1. Coronal X-ray Emissions in Partly Occulted Flares Paula Balciunaite, Steven Christe, Sam Krucker & R.P. Lin Space Sciences Lab, UC Berkeley limb thermal loop HXR footpointsHXR above the loop top source

2. Coronal X-ray Emissions in Partly Occulted Flares Paula Balciunaite, Steven Christe, Sam Krucker & R.P. Lin Space Sciences Lab, UC Berkeley limb thermal loop HXR footpointsHXR above the loop top source limb thermal loop HXR footpoints occulted HXR above the loop top source (Masuda et al. 1994) solar disk

3. ~20 large, long duration flares with occultation 4 nice events with footpoints occulted, but coronal emission visible Example: Nov 18, 2003 event Is above the loop top source thermal or non-thermal?

4. RHESSI X-ray observations Nov 18, 2003: GOES M4 night gradual variations below 10 keV >20keV emission is faint, with fast time variations

5. gradual variations below 10 keV >20keV emission is faint, with fast time variations RHESSI X-ray observations Nov 18, 2003: GOES M4 night limb >20 keV emission above thermal emission

6. gradual variations below 10 keV >20keV emission is faint, with fast time variations RHESSI X-ray observations Nov 18, 2003: GOES M4 night limb >20 keV emission above thermal emission Upwards motion ~5-40 km/s

7. Spectral evolution thermal emission dominates below ~15 keV soft power law spectrum ( g ~6) at higher energies soft-’hard’-soft

8. Energy deposition in coronal source Assuming THICK target model integrated: close to 1e31erg!  a lot of heating in non-thermal source Observed thermal source (GOES/RHESSI) contains ~1e30 erg Assuming THIN target model integrated: still ~1e30erg  significant heating is expected Is 20 keV source is a combination of thermal and nonthermal emission?

9. Multi-thermal fit? 3 thermal components fit spectra as well as a power law. Very hot temperatures needed, small EM (1e45 cm -3 ) How can fast variations be explained? Adiabatic compression? T 1 ~ 17 MK T 2 ~ 28 MK T 3 ~ 80 MK background

10. Summary Flares with occulted footpoints: below ~15 keV, thermal emission from corona above ~15 keV, emission with fast time variation (10’s of s) >15 keV emission is above thermal loops, moves upwards faint emission with soft spectrum ( g ~6)

11. Summary Flares with occulted footpoints: below ~15 keV, thermal emission from corona above ~15 keV, emission with fast time variation (10’s of s) >15 keV emission is above thermal loops, moves upwards faint emission with soft spectrum ( g ~6) Problems with non-thermal interpretation is density high enough? Trapping? a lot of energy is deposited in corona  heating Problems with thermal interpretation short time variations very high temperatures

13. November 18, 2003: M4.5 E18N00 Impulsive & decay phase: Partly occulted event, later post flare loops are seen impulsive phase peak decay no emission from disk! movie

14. November 18, 2003: M4.5 E18N00 Pre-event: GOES emission from flare on disk Ejection of plasma seen in SXI images acceleration ~30 km/s ~120 km/s

15. Plasmoid ejection possibly lines up with CME LASCO CME SXI current sheet? Jun Lin et al. 2005, ApJ

16. Spectral variations Spectral variations are soft-’hard’-soft.

17. Above loop top source moves upwards in time Velocities between 5-40 km/s. Similar velocities as generally observed for footpoint motions ~30 min

18. Aug 19, 2004 Masuda flare

19. July 12, 2004 Footpoint and coronal source seen.