Presentation on theme: "The synthetic emission spectra for the electron non-thermal distributions by using CHIANTI Elena Dzifčáková Department of Astronomy, Physics of the Earth."— Presentation transcript:
The synthetic emission spectra for the electron non-thermal distributions by using CHIANTI Elena Dzifčáková Department of Astronomy, Physics of the Earth and Meteorology FMPhI Comenius University, Bratislava
Why to use the CHIANTI database CHIANTI contains atomic data for the majority of the astronomical interesting ions and has a very good software support. CHIANTI allows quick computation and analysis of solar spectra and it is an important diagnostic tool of physical parameters of the solar plasma. The database contains only the collision strengths averaged through the Maxwell distribution. Their approximation function depends on the type of the transition and is performed by 5-point spline functions (Burgess and Tully, 1992).
The often used approximation of the collision strength is a functional form (Abramowitz and Stegun, 1965), where C k and D are coefficients and u=E i /E ij : The collision strength approximation The advantage of this approximation is the simple analytical evaluation of its integral over a distribution function.
The high energy behaviour of electric dipole transitions non electric dipole, non exchange transitions exchange transitions
The collision strength averaged over the Maxwell distribution where y=E ij /kT and E k is an exponential integral of order k. The coefficients C k and D can be evaluated from CHIANTI by the least square method.
The conditions for the coefficients C k and D : Electric dipole transitions Non electric dipole, non exchange transitions Exchange transitions
How precise is the collision strength determined by this inverse technique? Electric dipole transitions - no problems with the approximation & good agreement with data (TIPbase) Fe XV 3s 2 1 S 0 -3s3p 1 P 1 (284.16 Å)
The electric dipole transitions Fe XV 3s3p 3 P 1 - 3s3d 3 D 2 Fe XV 3s3p 3 P 2 - 3s3d 3 D 3
Non electric dipole, non exchange transitions Fe XV 3s 2 1 S 0 - 3p 2 1 D 2 Fe XV 3s3p 3 P 1 - 3p3d 3 F 3
Problem - higher high energy limit of from CHIANTI than from data (TIPbase) Fe XV 3s3p 3 P 0 -3p3d 3 F 3 Fe XV 3s3p 3 P 2 - 3p3d 3 P 2
Exchange transitions O VII 1s 2 1 S - 1s2p 3 P
The minimisation of the influence of possible errors The numerical problems were often with the exchange transitions where the -s can be approximated only by using three or two coefficients. But the fulfilment of the conditions for coefficients guarantees the correct behaviour of for high and threshold energies. The simplest expressions for correspond to expressions which have been often used e.g. by Mewe (1972). It is difficult to compare data for all transitions of every ion. Possible errors in the approximation of cannot be excluded in present time. Their influence on the computation of non-th have been minimised by using:
Non-thermal distributions: kappa distribution
Non-thermal distributions: power distribution Pseudo-temperature
Computation of the line intensity Several programs for analytic computation of the electron excitation rate for the non-thermal distributions have been included into CHIANTI software and small modifications of some original routines have been done. New data include: ionization equilibrium: C, N, O, Ne, Mg, Al, Si, S, Ar, Ca and Fe for =2, 3, 5, 7, 10, 25 ( -distribution) Si, Ca and Fe for n=1, 3, 5, 7, 9, 11, 13, 15, 17, 19 (power distribution) parameters for approximation of for all the ions above Changes in line intensity depend on the changes in the ionization equilibrium and excitation equilibrium. What can we expect for different distributions?
Changes in the ionization equilibrium kappa distribution full line - Maxwell distribution dashed line - kappa-distribution, = 2
Changes in the ionization equilibrium Power distribution
The changes in electron excitation rate kappa distribution power distribution
Changes in spectrum - kappa distribution Maxwell distribution =7 =2 Log T = 6.2
Changes in spectrum - kappa distribution Maxwell distribution =7 =3 DEM: quiet sun
Kappa distribution - strong enhancement of CIV lines DEM: active region Maxwell distribution =5 =2
Changes in spectrum - power distribution Maxwell distribution Log = 6.2 n=5n=15
Changes in spectrum - power distribution Maxwell distribution DEM: quiet sun n=7n=15
By using the modification of CHIANTI we are able to: model the influence of the shape of the electron distribution function on the spectrum find the lines whose intensities are sensitive to the shape of the electron distribution function search for the lines which are suitable for the diagnostics of the non-thermal distributions
To do... the computation of the ionization equilibrium for the power distribution for the other elements the replacement of the parameters for the approximation of from CHIANTI by the parameters derived from TIPbase wherever it is possible the modification of the other original CHIANTI routines for the kappa and power distributions (the computation of DEM, electron excitation rates…)
Ďakujem za pozornosť Thank you very much for your attention
kappa distribution, iron Dzifčáková, 2005, to be published
kappa distribution, C and O Dzifčáková, Kulinová 2003, SP 218