# Presentation: 947792

## Relationship Between Flares and GLEs 

- Gerald Share1,2, Ronald Murphy2

- 1 UMD, 2NRL

- Supported under NASA Grants NNX07AH81G, NNX07AO74G, and NNG06GG14G.

## List of gamma-ray events with spectroscopic data associated with SEP events from 1980 to 2005 (the GLE on 2006 Dec 16 is missing from this list.)

## 4 topics that I plan to discuss:

- Does the accelerated-particle population producing gamma-ray line flares have an ‘impulsive SEP’ composition?
- What do gamma-ray observations tell us about particle acceleration during the 2005 January 20 GLE?
- Is spectral hardening in hard X-ray flares associated with GLEs/SEPs?
- Are spectral breaks observed in SEP electron events associated with similar breaks in flare bremsstrahlung spectra?
- Other Topics?

## New gamma-ray line studies of SMM data provide a modified view of accelerated particle composition and ambient abundances during flares.

- Updated nuclear cross sections based on TALYS code (Ron Murphy, Benz Kozlovsky, Juergen Kiener).
- SMM/GRS detector response improved with MC.
- Fits made to 12 nuclear line flares (4 GLE and 6 SEP)

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## Fits to the 1989 October 19 flare showing the total fit, bremsstrahlung, direct interaction (i.e. accelerated p and on ambient elements, inverse interaction (i.e. heavy ions on ambient elements), -4He, and 0.511/2.223 MeV line components and Compton-scattered 2.2 MeV line.

- Fits to the 1989 October 19 flare showing the total fit, bremsstrahlung, direct interaction (i.e. accelerated p and on ambient elements, inverse interaction (i.e. heavy ions on ambient elements), -4He, and 0.511/2.223 MeV line components and Compton-scattered 2.2 MeV line.

## 1981 April 27 chi2 contour plots for spectral index and /p ratio. From Monte Carlo studies a 2 = 3.5 has a 68% probability.  

- Curve marked 186 shows the indices and /p  ratios consistent with photospheric He/O (Asplund abundances) for the flux measured in the -4He fusion lines (the other dotted curves show the 1 sigma statistical uncertainty in the line measurement).

## In order to estimate the ambient abundances (normalized to O) for the flare we use the parameters for the best fitting /p ratio and spectral index consistent with the Asplund photospheric He/O.

- In order to estimate the ambient abundances (normalized to O) for the flare we use the parameters for the best fitting /p ratio and spectral index consistent with the Asplund photospheric He/O.
- C/O ratio just below photospheric and coronal values; Ne/O is ~12%  (note this is lower the value adopted by Ramaty et al.,) the low FIP elements do not appear to be significantly enhanced over photospheric values.

## The ambient C abundance relative to O for twelve SMM flares (errors include +- 1 sigma range in Asplund He/O).  The average ratio appears to be below coronal and photopheric abundances but may be consistent when uncertainties in both the abundances and our measurements are fully taken into account.

## The ambient Ne abundance relative to O for twelve SMM flares.  The average ratio appears to be consistent with a value between 15 and 20%, consistent with adopted photospheric and coronal abundances.

## The ambient Mg abundance relative to O for twelve SMM flares.  The average ratio appears to be consistent with photospheric values but is not consistent with coronal abundances as determined by gradual SEP measurements.

## The ambient Si abundance relative to O for twelve SMM flares.  The average ratio is in between photospheric and coronal values. It is important to note that the line is near the instrumental backscatter peak of the neutron- capture line which could affect the measurement.

## The ambient Fe abundance relative to O for twelve SMM flares.  The average ratio appears to be consistent with photospheric values and not consistent with that found in the corona.  There is therefore no consistent evidence for a FIP effect in the ambient medium where the ions interact.

## Results of our fits on the 1989 October 19 flare at heliocentric of 30o. The He/O ratio (dotted curves) consistent with the Asplund et al. photospheric abundance is consistent with the chi2 contours from our fits. The accelerated ion spectrum is consistent with a power law with index between ~3.2 and 4.2.

