Line, recombination, and bremsstrahlung emissions of solar corona in lambda less than 10 angstro

Fetisov, E. P.

English

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National Aeronautics and Space Administration 
Goddard Space F l i g h t  Center 
Contract No. ~UAS-5-2078 
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CFSTI PRICE(S) S 
GPO PRICE 
ST - SP - 10153 
ff 653 July 85 
SOLAR CORONA EMISSION IN '.THE SPECTRUM REGION 
X < l O  i L  
bY 
E. P. Fttisov 
10 J U N E  1964 
https://ntrs.nasa.gov/search.jsp?R=19660030616 2020-03-16T17:52:28+00:00Z
DRAFT TR.M?lSUTION 
1. 
S T  - SP - 10 152 
SOLAR CORONA EMISSION I N  TBE SPZCTXUM REGION 
X a o  i* 
by E. P. Fetisov 
0 
The spectral emission flux of the corona in the < 10 A 
region has been determined theoretically. Considered are the line, 
recombination and bremstrahlung emissions. The continuous emission 
from heavy ion recombinations prevails. The theoretical flux is less 
than that observed, which is evidence of corona86 high nonhomogeneity. 
* *  
The hard emission of the solar corona ha6 been lately the 
object of intensive study. However, the available experiments in the 
X-ray region provide only the aggregate intensity in separate portions 
of the spectrum and a fairly rough llsmoothedtt pattern of spectral dis- 
tribution. These measurements do not allow the ascertaining of the 
question of line contribution, of correlation between the free-free 
and recombination emissions. In the current work the corona emission 
flux in the region < 10 'A is determined theoretically. The line, 
recombination and bremstrahlung emission, occurring at electron motion 
in the field of ions under solar corona conditions, are considered here. 
In order to compute the emission intensity, it is necessary to 
know, first of all, the relative concentrations of ions in chemical 
elements' corona. Inasmuch as the Sach formula is inapplicable in the 
corona, in order to compute the concentration we must determine tho 
* IZLUCHEIKKE S 0 L " O Y  KORONY V OBL4STI SPnCTh MROCHE 10 A. 
2 .  
c r o s s  s e c t i o n s  of i on iza t ion  and recombination processes.  Since s u f f i -  
c i e n t l y  well-founded formulas fo r  c r o s s  s e c t i o n s  a r e  not  ava i l ab le ,  w e  
conducted two conputations i n  the cu r ren t  work. F o r m l a s  obtained i n  [l] 
were u t i l i z e d  i n  the first ca l cu la t ion  and those obtained i n  C23 - i n  
the  second one. Both methods give c lose  va lues  f o r  the  20 considered 
elements ( such elements as Pa, C r ,  Fe, S, C a  drop ou t  somewhat) . I n  
t he  second case the  c o n c e i i t i a t k z s  s r e  somewhat lower, which l e a d s  t o  
higher  temperature determined from the  i o n i z a t i o n  equilibrium. 
The f lux of the continuous as we l l  as o f  l i n e  emission is pro- 
p o r t i o n a l  t o  the  i n t e g r a l  of the square of e l ec t ron  dens i ty  over the  
volume of t h e  corona. The val-ue of 3.2 010~9 is taken f o r  t h i s  quan- 
t i t y ,  which corresponds t o  the  Baumbach formula. In  consider ing t h e  
bound-free t r a n s i t i o n s  we l imi t ed  ourse lves  by the recombination a t  
b a s i c  l e v e l ,  The accouiitinc of t r a n s i t i o n s  t o  upper l e v e l s  may inc rease  
t h e  recombination emission (though i n s i g n i f i c a n t l y ) .  The l i n e  emission 
is considered i n  the  assumptian t h a t  t h e  ions  are e x c i t e d  by e l e c t r o n  
impact and are de-excited by way of spontaneous t r a n s i t i o n s ,  the  compu- 
t a t i o n  being at  the  same time conducted i n  the Born approximation. 
