https://sprg.ssl.berkeley.edu/~tohban/wiki/index.php?title=The_Fe_and_Fe/Ni_line_features_II&feed=atom&action=historyThe Fe and Fe/Ni line features II - Revision history2024-03-28T18:02:21ZRevision history for this page on the wikiMediaWiki 1.16.0https://sprg.ssl.berkeley.edu/~tohban/wiki/index.php?title=The_Fe_and_Fe/Ni_line_features_II&diff=11110&oldid=prevSchriste at 14:10, 15 September 20182018-09-15T14:10:34Z<p></p>
<table style="background-color: white; color:black;">
<col class='diff-marker' />
<col class='diff-content' />
<col class='diff-marker' />
<col class='diff-content' />
<tr valign='top'>
<td colspan='2' style="background-color: white; color:black;">← Older revision</td>
<td colspan='2' style="background-color: white; color:black;">Revision as of 14:10, 15 September 2018</td>
</tr><tr><td colspan="2" class="diff-lineno">Line 31:</td>
<td colspan="2" class="diff-lineno">Line 31:</td></tr>
<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>In a survey of 30 flares compiled by Cristina Chifor (GSFC/CUA), it would appear that sometimes the Fe line equivalent width is not far from the theoretical curve (see the data points in the figure above), but with a small displacement of the observed points to the right (higher T side) of the curve.</div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>In a survey of 30 flares compiled by Cristina Chifor (GSFC/CUA), it would appear that sometimes the Fe line equivalent width is not far from the theoretical curve (see the data points in the figure above), but with a small displacement of the observed points to the right (higher T side) of the curve.</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>It is possible that this is due to slightly incorrect atomic rates involved in the calculation of ionization fractions. A separate study of the Fe line to Fe/Ni line ratio (by Amir Caspi, UC Berkeley) is finding some agreement with theory, but with a tendency for the observed points to be lower than the theoretical curve (i.e. the Fe/Ni line is a little stronger than expected). There is, incidentally, a nice agreement of RHESSI continuum flux at about 4 keV (the low-energy end of the spectrum) with simultaneous observations with Janusz Sylwester's RESIK crystal spectrometer on CORONAS-F for flares in 2002 and 2003 (see [[The Fe and Fe/Ni line features <del class="diffchange diffchange-inline">II</del>|<del class="diffchange diffchange-inline">previous </del>nugget]]).</div></td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div>It is possible that this is due to slightly incorrect atomic rates involved in the calculation of ionization fractions. A separate study of the Fe line to Fe/Ni line ratio (by Amir Caspi, UC Berkeley) is finding some agreement with theory, but with a tendency for the observed points to be lower than the theoretical curve (i.e. the Fe/Ni line is a little stronger than expected). There is, incidentally, a nice agreement of RHESSI continuum flux at about 4 keV (the low-energy end of the spectrum) with simultaneous observations with Janusz Sylwester's RESIK crystal spectrometer on CORONAS-F for flares in 2002 and 2003 (see [[The Fe and Fe/Ni line features <ins class="diffchange diffchange-inline">I</ins>|<ins class="diffchange diffchange-inline">earlier RHESSI </ins>nugget]]).</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>We have been investigating how to deal with the fact that flare plasmas are not likely to be isothermal except possibly at the late stages of long-duration flares. They may be multi-thermal, with unresolved and physically different structures on the line of sight, or they may also be non-thermal, in which case the plasma particles do not follow the Boltzmann velocity distribution. In the former case we speak of differential emission measures (DEM), which show the spectrum of contributions from different-temperature regions. We get the necessary information from line, continuum, and broad-band observations. We hope to make some progress in studying these effects, which could help to clear up some of the discrepancies which we are seeing and at the same time explain the physics of solar flares a little better.</div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>We have been investigating how to deal with the fact that flare plasmas are not likely to be isothermal except possibly at the late stages of long-duration flares. They may be multi-thermal, with unresolved and physically different structures on the line of sight, or they may also be non-thermal, in which case the plasma particles do not follow the Boltzmann velocity distribution. In the former case we speak of differential emission measures (DEM), which show the spectrum of contributions from different-temperature regions. We get the necessary information from line, continuum, and broad-band observations. We hope to make some progress in studying these effects, which could help to clear up some of the discrepancies which we are seeing and at the same time explain the physics of solar flares a little better.</div></td></tr>
