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HIGH DIELECTRONIC SATELLITE LINES IN SOLAR FLARE SPECTRA
L. Steenman-Clark, F. Bely Dubau, J. Dubau, P. Faucher, Aurélie Gabriel, M.
Loulergue, S. Volonté
To cite this version:
L. Steenman-Clark, F. Bely Dubau, J. Dubau, P. Faucher, Aurélie Gabriel, et al.. HIGH DIELEC-
TRONIC SATELLITE LINES IN SOLAR FLARE SPECTRA. Journal de Physique Colloques, 1979,
40 (C1), pp.C1-98-C1-101. �10.1051/jphyscol:1979118�. �jpa-00218398�
JOURNAL DE PHYSIQUE
Colloque
C1,supplkment au n o 2 , Tome 40, fkvrier 1979, page C1-98
HIGH DIELECTRONIC SATELLITE LINES IN SOLAR FLARE SPECTRA.
L.
Steenman- lark*,
F.el^-~ubau*,
J.
~ubau', P. ~aucher*, A.H. Gabriel", M. ~ouler~ue',*
Observatoire de Nice, B.P. n0252, 06007 NICE CEDEX, France.+ Observatoire de Meudon, 92190 MEUDON, France.
/ f Appleton Laboratory, Astrophysics Research Division, Culham
Laboratory, Abingdon, Oxfordshire, England.
# Ddpartement dlAstrophysique, UniversitC de Mons, 7000 MONS, Belgique.
R6sumB.- Les raies de r6sonance des ions fortement ionis6s des s6ries iso6lectroniques de l1hydrog6ne et de 11h61ium et les raies satellites associees sont utilisdes pour ddtermi- ner la temp6rature dlectronique et 1'6volution du plas a lors des
eruptions
solaires. Des calculs du rapport d'intensit6 des raies satellites ls'n~-ls2Pn~ a la raie de resonance 1 s ~ - l s 2 ~ ont 6t6 effectu6s pour les raies du Fe XXIV pour n = 2, 3, 4. Les rdsultats ob- tenus ont permis l'identification de nombreuses raies du seul spectre 1 haute rdsolution d'hruption solaire obtenu jusqu'ici par satellite et donnent une meilleure estimation de 11intensit6 de la raie de r6sonance en dgterminant les contributions dues aux raies satel- lites correspondant B n 2 3.Abstract.- Resonance lines of highly ionized H and He-like ions and their associated sa- tellite lines are used to determine the electron temperature and the transient state of the plasma in solar flares. The intensity ratio of the satellite lines l~~nll-ls2~nL to the resonance line ls2-1s2p has been calculated for the n = 2, 3 and
4
shells of Fe XXIV.The results have enabled the identification of many lines in the only available high resolution solar flare iron spectrum and give a good estimate of the spectral intensity in the resonance line by evaluating the contribution due to the blending of the satellites with n 2 3.
I. SATELLITE LINES IN THE SPECTRA OF H-LIKE AND like and He-like resonance lines and a number of He-LIKE IONS.
associated satellites. The prominent satellites Resonance lines of highly ionized H-like have n = 2 and are well separated from the parent and He-like ions and their associated satellites resonance line, those with n = 3 lie closer, while can be used to calculate electron temperature and satellites with n z 4 are usually blended with the the transient state of the plasma, both of which resonance line. As first suggested by Gabriel et are important in the study of solar flare proces- al.
117,
the satellite lines are formed by the me-ses. chanism of dielectronic recombination i.e. the
capture oE a free electron by the recombining ion Satellite lines are situated mainly on in an excited state, and this leads to the inten- the long wavelength side of the resonance lines of sity ratio of the satellites to the resonance line highly ionized ions. We are principally interested being temperature sensitive but independent of elec- in the following lines : tron density. Following Gabriel
~ 2 7 ,
this ratio canbe written as
Resonance 2p + Is + hv T
Satellites 2pnll -+ lsnL + hv for n
z
2' s
- - - Fl(T,) x F2(S) (1) IR
He~like-lings
Resonance ls2p -+ ls2 + hv
-
E
where F I (Te) = 1.104 x 1 0-l2
2
exp { (E~-E~)/~T~)).Te Satellites Is2pnE + lsLn!2 + hv for n 2 2
Te is the electron temperature in deg K, Eo is the Satellite lines are interpreted as the
energy of the resonance transition and ES (both in resonance transition in the presence of an additio-
eV) that of the satellite state measured from the nal electron bound in an outer orbit nll. Figure 1
ground state of the recombining ion. The line fat- is a schematic energy level diagram showing the H-
tor is defined as
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1979118
N ~ i
where F' I (TZ) = - is the Li-like to He-like ion N ~ e
where gS is the statistical weight of the satellite state, A and A are transition probabilities for decay by autoionization and radiation respectively
- 1
(in sec ) . ZAr is the total radiative decay rate to all possible lower states. Since the ratio (I) varies as Z4 (2 is the nucleus charge), the satel- lites are weak in low Z ions (Z 10) but become comparable with the resonance line in heavier ele- ments ( Z 2 20-30).
