2nd RHESSI/NESSI

1

• 2nd RHESSI/NESSI
• WORKSHOP
  -Distribution Functions of
• Energetic Flare
  Particles -
• Glasgow, Scotland,  
• March 24-26, 2004
• How far can we go in quantitative
  determination (inference) of the (spectral,
  space, time) distribution functions of energetic
  flare electrons and ions from Hard X-Ray, 
  gamma-ray, and other data, starting from raw
  observations. Pure theory, model fitting, flare
  phases and such data morphology, are discouraged.

2

• Team 1 FROM RAW DATA TO PHOTON DISTRIBUTIONS
  (led by Richard Schwartz,TBC) ? countsgt photons
  (detector response)
• - Instrumental calibration and background
  effects. - Line and continuum issues - Images,
  spectra and spectral images, bearing in mind
  temporal    variation/modulation - Direct use
  of modulation data as opposed to reconstructions
• Team 2 FROM PHOTONS TO RADIATION SOURCE
  STRUCTURE (led by Chris Johns-Krull) ?photons to
  particles (inversion of the photon spectra)-
  Photon spectra and images -gt radiation source
  (volume or line of sight    integrated) particle
  distributions. - Inversion and forward fitting
  approaches. - Effects of method and cross
  section  and albedo.
• Team 3 FROM SITES OF RADIATION TO PARTICLE
  SOURCES (led by Hugh Hudson) ?the rest of the
  problem- Particle energy loss, pitch angle
  scattering and dispersion, drifts - Mapping
  through realistic coronal magnetic models -
  Particle "escape" onto open magnetic lines -
  Energy and particle transport

3

• Team 1 FROM RAW DATA TO PHOTON DISTRIBUTIONS
  (led by Richard Schwartz,TBC)
• Progress since May 2003 roll database
  aspect gaps livetime corrections pixon
• forward fitting provision for image
  with weighting (especially
• useful for 2.2 MeV imaging) SPEX
  pile-up correction for
• spectroscopy decimation correction
  response matrix
• improvement quick look lightcurve
  image with decimation
• attenuator correction
  ???????????????
• ??????..
• Near term / intermediate term
• livetime correction in back projection
  estimation of source
• size improving image evaluation
  harmonics stacker
• Fourier-based imaging algorithm
  implement visibility

4

• Imaging / Spectroscopy overview
• livetime pile-up (Sam Krucker)
• ??????pile-up????????
• (1) ???livetime is high(??80)
• (2) ???????grid masked
  ?7?23?????,???grid ? 40keV pile-up peak
• ???????,?????livetime????grid
• ????????,???,?????grid????
• ?????livetime?less pile-up???????????
• (?????????,??????)
• Improving Imaging / Spectroscopy (Golden
  Hurford)
• ???????????
• resolve subcollimators difference
  improving forward fitting
• stacker implement visibility
  implement algorithm MEM.

5

• imaging  (eg source sizes, photometry,
  algorithms)
• ?????????????
• FWHM / resolution lt 0.5
  relative visibility gt 0.8
• FWHM / resolution gt 1.3
  relative visibility lt 0.2
• 0.5 lt FWHM / resolution lt 1.3
  sensitive to source size
• ????
• no friendly tools
• MEM-SATO overestimated
• MEM-VIS underestimated
• CLEAN ??
• Forward fitting / PIXON is an
  option
• ??????
• Albedo multi-component source
•  Demodulation ??????????????
• remove????, summed?????????Arzner
• Hurford. ???????RHESSI?HXRS????