</table>Schristehttps://sprg.ssl.berkeley.edu/~tohban/wiki/index.php?title=The_Fe_and_Fe/Ni_line_features_II&diff=11109&oldid=prevSchriste at 14:08, 15 September 20182018-09-15T14:08:48Z<p></p>
<table style="background-color: white; color:black;">
<col class='diff-marker' />
<col class='diff-content' />
<col class='diff-marker' />
<col class='diff-content' />
<tr valign='top'>
<td colspan='2' style="background-color: white; color:black;">← Older revision</td>
<td colspan='2' style="background-color: white; color:black;">Revision as of 14:08, 15 September 2018</td>
</tr><tr><td colspan="2" class="diff-lineno">Line 16:</td>
<td colspan="2" class="diff-lineno">Line 16:</td></tr>
<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>== What RHESSI is finding? ==</div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>== What RHESSI is finding? ==</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>It has taken a long time to try to understand the various RHESSI instrumental characteristics at energies less than 20 keV. The spectra are analyzed by taking count rate spectra and finding the best-fit underlying spectral continuum to determine the temperature, and then fitting the line features which appear as excess emission above the continuum level. See the first figure of the earlier RHESSI science nugget, which shows two features due mainly to highly-ionized iron above a smooth X-ray continuum. The lines are at 6.7 keV (the "Fe feature") and at 8 keV (the "Fe-Ni" feature because some small fraction of nickel emission lines appears in the fit). To show how complicated this is, we show another spectrum in the figure below. This spectrum is in "counts space," as gotten directly from the detector, rather than in the more theoretical "photon space" shown in the previous nugget - so it is not quite so pretty.</div></td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div>It has taken a long time to try to understand the various RHESSI instrumental characteristics at energies less than 20 keV. The spectra are analyzed by taking count rate spectra and finding the best-fit underlying spectral continuum to determine the temperature, and then fitting the line features which appear as excess emission above the continuum level. See the first figure of the earlier RHESSI science nugget, which shows two features due mainly to highly-ionized iron above a smooth X-ray continuum. The lines are at 6.7 keV (the "Fe feature") and at 8 keV (the "Fe-Ni" feature because some small fraction of nickel emission lines appears in the fit). To show how complicated this is, we show another spectrum in the figure below <ins class="diffchange diffchange-inline">from an event of [[Has event date:: April 26, 2003 03:11]]</ins>.</div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div>This spectrum is in "counts space," as gotten directly from the detector, rather than in the more theoretical "photon space" shown in the previous nugget - so it is not quite so pretty.</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;"></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"></td></tr>
<tr><td colspan="2" class="diff-lineno">Line 37:</td>
<td colspan="2" class="diff-lineno">Line 38:</td></tr>
<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>Ken Phillips has until recently been a senior research visitor at NASA/GSFC, and is now at MSSL in the UK; Cristina Chifor is a GSFC summer student from Trent University in Canada. The material in this nugget owes a lot also to Brian Dennis (GSFC).</div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>Ken Phillips has until recently been a senior research visitor at NASA/GSFC, and is now at MSSL in the UK; Cristina Chifor is a GSFC summer student from Trent University in Canada. The material in this nugget owes a lot also to Brian Dennis (GSFC).</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">Category</del>:<del class="diffchange diffchange-inline">Nugget</del>]]</div></td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div>[[<ins class="diffchange diffchange-inline">Has observation by</ins>:<ins class="diffchange diffchange-inline">: RHESSI| </ins>]]</div></td></tr>
</table>Schristehttps://sprg.ssl.berkeley.edu/~tohban/wiki/index.php?title=The_Fe_and_Fe/Ni_line_features_II&diff=10798&oldid=prevSchriste at 19:20, 22 August 20182018-08-22T19:20:59Z<p></p>
<table style="background-color: white; color:black;">
<col class='diff-marker' />
<col class='diff-content' />