## We obtained the accelerated abundances relative O for the 88 December 16 flare; the uncertainties are larger than for the ambient abundances.  C/O is consistent with photospheric value; the heavy nuclei (Ne, Mg, Si, and Fe) also have a combined abundance consistent with what is found in the photosphere.  It appears to be inconsistent with impulsive SEPs.  

##  The accelerated  C abundance relative to O for twelve SMM flares.  The average ratio appears to be somewhat below the photospheric, coronal, and impulsive SEP abundances. 

##                         G   S  S   S   S        S  S   G        G   G

- The accelerated heavy (combined Ne, Mg, Si, S, and Fe abundance normalized to Fe) relative to O for twelve SMM flares.  The average ratio does not appear to be consistent with the strong enhancement found in impulsive SEP events. GLE observations Tylka, Dietrich, et al 2001.

## We have roughly estimated the accelerated alpha/proton ratios for the 12 flares from using acceptable ranges of He/O from Asplund.  The average ratio is ~0.15.

## Current Status of our Studies

- Average ambient Mg and Fe abundance ratio consistent with photospheric abundances while ambient Si abundance appears to be between photospheric and corronal.  No consistent low FIP enhancement.
- The average Ne/O abundance in the lower chromosphere has been measured directly for the first time with a value of 0.15-0.20.
- Average accelerated heavy ion (Ne, Mg, Si, and Fe)/O abundance ratio consistent with that found in the corona and photosphere but not in  impulsive SEPs.
- The average accelerated alpha/proton ratio (~0.15 )  is elevated.

## Inferred Electron Spectra

- Best fitting bremsstrahlung photon spectra with uncertainties shown by the thin solid (blue lines).  The spectrum hardens significantly above a few hundred keV and then appears to role over.  Using SSW (Holman code) we fit the spectra by eye assuming that the electron spectrum is a sum of two power laws: a steep PL (dots) and a very hard PL which breaks at high energy (dashes).  The combined fit is shown by the bold curve.

## Estimated Spectral Parameters for the Accelerated Electron Spectra

-     			1981 April 27		1989 October 19
- PL Index 1		~4.6			~5.4
- e/sec (>100 keV)	~5 x 1033		~1.5 x 1034
- PL Index 2		~1.1			~1.05
- Break Energy 		~10 MeV		~22 MeV
- H.E. Index		~5.5			~10
- e/sec (>100 keV)	~2.8 x 1029		~1.5 x 1029
- Energy in electrons	~2.1 x 1030 erg		~1 x 1031 erg
- (>100 keV)
- Energy in ions		~6 x 1030 erg		~1 x 1031 erg
- (>1 MeV)

## What do gamma-ray observations tell us about particle acceleration during the 2005 January 20 GLE?

- “... the high-energy particles responsible for the pion-decay gamma rays and the majority of those responsible for the leading spike of the GLE belonged to the same population and were accelerated by the same mechanism.” Grechnev et al. 2008.
- “The observations lead us to propose two separate acceleration episodes in the typical GLE: 1) acceleration directly associated with the flare itself and located in the lower corona and 2) acceleration by a supercritical shock driven by the associated coronal mass ejection located at ~3-5 solar radii and farther in the upper corona.”  McCracken, Morall, and Stoker 2008.

## The bremsstrahlung and nuclear-line emission begin before the sharp rise of the >17 MeV emission and fall much more rapidly.   Bottom panel shows an estimate of the GLE injection profile derived from neutron monitor data shifted back to the Earth for comparison with the gamma-rays.

- Caveat: possible contamination from scattered 2.22 MeV line radiation

## >17 MeV

- Pion-decay

- n-capture

## RHESSI has observed what appears to be two distinct components of particle acceleration in the 2005 January 20 solar flare.