Fig. I - Energy level diagram showing the H-like and He-like resonance lines (IR) and their satellite transitions (IS).
A number of satellites have also a contribution resulting from the direct excitation of an inner- shell ground state electron
127
but this mechanism is not effective for H-like ion satellites. The in- tensity ratio due to inner-shell excitation is gi- ven byabundance which, in ionization equilibrium, is a function of electron temperature.
- f 1 Ar
F' ( S ) = -
2 f Aa + IAr
where and
7
are the effective oscillator strengths for excitation of the upper state, respectively of the satellite and the resonance line. The inner-shell contribution is usually small except for high Z ions in transient ionizing plasmas (as in solar flares) in which case NLi/NHe becomes large. For this rea- son the ion abundance ratio is assumed to be a func- tion of the ionization temperature, TZ, which is the temperature at which the actual value of NL i I N ~ e would exist in ionization equilibrium. Therefore the inner-shell contribution can be used to deter- nine TZ and provide information on the evolutionary state of the plasma. As seen from (I) and (2) the determination of T and TZ depends on the accuracy of the atomic parameters necessary for calculating F2(S) and FI2(S).
11. IMPORTANCE FOR SOLAR FLARE STUDIES.
Satellite lines to the H-like and He-like ions of solar abundant elements have been observed in the spectra of flares in the range ?. 1.5 A to
0
25 A. However only a few observations of sufficient resolution are presently available. For this reason observations of high spatial and time resolution are planned for the soft X-ray polychromator (XRF') on the Solar Maximum Mission satellite to be laun- ched by NASA during 1979-1980. This experiment aims to study flare spectra of H-like and He-like ions in the sequence from 0 to Ni; each of these ions emits a group of spectral lines over a narrow wavelength range. The present work concerns the interpretation of these lines in terms of the tem- perature structure and transient state of the fla- ring plasmas.
111. CALCULATION 0FIm)MIC DATA AND PRESENT RESULTS.
In order to provide the data required for this investigation extensive calculatios are being carried out with a package of computer programs which are modified versions of the University Col-
Cl-loO JOURNAL DE PHYSIQUE
l e g e London (UCL) programs. The energy l e v e l s , wa- v e l e n g t h s and r a d i a t i v e t r a n s i t i o n p r o b a b i l i t i e s a r e o b t a i n e d w i t h t h e atomic s t r u c t u r e programme SUPERSTRUCTURE
/j7.
This programme uses m u l t i c o n f i - g u r a t i o n wavefunctions based upon Thomas-Fermi type p o t e n t i a l s f o r s o l v i n g the SchrSdinger e q u a t i o n w i t h t h e B r e i t - P a u l i Hamiltonian. The e x c i t a t i o n c r o s s - s e c t i o r s a r e c a l c u l a t e d u s i n g two methods; t h e programme IMPACT/37
which s o l v e s the coupled i n t e - g r o - d i f f e r e n t i a l e q u a t i o n s and DISTORTED WAVE/57
which u s e s a p e r t u r b a t i o n method and from the modi- f i e d v e r s i o n of which t h e a u t o i o n i z a t i o n r a t e s a r e d i r e c t l y c a l c u l a t e d
/E7.
Previous work f o r i o n s with Z = 8 t o 26 d e a l t only with n = 2 s a t e l l i t e s
127, l f 7 , ~ e 7
and137.
Our n = 2 r e s u l t s f o r i r o n a r e i n s u b s t a n t i a l agreement w i t h t h e e a r l i e r c a l c u l a t i o n s . The n = 3 r e s u l t s have enabled many f e a t u r e s of the s o l a r f l a r e i r o n s p e c t r a recorded from the Intercosmos I V s a t e l l i t e/ i ~ 7
to be i d e n t i f i e d and explained~ 7 ~ 7 .
This i s i l l u s t r a t e d i n f i g u r e 2 where the s o l i d curve i s t h e observed f l a r e spectrum and t h e broken l i n e i s the c a l c u l a t e d spectrum i n c l u d i n g t h e n = 2, 3 r e - s u l t s . The c a l c u l a t e d spectrum has been o b t a i n e d by c o n v o l u t i o n w i t h . a g a u s s i a n p r o f i l e a f t e r i t e r a t i o n of Te and T Z according t o t h e method of Lion and Volontg (1978, p r i v a t e communication) i n o r d e r t o o b t a i n t h e b e s t f i t o v e r the e n t i r e s p e c t r a l range.The n = 3 and 4 r e s u l t s have provided t h e c o n t r i b u - t i o n of t h e s a t e l l i t e l i n e s w i t h n > 4 t o t h e reso- nance l i n e , w i t h regard t o i t s i n t e n s i t y , i t s h a l f width and i t s p o s i t i o n , allowing a more c o r r e c t ex- p r e s s i o n of t h e l i n e i n t e n s i t y r a t i o s ( t o be p u b l i - shed)
.