<col class='diff-marker' />
<col class='diff-content' />
<tr valign='top'>
<td colspan='2' style="background-color: white; color:black;">← Older revision</td>
<td colspan='2' style="background-color: white; color:black;">Revision as of 19:20, 22 August 2018</td>
</tr><tr><td colspan="2" class="diff-lineno">Line 12:</td>
<td colspan="2" class="diff-lineno">Line 12:</td></tr>
<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>As noted in the [[The Fe and Fe/Ni line features <del class="diffchange diffchange-inline">II</del>|earlier RHESSI nugget]] on this topic, a solar flare makes the already-hot solar corona still hotter. So hot, in fact, that the natural emission spectrum of the coronal plasma moves into the X-ray band (hotter means "harder" photons). That previous nugget explained the basic principles of solar X-ray emission-line spectroscopy (as done by RHESSI), and in this nugget we will show some of the actual observational results.</div></td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div>As noted in the [[The Fe and Fe/Ni line features <ins class="diffchange diffchange-inline">I</ins>|earlier RHESSI nugget]] on this topic, a solar flare makes the already-hot solar corona still hotter. So hot, in fact, that the natural emission spectrum of the coronal plasma moves into the X-ray band (hotter means "harder" photons). That previous nugget explained the basic principles of solar X-ray emission-line spectroscopy (as done by RHESSI), and in this nugget we will show some of the actual observational results.</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>== What RHESSI is finding? ==</div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>== What RHESSI is finding? ==</div></td></tr>
</table>Schristehttps://sprg.ssl.berkeley.edu/~tohban/wiki/index.php?title=The_Fe_and_Fe/Ni_line_features_II&diff=10577&oldid=prevSchriste at 15:36, 22 August 20182018-08-22T15:36:58Z<p></p>
<table style="background-color: white; color:black;">
<col class='diff-marker' />
<col class='diff-content' />
<col class='diff-marker' />
<col class='diff-content' />
<tr valign='top'>
<td colspan='2' style="background-color: white; color:black;">← Older revision</td>
<td colspan='2' style="background-color: white; color:black;">Revision as of 15:36, 22 August 2018</td>
</tr><tr><td colspan="2" class="diff-lineno">Line 6:</td>
<td colspan="2" class="diff-lineno">Line 6:</td></tr>
<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>|second_author = Christina Chifor</div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>|second_author = Christina Chifor</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>|publish_date = 2005-12-05</div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>|publish_date = 2005-12-05</div></td></tr>
<tr><td class='diff-marker'>-</td><td style="background: #ffa; color:black; font-size: smaller;"><div>|next_nugget = </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: [[Category:Nugget]] [[RHESSI Nugget Index::16]]}}</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">The Fe and Fe/Ni line features I</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: [[Category:Nugget]] </ins>[[<ins class="diffchange diffchange-inline">RHESSI Nugget Index::14</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>
<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>
</table>Schristehttps://sprg.ssl.berkeley.edu/~tohban/wiki/index.php?title=The_Fe_and_Fe/Ni_line_features_II&diff=10086&oldid=prevSchriste: /* Biographical Note */2018-01-03T18:35:43Z<p><span class="autocomment">Biographical Note</span></p>
<table style="background-color: white; color:black;">
<col class='diff-marker' />
<col class='diff-content' />
<col class='diff-marker' />
<col class='diff-content' />
<tr valign='top'>
<td colspan='2' style="background-color: white; color:black;">← Older revision</td>
<td colspan='2' style="background-color: white; color:black;">Revision as of 18:35, 3 January 2018</td>
</tr><tr><td colspan="2" class="diff-lineno">Line 34:</td>
<td colspan="2" class="diff-lineno">Line 34:</td></tr>
<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>We have been investigating how to deal with the fact that flare plasmas are not likely to be isothermal except possibly at the late stages of long-duration flares. They may be multi-thermal, with unresolved and physically different structures on the line of sight, or they may also be non-thermal, in which case the plasma particles do not follow the Boltzmann velocity distribution. In the former case we speak of differential emission measures (DEM), which show the spectrum of contributions from different-temperature regions. We get the necessary information from line, continuum, and broad-band observations. We hope to make some progress in studying these effects, which could help to clear up some of the discrepancies which we are seeing and at the same time explain the physics of solar flares a little better.