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

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.

RHESSI Fe & Fe/Ni complex (6.7keV) Dennis

•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.

Fe/Ni feature is a reliable indicator of presence of thermal plasma. Feature parameters determined by T, abundance

19-sep-2002 05:39

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

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.

• Average

Temperature : 10 MK (detector limited)

• Average Gamma

: 5-7

• Broad range of break

energies: peak ~ 10 keV.

RHESSI microflare statistics Christe

8500 RHESSI microflares from A1 to C1 analysed. Spectrum fitted with thermal+power law

NB – interpreting power-law section as thick target gives total non-thermal energies 1028 – 1030 ergs.

6 - 12 keV (dashed line)

25 – 50 keV (solid line)

Chromospheric Evaporation Gallagher

Electron energy flux and plasma flows measured as function of temperature in CDS/RHESSI impulsive phase.

upflows

downflows

Consistent with gentle evaporation - assuming target area 1018cm2

Preflare (pre-impulsive) phenomena Schmahl

Coronal source

RHESSI imaging shows hard coronal source 10 mins before impulsive phase onset

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

E < 10 keV, emission is gradual. E > 20keV the emission is faint, with fast time variations

Nov 18, 2003: GOES M4

>20 keV emissionabove thermal emission

Upwards motion ~5-40 km/s

HXR emission from 18-Nov-03 occulted flare Krucker

600 km/s

+

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

Impulsive phase:

Kinematics of LT & FPs is consistent LT: higher energies at higher heights

Altitude decrease of 3-Nov-2003 looptop source ~ 45 km/s „downward“. Simultaneous with change in spectrum

Kinematics of RHESSI sources Veronig

Spectral change corresponds to

a) increase of T (thermal emission) and/or

b) spectral hardening (non-thermal)

H footpoint separation

HXR source ‘height’

Motion of H kernels and coronal sources Ji

H flare footpoint separation decreases along with projected HXR source height at impulsive onset – 4 examples

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

RHESSI 25-50 keV RHESSI 50-100 keV

07:01:31 – 07:02:01

07:02:01 – 07:02:30

07:02:30 – 07:03:00

0.5 4.52.51.5 3.5 )log10-1(Vm

Rate of change of ‘magnetic flux’, d/dt, calculated from UV footpoint motions. HXR sources tend to be where ddt highest

UV footpoint motions and RHESSI sources Fletcher

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)

Pol. Levels: H 5.0, 6.0 % H: 5.0, 6.0 %

THEMIS flare spectropolarimetry Hénoux

H10:07 June 15 2001ra

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H, H 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

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10:07 June 15 2001

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

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

WG 4 presentations - Thursday 9th June