffraction arms, as in Fig. 1. Under normal circumstances, the shadow of the grids is removed though image pre-processing and the intensity is not sufficient to generate <del class="diffchange diffchange-inline">a </del>diffraction pattern. However, in cases where the intensity in a pixel (or group of pixels) becomes very high, diffraction patterns can be observed. Since this is most often observed when the intensity saturates the CCD, understanding the context of the AIA source images is often difficult. In a break from the norm, we use RHESSI data for context imaging. In this way, we can identify where along a loop the diffraction pattern originates and can therefore analyze the diffraction pattern as a function of both time and space (perpendicular to the diffraction angles at least). </div></td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins class="diffchange diffchange-inline">[http://en.wikipedia.org/wiki/</ins>Diffraction <ins class="diffchange diffchange-inline">Diffraction] </ins>patterns can frequently be seen in AIA images, such as in Figure 1. These are caused by the <ins class="diffchange diffchange-inline">thermal filters at the telescope aperture; these thin filters have supporting </ins>mesh <ins class="diffchange diffchange-inline">grids that each behave </ins>as a pair of perpendicular diffraction gratings, forming a pair of orthogonal diffraction patterns. Since each telescope houses two front grids, we observe eight diffraction arms, as in Fig. 1. Under normal circumstances, the shadow of the grids is removed though image pre-processing and the intensity is not sufficient to generate <ins class="diffchange diffchange-inline">an obvious </ins>diffraction pattern. However, in cases where the intensity in a pixel (or group of pixels) becomes very high, diffraction patterns can be observed. Since this is most often observed when the intensity saturates the CCD, understanding the context of the AIA source images is often difficult. In a break from the norm, we use RHESSI data for context imaging. In this way, we can identify where along a loop the diffraction pattern originates and can therefore analyze the diffraction pattern as a function of both time and space (perpendicular to the diffraction angles at least). </div></td></tr>
<tr><td class='diff-marker'>-</td><td style="background: #ffa; color:black; font-size: smaller;"><div> </div></td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div></div></td></tr>
<tr><td class='diff-marker'>-</td><td style="background: #ffa; color:black; font-size: smaller;"><div><del class="diffchange diffchange-inline">In a similar way to a prism dispersing white light into its colour components, dispersion is observed within diffraction patterns. Close to the source, the bright diffraction peaks are narrow but as higher orders of diffraction are observed, the bright peaks become more spread out. This is due to emission at different wavelengths (λ) being diffracted by different amounts. The distance from the source ''r<sub>m</sub>'' at any order ''(m)'' can be translated in to wavelength as ''λ = (r<sub>m</sub> x a)/m'' given ''a'', the spacing of the diffraction grid, in this case, the wire mesh (Ref. [1]). It is clear that the dispersion within a single order, ''δr'' and therefore the spectral resolution, ''δλ'', will increase with diffraction order ''m''. Thus, the large field of view provided by AIA offers a significant improvement on the spectral resolution available previously from TRACE diffraction patterns. Fig. 1 shows diffraction out to 52 orders, compared to ~23 orders observed with TRACE (Ref. [1]). This means that at the 52nd diffraction order in the 193 Å passband, 1 Å spectral resolution corresponds to 3”, or 5 pixels. </del></div></td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div></div></td></tr>
<tr><td class='diff-marker'>-</td><td style="background: #ffa; color:black; font-size: smaller;"><div> </div></td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div></div></td></tr>
<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins style="color: red; font-weight: bold; text-decoration: none;">In a similar way to how a [http://en.wikipedia.org/wiki/Prism_(optics) prism] disperses white light into its colour components, dispersion is observed within diffraction patterns. Close to the source, the bright diffraction peaks are narrow but as higher orders of diffraction are observed, the bright peaks become more spread out. This is due to emission at different wavelengths (λ) being diffracted by different amounts. The distance from the source ''r<sub>m</sub>'' at any order ''(m)'' can be translated in to wavelength as ''λ = (r<sub>m</sub> x a)/m'' given ''a'', the spacing of the diffraction grid, in this case, the wire mesh (Ref. [1]). It is clear that the dispersion within a single order, ''δr'' and therefore the spectral resolution, ''δλ'', will increase with diffraction order ''m''. Thus, the large field of view provided by AIA offers a significant improvement on the spectral resolution available previously from [http://trace.lmsal.com/ TRACE] diffraction patterns. Fig. 1 shows diffraction out to 52 orders, compared to ~23 orders observed with TRACE (Ref. [1]). This means that at the 52nd diffraction order in the 193 Å passband, 1 Å spectral resolution corresponds to 3”, or 5 pixels. </ins></div></td></tr>
<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"></td></tr>
<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>{| class="wikitable" style="margin: 1em auto 1em auto;"</div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>{| class="wikitable" style="margin: 1em auto 1em auto;"</div></td></tr>
</table>Hhudsonhttps://sprg.ssl.berkeley.edu/~tohban/wiki/index.php?title=DIY_spectroscopy:_Analyzing_AIA_diffraction_patterns&diff=4461&oldid=prevHhudson: touch-up2011-05-28T14:20:46Z<p>touch-up</p>