6

• Continuum spectroscopy gamma-ray issues
  Share, G.
• temporal variation (1 min for Oct.
  28 flare 2 min. for Nov. 2
• flare) of 200 keV, nuclear lines
  (???10), 511 keV
• line(????3), 511 keV line
  width(??10keV, 6
• keV?9 keV?2 keV)
• energy spectrum 110804111620
  for Oct. 28 flare
• ?? for
  Nov. 2 flare. Bgd ????,??
• 
  300keV????,??????10-
• 
  15keV,10.30????????
• explanation on 511 keV line
• constitute solar emission,
  bremsstrahlung, nuclear lines,
• 2.223 MeV line
• line width to use 6000 K
  fitting while the predicted 3g/2g
• too strong.
  The conclusion seems that it
• needs a
  higher density region at round 104 K
• while
  previous result (for July 23 flare) is that
• it needs a
  higher density region at round 105 K

7

• Gan, W.Q.
• see separate ppt file
• fluences are generally consistent
  with those of Share
• the spectrum is more or less the
  same(fluctuation above
• 8 MeV flux depends on time
  interval selected)
• complementary each other
• Trottet, G.
• Aug. 30, 2002, observed with both
  CORNAS and RHESSI.
• 511 keV is seen in count
  spectrum but it is in fact no
• gamma-ray line flare, if the
  photon spectrum is seen
• Oct. 28, 2003, observed with 210GHz,
  CORONAS,
• RHESSI, lightcurve comparisons
• Highlight presented the gamma-ray
  line spectrum of Oct.
• 28, observed with INTEGRAL.
  The C line and O line
• are very obvious, dissimilar
  to RHESSI observation!
• The analysis is being
  undertaken

8

• Hurford, G.
• 2.223 MeV images for other 3 flares are
  available!
• (but at the workshop he did not show his
  results, ???)
• Oct. 28 double source, similar to hard
  X-ray sources
• Oct. 29 single source, just between
  double hard X-ray sources
• Nov. 2 single source(?), between double
  hard X-ray sources(?)
• It seems that there are still not any
  definite conclusions
• between the gamma-ray sources and hard
  X-ray sources. It is
• especially stressed the difficulty for
  comparisons, like
• different time interval, detectors,
  movement, angular
• resolution, and so on

9

• Team 2 FROM PHOTONS TO RADIATION SOURCE
  STRUCTURE (led by Chris Johns-Krull)
• ?photons to particles (inversion of
  the photon spectra)
• Inverting photon spectra to recover electron
  spectra
• - Regularization Methods ??forward
  method????

July 23, 2003
Holman et al. Piana et al.
5.5s difference
10

• Regularization Methods ???Johns Lin ??????

• White Johns Lin (1992)
• Red Piana et al. 0th order
• regularization

11

• - Pile-up correction plus Albedo effect
• to use only livetime gt 80, with or
  without Albedo
• (???power-law????????)

No albedo
With albedo
12

• - Kontar ???
• 
  
• Regularization Methods?forward
  fitting??gap

???
20-30keV
Aug.20, 2002
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• Forward-fitting and the use of models to
  look for specific X-ray
• diagnostics (Brown, Holman,
  Kasparova, Massone, Zharkova)
• -Very flat X-ray spectrum (gamma lt 2
  below 80 keV) was
• detected at the burst maximum of 20
  Aug 2002 flare. Fitting of an
• isothermal component plus a double
  power-law electron flux
• distribution function in the thick
  target model revealed the low
• energy cutoff of 80 keV. Assuming
  different shapes of electron
• flux distribution below the low
  energy cutoff we investigate their
• influence on the photon spectrum.

14

• -ANISOTROPIC BREMSSTTRAHLUNG EMISSION
  FOR THE
• FLARE OF AUGUST 21, 2002
• Effects of albedo (C. Alexander, Brown,
  Johns-Krull, Schmahl)
• - ??Bai Ramaty (1978)??, ????????
• - ?regularization??????????
• - ?????,??a power-law, ???????
• - Albedo patch (Schmal)
• Goodness of fit criteria for derived electron
  spectra
• Methods to perform imaging spectroscopy (Lin,
  Schmahl)
• - Imaging spectroscopy of the 2002 Mar
  14 flare with two different
• ways parametric fits to photon
  spectra and forward fits from
• electron thick-target parameters

15

• Team 3 FROM SITES OF RADIATION TO PARTICLE
  SOURCES (led by Hugh Hudson)
• Focus area 1 Realistic magnetic fields
  drifts, scattering, energy losses, trapping,
  Neupert effect
• Focus area 2(radiation) Realistic
  magnetic fields Microwave and X-ray luminosity,
  coronal emission, Alfven speeds, cornucopia
  effect
• Focus area 3 Footpoint physics
• Focus area 4 radiative hydrodynamics

