Download - 5 th RHESSI workshop, Locarno. WG 4 Report
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
dial
tang
entia
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H
Int
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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
Hra
dial
tang
entia
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H
Int
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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