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<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>Diffraction patterns can frequently be seen in AIA images, such as in Figure 1. These are caused by the front filter grid support mesh behaving as a pair of perpendicular diffraction gratings, forming a pair of orthogonal diffraction patterns. Since each telescope houses two front grids, we observe eight diffraction arms, as in Fig. 1. Under normal circumstances, the shadow of the grids is removed though image pre-processing and the intensity is not sufficient to generate a diffraction pattern. However, in cases where the intensity in a pixel (or group of pixels) becomes very high, diffraction patterns can be observed. Since this is most often observed when the intensity saturates the CCD, understanding the context of the AIA source images is often difficult. In a break from the norm, we use RHESSI data for context imaging. In this way, we can identify where along a loop the diffraction pattern originates and can therefore analyze the diffraction pattern as a function of both time and space (perpendicular to the diffraction angles at least). </div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>Diffraction patterns can frequently be seen in AIA images, such as in Figure 1. These are caused by the front filter grid support mesh behaving as a pair of perpendicular diffraction gratings, forming a pair of orthogonal diffraction patterns. Since each telescope houses two front grids, we observe eight diffraction arms, as in Fig. 1. Under normal circumstances, the shadow of the grids is removed though image pre-processing and the intensity is not sufficient to generate a diffraction pattern. However, in cases where the intensity in a pixel (or group of pixels) becomes very high, diffraction patterns can be observed. Since this is most often observed when the intensity saturates the CCD, understanding the context of the AIA source images is often difficult. In a break from the norm, we use RHESSI data for context imaging. In this way, we can identify where along a loop the diffraction pattern originates and can therefore analyze the diffraction pattern as a function of both time and space (perpendicular to the diffraction angles at least). </div></td></tr>
<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"></td></tr>
<tr><td class='diff-marker'>-</td><td style="background: #ffa; color:black; font-size: smaller;"><div>In a similar way to a prism dispersing white light into its colour components, dispersion is observed within diffraction patterns. Close to the source, the bright diffraction peaks are narrow but as higher orders of diffraction are observed, the bright peaks become more spread out. This is due to emission at different wavelengths (λ) being diffracted by different amounts. The distance from the source ''r<sub>m</sub>'' at any order ''(m)'' can be translated in to wavelength as ''λ = (r<sub>m</sub> x a)/m'' given ''a'', the spacing of the diffraction grid, in this case, the wire mesh (Ref. [1]<del class="diffchange diffchange-inline">) 2000</del>). It is clear that the dispersion within a single order, ''δr'' and therefore the spectral resolution, ''δλ'', will increase with diffraction order ''m''. Thus, the large field of view provided by AIA offers a significant improvement on the spectral resolution available previously from TRACE diffraction patterns. Fig. 1 shows diffraction out to 52 orders, compared to ~23 orders observed with TRACE (<del class="diffchange diffchange-inline">Lin et al</del>. <del class="diffchange diffchange-inline">2000</del>). This means that at the 52nd diffraction order in the 193 Å passband, 1 Å spectral resolution corresponds to 3”, or 5 pixels. </div></td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div>In a similar way to a prism dispersing white light into its colour components, dispersion is observed within diffraction patterns. Close to the source, the bright diffraction peaks are narrow but as higher orders of diffraction are observed, the bright peaks become more spread out. This is due to emission at different wavelengths (λ) being diffracted by different amounts. The distance from the source ''r<sub>m</sub>'' at any order ''(m)'' can be translated in to wavelength as ''λ = (r<sub>m</sub> x a)/m'' given ''a'', the spacing of the diffraction grid, in this case, the wire mesh (Ref. [1]). It is clear that the dispersion within a single order, ''δr'' and therefore the spectral resolution, ''δλ'', will increase with diffraction order ''m''. Thus, the large field of view provided by AIA offers a significant improvement on the spectral resolution available previously from TRACE diffraction patterns. Fig. 1 shows diffraction out to 52 orders, compared to ~23 orders observed with TRACE (<ins class="diffchange diffchange-inline">Ref</ins>. <ins class="diffchange diffchange-inline">[1]</ins>). This means that at the 52nd diffraction order in the 193 Å passband, 1 Å spectral resolution corresponds to 3”, or 5 pixels. </div></td></tr>
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<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>|- </div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>|- </div></td></tr>
<tr><td class='diff-marker'>-</td><td style="background: #ffa; color:black; font-size: smaller;"><div>| [[File:2spectra.jpg|thumb|left|400px|'''Figure 2''': Top: AIA 193 Å dispersion spectrum (black) with background-subtracted EVE spectrum. Bottom: AIA 193 Å dispersion spectrum (black) with two isothermal [http://www.chianti.rl.ac.uk/ CHIANTI] spectra synthesized at 10<sup>7</sup> K (red) and 10<sup>6.2</sup> K (green) along with their combined contribution (dashed). ]]</div></td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div>| [[File:2spectra.jpg|thumb|left|400px|'''Figure 2''': Top: AIA 193 Å dispersion spectrum (black) with background-subtracted <ins class="diffchange diffchange-inline">[http://lasp.colorado.edu/eve </ins>EVE<ins class="diffchange diffchange-inline">] </ins>spectrum. Bottom: AIA 193 Å dispersion spectrum (black) with two isothermal [http://www.chianti.rl.ac.uk/ CHIANTI] spectra synthesized at 10<sup>7</sup> K (red) and 10<sup>6.2</sup> K (green) along with their combined contribution (dashed). ]]</div></td></tr>
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</table>Hhudsonhttps://sprg.ssl.berkeley.edu/~tohban/wiki/index.php?title=DIY_spectroscopy:_Analyzing_AIA_diffraction_patterns&diff=4460&oldid=prevHhudson: more small edits2011-05-28T14:16:49Z<p>more small edits</p>
