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X-RAY LINE-RATIO PLASMA DIAGNOSTICS APPLIED TO SOLAR ACTIVE REGIONS
D. Mckenzie
To cite this version:
D. Mckenzie. X-RAY LINE-RATIO PLASMA DIAGNOSTICS APPLIED TO SOLAR ACTIVE RE- GIONS. Journal de Physique Colloques, 1988, 49 (C1), pp.C1-55-C1-58. �10.1051/jphyscol:1988109�.
�jpa-00227429�
Colloque Cl, Suppl6ment au n03, Tome 49, Mars 1988
X-RAY LINE-RATIO PLASMA DIAGNOSTICS APPLIED TO SOLAR ACTIVE REGIONS
D.L. McKENZIE
Space Sciences Laboratory, The Aerospace Corporation, PO Box 92957, Los Angeles, CA 90009, U.S.A.
RESUME
Nous nous sommes s e r v i s d e s r a p p o r t s d e s i n t e n s i t e s d e s r a i e s d U ; m i s s i o n d e s r a y o n s X p o u r c o n s t a t e r l a t e m p g r a t u r e e t l a d e n s i t e 6 1 e c t r o n i q u $ d e l a couronne s o l a i r e . Les r a e p p r t s o n t d G r i v 6 d e p l u s d e c e n t s p e c t r e s d e s r e g i o n s s o l a i r e s a c t i v e s q u i o n t ete p r i s a v e c l ' i n s t r u m e n t SOLEX a u s a t e l l i t e P78-1 e n t r e mars e t novembre 1979. On p e u t se s e r v i r du r a p p o r t R d e 0-V11 pour mesurer l e s
d e n s i t & e l e c t r o n i q u e s d e l a couronne qugnd e l l e s d e p a s s e n t e n v i r o n 3 x 1 0 ~ cm-?.
E n v i r o n 10% s e u l e m e n t d e s r g g i o n s o b s e r v e e s o n t m a n t f e s t e d e p a r e i l l e s d e n s i t e s . Q u a n t a u r e s t e d e s r e g ' o n s , l e r a p p o r t R moyen e t e 3 , 7 , c e q u i c o r r e s p o n d a l a d e n s i t ; d e -2x104 cm-3. Nous avons m e s u r e s d e s t e m p e r a t u r e s , a u moyen d r a p p o r t G d e 11, d e Ne IX, e t d e Mg XI, a u s s i a u moyen du r a p p o r t R I = I ( l s q 'S
-
1 s 3 p l P ) / I ( l s q 'S
-
1s2p ' P ) d e9
V 1 1 e t d e Ne 1 X . Les c a l c u l s th;oriques-du r a p p o r t G en f o n c t i o n d e l a t e m p e r a t u r e q u i s o n t d i s p o n i b l e s donnent d e s r e s u l t a t s q u i n e s ' a c c o r d e n t p a s l e s u n s a v e c l e s a u t r e s . Les donnees du SOLEX c o n t r a i g n e n t a s s e z f o r t e m e n t l a v a l e u r du r a p p o r t G ; c e r t a i n s c a l c u l s n e s ' a c c o r d e n t p a s a v e c n o s o b s e r v a t $ o n s . En p l u s d e n o s donnees-du r a p p o r t G, nous n o u s 2ommes s e r v i s d e n o s d o n n e e s du r a p p o r t R , e t d e s donnees d e l a b o r a t o l r e pour r e s o u d r e l e s l n c o n s i s t a n c e s d e s c a l c u l s t h e o r i q u e s . Les t e m p e r a t u r e s mesurees d e s r e g i o n s a c t l v e s s o n t a u - d e s s o u s d e s t e m p 6 r a t u r e s 05 l a p r o d u c t i o n d e s r a i e s d 4 ; m i s s i o n u t i l i s e e s - d a n s les r a p p o r t s c i - d e s s u s e s t l a p l u s e f f i c a c e ; c e q u i m o n t r e que l a m e s u r e d ' e m i s s i o n diminue en f o n c t i o n de l a t e m p g r a t u r e a u - d e s s u s d ' e n v i r o n 1,8 MK.ABSTRACT
X-ray l i n e - r a t i o d i a g n o s t i c s o f t e m p e r a t u r e and d e n s i t y have been a p p l i e d t o o v e r 100 a c t i v e - r e g i o n s p e c t r a t a k e n by t h e SOLEX i n s t r u m e n t on t h e P78-1 s a t e l l i t e d u r i n g March-November 1979. The R r a t i o f o r 0 V11 a n b e used t o measure c o r o n a 1 e l e c t r o n d e n s i t i e s when t h e y e x c e e d a b o u t 3 x 1 0 ~ cm-
9 .
