Impact of nonthermal tails and nonthermal distributions on solar flare plasma diagnostics
Impact of nonthermal tails and nonthermal distributions on flare plasma diagnosticsJaroslav 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 Sciences Ondřejov, Czech Republic „From Atoms to Stars: The Impact of Spectroscopy on Astrophysics“, Celebrating the Career of Prof. Carole Jordan, Oxford, UK, July 27, 2011
OutlineI. The power-law distributions (nonthermal tails) Motivation: RHESSI flare observationsII. The n-distributions Definition 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 intensities Flare plasma diagnostics
I. The nonthermal tailsVeronig et al. (2010), ApJ 719, 655
The nonthermal tailsGabriel & 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 n1 2ε1/2 ε 2 fn (ε)dε Bn 3/2 eε/kBT dε kBT kBT Peak narrower than Maxwellian Very few low-energy electrons Pseudo-temperature t : 3 n E kt 1 kT 2 2 Seely, Feldman & Doschek (1987), ApJ 319, 541 Dzifčáková (1998), SoPh 187, 317
The n-distributionsChanges in ionization and excitation equilibrium – line intensitiesContribution functions - narrower and shifted to different tDzifčáková & Tóthová (2007), SoPh 240, 211; Dudík et al. (2011), AA 529, A103
Diagnostics from observationsDzifčáková et al. (2008), AA 488, 311Kulinová et al. (2011), AA, accepted
Theoretical f-b continuum Dudík et al. (2011), in prep.
Physical background - driftsKarlický, Dzifčáková & Dudík (2011), in prep.:„Moving Maxwell“ (Maxwellian with a drift velocity v0)can be written asWith the f(E,v0) having the same gradient as the n-distribution.
III. The composed np-distributionsDzifčáková, 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 distributionConditions for EC :- the power-law tail does not affect the plasma bulk- less than 10% discontinuity at EC
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