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<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>Diffraction patterns can frequently be seen in AIA images, such as in Figure 1. These are caused by the front filter grid support mesh behaving as a pair of perpendicular diffraction gratings, forming a pair of orthogonal diffraction patterns. Since each telescope houses two front grids, we observe eight diffraction arms, as in Fig. 1. Under normal circumstances, the shadow of the grids is removed though image pre-processing and the intensity is not sufficient to generate a diffraction pattern. However, in cases where the intensity in a pixel (or group of pixels) becomes very high, diffraction patterns can be observed. Since this is most often observed when the intensity saturates the CCD, understanding the context of the AIA source images is often difficult. In a break from the norm, we use RHESSI data for context imaging. In this way, we can identify where along a loop the diffraction pattern originates and can therefore analyze the diffraction pattern as a function of both time and space (perpendicular to the diffraction angles at least). </div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>Diffraction patterns can frequently be seen in AIA images, such as in Figure 1. These are caused by the front filter grid support mesh behaving as a pair of perpendicular diffraction gratings, forming a pair of orthogonal diffraction patterns. Since each telescope houses two front grids, we observe eight diffraction arms, as in Fig. 1. Under normal circumstances, the shadow of the grids is removed though image pre-processing and the intensity is not sufficient to generate a diffraction pattern. However, in cases where the intensity in a pixel (or group of pixels) becomes very high, diffraction patterns can be observed. Since this is most often observed when the intensity saturates the CCD, understanding the context of the AIA source images is often difficult. In a break from the norm, we use RHESSI data for context imaging. In this way, we can identify where along a loop the diffraction pattern originates and can therefore analyze the diffraction pattern as a function of both time and space (perpendicular to the diffraction angles at least). </div></td></tr>
<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"></td></tr>
<tr><td class='diff-marker'>-</td><td style="background: #ffa; color:black; font-size: smaller;"><div>In a similar way to a prism dispersing white light into its colour components, dispersion is observed within diffraction patterns. Close to the source, the bright diffraction peaks are narrow but as higher orders of diffraction are observed, the bright peaks become more spread out. This is due to emission at different wavelengths (λ) being diffracted by different amounts. The distance from the source ''r<sub>m</sub>'' at any order ''(m)'' can be translated in to wavelength as ''λ = (r<sub>m</sub> x a)/m'' given ''a'', the spacing of the diffraction grid, in this case, the wire mesh (<del class="diffchange diffchange-inline">Lin et al</del>. 2000). It is clear that the dispersion within a single order, ''δr'' and therefore the spectral resolution, ''δλ'', will increase with diffraction order ''m''. Thus, the large field of view provided by AIA offers a significant improvement on the spectral resolution available previously from TRACE diffraction patterns. Fig. 1 shows diffraction out to 52 orders, compared to ~23 orders observed with TRACE (Lin et al. 2000). This means that at the 52nd diffraction order in the 193 Å passband, 1 Å spectral resolution corresponds to 3”, or 5 pixels. </div></td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div>In a similar way to a prism dispersing white light into its colour components, dispersion is observed within diffraction patterns. Close to the source, the bright diffraction peaks are narrow but as higher orders of diffraction are observed, the bright peaks become more spread out. This is due to emission at different wavelengths (λ) being diffracted by different amounts. The distance from the source ''r<sub>m</sub>'' at any order ''(m)'' can be translated in to wavelength as ''λ = (r<sub>m</sub> x a)/m'' given ''a'', the spacing of the diffraction grid, in this case, the wire mesh (<ins class="diffchange diffchange-inline">Ref</ins>. <ins class="diffchange diffchange-inline">[1]) </ins>2000). It is clear that the dispersion within a single order, ''δr'' and therefore the spectral resolution, ''δλ'', will increase with diffraction order ''m''. Thus, the large field of view provided by AIA offers a significant improvement on the spectral resolution available previously from TRACE diffraction patterns. Fig. 1 shows diffraction out to 52 orders, compared to ~23 orders observed with TRACE (Lin et al. 2000). This means that at the 52nd diffraction order in the 193 Å passband, 1 Å spectral resolution corresponds to 3”, or 5 pixels. </div></td></tr>
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<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>|- </div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>|- </div></td></tr>
<tr><td class='diff-marker'>-</td><td style="background: #ffa; color:black; font-size: smaller;"><div>| [[File:2spectra.jpg|thumb|left|400px|'''Figure 2''': Top: AIA 193 Å dispersion spectrum (black) with background-subtracted EVE spectrum. Bottom: AIA 193 Å dispersion spectrum (black) with two isothermal CHIANTI spectra synthesized at 10<sup>7</sup> K (red) and 10<sup>6.2</sup> K (green) along with their combined contribution (dashed). ]]</div></td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div>| [[File:2spectra.jpg|thumb|left|400px|'''Figure 2''': Top: AIA 193 Å dispersion spectrum (black) with background-subtracted EVE spectrum. Bottom: AIA 193 Å dispersion spectrum (black) with two isothermal <ins class="diffchange diffchange-inline">[http://www.chianti.rl.ac.uk/ </ins>CHIANTI<ins class="diffchange diffchange-inline">] </ins>spectra synthesized at 10<sup>7</sup> K (red) and 10<sup>6.2</sup> K (green) along with their combined contribution (dashed). ]]</div></td></tr>
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<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"></td></tr>