**RHESSI has observed what appears to be two distinct components of particle acceleration in the 2005 January 20 solar flare.**
**There is a ‘normal’ impulsive component beginning at ~06:42 UT, peaking at ~06:47 UT, lasting about 10 minutes, evidenced by electron bremsstrahlung and nuclear-line radiation from accelerated ions interacting at footpoints.**
**A harder photon component rose within ~1 min, peaking at ~06:46 UT, consistent with pion-decay radiation; emission lasted for ~2 hours (long-duration gamma-ray flare).**

## Comparison of accelerated particles interacting at the Sun and observed in space (Mewaldt, priv. comm. 2005)

**Total number of protons >30 MeV:**
**  ****Solar flare impulsive component: (2.8 ± 0.8) x 10****32**
**  ****Solar flare high-energy component: ******** 0.7 x 10****32**
**  ****Event integrated SEPs: 210 x 10****32**** **
**Power-law spectral index:**
**  ****Solar flare impulsive component: ~3.0**
**  ****Solar flare high-energy component: ~2**
**  ****Event integrated SEPs: 2.15**

## In 1995 Kiplinger found that soft-hard-harder (SHH) spectral evolution in hard X rays “either over flux peaks or during flux decays” are indicators of an ensuing SEP event.  This appears to have been confirmed by a RHESSI study of 5 flares in 2005 January.

## Four additional flares that appear to exhibit spectral hardening

- (Does delayed gamma-ray line emission play a role in the apparent hardening in the four 2005 January flares?)
- (Work done with Allan Tylka)

## Yohkoh ~100-200 keV counting rate (top panel) and ~100 – 200 keV/~50 – 100 keV hardness ratio (bottom panel) for the second peak of the 1998 May 6 solar flare (GLE).

## RHESSI 100-200 keV counting rate (top panel) and 100 – 200 keV/50 – 100 keV hardness ratio (bottom panel) for the second peak of the 2002 April 21 solar flare (SEP).

## RHESSI 100-200 keV counting rate (top panel) and 100 – 200 keV/50 – 100 keV hardness ratio for the 2006 December 6 solar flare (SEP).

## RHESSI 100-200 keV counting rate (top panel) and 100 – 200 keV/50 – 100 keV hardness ratio for the 2006 December 13 solar flare (GLE).

## Three flares that do not appear to exhibit spectral hardening.

## Yohkoh counting rate for the 14 July 2000 flare (GLE) in ~100-200 keV (top panel) and ~100 – 200 keV/~50 – 100 keV hardness ratio (bottom panel).

## Yohkoh counting rate in ~100-200 keV counting rate (top panel) and ~100 – 200 keV/~50 – 100 keV hardness ratio for the 2001 April 15 solar flare (GLE).

## RHESSI 100-200 keV counting rate (top panel) and 100 – 200 keV/50 – 100 keV hardness ratio for the 2003 November 02 solar flare (GLE).

## Thus soft-hard-harder (SHH) spectral evolution is not a necessary condition for production of an SEP event and does not appear to be an appropriate predictor for such events.

## Correlated observations of electron spectra in space and at the Sun

- Paul Evenson discussed observations of electrons in space by ISEE-3 (Moses et al 1989).  The event integrated spectra associated with ‘impulsive-type’ soft X-ray flares exhibited hardening between ~0.5 MV and 15 MV.
- We studied 18 of these events associated with flares observed by SMM to determine whether spectral breaks in electrons in space and in electrons producing bremsstrahlung at the Sun were correlated.
- This was done in only a cursory manner.  We broke up the events into two groups: those exhibiting a visible hardening in the few hundred keV range in the combined  SMM HXRBS/GRS spectra and those that did not.

## There is some indication for a correlation between the spectral breaks seen in space and at the Sun but there are counter-examples.

- We determine the average  change in spectral index (hardening) of particles in space for two cases.
- Case 1: No clear evidence for hardening in the solar hard X-ray/gamma-rays:  ~1.5
- Case 2: Evidence for hardening in the solar hard X-ray/gamma-rays:  ~2.3

## Combined HXRBS/GRS bremsstrahlung spectra for ISEE events with spectral index changes >2.95

## Combined HXRBS/GRS bremsstrahlung spectra for ISEE events with spectral index change <0.88

##   06:44-06:56 UT

**TRACE 1600A  at  06:52:30 UT**
**250 – 500 keV  **30, 50, 70, 90% contours
**2215-2231 keV centroid   1-******** error circle**

- Hurford et al. (2006) have shown that virtually all of the accelerated ions during the impulsive phase interact in the Northern footpoint.  No imaging of the later phase appears possible.  Annihilation line measurements may provide some information on this later phase.

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