</div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>We have been investigating how to deal with the fact that flare plasmas are not likely to be isothermal except possibly at the late stages of long-duration flares. They may be multi-thermal, with unresolved and physically different structures on the line of sight, or they may also be non-thermal, in which case the plasma particles do not follow the Boltzmann velocity distribution. In the former case we speak of differential emission measures (DEM), which show the spectrum of contributions from different-temperature regions. We get the necessary information from line, continuum, and broad-band observations. We hope to make some progress in studying these effects, which could help to clear up some of the discrepancies which we are seeing and at the same time explain the physics of solar flares a little better.</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">== </del>Biographical Note<del class="diffchange diffchange-inline">==</del></div></td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins class="diffchange diffchange-inline">'''</ins>Biographical Note<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>Ken Phillips has until recently been a senior research visitor at NASA/GSFC, and is now at MSSL in the UK; Cristina Chifor is a GSFC summer student from Trent University in Canada. The material in this nugget owes a lot also to Brian Dennis (GSFC).</div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>Ken Phillips has until recently been a senior research visitor at NASA/GSFC, and is now at MSSL in the UK; Cristina Chifor is a GSFC summer student from Trent University in Canada. The material in this nugget owes a lot also to Brian Dennis (GSFC).</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>[[Category:Nugget]]</div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>[[Category:Nugget]]</div></td></tr>
</table>Schristehttps://sprg.ssl.berkeley.edu/~tohban/wiki/index.php?title=The_Fe_and_Fe/Ni_line_features_II&diff=10085&oldid=prevSchriste at 18:35, 3 January 20182018-01-03T18:35:22Z<p></p>
<table style="background-color: white; color:black;">
<col class='diff-marker' />
<col class='diff-content' />
<col class='diff-marker' />
<col class='diff-content' />
<tr valign='top'>
<td colspan='2' style="background-color: white; color:black;">← Older revision</td>
<td colspan='2' style="background-color: white; color:black;">Revision as of 18:35, 3 January 2018</td>
</tr><tr><td colspan="2" class="diff-lineno">Line 3:</td>
<td colspan="2" class="diff-lineno">Line 3:</td></tr>
<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>|title = Nugget Details</div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>|title = Nugget Details</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>|number = 15</div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>|number = 15</div></td></tr>
<tr><td class='diff-marker'>-</td><td style="background: #ffa; color:black; font-size: smaller;"><div>|first_author = Ken Phillips <del class="diffchange diffchange-inline">and</del></div></td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div>|first_author = Ken Phillips</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>|second_author = Christina Chifor</div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>|second_author = Christina Chifor</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>|publish_date = 2005-12-05</div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>|publish_date = 2005-12-05</div></td></tr>
</table>Schristehttps://sprg.ssl.berkeley.edu/~tohban/wiki/index.php?title=The_Fe_and_Fe/Ni_line_features_II&diff=2512&oldid=prevSchriste at 01:31, 23 January 20102010-01-23T01:31:48Z<p></p>
<table style="background-color: white; color:black;">
<col class='diff-marker' />
<col class='diff-content' />
<col class='diff-marker' />
<col class='diff-content' />
<tr valign='top'>
<td colspan='2' style="background-color: white; color:black;">← Older revision</td>
<td colspan='2' style="background-color: white; color:black;">Revision as of 01:31, 23 January 2010</td>
</tr><tr><td colspan="2" class="diff-lineno">Line 12:</td>
<td colspan="2" class="diff-lineno">Line 12:</td></tr>