<tr><td class='diff-marker'>-</td><td style="background: #ffa; color:black; font-size: smaller;"><div>With a spectral resolution of up to 0.7 Å, we can resolve individual spectral lines within the dispersion spectrum. To help identify the lines of interest, we can compare the dispersion pattern to SDO/EVE spectra (Fig. 2, top). This is especially helpful in identifying blended lines, which we may not otherwise resolve. With the primary lines of interest identified, the dispersion spectrum can be modeled using a combination of isothermal CHIANTI spectra, such as those shown in the bottom panel of Fig. 2. The scaling factors (1.8x10<sup>50</sup> and 6x10<sup>47</sup> cm<sup>-3</sup> for the high and low temperature component respectively) correspond to the emission measure of the plasma at that temperature. Repeating this process for many passbands will give us access to the temperature and emission measure of a range of spectral lines which, when combined, will result in the differential emission measure (DEM) of the plasma in saturated flaring pixel. </div></td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div>With a spectral resolution of up to 0.7 Å, we can resolve individual spectral lines within the dispersion spectrum. To help identify the lines of interest, we can compare the dispersion pattern to SDO/EVE spectra (Fig. 2, top). This is especially helpful in identifying blended lines, which we may not otherwise resolve. With the primary lines of interest identified, the dispersion spectrum can be modeled using a combination of isothermal </div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins class="diffchange diffchange-inline">[http://www.chianti.rl.ac.uk/ </ins>CHIANTI<ins class="diffchange diffchange-inline">] </ins>spectra, such as those shown in the bottom panel of Fig. 2. The scaling factors (1.8x10<sup>50</sup> and 6x10<sup>47</sup> cm<sup>-3</sup> for the high and low temperature component respectively) correspond to the emission measure of the plasma at that temperature. Repeating this process for many passbands will give us access to the temperature and emission measure of a range of spectral lines which, when combined, will result in the differential emission measure (<ins class="diffchange diffchange-inline">[http://groundtruth.info/AstroStat/slog/2008/eotw-dem/ </ins>DEM<ins class="diffchange diffchange-inline">]</ins>) of the plasma in saturated flaring pixel. </div></td></tr>
<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins style="color: red; font-weight: bold; text-decoration: none;">== Conclusions ==</ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins style="color: red; font-weight: bold; text-decoration: none;">Applying this technique to all diffracted AIA images at the high cadence of 12 seconds we can investigate how the DEM function varies with time at various points within the flare. While the spectral resolution and range may not compare to the likes of [http://msslxr.mssl.ucl.ac.uk:8080/SolarB/Solar-B.jsp EIS] or [http://lasp.colorado.edu/eve EVE], we are still achieving <1 Å resolution. This is a unique way of optimizing the compromises required to investigate the dynamic nature of a flare DEM function. While this analysis is still in the very early stages, it will provide very useful and detailed results in the future.</ins></div></td></tr>
<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins style="color: red; font-weight: bold; text-decoration: none;">== References ==</ins></div></td></tr>
<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"></td></tr>
<tr><td class='diff-marker'>-</td><td style="background: #ffa; color:black; font-size: smaller;"><div><del class="diffchange diffchange-inline">== Conclusions ==</del></div></td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins class="diffchange diffchange-inline">[</ins>1<ins class="diffchange diffchange-inline">] [http://adsabs</ins>.<ins class="diffchange diffchange-inline">harvard</ins>.<ins class="diffchange diffchange-inline">edu/abs/2001SoPh</ins>.<ins class="diffchange diffchange-inline">.198..385L Diffraction Pattern Analysis of Bright TRACE Flares]</ins></div></td></tr>
<tr><td class='diff-marker'>-</td><td style="background: #ffa; color:black; font-size: smaller;"><div><del class="diffchange diffchange-inline">Applying this technique to all diffracted AIA images at the high cadence of 12 seconds we can investigate how the DEM function varies with time at various points within the flare. While the spectral resolution and range may not compare to the likes of EIS or EVE, we are still achieving <</del>1 <del class="diffchange diffchange-inline">Å resolution</del>. <del class="diffchange diffchange-inline">This is a unique way of optimizing the compromises required to investigate the dynamic nature of a flare DEM function</del>. <del class="diffchange diffchange-inline">While this analysis is still in the very early stages, it will provide very useful and detailed results in the future</del>.</div></td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div></div></td></tr>
</table>Hhudsonhttps://sprg.ssl.berkeley.edu/~tohban/wiki/index.php?title=DIY_spectroscopy:_Analyzing_AIA_diffraction_patterns&diff=4459&oldid=prevHhudson: /* Introduction */ revision with links2011-05-28T14:06:17Z<p><span class="autocomment">Introduction: </span> revision with links</p>
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<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>==Introduction ==</div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>==Introduction ==</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"></td></tr>
<tr><td class='diff-marker'>-</td><td style="background: #ffa; color:black; font-size: smaller;"><div>The EUV portion of the spectrum <del class="diffchange diffchange-inline">provides us with vital </del>and <del class="diffchange diffchange-inline">interesting knowledge </del>of the <del class="diffchange diffchange-inline">Sun</del>. <del class="diffchange diffchange-inline">However, obtaining such information requires some compromise</del>. With EUV <del class="diffchange diffchange-inline">rastering slit </del>spectroscopy<del class="diffchange diffchange-inline">, </del>we sacrifice <del class="diffchange diffchange-inline">cadence and spatial </del>resolution for spectral resolution. With EUV imaging, we can achieve superb cadence and spatial resolution but we sacrifice spectral response. <del class="diffchange diffchange-inline">With </del>an irradiance instrument like EVE, we can obtain the spectral resolution and range along with very high cadence, but at a cost of spatial resolution. Here, we are striking a different balance by taking saturated AIA images and doing <del class="diffchange diffchange-inline">“DIY spectroscopy”</del>: we are using the artifacts of diffraction and dispersion to deconvolve the spectrum observed by AIA from its original single flux per pixel value into the original spectral line components.</div></td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div>The EUV portion of the spectrum <ins class="diffchange diffchange-inline">reflects the physics of the solar</ins></div></td></tr>
