EUV EMISSION LINE RATIOS FOR Si IV IN THE SOLAR TRANSITION REGION

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EUV EMISSION LINE RATIOS FOR Si IV IN THE SOLAR TRANSITION REGION

F. Keenan, J. Doyle

To cite this version:

F. Keenan, J. Doyle. EUV EMISSION LINE RATIOS FOR Si IV IN THE SOLAR TRANSITION RE- GION. Journal de Physique Colloques, 1988, 49 (C1), pp.C1-227-C1-229. �10.1051/jphyscol:1988146�.

�jpa-00227466�

JOURNAL DE PHYSIQUE

Colloque

C1, Suppliiment

au n 0 3 , Tome 49, Mars 1988

EUV EMISSION LINE RATIOS FOR Si IV IN THE SOLAR TRANSITION REGION

F.P. KEENAN and J.G. DOYLE'

Department of Pure and Applied Physics, Queen's University.

GB-Belfast

BT7

INN, Northern Ireland

* ~ r m a g h Observatory, G B - ~ m a g h sr61

9 D G .

Northern Ireland

b b s t r a c t . T h e o r e t i c a l e l e c t r o n t e m p e r a t u r e s e n s i t i v e e m i s s i o n l i n e r a t i o s i n S i I V i n v o l v i n g t h e 3d 2~

-

^3p 2~ and 4 s 2~

-

^{3p 2~} m u l t i p l e t s a t *1125A and 8168 r e s p e c t i v e l y a r e d e r i v e d u s i n g R - m a t r i x e l e c t r o n e n c i t a t i o n r a t e c a l c u l a t i o n s . A c o m p a r i s o n o f t h e s e w i t h o b s e r v a t i o n a l d a t a f o r a s o l a r a c t i v e r e g i o n o b t a i n e d w i t h t h e H a r v a r d 5-055 s p e c t r o m e t e r on b o a r d S k y l a b r e v e a l s t h a t t h e r e i s good a g r e e m e n t b e t w e e n t h e o r y and o b s e r v a t i o n f o r t h e r a t i o t h a t i n c l u d e s t h e 2 ~ s 1 2 , 5 f 2

-

2 ~ 3 1 2 t r a n s i t i o n a t ,1128.38, T h i s i s i n c o n t r a s t t o t h e f i n d i n g s o f Keenan, D u f t o n and K i n g s t o n , and p r o v i d e s s u p p o r t f o r t h e a t o m i c d a t a a d o p t e d i n t h e c a l c u l a t i o n s . However t h e 2 ~ s 1 2

-

2 ~ i 1 2 l i n e a t 1122.5h a p p e a r s t o b e s e v e r e l y b l e n d e d , a s i t l e a d s t o e l e c t r o n t e m p e r a t u r e e s t i m a t e s t h l t d i f f e r s i g n i f i c a n t l y f r o m t h a t e x p e c t e d i n i o n i s a t i o n e q u i l i b r i u m . The f a c t t h a t t h e 1(1122.51)/1(1128.38) i n t e n s i t y r a t i o s d e t e r m i n e d f r o m s e v e r a l f l a r e s p e c t r a a r e c l o s e r t o t h e ~ r y t h a n t h a t f o r t h e a c t i v e r e g i o n i n d i c a t e s t h a t t h e b l e n d i n g i s p r o b a b l y due t o s p e c i e s w i t h r e l a t i v e l y l o w i o n i s a t i o n p o t e n t i a l s , s u c h a s a n Fe 1 1 1 t r a n s i t i o n a t 1122,538, a s s u g g e s t e d p r e v i o u s l y b y B u r t o n and R i d g e l e y , a n d F e l d m a n and Doschek. E l e c t r o n t e m p e r a t u r e s deduced f o r a s u n s p o t a r e much l o w e r t h a n t h a t p r e d i c t e d f r o m i o n i s a t i o n b a l a n c e c a l c u l a t i o n s , i n a g r e e m e n t w i t h e a r l i e r r e s u l t s , and i m p l y t h a t a c o o l i n g f l o w may b e p r e s e n t ,