The XRP spectrum r e g i o n i s dominated by t h e i o n s of o t h e r v a r i o u s s o l a r abundant elements.
We propose t o extend t h i s t h e o r e t i c a l work t o 0 , Mg, S i and Ca. C a l c u l a t i o n s have been s t a r t e d f o r
t h e s a t e l l i t e s t o t h e 0 V I I resonance l i n e . Our pre- l i m i n a r y r e s u l t s compare w e l l w i t h previous c a l c u l a - t i o n s f o r n = 2
/ g
and a l s o w i t h measurements of e.g. N i c o l o s i and Tondello/i27
who observed t h e 0 V I I s a t e l l i t e s i n a l a s e r produced plasma i . e . i n emission c o n d i t i o n s d i f f e r e n t from t h o s e of t h e s o l a r corona. High r e s o l u t i o n s p e c t r a of t h e s o l a r a c t i v e r e g i o n taken during t h e OSO 8 f l i g h t a r e- -
a v a i l a b l e
112/.
S i l i c o n and magnesium a r e p a r t i c u - l a r l y w e l l observed and a r e a l s o seen i n l a s e r o r Tokamak s p e c t r a . I t i s found from t h e p r e l i m i n a r yc a l c u l a t i o n s f o r Mg X I , t h a t t h e H-like s a t e l l i t e s t a t e s 2pn.t mix s t r o n g l y w i t h Zsn(9.
+
I ) . Consequept- l y t h e a u t o i o n i z a t i o n r a t e s f o r t h e s e s t a t e s may have t o be o b t a i n e d by s o l v i n g t h e coupled i n t e g r o - d i f f e r e n t i a l e q u a t i o n s using IMPACT. Moreover cas- cades from t h e 2sns s t a t e s t o 2s2p appear t o be a l - most a s important a s a u t o i o n i z a t i o n of t h e l a t t e r s t a t e so t h a t a f u l l s t a t i s t i c a l e q u i l i b r i u m c a l c u - l a t i o n w i l l have t o be performed i n o r d e r t o o b t a i n t h e p o p u l a t i o n of t h e 2s2p s a t e l l i t e s t a t e ( t o be p u b l i s h e d ) .Fig. 2
-
I r o n s o l a r f l a r e spectrum recorded from Intercosmos I V (Grineva e t a l . , 1973) and t h e f i t t e d t h e o r e t i c a l spectrum (broken l i n e ) .Such c a l c u l a t i o n s a r e of d i r e c t i n t e r e s t f o r t h e XRP experiment and w i l l add s u b s t a n t i a l l y to t h e i n t e r p r e t a t i o n of i t s o b s e r v a t i o n a l d a t a . Aswell t h e s t u d y of s e v e r a l members of t h e same i s o - e l e c t r o n i c sequence w i l l permit us t o s t u d y a more extended temperature range and so o b t a i n a b e t t e r model f o r t h e emissive r e g i o n , i n p a r t i c u l a r f o r
t h e time a n a l y s i s of t h e e v o l u t i o n of a s o l a r f l a r e .
REFERENCES
/ T i
G a b r i e l , A.H., J o r d a n , C., P a g e t , T.M., C r o c ./87
G o l d s m i t h , S . , J . Phys. B1,
2315 ( 1 9 7 4 ) .--
6 t h I n t . Conf. P h y s i c s o f E l e c t r o n i c a n d Ato-mic C o l l i s i o n s M a s s a c h u s s e t t s : MtT P r e s s --
/97
B h a l l a , C.P.. G a b r i e l , A.H., P r e s n y a k o v , L.P.,D. 5 5 8 ( 1 9 6 9 ) . M.N.R.A.S.
172,
359 ( 1 9 7 5 ) ./77
G a b r i e l , A.H., M.N.R.A.S.160,
99 ( 1 9 7 2 ) .--
--- -
/I;/ G r i n e v a , Y u . I . , K a r e v , V . I . , K a r n e e v , V.V., Mandelstam, S.L., V a i n s t e i n , L.A., V a s i l y e v ,
/57
E i s s n e r , W . , J o n e s , M . , Nussbaumer, H. Comput.--
B.N., Z i t n i k , I.A., S o l a r P h y s i c s2,
441P h y s . C o m u n .
8,
270 ( 1 9 7 4 ) . (1 9 7 3 ) ./57
S c a t o n , M. J . , W i l s o n , P.M.H., J. P h y s . B5,
-- /Ti7
Bely-Dubau, F . , G a b r i e l , A.H., V o l o n t 6 , S.L1 ( 1 9 7 2 ) . M.N.R.A.S., i n p r e s s ( 1 9 7 8 ) .