<tr><td class='diff-marker'>-</td><td style="background: #ffa; color:black; font-size: smaller;"><div> </div></td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins class="diffchange diffchange-inline">[http://en.wikipedia.org/wiki/Chromosphere chromosphere] </ins>and <ins class="diffchange diffchange-inline">[http://solarscience.msfc.nasa.gov/t_region.shtml transition region] and in this Nugget we show</ins></div></td></tr>
<tr><td class='diff-marker'>-</td><td style="background: #ffa; color:black; font-size: smaller;"><div> </div></td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins class="diffchange diffchange-inline">how an unheralded design feature </ins>of the </div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins class="diffchange diffchange-inline">[http://sdo</ins>.<ins class="diffchange diffchange-inline">gsfc</ins>.<ins class="diffchange diffchange-inline">nasa.gov/ SDO]/[http://aia.lmsal.com/ AIA] instrument</ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins class="diffchange diffchange-inline">allows us to study flare spectra pixel by pixel. </ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div>With <ins class="diffchange diffchange-inline">the typical approach to </ins>EUV </div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins class="diffchange diffchange-inline">[http://en.wikipedia.org/wiki/Spectroscopy </ins>spectroscopy<ins class="diffchange diffchange-inline">] - a scanning slit - </ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div>we sacrifice resolution <ins class="diffchange diffchange-inline">in time and space </ins>for <ins class="diffchange diffchange-inline">the sake of </ins>spectral resolution. </div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div>With <ins class="diffchange diffchange-inline">direct </ins>EUV imaging<ins class="diffchange diffchange-inline">, the main purpose of AIA</ins>, we can achieve superb </div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div>cadence and spatial resolution but we sacrifice spectral response. </div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins class="diffchange diffchange-inline">Finally, with </ins>an irradiance instrument like </div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins class="diffchange diffchange-inline">[http://lasp.colorado.edu/eve/ </ins>EVE<ins class="diffchange diffchange-inline">]</ins>, we can obtain the </div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div>spectral resolution and range along with very high cadence, but at a cost of </div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins class="diffchange diffchange-inline">not having any </ins>spatial resolution <ins class="diffchange diffchange-inline">at all</ins>. </div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div>Here, we are striking a different balance by taking saturated AIA</div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div>images and doing </div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins class="diffchange diffchange-inline">[http://en.wikipedia.org/wiki/Wikipedia:TLAs_from_AAA_to_DZZ DIY] </ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins class="diffchange diffchange-inline">spectroscopy</ins>: we are using the artifacts of</div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div>diffraction and dispersion to deconvolve the spectrum observed by</div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div>AIA from its original single<ins class="diffchange diffchange-inline">-</ins>flux<ins class="diffchange diffchange-inline">-</ins>per<ins class="diffchange diffchange-inline">-</ins>pixel value into the original</div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div>spectral line components.</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"></td></tr>
<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>{| class="wikitable" style="margin: 1em auto 1em auto;"</div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>{| class="wikitable" style="margin: 1em auto 1em auto;"</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>|- </div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>|- </div></td></tr>
<tr><td class='diff-marker'>-</td><td style="background: #ffa; color:black; font-size: smaller;"><div>| [[File:diffraction_image.png|thumb|center|700px|'''Figure 1''': Diffraction patterns observed in the [http://aia.lmsal.com/ AIA] 193 Å passband. The diffraction spikes, in this case, extend out into the corona right out to the limit of the AIA field of vew. ]]</div></td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div>| [[File:diffraction_image.png|thumb|center|700px|'''Figure 1''': Diffraction patterns observed in the [http://aia.lmsal.com/ AIA] 193 Å passband. The diffraction spikes, in this case, extend out into the corona right out to the limit of the AIA field of vew <ins class="diffchange diffchange-inline">(inset). Note that each blob within the pattern is actually an image of the source, dispersed in wavelength</ins>. ]]</div></td></tr>
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<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>== Technique ==</div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>== Technique ==</div></td></tr>
</table>Hhudsonhttps://sprg.ssl.berkeley.edu/~tohban/wiki/index.php?title=DIY_spectroscopy:_Analyzing_AIA_diffraction_patterns&diff=4458&oldid=prevHhudson: improved Fig. 12011-05-28T12:47:05Z<p>improved Fig. 1</p>
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<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>|first_author = C. L. Raftery</div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>|first_author = C. L. Raftery</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>|second_author = </div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>|second_author = </div></td></tr>
