1. RHESSI observations of LDE flares – extremely long persisting HXR sources Mrozek, T., Kołomański, S., Bąk-Stęślicka, U. Astronomical Institute University of Wrocław

2. Questions How long? Spatial scale Where? After the maximum of the flare; not during the impulsive phase

3. YOHKOH results - SXR Kołomański, S., 2007: >6h duration >3 orbits of YOHKOH starting from the maximum of the flare

4. YOHKOH results - SXR Different sources observed at the same time suggest that the energy reales takes place in different locations Typical sizes of the SXR sources are 1.0-1.5x10 4 km

5. YOHKOH results - HXR HXR emission in the L channel (14-23 keV) was observed up to 40 minutes after the maximum of the flare

6. YOHKOH results - HXR Rise phase – coronal and footpoint sources Decay phase - HXR source observed 40 minutes after the maximum of the flare. It is 10 times longer than characteristic cooling time of such source – indirect proof for the energy release long after the maximum of the flare.

7. RHESSI & LDEs - motivation Better spatial resolution – more detailed investigation of sources Better sensitivity - weak, coronal sources could be detected long after the maximum of the flare Better energy resolution – more detailed analysis of LDEs spectra, searching for different types of sources (very hot thermal, non-thermal)

8. RHESSI & LDE Feb. 2002 – Feb. 2008 ~ 160 LDE flares found with the use of GOES lightcurves ~ 50 which last longer than 3 hours in RHESSI observations 30 July 2005 X1.3 >10 h

9. Method 2-minutes intervals: -with attenuators out - outside the radiation belts - far from the SAA Thus, for 10 hours decay we have only three time intervals for imaging and spectroscopy (for this flare, in other cases we can have up to 9-10 intervals)

10. Method Images: Time interval: 11:38 – 11:40 Grids: 3,4,5,6,8,9 Pixel size: 1” 4-6 keV10-12 keV15-23 keV

11. Method The signal in the 12-25 keV interval is observed (11:40 UT – 6 hours after the maximum) - why we can’t obtain images?

12. Method Because of the size of sources? grid number time

13. Method We have to choose detectors in more flexible way – sources are large, but the result is realiable

14. 30 July 2005 - images Comparison with EIT 195 Å RHESSI images reconstructed with the use of PIXON method Red contours – 6-7 keV Blue contours – 15-25 keV 6 hours after the maximum of the flare

15. 30 July 2005 - spectra double thermal

16. 30 July 2005 - spectra thermal + thin target

17. 30 July 2005 - spectra thermal + thick target

18. 30 July 2005 - spectra thermal + broken power-law

19. 30 July 2005 How long? HXR emission in 15-25 keV is observed 6 hours after the maximum - we need an energy release existing for such long time To balance the thermal and conductive losses we need a heating of the order of 1 erg s -1 cm -3 (10 28 erg s -1 from the whole volume) Spatial scale: the order of 10 4 km Where?

20. 7 Nov 2003 B4.7 S29W90 30-40 degrees behind the limb

21. Extremely weak

22. Conclusions LDEs are observed by RHESSI however the analysis is very complicated due to attenuators, radiation belts, SAA and other HXR sources (above 15 keV) are visible even 6 hours after the maximum of the flare. Long-lasting HXR sources are located above structures seen in different wavelengths and have large sizes. For long-lasting HXR sources located far above the solar limb we do not detect significant non-thermal or hot components.