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 Ck and D are coefficients and u=Ei/Eij:

The collision strength approximation

max

0

lnk

k

kk uDuC

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

)ln(uD

.const

2/. Econst

,0C

,/ 22 EC

0D

010 DCC

Econst ln.

The collision strength averaged over the Maxwell distribution

,exp1

ij

iijiijij E

Ed

kT

EE

,max

110

yk

kkk eDEyEyCC

where y=Eij/kT and Ek is an exponential integral of order k. The coefficients Ck and D can be evaluated

from CHIANTI by the least square method.

,exp101716.221

8

i

ijijHY

kT

E

kTI

v

The conditions for the coefficients Ck and D :

Electric dipole transitions

Non electric dipole, non exchange transitions

Exchange transitions

,/4 ijijij EfD

max

0

1k

kk uCy

,0D ,0 0Cy 1max

0

uCyk

kk

,010 DCC ,01

udyy

1max

2

uCyk

kk

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 3s2 1S0-3s3p 1P1 (284.16 Å)

The electric dipole transitions

Fe XV 3s3p 3P1 - 3s3d 3D2 Fe XV 3s3p 3P2 - 3s3d 3D3

Non electric dipole, non exchange transitions

Fe XV 3s2 1S0 - 3p2 1D2 Fe XV 3s3p 3P1 - 3p3d 3F3

Problem - higher high energy limit of from CHIANTI than from data (TIPbase)

Fe XV 3s3p 3P0 -3p3d 3F3 Fe XV 3s3p 3P2 - 3p3d 3P2

Exchange transitions

O VII 1s2 1S - 1s2p 3P

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:

.approxMaxwell

approxthnonCHIANTI

Maxwellthnon

Non-thermal distributions:kappa distribution

,5.1

12

21123

dEEkT

EkT

mAdEEf

235.15.0

1

A

2/3kTE

NkTp

Non-thermal distributions:power distribution

dEEkTE

kTE

kTm

BEfn

n 21

exp2

2123

,122

21

nBn .12 kTnE

kTn

k22

23

2/3 kE

Pseudo-temperature

Nkp

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 regionMaxwell distribution

=5 =2

Changes in spectrum - power distribution

Maxwell distribution

Log = 6.2

n=5 n=15

Changes in spectrum - power distribution

Maxwell distribution

DEM: quiet sun

n=7 n=15

Satellite lines

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 pozornosťThank you very much for

your attention

kappa distribution, iron

Dzifčáková, 2005, to be published

kappa distribution, C and ODzifčáková, Kulinová 2003, SP 218