<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>As noted in the [[<del class="diffchange diffchange-inline">earlier RHESSI nugget|</del>The Fe and Fe/Ni line features II]] on this topic, a solar flare makes the already-hot solar corona still hotter. So hot, in fact, that the natural emission spectrum of the coronal plasma moves into the X-ray band (hotter means "harder" photons). That previous nugget explained the basic principles of solar X-ray emission-line spectroscopy (as done by RHESSI), and in this nugget we will show some of the actual observational results.</div></td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div>As noted in the [[The Fe and Fe/Ni line features II<ins class="diffchange diffchange-inline">|earlier RHESSI nugget</ins>]] on this topic, a solar flare makes the already-hot solar corona still hotter. So hot, in fact, that the natural emission spectrum of the coronal plasma moves into the X-ray band (hotter means "harder" photons). That previous nugget explained the basic principles of solar X-ray emission-line spectroscopy (as done by RHESSI), and in this nugget we will show some of the actual observational results.</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>== What RHESSI is finding? ==</div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>== What RHESSI is finding? ==</div></td></tr>
</table>Schristehttps://sprg.ssl.berkeley.edu/~tohban/wiki/index.php?title=The_Fe_and_Fe/Ni_line_features_II&diff=2511&oldid=prevSchriste: added category2010-01-23T01:31:11Z<p>added category</p>
<table style="background-color: white; color:black;">
<col class='diff-marker' />
<col class='diff-content' />
<col class='diff-marker' />
<col class='diff-content' />
<tr valign='top'>
<td colspan='2' style="background-color: white; color:black;">← Older revision</td>
<td colspan='2' style="background-color: white; color:black;">Revision as of 01:31, 23 January 2010</td>
</tr><tr><td colspan="2" class="diff-lineno">Line 36:</td>
<td colspan="2" class="diff-lineno">Line 36:</td></tr>
<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>== Biographical Note==</div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>== Biographical Note==</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>Ken Phillips has until recently been a senior research visitor at NASA/GSFC, and is now at MSSL in the UK; Cristina Chifor is a GSFC summer student from Trent University in Canada. The material in this nugget owes a lot also to Brian Dennis (GSFC).</div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>Ken Phillips has until recently been a senior research visitor at NASA/GSFC, and is now at MSSL in the UK; Cristina Chifor is a GSFC summer student from Trent University in Canada. The material in this nugget owes a lot also to Brian Dennis (GSFC).</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;"></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;">[[Category:Nugget]]</ins></div></td></tr>
</table>Schristehttps://sprg.ssl.berkeley.edu/~tohban/wiki/index.php?title=The_Fe_and_Fe/Ni_line_features_II&diff=2510&oldid=prevSchriste at 01:30, 23 January 20102010-01-23T01:30:26Z<p></p>
<table style="background-color: white; color:black;">
<col class='diff-marker' />
<col class='diff-content' />
<col class='diff-marker' />
<col class='diff-content' />
<tr valign='top'>
<td colspan='2' style="background-color: white; color:black;">← Older revision</td>
<td colspan='2' style="background-color: white; color:black;">Revision as of 01:30, 23 January 2010</td>
</tr><tr><td colspan="2" class="diff-lineno">Line 1:</td>
<td colspan="2" class="diff-lineno">Line 1:</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;">{{Infobox Nugget</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;">|name = Nugget</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;">|title = Nugget Details</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;">|number = 15</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;">|first_author = Ken Phillips and</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;">|second_author = Christina Chifor</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;">|publish_date = 2005-12-05</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;">|next_nugget = </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;">|previous_nugget = [[The Fe and Fe/Ni line features I]]</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;">}}</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;"></ins></div></td></tr>
<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 colspan="2" class="diff-lineno">Line 8:</td>