<tr><td class='diff-marker'>-</td><td style="background: #ffa; color:black; font-size: smaller;"><div>|publish_date = <del class="diffchange diffchange-inline">26 </del>May 2011</div></td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div>|publish_date = <ins class="diffchange diffchange-inline">30 </ins>May 2011</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>|next_nugget = TBD</div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>|next_nugget = TBD</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>|previous_nugget = [http://sprg.ssl.berkeley.edu/~tohban/wiki/index.php/EVE/ESP_and_the_Neupert_Effect EVE/ESP_and_the_Neupert_Effect]</div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>|previous_nugget = [http://sprg.ssl.berkeley.edu/~tohban/wiki/index.php/EVE/ESP_and_the_Neupert_Effect EVE/ESP_and_the_Neupert_Effect]</div></td></tr>
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<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>|- </div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>|- </div></td></tr>
<tr><td class='diff-marker'>-</td><td style="background: #ffa; color:black; font-size: smaller;"><div>| [[File:diffraction_image.<del class="diffchange diffchange-inline">jpg</del>|thumb|<del class="diffchange diffchange-inline">left</del>|<del class="diffchange diffchange-inline">400px</del>|'''Figure 1''': Diffraction patterns observed in the AIA 193 Å passband. ]]</div></td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div>| [[File:diffraction_image.<ins class="diffchange diffchange-inline">png</ins>|thumb|<ins class="diffchange diffchange-inline">center</ins>|<ins class="diffchange diffchange-inline">700px</ins>|'''Figure 1''': Diffraction patterns observed in the <ins class="diffchange diffchange-inline">[http://aia.lmsal.com/ </ins>AIA<ins class="diffchange diffchange-inline">] </ins>193 Å passband<ins class="diffchange diffchange-inline">. The diffraction spikes, in this case, extend out into the corona right out to the limit of the AIA field of vew</ins>. ]]</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>|| </div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>|| </div></td></tr>
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</table>Hhudsonhttps://sprg.ssl.berkeley.edu/~tohban/wiki/index.php?title=DIY_spectroscopy:_Analyzing_AIA_diffraction_patterns&diff=4456&oldid=prevClaireRaftery at 23:13, 26 May 20112011-05-26T23:13:24Z<p></p>
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<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>|publish_date = 26 May 2011</div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>|publish_date = 26 May 2011</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>|next_nugget = TBD</div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>|next_nugget = TBD</div></td></tr>
<tr><td class='diff-marker'>-</td><td style="background: #ffa; color:black; font-size: smaller;"><div>|previous_nugget = [http://sprg.ssl.berkeley.edu/~tohban/wiki/index.php/EVE/ESP_and_the_Neupert_Effect]</div></td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div>|previous_nugget = [http://sprg.ssl.berkeley.edu/~tohban/wiki/index.php/<ins class="diffchange diffchange-inline">EVE/ESP_and_the_Neupert_Effect </ins>EVE/ESP_and_the_Neupert_Effect]</div></td></tr>
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<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>Diffraction patterns can frequently be seen in AIA images, such as in Figure 1. These are caused by the front filter grid support mesh behaving as a pair of perpendicular diffraction gratings, forming a pair of orthogonal diffraction patterns. Since each telescope houses two front grids, we observe eight diffraction arms, as in Fig. 1. Under normal circumstances, the shadow of the grids is removed though image pre-processing and the intensity is not sufficient to generate a diffraction pattern. However, in cases where the intensity in a pixel (or group of pixels) becomes very high, diffraction patterns can be observed. Since this is most often observed when the intensity saturates the CCD, understanding the context of the AIA source images is often difficult. In a break from the norm, we use RHESSI data for context imaging. In this way, we can identify where along a loop the diffraction pattern originates and can therefore analyze the diffraction pattern as a function of both time and space (perpendicular to the diffraction angles at least). </div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>Diffraction patterns can frequently be seen in AIA images, such as in Figure 1. These are caused by the front filter grid support mesh behaving as a pair of perpendicular diffraction gratings, forming a pair of orthogonal diffraction patterns. Since each telescope houses two front grids, we observe eight diffraction arms, as in Fig. 1. Under normal circumstances, the shadow of the grids is removed though image pre-processing and the intensity is not sufficient to generate a diffraction pattern. However, in cases where the intensity in a pixel (or group of pixels) becomes very high, diffraction patterns can be observed. Since this is most often observed when the intensity saturates the CCD, understanding the context of the AIA source images is often difficult. In a break from the norm, we use RHESSI data for context imaging. In this way, we can identify where along a loop the diffraction pattern originates and can therefore analyze the diffraction pattern as a function of both time and space (perpendicular to the diffraction angles at least). </div></td></tr>
<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"></td></tr>