I n

a

r e c e n t paper Keenan e t al. l used electron e x c i t a t i o n r a t e s calculated w i t h t h e R-matrix code2 t o d e r i v e t h e t h e o r e t i c a l electron t e m p r a t u r e s e n s i t i v e emission l i n e r a t i o s R, = I ( 3 d ,D3

,, -

3 p ,)/1(3p +P,/,

-

3 s ,Sf ,) and R, = I ( 3 d 'D,

,,

,/,

-

3p z ~ , I , ) / ~ ( l p 2 6 :

, -

3 s 2 d l ,) f o r t h e s o d i m - l d e ions An. I11 and S i

f;.

A comparison of t h e

M

11f r e s u l t s

w i ( h

high resolution ( - 0.06fi) s o l a r d a t a o b t a i n e d w i t h t h e Naval Research Laboratory's S082-B s p c t r o g r a p h on board Skylab shaved reasomble agreenent b e b e e n theory and o b s e r v a t i o n ( s e e a l s o Doschek and ~ e l d r n a n ~ ) , but a similar analysis f o r S i N using lcw resolution 1- 291) E W s a t e l l i t e s p e c t r a f o r t h e q u i e t sun and a n a c t i v e r e g i o n revealed t h a t t h e calculations and observational d a t a were incanpatible. Keenan e t a l . came t o t h e c o n c l u s i o n t h a t blending of the ZD31,,,

, -

zP3

,

t r a n s i t i o n a t 1128.381 with l i n e s a r i s i n g f r m ions with relatively lcw ionisation b t e n t i a l s was probably r e s p n s i b l e f o r this discrepancy.

I n t h i s p a p e r we determine S i

N

, l i n e s t r e n g t h s from somewhat h i g h e r resolution

E W

s p c t r m t e r s o l a r observations obtained with t h e Harvard i n s t r u m e n t on board Skylab, and investigate i f t h e disagreement between theory

and

observation found by Keenan e t al.l rray be removed.

2.

Theoretical

ratios

The atomic d a t a adopted i n t h e present calculations have been discussed by Keenan e t

a l .

^{l .} B r i e f l y , t h e model i o n c o n s i s t e d of t h e £cur lcwest LS states, namely 3 s

+s,

3p %P, 3d I D and 4 s *S, making a t o t a l of s i x l e v e l s when t h e f i n e s t r u c t u r e s p l i t t i n g is included. (Henceforth t h e two 2S terms w i l l be denoted by t h e s u b s c r i p t s L ( f o r 1 ower ) and U ( f o r upper) respectively t o avoid confusion. )

The only atomic processes considered were c o l l i s i o n a l e x c i t a t i o n and d e - e x c i t a t i o n by e l e c t r o n s and spontaneous r a d i a t i v e decay. and t h e plasma

was

assumed t o be o p t i c a l l y thin.

I n F i g u r e 1 t h e t h e o r e t i c a l emission l i n e r a t i o s R, = I ( 2 D ,

,,

^{, / ,}

-

fP,/, ) / I ( * S u

-

^{ZP,/,) =} 1(1128.3~)/1(815.0~) and R, = I ( 2 D 3

,, , , -

2 P , , , h ~ ( z ~ U

-

%P,

,

^{) =} 1(1128.3&/1(818.lft) a r e p l o t t e d a s a function of e f e c d o n t e m p r a t u r e f o r a rAnge of v a l u e s of l o g Te about t h a t of maximum S i

N

fractional abundance i n i o n i s a t i o n equilibrium4, l o g Tma = 4.8. We n o t e t h a t t h e r a t i o s R, = I(zD,

, -

'P ) / I ( ~ S "

-

^{,P, =} I ( I ~ z z . ~ ~ / I ( ~ ~ ~ . o A ) and R6 = I ( ~

-

D^{z ~ x} ~ , ) / I ( Z ~ ~ ~ ~

-

2~:/za) = 1(1122.~81)/$(818.181) a r e related t o those i n Figure 1 by the exptessions:

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1988146

JOURNAL

DE

PHYSIQUE

3 .