<td colspan="2" class="diff-lineno">Line 19:</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;"></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>'''Figure 1''': This is an actual RHESSI spectral fit, made with our wonderful nonlinear parameter-fitting software SPEX. It shows "counts space", ie raw data, as the uppermost histogram (black). The different-colored histograms below it show the different features in the fit at this particular time interval: yellow is the Fe feature, magenta the Fe-Ni feature, blue a troublesome artifact (we think), and purple the background. Click on the figure for a larger version.</div></td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins class="diffchange diffchange-inline">[[Image:15_ctspectra_lines.gif|thumb|600px|center|</ins>'''Figure 1''': This is an actual RHESSI spectral fit, made with our wonderful nonlinear parameter-fitting software SPEX. It shows "counts space", ie raw data, as the uppermost histogram (black). The different-colored histograms below it show the different features in the fit at this particular time interval: yellow is the Fe feature, magenta the Fe-Ni feature, blue a troublesome artifact (we think), and purple the background. Click on the figure for a larger version.<ins class="diffchange diffchange-inline">]]</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>Each Fe spectral feature is a unique function of "the" temperature, ie the temperature of the plasma that actually emits the radiation detected. Thus we can use the line ratio to determine this temperature and to compare it with the continuum temperature. As readers of the previous nugget will be aware, the continuum reflects different physics. Comparing a line flux with the continuum gives the equivalent width, a standard tool used by astronomers for determining an elemental abundance, for example.</div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>Each Fe spectral feature is a unique function of "the" temperature, ie the temperature of the plasma that actually emits the radiation detected. Thus we can use the line ratio to determine this temperature and to compare it with the continuum temperature. As readers of the previous nugget will be aware, the continuum reflects different physics. Comparing a line flux with the continuum gives the equivalent width, a standard tool used by astronomers for determining an elemental abundance, for example.</div></td></tr>
<tr><td colspan="2" class="diff-lineno">Line 15:</td>
<td colspan="2" class="diff-lineno">Line 26:</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;"></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>'''Figure 2''': How the equivalent width of the Fe feature compares with theory for many points during a particular solar flare. Basically the flare evolution moves the points up in temperature rapidly, then more slowly downwards. At this level, the discrepancy is probably not significant yet.</div></td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div><ins class="diffchange diffchange-inline">[[Image:15_fe_eqwidth.gif|thumb|center|600px|</ins>'''Figure 2''': How the equivalent width of the Fe feature compares with theory for many points during a particular solar flare. Basically the flare evolution moves the points up in temperature rapidly, then more slowly downwards. At this level, the discrepancy is probably not significant yet.<ins class="diffchange diffchange-inline">]]</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>In a survey of 30 flares compiled by Cristina Chifor (GSFC/CUA), it would appear that sometimes the Fe line equivalent width is not far from the theoretical curve (see the data points in the figure above), but with a small displacement of the observed points to the right (higher T side) of the curve.</div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>In a survey of 30 flares compiled by Cristina Chifor (GSFC/CUA), it would appear that sometimes the Fe line equivalent width is not far from the theoretical curve (see the data points in the figure above), but with a small displacement of the observed points to the right (higher T side) of the curve.</div></td></tr>
</table>Schristehttps://sprg.ssl.berkeley.edu/~tohban/wiki/index.php?title=The_Fe_and_Fe/Ni_line_features_II&diff=2507&oldid=prevSchriste: New page: == Introduction == As noted in the The Fe and Fe/Ni line features II on this topic, a solar flare makes the already-hot solar corona still hotter. So hot, in fac...2010-01-23T01:23:25Z<p>New page: == Introduction == As noted in the <a href="/~tohban/wiki/index.php?title=Earlier_RHESSI_nugget&action=edit&redlink=1" class="new" title="Earlier RHESSI nugget (page does not exist)">The Fe and Fe/Ni line features II</a> on this topic, a solar flare makes the already-hot solar corona still hotter. So hot, in fac...</p>
<p><b>New page</b></p><div>== Introduction ==<br />
<br />
As noted in the [[earlier RHESSI nugget|The Fe and Fe/Ni line features II]] on this topic, a solar flare makes the already-hot solar corona still hotter. So hot, in fact, that the natural emission spectrum of the coronal plasma moves into the X-ray band (hotter means "harder" photons). That previous nugget explained the basic principles of solar X-ray emission-line spectroscopy (as done by RHESSI), and in this nugget we will show some of the actual observational results.<br />