16
Hard X-ray source structure
Observations Mainly (double) footpoint
sources (Hoyng et al. 1981, Sakao
1994) Sometimes faint above the loop-top
source (Masuda et al. 1994)
Theory Modelling expected source height
structure for thick-target HXR emission
confirms predominance of footpoint
emission (Brown McClymont 1975, Emslie 1981,
Brown et al. 2002)
17
Microwave brightness distribution along flaring
loops (f 34 GHz).
18
What is the physical reason for the existence of
loop-top sources?
We consider that the most probable explanation of
the loop-top source is a strong concentration
of mildly relativistic electrons in the upper
part of a flaring loop. This strong
concentration can occur if there exists a strong
pitch-angle anisotropy of high energy electrons
perpendicular to magnetic field lines. A loss
cone anisotropy produced by the simple cut of the
initial isotropic pitch-angle distribution is not
enough to explain the observed microwave
brightness distribution. To obtain such a strong
pitch-angle anisotropy, we need either some
specific anisotropic acceleration/ injection of
mildly relativistic electrons, or a specific
transport effect producing highly anisotropic
distributions of trapped mildly relativistic
electrons. So, these findings put important new
constraints on the particle acceleration/
injection mechanisms and the kinetics of high
energy electrons in flaring magnetic loops
19
Veronig et al.
20
Observations EIT/RHESSI at last peak
21
Interpretation II Origin of high coronal N
f ( P(25), A, ? )
1.3 ? 1020 cm?2
f ( T )
4.9 ? 1020 cm?2
f ( n, L )
4.5 ? 1020 cm?2
? N conductively driven
22
Conclusions (for now)
14 April 2002, 2355 UT flare HXR source in
which the HXR emission is almost entirely in a
coronal loop so dense as to be collisionally
thick at electron energies up to 60 keV.

• L1) Loop column density N observed is consistent
  with the coronal
• thick-target interpretation of the HXR image.

2)This N is consistent with chromospheric
evaporation by thermal conduction flux from the
hot coronal plasma rather than by electron beam
heating.
3)T of the hot loop plasma (and hence the
conductively driven N value) is consistent with
thick-target collisional heating by electrons.
23
Petrosian
24
(No Transcript)
25
(No Transcript)
26

• Emslie e, p ???????
• ?????condensation, ???????
• ???????? ???????

27
(No Transcript)
28

• Allred ?????????RADYN(Carlsson 1997)
• ?H?He?CaII?MgII?,????????
• ???????????
• ??????Emslie(1978)?????
• ????Vernazza et al. (1981)
• ???????,Tlt107 K

29
Propagation Questions

• To what extent are electron footpoints smeared
  out by drift motions? Being studied maybe?
• To what extent can ions and electrons be
  separated spatially? Considerably
• Do separatrices correspond to ribbons, or
  (Metcalf et al, 2003) are they intriguingly
  related? Being studied
• Does trapping and Coulomb loss explain 34-GHz
  looptop sources? Being studied probably?!
• At what time scale does the steady-state
  approximation break down? Experts discussing

30
Radiation Questions

• Does trapping and Coulomb loss explain 34-GHz
  looptop sources? Being studied probably?!
• Can a coronal loop be dense enough to stop 60 keV
  electrons? Yes new input to models
• Do RHESSI observatinos suggest a coronal current
  sheet? Yes being studied
• Can realistic field extrapolations help to
  understand flare X-ray sources? Being studied

31
Footpoint Questions

• Do electron-heated atmospheres produce thick
  enough transition regions to explain the 511-keV
  line width? No
• Do proton-heated atmospheres produce thick
  enough transition-region material to explain the
  511-keV line width? Being studied
• Do we understand footpoint DEMs well enough to
  explain ribbon radiation? Being studied
• Do we understand why hard X-ray footpoint
  structures are so concentrated in the ribbons?
  Being studied