M is for Magnifique

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== Introduction ==
== Introduction ==
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On October 12th, new magnetic flux began to emerge in the middle of the negative-polarity region of active region 11112.  This emerging flux continued to grow over the next few days stressing the already existing fields and presumably building up magnetic energy.  A few days later, on October 16th, the pent-up energy was finally released through an M-class flare (SOL2010-10-16T19:12).  The region went on to produce a few C-class events before rotating around the limb, but in a sense its master work was over.  This Nugget concerns this M-class flare which was simultaneously observed by [RHESSI] and SDO.  In this Nugget, we focus on the AIA observations, which are unique due to the fact that this is the first flare for which AIA's automatic exposure control was enabled.  In a future Nugget, we will take a look at the SDO EVE observations, a subject which we have already visited in a [http://sprg.ssl.berkeley.edu/~tohban/wiki/index.php/SDO_EVE_Flare_Observation previous Nugget].
+
On October 12th, new magnetic flux began to emerge in the middle of the negative-polarity region of active region 11112.  This emerging flux continued to grow over the next few days stressing the already existing fields and presumably building up magnetic energy.  A few days later, on October 16th, the pent-up energy was finally released through an M-class flare (SOL2010-10-16T19:12).  The region went on to produce a few C-class events before rotating around the limb, but in a sense its master work was over.  This nugget concerns this M-class flare which was simultaneously observed by [RHESSI] and SDO.  Here, we focus on the AIA observations, which are unique due to the fact that this is the first flare for which AIA's automatic exposure control was enabled.  In a future nuggets, we will take a look at the SDO EVE observations, a subject which we have already visited in a [SDO EVE Flare Observation|previous Nugget], and other topics such as loop oscillations which AIA is particularly good at observing.
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== AR 11112 ==
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== Intro to AIA ==
== Intro to AIA ==
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First a quick intro to SDOs AIA since we have not yet discussed this important new instrument.  The Atmospheric Imaging Assembly (AIA) is one of three instruments on board the Solar Dynamics Observatory (SDO). AIA consists of four telescopes, each imaging at multiple wavelengths, and provides full disk solar images with a pixel size of 0.6 arcseconds and a time cadence of around 12 seconds. Unlike RHESSI, SDO observes the Sun continuously, barring occasional eclipse periods. These guaranteed observations coupled with the unprecedented combination of spatial and temporal resolution have opened up a treasure trove of possibilities for solar wave observations.
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The Atmospheric Imaging Assembly (AIA) is one of three instruments on board the Solar Dynamics Observatory (SDO). AIA consists of four telescopes, each imaging at multiple wavelengths, and provides full disk solar images with a pixel size of 0.6 arcseconds and a time cadence of around 12 seconds. Unlike RHESSI, SDO observes the Sun continuously, barring occasional eclipse periods. These guaranteed observations coupled with the unprecedented combination of spatial and temporal resolution have opened up a treasure trove of possibilities for solar wave observations.
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[[File:Sdo_wavelengths.png]]
[[File:Sdo_wavelengths.png]]
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AIA takes solar images at the traditional SOHO/EIT wavelengths of 171 A and 193 A, but also in the 94 A, 131 A, 211 A, 304 A and 335 A bands. Thus for the first time simultaneous full disk imaging of the Sun at a number of different temperatures is possible.
+
AIA takes solar images at the traditional SOHO/EIT wavelengths of 171 A and 193 A, but also in the 94 A, 131 A, 211 A, 304 A and 335 A bands. Thus, for the first time, simultaneous consistent high-resolution full disk imaging of the Sun at a broad range of different temperatures is possible (see Figure 1).  Combined with RHESSI observations, interesting new discoveries are surely on the horizon.
== Automatic Exposure Compensation (AEC) ==
== Automatic Exposure Compensation (AEC) ==
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The large increase in flux during flares poses a problem for most detectors.  In RHESSIs case, we use movable metal shutters which come in automatically when needed and block out the large thermal fluxes at low energies.  For an EUV imager such as AIA, high fluxes can be mitigated by simply changing the exposure time of the images just like in optical photography.  The October 16th flare is the first flare for which automatic exposure compensation (AEC) was on therefore it provides an interesting test case for the SDO's team current strategy for AEC.  The following movie shows AEC in action.
{{#widget:YouTube|id=B-wKkuj4b_o}}
{{#widget:YouTube|id=B-wKkuj4b_o}}
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The flickering is due to the fact that AEC is only enabled every other frame.  This strategic choice is to make sure that there is always an ''overexposed'' frame available throughout the flare in order to be able to see the fainter global structure.  Another point to make here is that AEC works on every AIA channel independently.  A closer look at an ''underexposed'' compared to ''overexposed frame'' can be seen in Figure 1.
== Waves? ==
== Waves? ==

Revision as of 16:47, 1 December 2010

Contents

Introduction

On October 12th, new magnetic flux began to emerge in the middle of the negative-polarity region of active region 11112. This emerging flux continued to grow over the next few days stressing the already existing fields and presumably building up magnetic energy. A few days later, on October 16th, the pent-up energy was finally released through an M-class flare (SOL2010-10-16T19:12). The region went on to produce a few C-class events before rotating around the limb, but in a sense its master work was over. This nugget concerns this M-class flare which was simultaneously observed by [RHESSI] and SDO. Here, we focus on the AIA observations, which are unique due to the fact that this is the first flare for which AIA's automatic exposure control was enabled. In a future nuggets, we will take a look at the SDO EVE observations, a subject which we have already visited in a [SDO EVE Flare Observation|previous Nugget], and other topics such as loop oscillations which AIA is particularly good at observing.

Intro to AIA

First a quick intro to SDOs AIA since we have not yet discussed this important new instrument. The Atmospheric Imaging Assembly (AIA) is one of three instruments on board the Solar Dynamics Observatory (SDO). AIA consists of four telescopes, each imaging at multiple wavelengths, and provides full disk solar images with a pixel size of 0.6 arcseconds and a time cadence of around 12 seconds. Unlike RHESSI, SDO observes the Sun continuously, barring occasional eclipse periods. These guaranteed observations coupled with the unprecedented combination of spatial and temporal resolution have opened up a treasure trove of possibilities for solar wave observations.

Sdo wavelengths.png

AIA takes solar images at the traditional SOHO/EIT wavelengths of 171 A and 193 A, but also in the 94 A, 131 A, 211 A, 304 A and 335 A bands. Thus, for the first time, simultaneous consistent high-resolution full disk imaging of the Sun at a broad range of different temperatures is possible (see Figure 1). Combined with RHESSI observations, interesting new discoveries are surely on the horizon.

Automatic Exposure Compensation (AEC)

The large increase in flux during flares poses a problem for most detectors. In RHESSIs case, we use movable metal shutters which come in automatically when needed and block out the large thermal fluxes at low energies. For an EUV imager such as AIA, high fluxes can be mitigated by simply changing the exposure time of the images just like in optical photography. The October 16th flare is the first flare for which automatic exposure compensation (AEC) was on therefore it provides an interesting test case for the SDO's team current strategy for AEC. The following movie shows AEC in action.

The flickering is due to the fact that AEC is only enabled every other frame. This strategic choice is to make sure that there is always an overexposed frame available throughout the flare in order to be able to see the fainter global structure. Another point to make here is that AEC works on every AIA channel independently. A closer look at an underexposed compared to overexposed frame can be seen in Figure 1.

Waves?

Conclusion

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