<tr><td class='diff-marker'>-</td><td style="background: #ffa; color:black; font-size: smaller;"><div>In a similar way to a prism dispersing white light into its colour components, dispersion is observed within diffraction patterns. Close to the source, the bright diffraction peaks are narrow but as higher orders of diffraction are observed, the bright peaks become more spread out. This is due to emission at different wavelengths (λ) being diffracted by different amounts. The distance from the source ''<del class="diffchange diffchange-inline">r_m</del>'' at any order ''(m)'' can be translated in to wavelength as ''λ = (<del class="diffchange diffchange-inline">r_m </del>x a)/m'' given ''a'', the spacing of the diffraction grid, in this case, the wire mesh <del class="diffchange diffchange-inline"><ref></del>Lin et al. 2000<del class="diffchange diffchange-inline"></ref></del>. It is clear that the dispersion within a single order, ''δr'' and therefore the spectral resolution, ''δλ'', will increase with diffraction order ''m''. Thus, the large field of view provided by AIA offers a significant improvement on the spectral resolution available previously from TRACE diffraction patterns. Fig. 1 shows diffraction out to 52 orders, compared to ~23 orders observed with TRACE (Lin et al. 2000). This means that at the 52nd diffraction order in the 193 Å passband, 1 Å spectral resolution corresponds to 3”, or 5 pixels. </div></td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div>In a similar way to a prism dispersing white light into its colour components, dispersion is observed within diffraction patterns. Close to the source, the bright diffraction peaks are narrow but as higher orders of diffraction are observed, the bright peaks become more spread out. This is due to emission at different wavelengths (λ) being diffracted by different amounts. The distance from the source ''<ins class="diffchange diffchange-inline">r<sub>m</sub></ins>'' at any order ''(m)'' can be translated in to wavelength as ''λ = (<ins class="diffchange diffchange-inline">r<sub>m</sub> </ins>x a)/m'' given ''a'', the spacing of the diffraction grid, in this case, the wire mesh <ins class="diffchange diffchange-inline">(</ins>Lin et al. 2000<ins class="diffchange diffchange-inline">)</ins>. It is clear that the dispersion within a single order, ''δr'' and therefore the spectral resolution, ''δλ'', will increase with diffraction order ''m''. Thus, the large field of view provided by AIA offers a significant improvement on the spectral resolution available previously from TRACE diffraction patterns. Fig. 1 shows diffraction out to 52 orders, compared to ~23 orders observed with TRACE (Lin et al. 2000). This means that at the 52nd diffraction order in the 193 Å passband, 1 Å spectral resolution corresponds to 3”, or 5 pixels. </div></td></tr>
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<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>|- </div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>|- </div></td></tr>
<tr><td class='diff-marker'>-</td><td style="background: #ffa; color:black; font-size: smaller;"><div>| [[File:2spectra.jpg|thumb|left|400px|'''Figure 2''': Top: AIA 193 Å dispersion spectrum (black) with background-subtracted EVE spectrum. Bottom: AIA 193 Å dispersion spectrum (black) with two isothermal CHIANTI spectra synthesized at 10<del class="diffchange diffchange-inline">^</del>7 K (red) and 10<del class="diffchange diffchange-inline">^</del>6.2 K (green) along with their combined contribution (dashed). ]]</div></td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div>| [[File:2spectra.jpg|thumb|left|400px|'''Figure 2''': Top: AIA 193 Å dispersion spectrum (black) with background-subtracted EVE spectrum. Bottom: AIA 193 Å dispersion spectrum (black) with two isothermal CHIANTI spectra synthesized at 10<ins class="diffchange diffchange-inline"><sup></ins>7<ins class="diffchange diffchange-inline"></sup> </ins>K (red) and 10<ins class="diffchange diffchange-inline"><sup></ins>6.2<ins class="diffchange diffchange-inline"></sup> </ins>K (green) along with their combined contribution (dashed). ]]</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>|| </div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>|| </div></td></tr>
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<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"></td></tr>
<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"></td></tr>
<tr><td class='diff-marker'>-</td><td style="background: #ffa; color:black; font-size: smaller;"><div>With a spectral resolution of up to 0.7 Å, we can resolve individual spectral lines within the dispersion spectrum. To help identify the lines of interest, we can compare the dispersion pattern to SDO/EVE spectra (Fig. 2, top). This is especially helpful in identifying blended lines, which we may not otherwise resolve. With the primary lines of interest identified, the dispersion spectrum can be modeled using a combination of isothermal CHIANTI spectra, such as those shown in the bottom panel of Fig. 2. The scaling factors (1.8x10<del class="diffchange diffchange-inline">^</del>50 and 6x10<del class="diffchange diffchange-inline">^</del>47 cm<del class="diffchange diffchange-inline">^</del>-3 for the high and low temperature component respectively) correspond to the emission measure of the plasma at that temperature. Repeating this process for many passbands will give us access to the temperature and emission measure of a range of spectral lines which, when combined, will result in the differential emission measure (DEM) of the plasma in saturated flaring pixel. </div></td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div>With a spectral resolution of up to 0.7 Å, we can resolve individual spectral lines within the dispersion spectrum. To help identify the lines of interest, we can compare the dispersion pattern to SDO/EVE spectra (Fig. 2, top). This is especially helpful in identifying blended lines, which we may not otherwise resolve. With the primary lines of interest identified, the dispersion spectrum can be modeled using a combination of isothermal CHIANTI spectra, such as those shown in the bottom panel of Fig. 2. The scaling factors (1.8x10<ins class="diffchange diffchange-inline"><sup></ins>50<ins class="diffchange diffchange-inline"></sup> </ins>and 6x10<ins class="diffchange diffchange-inline"><sup></ins>47<ins class="diffchange diffchange-inline"></sup> </ins>cm<ins class="diffchange diffchange-inline"><sup></ins>-3<ins class="diffchange diffchange-inline"></sup> </ins>for the high and low temperature component respectively) correspond to the emission measure of the plasma at that temperature. Repeating this process for many passbands will give us access to the temperature and emission measure of a range of spectral lines which, when combined, will result in the differential emission measure (DEM) of the plasma in saturated flaring pixel. </div></td></tr>
