impact of nonthermal tails and nonthermal distributions on solar flare plasma diagnostics
DESCRIPTION
Talk presented by Jaroslav Dudík et al. at the symposium From Atoms to Stars:the impact of Spectroscopy on Astrophysics, 26th-28th July 2011, Oxford, UKTRANSCRIPT
Jaroslav Dudík 1,2, Elena Dzifčáková 2, Michal Homola 1, Marian Karlický 2, Alena Kulinová 1,2, Jana Kašparová 2
1 – DAPEM, Faculty of Mathematics, Physics and Informatics,Comenius University, Bratislava, Slovakia
2 - Astronomical Institute of the Academy of SciencesOndřejov, Czech Republic
„From Atoms to Stars: The Impact of Spectroscopy on Astrophysics“, Celebrating the Career of Prof. Carole Jordan, Oxford, UK, July 27, 2011
Impact of nonthermal tailsand nonthermal distributions
on flare plasma diagnostics
Outline
I. The power-law distributions (nonthermal tails)Motivation: RHESSI flare observations
II. The n-distributionsDefinition and properties Seely et al. (1987)
Diagnostics from observations Dzifčáková et al. (2008)
Kulinová et al. (2011)
Physical background Karlický et al. (2011), in prep.
The nonthermal continuum Dudík et al. (2011), in prep.
III. The composed np-distributions Dzifčáková et al. (2011)
Construction: „know how“Effect on ionization equilibrium and line intensitiesFlare plasma diagnostics
I. The nonthermal tails
Veronig et al. (2010), ApJ 719, 655
The nonthermal tails
Gabriel & Phillips (1979),
MNRAS 189, 319:
Effect on the Fe XXIVd / Fe XXV
satellite/allowed line ratios
- excess excitation of the Fe XXV line
- decrease of the ratio by up to 40%
However, an increase is observed
(even with respect to Maxwellian):
Seely, Feldman & Doschek (1987),
ApJ, 319, 541
II. The n-distributions
B
11/2 2
ε/
3/2BB
2ε ε(ε) ε e ε
n
k Tn nf d B d
k Tk T
Peak narrower than MaxwellianVery few low-energy electrons
Pseudo-temperature t :
Seely, Feldman & Doschek (1987),ApJ 319, 541Dzifčáková (1998), SoPh 187, 317
t
31
2 2
nE k kT
The n-distributions
Changes in ionization and excitation equilibrium – line intensities
Contribution functions - narrower and shifted to different t
Dzifčáková & Tóthová (2007), SoPh 240, 211; Dudík et al. (2011), AA 529, A103
Diagnostics from observations
Dzifčáková et al. (2008), AA 488, 311
Kulinová et al. (2011), AA, accepted
Observed spectra - RESIK
Diagnostics - results
Theoretical f-b continuum
Dudík et al. (2011), in prep.
Physical background - drifts
Karlický, Dzifčáková & Dudík (2011), in prep.:
„Moving Maxwell“ (Maxwellian with a drift velocity v0)
can be written as
With the f(E,v0) having the same gradient as the n-distribution.
Physical background - drifts
Diagnostics - RHESSI
Kulinová et al. (2011), AA, accepted
Diagnostics - RHESSI
III. The composed np-distributions
Dzifčáková, Homola & Dudík (2011), AA 531, A111:
Composed np-distribution: Bulk (n) + Tail (p)
n – index n describing the bulkp – power-law index of the high-energy tailEC – low-energy cutoff for the power-law taila/b – bulk/tail ratio, a + b = 1
Construction of the distribution
Conditions for EC :
- the power-law tail does not affect the plasma bulk
- less than 10% discontinuity at EC
Construction of the distribution
Ionization equilibrium – tail only
Ionization equilibrium – bulk + tail
Si XIId, XIII, XIV flare spectra
Conclusions
High-energy tail can change the ionization equilibrium
Changes the temperature diagnostics from ratios of allowed lines
Nonthermal bulk necessary to explain the Si XIId / Si XIII ratios
- has a physical explanation – drift velocities (return current)
- can also be diagnosed from RHESSI at < 6 keV
Composed distributions offer simple parametrization
of the true electron energy distributions in flares
Easy calculation of spectra using modified CHIANTI
Thank you for your attention