5 th RHESSI workshop, Locarno. WG 4 Report

1. 5th RHESSI workshop, Locarno. WG 4 Report Participants: Steven Christe Säm Krucker Brian Dennis Monique Pick Lyndsay Fletcher Ed Schmahl Peter Gallagher Manuela Temmer Jean-Claude Hénoux Mikko Vaananen Hugh Hudson Astrid Veronig Haishen Ji

2. Programme Overview: • (1) Presentations by each participant (2 by Brian) • (2) Joint discussions with: • WG3 on coronal sources • WG5 on (new) observations for focus of theory group • WG2 on annihilation line, FIP effect, atmospheric structure • (3) Small group discussions and planning.

3. RHESSI Fe & Fe/Ni complex (6.7keV) Dennis Fe/Ni feature is a reliable indicator of presence of thermal plasma. Feature parameters determined by T, abundance • Centroid energy varies with T & count rate. • Equivalent width varies with T • But does not agree with current theoretical predictions • Fe to Fe/Ni ratio varies with T. • Different dependence for different flares.

4. Multi-instrument DEM McTiernan GOES+RHESSI differential emission measure calculations done for first time. An example • 3 components – worrying large systematic errors between peaks • Lowest T peak drops below significance early • Position of peaks does not seem to vary through flare • Will be extended to include CDS and XRM data 19-sep-2002 05:39

5. Update on the SMART-1 X-ray Solar Monitor Vaananen XRM measures 1-20 keV with energy resolution of 0.34 keV. Especially interesting for comparison with Fe/Ni complex. A number of flares observed: RHESSI/XSM inter-calibration work is proceeding.

6. RHESSI microflare statistics Christe 8500 RHESSI microflares from A1 to C1 analysed. Spectrum fitted with thermal+power law • Average Temperature : 10 MK (detector limited) • Average Gamma : 5-7 • Broad range of break energies: peak ~ 10 keV. NB – interpreting power-law section as thick target gives total non-thermal energies 1028 – 1030 ergs.

7. downflows upflows Chromospheric Evaporation Gallagher Electron energy flux and plasma flows measured as function of temperature in CDS/RHESSI impulsive phase. 25 – 50 keV (solid line) 6 - 12 keV (dashed line) Consistent with gentle evaporation - assuming target area 1018cm2

8. Preflare (pre-impulsive) phenomena Schmahl RHESSI imaging shows hard coronal source 10 mins before impulsive phase onset Coronal source Spectrum well-fitted by broken powerlaw down to 5 keV Thermal component never dominates – like July 23rd 2002 Flare related to nice CME in MLSO

9. HXR emission from 18-Nov-03 occulted flare Krucker E < 10 keV, emission is gradual. E > 20keV the emission is faint, with fast time variations >20 keV emission above thermal emission Upwards motion ~5-40 km/s Nov 18, 2003: GOES M4

10. + Rapidly moving Type III burst sources Pick Series of Type III bursts, with sources moving outwards in corona along path of CME (temporal relation not clear) Potential reconstruction  Type IIIs, CME moving along open field 600 km/s

11. Kinematics of RHESSI sources Veronig Altitude decrease of 3-Nov-2003 looptop source ~ 45 km/s „downward“. Simultaneous with change in spectrum Spectral change corresponds to a) increase of T (thermal emission) and/or b) spectral hardening (non-thermal) Impulsive phase: • Kinematics of LT & FPs • is consistent • LT: higher energies at higher heights

12. Ha footpoint separation HXR source ‘height’ Motion of Ha kernels and coronal sources Ji Ha flare footpoint separation decreases along with projected HXR source height at impulsive onset – 4 examples

13. HXR footpoints and flare ribbons 17-Jan-05 Temmer HXR footpoints tracked and ‘reconnection rate’ (vB) measured. Tracks HXR flux well for one footpoint, but not the other

14. RHESSI 50-100 keV RHESSI 25-50 keV 07:02:30 – 07:03:00 4.5 0.5 1.5 2.5 3.5 UV footpoint motions and RHESSI sources Fletcher Rate of change of ‘magnetic flux’, dF/dt, calculated from UV footpoint motions. HXR sources tend to be where dF/dt highest 07:01:31 – 07:02:01 07:02:01 – 07:02:30

15. RHESSI and white light observations Hudson WL coincides with HXR source locations, but WL source sizes consistent with TRACE PSF (3-4 px = ~ 1000 km  area ~ 1016-17 cm2)

16. Hb Ha Ha Int. Ha Int. radial radial tangential tangential 10:07 June 15 2001 10:07 June 15 2001 THEMIS flare spectropolarimetry Hénoux Ha, Hb and NaD2 lines linearly polarized in impulsive phase (1 flare). Polarization patches at the outer edge of the kernels. Polarization properties consistent with electron beams and their associated return current Pol. Levels: Ha 5.0, 6.0 % Hb: 5.0, 6.0 %

18. WG4 Presentations - Wednesday 8th June 10:45 - 11:00 Introduction + preliminaries 11:00 - 11:30 Dennis - Separation of Thermal and Nonthermal Emissions 11:30 - 12:00 McTiernan - Multi-Instrument Differential Emission Measure Lunch 14:00 - 14:30 Vaananen – XSM:A stellar X-ray Spectroscope for the Sun 14:30 – 15:00 Christe - Microflare Statistics and Frequency Distribution 15:00 - 15:30 Schmahl - Hard & soft X-ray and EUV pre-flare phenomena Coffee break 16:00 - 16:30 Gallagher - Chromospheric and Transition Region Response 16:30 – 17:00 Temmer - Hard X-ray emission & flare ribbon expansion 17:00 - 17:30 Ji - Converging motion of solar flare kernels

19. WG 4 presentations - Thursday 9th June Joint session with WG3 8.30 – 10.15 Bone – multiwavelength observations of a partially occulted flare Krucker – Coronal HXR sources in partly occulted flares Dauphin - Veronig – X-ray looptop altitude decrease in an X-class flare Coffee 10:45 – 11:15 Hudson - Implications of compact footpoints 11:15 – 11:45 Henoux - Flare impact polarization observed with THEMIS 11:45 – 12:15 Fletcher - UV ribbons and Hard X-ray footpoints Lunch 14:00 – 14:30 Pick – Evidence for magnetic reconnection 14:30 – 15:30 All - Discussion with WG5 Friday 10th June Dennis – Flare vs. CME energy