Only a b o u t 10% o f t h e o b s e r v e d r e g i o n s showed e v i d e n c e o f d e n s i t i e s t h i s h i g h . For t h e rest o f t h e r e g i o n s , t h e a v e r a g e R v a l u e was 3 . 7 , c o r r e s p o n d i n g t o a d e n s i t y o f -2xlo9 cm-3.T e m p e r a t u r e s h a e been mea u r e d w i h t h e G r a 10s of 0 V I I , Ne IX, and Mg XI and t h e
'i 'i'
r a t i o R, = I ( l s 3 'S -1s3p P > / I ( l s B 'S -1s2p P ) f o r 0 VII and Ne IX. E x i s t i n g theoretical c a l c u l a t i o n s o f t h e G r a t i o as a f u n c t i o n o f t e m p e r a t u r e g i v e d i f f e r i n g r e s u l t s . The SOLEX d a t a c o n s t r a i n t h e G - r a t i o r a t h e r t i g h t l y ; some o f t h e
c a l c u l a t i o n s a r e n o t i n a c c e p t a b l e agreement w i t h o b s e r v a t i o n s . I n a d d i t i o n t o t h e s o l a r G - r a t i o d a t a , measured s o l a r R I r a t i o s and l a b o r a t o r y d a t a h a v e been u s e d t o r e s o l v e t h e i n c o n s i s t e n c i e s i n t h e t h e o r e t i c a l c a l c u l a t i o n s . The measured a c t i v e - r e g i o n t e m p e r a t u r e s a r e l o w e r t h a n t h e t e m p e r a t u r e s o f most e f f i c i e n t p r o d u c t i o n o f t h e l i n e e m i s s i o n s i n v o l v e d i n t h e d i a g n o s t i c r a t i o s . T h i s i n d i c a t e s . t h a t t h e e m i s s i o n - m e a s u r e d i s t r i b u t i o n is a d e c r e a s i n g f u n c t i o n o f t e m p e r a t u r e a b o v e a p p r o x i m a t e l y 1.8 MK.
I . INTRODUCTION
A c t i v e r e g i o n s i n t h e s o l a r c o r o n a have t e m p e r a t u r e s h i g h e r t h a n 1 x 1 0 ~ K ( 1 MK) and e m i t c o p i o u s l y i n t h e X-ray r e g i o n o f t h e spectrum. R e c e n t l y , t h e o r i s t s h a v e d e v e l o p e d d i a g n o s t i c s o f p l a s m a t e m p e r a t u r e and d e n s i t y b a s e d upon X-ray l i n e s p e c t r a . For t h e s t u d y o f n o n f l a r i n g s o l a r a c t i v e r e g i o n s , d i a g n o s t i c s from t h e h e l i u m - l i k e i o n V I I , Ne
i
X , and Mg X a r e p a r t ' c u l a r l y s u i t ai
1 re b a s e d on t t e l ' n e s i s q9q - t s ~ p P ( r ) , IS' 'S -
1 . 2 ~ (i), i s @ ' i :;::T- 4s
( f ) ,
and l s 2 'S -
l s 3 p P. D e n s i t i e s a r e measured w i t h t h e r a t i o R = f / i f o r 0 V11 ,
a n d
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1988109
Cl-56 JOURNAL
DE
PHYSIQUEfemperatures by t h e r a t i o G = ( f + i ) / r f o r a l l t h r e e i o n s and R 1 = 1 ( l s 2 'S
-
l s 3 p P ) / r f o r 0 V11 and Ne IX. These d i a g n o s t i c s were a p p l i e d t o more than 100 s p e c t r a from n o n f l a r i n g a c t i v e r e g i o n s c o l l e c t e d by t h e SOLEX B s p e c t r o m e t e r aboard t h e P78-1 s a t e l l i t e d u r i n g t h e p e r i o d March-November 1979. The s t u d y had twopurposes: t o determine t h e g e n e r a l p r o p e r t i e s o f n o n f l a r i n g a c t i v e r e g i o n s and t o e v a l u a t e t h e p u b l i s h e d t h e o r e t i c a l c a l c u l a t i o n s of t h e d i a g n o s t i c l i n e r a t i o s .
