RHESSI Paris workshop, 27-Jul-2004

Joint session on atmospheric response: a dialog with Gerry Share

Allred: introduction to thesis
 * Preflare atmosphere (VAL-3C) showing run of parameters with height
 * RADYN (Mats Carlsson) code solves the dynamics via energy balance and
  radiative transfer, relaxing to an equilibrium state after a perturbation
 * Energy equation. In RADYN one sets T_e = T_p. Somov demurs...
 * Temperature evolution following perturbation
 * Many transitions (9-level H)
 * Electron energy deposition following double power law
 * Fokker-Planck approach is better; see Zharkova
 * APED database (Raymond-Smith derivative of CHIANTI)
Discussion - huge amounts of discussion are not being recorded here. This
  is a learning experience for all participants, it seems. Sorry for the
  incomplete record! Henoux, Murphy, Somov, Fletcher, Emslie, Allred, Hudson,
  and especially Share are all happily yapping away.
 * Future developments: Fokker-Planck, return current, multi-filament. See
  Mauas & Gomez (1997) for improved particle transport, for example
 
Emslie: how protons differ
 * protons heat deeper (Sorry! these are incomplete notes; on the other
  hand, these are preliminary results.) 

Share: reprise on RHESSI 511 observations
 * see oct18_040727.txt for discussion
Discussion of how to get higher ionization at greater densities, without
  regard to heating (Emslie, Fang, Hudson)

Bianda: impact polarization
 * IRSOL Switzerland, ZIMPOL instrument from Zurich
 * history of impact polarization (Henoux)
 * Observations with Q parallel to limb of M1.0 flare 2-aug-02 10:51 UT
 * M3.9 18 Nov 03 8:31
 * small 7-Jul-03, find slow signal ~0.04% (negative Q radial); no U 
  observations
 * filter technique uses line center, rather than wings
 * X17 28-Oct-03 (I,Q,U,V) with slits in the right places for both electrons
  and protons, based on RHESSI images 
 * impact polarization not detected in 30 events, 0.4% upper limit in
  October 28
Discussion * * *

Hudson: White-light flares
 * * *

Mrozek: evaporation
 * plots of centroid positions of RHESSI sources for many events, following
  Brown & Aschwanden
 * good example of 3-aug-02 19:08 (?) 
 * successive 20-sec intervals show increasing centroid curves, say 5"
  at 30 keV or so, consistent with evaporation flow
Discussion (Emslie, Allred, Fletcher, Hudson, Hurford) of velocities and image
  structure
 * conclusions: similar results to Brown-Aschwanden, not clear if 
  inconsistent with standard models 
Discussion of everything, tune in tomorrow for more detail