The inc rease  i n  population of upFer l e v e l s  at  the expense of recooibifia- 
t i o n  w a s  disregarded, as w a s  done in o t h e r  works. 
The r e s u l t s  of computations are p a r t i a l l y  presented in Table 1. 
i n  which the  f lux of continuous a i d  l i n e  emissions, summed up by a l l  
heavy element ions ,  the emission of hydrogen and helium and also the  
t o t a l  emission f l u x  of the corona i n  the  reg ion  s h o r t e r  than 10 1, 
a r e  given in erg/ cm2 eec. Two &fumns for each temperature correspond 
t o  t h e  c a l c u l a t i o n  of  i o n  concentrat ion by two different formulas. It 
fo l lows  from t h e  Table t h a t  the continuous emission is prevalent .  A t  the 
same time, for temperature t o  3 mil l ion  degrees the  main con t r ibu t ion  
i s  condi t ioned by heavy element ion recombination. Let u s  note t h a t  
b a s i c a l l y  these  are the  N, 0, Fe, Ng, H, H e  ions ,  whose l i m i t  wave- 
l eng ths  a r e  of the  order  of 10 A or more. The l i n e  emission flux is 
s i g n i f i c a n t l y  lesser and the l i n e s  cont r ibu te  notably only f o r  tempera- 
t u r e s  above 3 - lo6 0 K. P a r t i c u l a r l y  s u b s t a n t i a l ' i s  tlle emission of i ons  
MgXI, N a  X, N e X ,  N e  X, S i X I I I  and Fe XVII - Fe XVIII. 
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TTote a l s o  t h a t  the  obtained f l u x  va lues  p r a c t i c a l l y  charac te r -  
i z e  only the  r e l a t i v e  r o l e  of the va r ious  emission processes.  Only a t  
temperatures of the order  of  1 - 1.5 1060h t h e  cons idera t ion  of the  
absolu te  values  of a l l  corona emission fluxes makes sense,  inasmuch as 
higher temperature values  cannot be conbined w i t h  the  emission i n  o the r  
reg ions  of the  spectrum, and with radioemission in p a r t i c u l a r .  The expe- 
r i n e n t a l  va lues  of t he  f l u x  i n  the  2 - 10 A reg ion  
years  i s  of the  order  of 
s i g n i f i c a n t l y  exceeds the  data  of Table 1. 
0 [3, 41 in t he  d u m  
- 10 -3 erg/cm2 sec ,  which a t  T < 2 lo6 O K  
A more p rec i se  value for t h e  e l ec t ron  dens i ty  w i l l  somewhat 
i nc rease  the  t h e o s e t i c a l  values of the  f lux.  The remaining discrepancy 
can be p a r t l y  connected with the con t r ibu t ion  bynonthermal mechanisms 
of emission, and on the o the r  hand, i t  p o i n t s  t o  ail e s s e n t i a l l y  inhono- 
genous charac te r  of the corona. Taking i n t o  account the  presence of conden- 
s a t i o n s ,  c o n s t i t u t i n g  centesimal f r a c t i o n s  of corona volume, t he  experi-  
mental  and t h e o r e t i c a l  values  of f l u x e s  can be matched. 
I n  conclusion I should l ike  t o  exp-ezs my g r a t i t u d e  t o  So L. 
I iandel*shtan, L. A. Vaynsteyn and Yu. N. Zhivkyuk, f o r  t h e i r  i n t e r e s t  
and the valuable  corl;:ents. 
I n s t i t u t e  of Physics  i n  the name of 
P. N. Lebedev 
of  t he  USSR Academy of Sciences. 
Received on 
11 February 1963. 
Translated by ANDRE L; BRICHAMl 
under Contract No. NAS-5-2078 
a t  Consultants & Designers, Inc. 
Arlington, V i r g i n i a  
10 June 1964. 
I 
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R E F E R E N C E S  
GODDARD SIC 
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640 
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YLLlPs 
Sonett (3) 
J K  
Newburn (3) 
I S  
Jastror (5) 
NRL 
Friedman 


Solar corona emission in the spectrum region lambda less than 10 angstrom

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