A b r i e f a c c o u n t o f t h e d a t a a c q u i s i t i o n and s e l e c t i o n is needed i n o r d e r t o e s t a b l i s h t h e n a t u r e o f t h e d a t a s e t . The SOLEX B Bragg c r y s t a l s p e c t r o m e t e r used a rubidium a c i d p h t h a l a t e (RAP) c r y s t a l and was equipped with a c o l l i m a t o r having a one-arc-minute-square f i e l d o f view. Throughout t h e P78-1 m i s s i o n , t h e
s p e c t r o m e t e r s were always pointed a t t h e a c t i v e r e g i o n t h a t appeared most l i k e l y t o produce a n X-ray f l a r e . A s a r e s u l t , t h e b r i g h t e s t and l o n g e s t l a s t i n g r e g i o n s tended t o be s e l e c t e d f o r o b s e r v a t i o n . The f i n a l d a t a s e l e c t i o n f o r t h e s t u d y was made s o a s t o o b t a i n s p e c t r a from a wide v a r i e t y o f n o n f l a r i n g r e g i o n s . The r e s u l t i n g d a t a s e t c o n s i s t e d o f 111 s p e c t r a from 30 d i f f e r e n t a c t i v e r e g i o n s . Each spectrum was t h e sum o f up t o 13 c o n s e c u t i v e s p e c t r a l s c a n s over t h e wavelength r a n g e 7.7-23.0 1. Data a c q u i s i t i o n f o r a s i n g l e spectrum took up t o 2197 s e c o n d s .
11. RESULTS
The e l e c t r o n d e n s i t y n is r e l a t e d t o t h e R r a t i o by [ l ] :
The parameters n and R* a r e both slowly varying f u n c t i o n s o f t e e r a t r e . Recent c a l c u l a t i o n s [2-5] a r e m agreement, w i t h R.
7
3 . 9 and n = 3x13' cm-y f o r TM = 1.8 MK, t h e t e m p e r a t u r e o f most e f f i c i e n t production o f t h e8
V11 l i n e s . The r , i , and f l i n e f l u x e s f o r 0 V11 were determined through t h e u s e of a l i n e - p r o f i l e f i t t i n g procedure [ 6 ] . For 73 o f t h e s p e c t r a , t h e f i t s were good enough t h a t t h e R r a t i o could be determined. The histogram i n F i g u r e 1 summarizest h e r e s u l t s . For t h e 73 s p e c t r a , t h e mean v a l u e of R
was 3.61, b u t t h e d a t a were 14 n o t c o n s i s t e n t w i t h t h e
assumption t h a t R was 12
normally d i s t r i b u t e d a b o u t t h i s mean. When all. s p e c t r a
f o r which R + 2 0 < 3.7 ( U = 10 s t a n d a r d d e v i a t i o n o f R) a r e S
C 0
e l i m i n a t e d , t h e remaining K 8
d a t a a r e c o n s i s t e n t with t h e V) LL
assumption o f a normal 0
g
6d i s t r i b u t i o n a b o u t a mean of
3.69. The R v a l u e s f o r t h i s
5
d i s t r i b u t i o n a r e shown w i t h = 4 h a t c h i n g i n Figu e 1 For R
= 3.69, n = 2x10S cmL3. For 2
t h e remaining e i g h t s p e c t r a ,
t h e d e n s i t y can be 0
determined from t h e R r a t i o ; 3 0 3 2 3 4 3 6 3 8 4 0 4 2 4 4
t h e v a l u s a r i n t h e range R(0 VII)
(4-8)x1O8 cm-?. D e n s i t i e s
h i g h enough t o b e measured Figure 1 . The o c c u r r e n c e o f R(0 V I I ) .
by t h e 0 V11 R r a t i o occur Hatched d a t a have R + 2 0 > 3.7, and r e l a t i v e l y r a r e l y i n were t h e r e f o r e i n t h e low-density n o n f l a r i n g a c t i v e r e g i o n s . l i m i t .
