# Presentation: 540488

## RHESSI data: Apr 21 2002 and Aug 24 2002

**NOTE:**
** ****Confined to emission at Sun**
** ****HXR emission presumed dominated by electrons**
** ****HXR emission confined to ‘closed’ structures**

**APR 21 2002**

**AUG 24 2002**

## Apr 21 2002 TRACE movie

**TRACE data**
**shows interesting morphological evolution**

## Apr 21 2002 RHESSI data

**RHESSI data**
**shows multiple bursts of hard X-rays.**

## 

Red contours from RHESSI show 12 – 25 keV X-ray flux.
Blue contours from RHESSI show 50 – 100 keV X-ray flux.
Colour scale shows EUV emission from Fe XII at ~1.5 MK and from Fe XXIV at 15 – 20 MK.

**Red contours from RHESSI show 12 – 25 keV X-ray flux.**
**Blue contours from RHESSI show 50 – 100 keV X-ray flux.**
**Colour scale**** ****shows EUV emission from Fe XII at ~1.5 MK and from Fe XXIV at 15 – 20 MK.**

**Apr 21 2002 RHESSI/TRACE**

## Apr 21 2002 RHESSI/TRACE

**Apr 21 2002 RHESSI/TRACE**

**Multi-footpoint structure in HXRs**

## RHESSI Spectra

**Apr 21 2002 RHESSI Imaging Spectra**

## Apr 21 2002 Dynamic Evolution

**Apr 21 2002 Dynamic Evolution**

## Apr 21 2002 Dynamic Evolution

**From Gallagher, Lawrence and Dennis (2003)**

**Peak acceleration coincides with peak of hard X-ray production (see also Zhang, 2001)**

## Aug 24 2002 TRACE movie

- A

- B

**Aug 24 2002 TRACE movie**

**TRACE data**
**shows ejected structure at beginning of flare.**
**Also note that loop footpoints are occulted by limb.**

## Aug 24 2002 RHESSI data

**RHESSI night occurred prior to flare maximum**

## Aug 24 2002 RHESSI data

- B

- C

**Aug 24 2002 RHESSI data**

**00:36 – 00:38**

**00:50 – 00:55**

**10 – 16 keV**

**16 – 22 keV**

**22 – 28 keV**

**28 – 34 keV**

**34 – 40 keV**

**40 – 46 keV**

**10 – 16 keV**

**16 – 22 keV**

**22 – 28 keV**

**28 – 34 keV**

**34 – 40 keV**

**40 – 46 keV**

**Flare HXR footpoints occulted, hence lack **
**of high energy emission**

## Aug 24 2002 RHESSI/TRACE data

**TRACE 195 with RHESSI 10 – 16 keV contours**

**TRACE 00:46 UT  **
**RHESSI 00:45 – 00:50  UT**

**TRACE 00:50 UT  **
**RHESSI 00:50 – 00:55  UT**

## Comparison of these Events

** ****Both events have roughly the same soft X-ray magnitude and evolution**
**	****- Apr 21 has broader SXR profile****  **
**	****	****-more energy injection?   [Aug 24 partially occulted]**
** ****Both show development of large-scale curvilinear arcade (typical of large flares)**
** ****Both display high energy (hot?) coronal source with complementary emission in TRACE**
** ****Both show outward-moving loop structures near start of flare**
**	****- 120 km/s  for Apr 21 and ~60 km/s for Aug 24**** **

**Qualitatively, these two flares are very similar at X-ray energies.**

## Points for Discussion

** ****Two principal times of interest**
** ****Flare initiation – early evolution of morphological features**
** ****Peak of HXR emission – maximum energy injection rate**
** ****Need to determine relationship of seed population to shock accelerated population**
** ****Shock spectra/abundances reflect flare generated particle spectra**
** ****Shock selectively accelerates part of total particle distribution**
** ****Magnetic topology**
** ****Maybe it is all in the availability of open magnetic field lines**

**RHESSI/TRACE can help determine initiation properties, dynamic evolution in low corona, reconnection rate/acceleration properties, electron/ion properties when available, ...**