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</table>ClaireRafteryhttps://sprg.ssl.berkeley.edu/~tohban/wiki/index.php?title=DIY_spectroscopy:_Analyzing_AIA_diffraction_patterns&diff=4454&oldid=prevClaireRaftery: Created page with "{{Infobox Nugget |name = Nugget |title = DIY spectroscopy: Analyzing AIA diffraction patterns |number = 152 |first_author = C. L. Raftery |second_author = |publish_date = 26 May..."2011-05-26T22:55:12Z<p>Created page with "{{Infobox Nugget |name = Nugget |title = DIY spectroscopy: Analyzing AIA diffraction patterns |number = 152 |first_author = C. L. Raftery |second_author = |publish_date = 26 May..."</p>
<p><b>New page</b></p><div>{{Infobox Nugget<br />
|name = Nugget<br />
|title = DIY spectroscopy: Analyzing AIA diffraction patterns<br />
|number = 152<br />
|first_author = C. L. Raftery<br />
|second_author = <br />
|publish_date = 26 May 2011<br />
|next_nugget = TBD<br />
|previous_nugget = [http://sprg.ssl.berkeley.edu/~tohban/wiki/index.php/EVE/ESP_and_the_Neupert_Effect]<br />
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<br />
==Introduction ==<br />
<br />
The EUV portion of the spectrum provides us with vital and interesting knowledge of the Sun. However, obtaining such information requires some compromise. With EUV rastering slit spectroscopy, we sacrifice cadence and spatial resolution for spectral resolution. With EUV imaging, we can achieve superb cadence and spatial resolution but we sacrifice spectral response. With an irradiance instrument like EVE, we can obtain the spectral resolution and range along with very high cadence, but at a cost of spatial resolution. Here, we are striking a different balance by taking saturated AIA images and doing “DIY spectroscopy”: we are using the artifacts of diffraction and dispersion to deconvolve the spectrum observed by AIA from its original single flux per pixel value into the original spectral line components.<br />
<br />
<br />
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| [[File:diffraction_image.jpg|thumb|left|400px|'''Figure 1''': Diffraction patterns observed in the AIA 193 Å passband. ]]<br />
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<br />
== Technique ==<br />
<br />
Diffraction patterns can frequently be seen in AIA images, such as in Figure 1. These are caused by the front filter grid support mesh behaving as a pair of perpendicular diffraction gratings, forming a pair of orthogonal diffraction patterns. Since each telescope houses two front grids, we observe eight diffraction arms, as in Fig. 1. Under normal circumstances, the shadow of the grids is removed though image pre-processing and the intensity is not sufficient to generate a diffraction pattern. However, in cases where the intensity in a pixel (or group of pixels) becomes very high, diffraction patterns can be observed. Since this is most often observed when the intensity saturates the CCD, understanding the context of the AIA source images is often difficult. In a break from the norm, we use RHESSI data for context imaging. In this way, we can identify where along a loop the diffraction pattern originates and can therefore analyze the diffraction pattern as a function of both time and space (perpendicular to the diffraction angles at least). <br />
<br />
In a similar way to a prism dispersing white light into its colour components, dispersion is observed within diffraction patterns. Close to the source, the bright diffraction peaks are narrow but as higher orders of diffraction are observed, the bright peaks become more spread out. This is due to emission at different wavelengths (λ) being diffracted by different amounts. The distance from the source ''r_m'' at any order ''(m)'' can be translated in to wavelength as ''λ = (r_m x a)/m'' given ''a'', the spacing of the diffraction grid, in this case, the wire mesh <ref>Lin et al. 2000</ref>. It is clear that the dispersion within a single order, ''δr'' and therefore the spectral resolution, ''δλ'', will increase with diffraction order ''m''. Thus, the large field of view provided by AIA offers a significant improvement on the spectral resolution available previously from TRACE diffraction patterns. Fig. 1 shows diffraction out to 52 orders, compared to ~23 orders observed with TRACE (Lin et al. 2000). This means that at the 52nd diffraction order in the 193 Å passband, 1 Å spectral resolution corresponds to 3”, or 5 pixels. <br />
<br />
<br />
<br />
{| class="wikitable" style="margin: 1em auto 1em auto;"<br />
|- <br />
| [[File:2spectra.jpg|thumb|left|400px|'''Figure 2''': Top: AIA 193 Å dispersion spectrum (black) with background-subtracted EVE spectrum. Bottom: AIA 193 Å dispersion spectrum (black) with two isothermal CHIANTI spectra synthesized at 10^7 K (red) and 10^6.2 K (green) along with their combined contribution (dashed). ]]<br />
|| <br />
|}<br />
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With a spectral resolution of up to 0.7 Å, we can resolve individual spectral lines within the dispersion spectrum. To help identify the lines of interest, we can compare the dispersion pattern to SDO/EVE spectra (Fig. 2, top). This is especially helpful in identifying blended lines, which we may not otherwise resolve. With the primary lines of interest identified, the dispersion spectrum can be modeled using a combination of isothermal CHIANTI spectra, such as those shown in the bottom panel of Fig. 2. The scaling factors (1.8x10^50 and 6x10^47 cm^-3 for the high and low temperature component respectively) correspond to the emission measure of the plasma at that temperature. Repeating this process for many passbands will give us access to the temperature and emission measure of a range of spectral lines which, when combined, will result in the differential emission measure (DEM) of the plasma in saturated flaring pixel. <br />
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== Conclusions ==<br />
Applying this technique to all diffracted AIA images at the high cadence of 12 seconds we can investigate how the DEM function varies with time at various points within the flare. While the spectral resolution and range may not compare to the likes of EIS or EVE, we are still achieving <1 Å resolution. This is a unique way of optimizing the compromises required to investigate the dynamic nature of a flare DEM function. While this analysis is still in the very early stages, it will provide very useful and detailed results in the future.</div>ClaireRaftery