The r - l i n e f l u x f o r 0 V11 is s i g n i f i c a n t l y a t t e n u a t e d by resonance s c a t t e r i n g i n t h e corona. The v a r i a t i o n i n t h e 0 V11 G r a t i o due t o resonance s c a t t e r i n g exceeds t h a t due t o t e m p e r a t u r e [ 6 ] ; hence t h i s r a t i o is u n s u i t a b l e a s a t e m p e r a t u r e d i a g n o s t i c f o r i n d i v i d u a l a c t i v e r e g i o n s . However, an a v e r a g e t e m p e r a t u r e f o r a l a r g e number o f s p e c t r a can be o b t a i n e d by, in e f f e c t , e x t r a p o l a t i n g t h e d a t a t o t h e p o i n t where t h e r e is no i n t e r v e n i n g m a t e r i a l between t h e o b s e r v e r and t h e e m i t t i n g a c t i v e r e g i o n [ 6 ] . When t h i s procedure is a p p l i e d t o t h e d a t a , we f i n d Go = 1.07- 0.92, c o r r e s p o n d i n g t o a temperature range o f 1.7-2.4 MK a c c o r d i n g t o t h e
c a l c u l a t i o n s o f Pradhan [31 and 1.2-1.6 MK a c c o r d i n g t o t h e work o f Keenan, T a y a l , and Kingston [ 5 ] . Both o f t h e s e c a l c u l a t i o n s a r e c o n s i s t e n t w i t h t h e s o l a r d a t a and i n e q u a l l y good a g r e e a e n t with tokamak d a t a [ 7 ] when i t is a d j u s t e d t o c o r r e s p o n d t o corona1 d e n s i t i e s .
a temperature d i a g n o s t i c . When R 1 i s c o r r e c t e d f o r resonance s c a t t e r i n g [ 8 1 , t h e d e r i v e d t e m p e r a t u r e s c l u s t e r around 1.0 MK. A temperature t h i s low is n o t c r e d i b l e because t h e 0 V11 l i n e e m i s s i v i t i e s a r e t o o low. E r r o r s due t o u n c e r t a i n t i e s i n t h e s p e c t r o m e t e r r e s p o n s e f u n c t i o n may be a s high a s 20% f o r t h i s r a t i o . I t is u n l i k e l y t h a t e r r o r s i n t h e t h e o r e t i c a l c a l c u l a t i o n s a r e l a r g e enough ( > 3 5 % ) to make t h e d a t a c o n s i s t e n t with temperatures h i g h e r than TM. We conclude t h a t T
<
1.8 MK nd t h e r e f o r e t h a t t h e d i f f e r e n t i a l emission measure ( t h e volume i n t e g r a l of n' a s a f u n c t i o n o f temperature) peaks a t a temperature lower than t h i s .The histogram i n Figure 2 shows t h e occurrence of G - r a t i o v a l u e s f o r Ne IX.
G(Ne IX) i s found t o be
c o r r e l a t e d with G(0 V I I ) , 24 8
which s u g g e s t s t h a t
r e s o n a n c e - s c a t t e r i n g e f f e c t s 20 i n Ne IX cannot be ignored,
b u t t h e lower abundance of a 6
Ne compared t o 0 a s s u r e s
g
16 t h a t t h e s e e f f e c t s a r e n o tl a r g e . The h a t c h i n g i n
2
12 5'F i g u r e 2 d e n o t e s s p e c t r a f o r 4
which G(0 VII)
<
1.50; f o r m Ct h e o t h e r s p e c t r a , resonance 8 s c a t t e r i n g can be expected
t o change G(Ne IX) by more 2
t h a n a few p e r c e n t . The 4 c a l c u l a t i o n s o f Pradhan [ 3 ]
and Keenan e t a l . [ g ] a r e 0
superposed on t h e histogram 070 080 090 100 110 1 2 0 130 0
( t h o s e o f Wolfson a l . r , k l o IYI
[ l 0 1 and Pradhan and %l1 [ 2 ] Figure 2 . The occurrence of G(Ne IX).