<br />
== What RHESSI is finding? ==<br />
<br />
It has taken a long time to try to understand the various RHESSI instrumental characteristics at energies less than 20 keV. The spectra are analyzed by taking count rate spectra and finding the best-fit underlying spectral continuum to determine the temperature, and then fitting the line features which appear as excess emission above the continuum level. See the first figure of the earlier RHESSI science nugget, which shows two features due mainly to highly-ionized iron above a smooth X-ray continuum. The lines are at 6.7 keV (the "Fe feature") and at 8 keV (the "Fe-Ni" feature because some small fraction of nickel emission lines appears in the fit). To show how complicated this is, we show another spectrum in the figure below. This spectrum is in "counts space," as gotten directly from the detector, rather than in the more theoretical "photon space" shown in the previous nugget - so it is not quite so pretty.<br />
<br />
<br />
'''Figure 1''': This is an actual RHESSI spectral fit, made with our wonderful nonlinear parameter-fitting software SPEX. It shows "counts space", ie raw data, as the uppermost histogram (black). The different-colored histograms below it show the different features in the fit at this particular time interval: yellow is the Fe feature, magenta the Fe-Ni feature, blue a troublesome artifact (we think), and purple the background. Click on the figure for a larger version.<br />
<br />
Each Fe spectral feature is a unique function of "the" temperature, ie the temperature of the plasma that actually emits the radiation detected. Thus we can use the line ratio to determine this temperature and to compare it with the continuum temperature. As readers of the previous nugget will be aware, the continuum reflects different physics. Comparing a line flux with the continuum gives the equivalent width, a standard tool used by astronomers for determining an elemental abundance, for example.<br />
<br />
The figure below shows how these equivalent widths, from many points in time, compare with the theoretical prediction of equivalent width vs. temperature. This is the sort of plot that would show up abundance anomalies for iron, which would provide an interesting clue to the flare development.<br />
<br />
<br />
'''Figure 2''': How the equivalent width of the Fe feature compares with theory for many points during a particular solar flare. Basically the flare evolution moves the points up in temperature rapidly, then more slowly downwards. At this level, the discrepancy is probably not significant yet.<br />
<br />
In a survey of 30 flares compiled by Cristina Chifor (GSFC/CUA), it would appear that sometimes the Fe line equivalent width is not far from the theoretical curve (see the data points in the figure above), but with a small displacement of the observed points to the right (higher T side) of the curve.<br />
<br />
It is possible that this is due to slightly incorrect atomic rates involved in the calculation of ionization fractions. A separate study of the Fe line to Fe/Ni line ratio (by Amir Caspi, UC Berkeley) is finding some agreement with theory, but with a tendency for the observed points to be lower than the theoretical curve (i.e. the Fe/Ni line is a little stronger than expected). There is, incidentally, a nice agreement of RHESSI continuum flux at about 4 keV (the low-energy end of the spectrum) with simultaneous observations with Janusz Sylwester's RESIK crystal spectrometer on CORONAS-F for flares in 2002 and 2003 (see [[The Fe and Fe/Ni line features II|previous nugget]]).<br />
<br />
We have been investigating how to deal with the fact that flare plasmas are not likely to be isothermal except possibly at the late stages of long-duration flares. They may be multi-thermal, with unresolved and physically different structures on the line of sight, or they may also be non-thermal, in which case the plasma particles do not follow the Boltzmann velocity distribution. In the former case we speak of differential emission measures (DEM), which show the spectrum of contributions from different-temperature regions. We get the necessary information from line, continuum, and broad-band observations. We hope to make some progress in studying these effects, which could help to clear up some of the discrepancies which we are seeing and at the same time explain the physics of solar flares a little better.<br />
<br />
== Biographical Note==<br />
Ken Phillips has until recently been a senior research visitor at NASA/GSFC, and is now at MSSL in the UK; Cristina Chifor is a GSFC summer student from Trent University in Canada. The material in this nugget owes a lot also to Brian Dennis (GSFC).</div>Schriste