gave i m p l a u s i b l y high Hatched d a t a had G(0 VII) < 1.50
t e m p e r a t u r e s ) . The 'hatched and a r e n o t expected t o be a f f e c t e d d a t a a r e c o n c e n t r a t e d i n t h e s i g n i f i c a n t l y by resonance
range G = 0.80-0.95; t h e s c a t t e r i n g .
corresponding temperature
range is 3.6-5.5 MK according t o t h e former paper and 2.2-3.8 MK according t o t h e l a t t e r . TM f o r Ne IX is 4.2 MK. The i n t e r p r e t a t i o n o f t h e s e r e s u l t s depends upon which c a l c u l a t i o n is deemed c o r r e c t . The R1 r a t i o f o r Ne IX p r o v i d e s a means f o r checking t h e g e n e r a l range o f temperatures obtained from t h e G r a t i o . Keenan e t a l . [ g ] analyzed a spectrum d e r i v e d by summing 271 i n d i v i d u a l SOLEX B s c a n s on
n o n f l a r i n g a c t i v e r e g i o n s . They found R 1 = 0.088 2 0.004, which corresponds t o a t e m p e r a t u r e o f 1.9 MK. For T = TM, R, = 0.132, f u l l y 50% higher t h a n t h e measured v a l u e . T h i s s u p p o r t s t h e lower temperature range f o r t h e Ne IX G measurements.
For Mg XI, only t h e G r a t i o could be a p p l i e d a s a temperature d i a g n o s t i c ; t h e SOLEX B s p e c t r o m e t e r cannot measure R I . T h e o r e t i c a l c a l c u l a t i o n s by Keenan, T a y a l , and Kingston [ l 1 1 g i v e temperatures i n t h e range 3-6 MK when a p p l i e d t o o u r d a t a . TM f o r Mg X I i s 7 MK. The c a l c u l a t i o n s by Wolfson e t a l . 1101, t h e only o t h e r o n e s a v a i l a b l e , g i v e implausibly high temperatures f o r some o f o u r s p e c t r a .
111. SUMMARY
D i a g n o s t i c s based upon t h e l i n e emission from helium-like i o n s have been a p p l i e d t o o v e r 100 nonflaring-active-region s p e c t r a obtained by t h e SOLEX B s p e c t r o m e t e r . Measurements based upon t h e R r a t i o in 0 V11 found t h a t almost a l l o f t h e e g i o n s were i n t h e low-density l i m i t ; t h a t is, e l e c t r o n d e n s i t i e s were -3x109 cm-5 o r lower. Temperature measurements based on t h e G and R1 r a t i o s were lower t h a n t h e t e m p e r a t u r e s a t which t h e l i n e s involved i n t h e r a t i o s were produced most
e f f i c i e n t l y . T h i s i n d i c a t e s t h a t t h e d i f f e r e n t i a l emission-measure f u n c t i o n d e c r e a s e s with temperature above 1.8 MK. C a l c u l a t i o n s o f t h e G and R1 r a t i o s were compared w i t h t h e s o l a r o b s e r v a t i o n s . Those o f Pradhan [31 and Keenan and h i s co- workers [ 5 , 9 , 1 1 ] were c o n s i s t e n t with t h e d a t a , while some o f t h e o t h e r c a l c u l a t i o n s
[ 2 , 1 0 ] gave implausibly high temperatures i n some c a s e s . The R c a l c u l a t i o n s f o r 0 V11 gave t e m p e r a t u r e s t h a t were implausibly low. More o b s e r v a t i o n s and perhaps 1.
independent t h e o r e t i c a l c a l c u l a t i o n s a r e needed t o e s t a b l i s h t h i s p o t e n t i a l l y u s e f u l d i a g n o s t i c . A more d e t a i l e d account o f t h e study is i n Reference 12.
Cl-58 JOURNAL DE PHYSIQUE
T h i s work was s u p p o r t e d by t h e U.S. Air Force Space D i v i s i o n under C o n t r a c t F04701-85-C-0086 P00016 and by t h e Aerospace Sponsored Research Program.
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