Cixenrational

data

The 'D

- "

^{and ,Su}

^-

'P m u l t i p l e t s i n S i

IV

h ebeen observed i n s o l a r s p e c t r a o b t a i n e d w i t h t h e Harvard S-055

RTV

spectrcaneter f l w n on Skylab during 1973174. This instrument could e i t h e r operate i n

a raster

mode or

s p c t r a l

scanning mode c o v e r i n g t h e wavelength range 280-1350A. @ r a t i n g i n t h e s ~ e c t r o m e t e r mode, t h e i n s t r u m e n t observed a s p a t i a l

area

of 5 x 5

arc

s e c with

a s~ectral

resolution of approximately 1.68, u s i n g a n i n t e g r a t i o n

t i m e

of 0.04

sec

and a s t e p length of 0.2112A. A f u l l d e s c r i p t i o n of t h e instrument and

its

c a l i b r a t i o n

may

be fcund i n Reeves e t 6 .

I n T a b l e 1

we

s u m m a r i s e S i

IV

l i n e r a t i o s observed i n s e v e r a l

solar

f e a t u r e s . These i n c l u d e ( a ) t h e l a r g e two r i b b o n f l a r e of 7 S e p t e m b e r 1973 ( d i s c u s s e d by ~ o y l e 7 ) .

( b )

a n a c t i v e r e g i o n n e a r t h e l i m b o b s e r v e d o n 1 6 December 1 9 7 3 ~ and ( c ) a s u n s p o t plume n e a r d i s c c e n t r e r e c o r d e d o n 29 August 19739. Due

t o

t h e s t r o n g Lyman continuum i n t h e f l a r e observations.

no

measurements of t h e - ZP m u l t i p l e t a t

-

816A a r e a v a i l a b l e f o r these features.

Only t h e ,Su

-

^aP3 /, compnent of t h i s m u l t i p l e t

a t

818.1W could be resolved i n t h e s u n s p o t and a c t i v e r e g i o n o b s e r v a t i o n s ,

as

t h e

-

^'PI

,

l i n e a t 815.0A

is

severely blended with t h e strong 3sa3p aP,l, - 3s3p2 2S,l, S

Id

l i n e a t 816.0A.

a b l e 1. O b s e r v e d S i IV l i n e r a t i o s R = I ( l l 2 2 . 5 A ) 1 1 ( 1 1 2 8 . 3 A ) ,

= 1 ( 1 1 2 8 . 3 ~ ) 1 1 ( 8 l 8 . 1 ~ ) and R, = 1(1122.5~)/1(818.11). along with t h e derived logarithmic e l e c t r o n t e m ~ e r a t u r e s £ran R,

and

R,.

SdLm

Feature

R R, R, l ~ g T e ( R , ) l o g T e ( R 3

16 Dec 1973 Active Region 1.05 8.0 8.3 4.64 4.43

29 Aug 1973 S u n s p t 0.83 10.4 8.6 4.56 4.42

7 Sept 1973 F l a r e 1255UT 0.69

- - - -

7 Sept 1973 F l a r e 1403UT 0.73

- - -

-

7 Sept 1973 F l a r e 155UT 0.73

- - -

- 4.

Results

and d i s a x s s i w

I n T a b l e 1 t h e derived logarithmic e l e c t r o n t e m p r a t u r e s from R, and R, a r e summarised. An i n s p e c t i o n of t h e Table r e v e a l s t h a t t h e value of l o g Te e s t i n n t e d f u r t h e a c t i v e region £ran R,

is

c l o s e

t o

t h e

tanprature

of maximm S i N

I I I I I

- - - -

P i a u r e 1. The t h e o r e t i c a l m i s s i o n - l i n e r a t i o s R, = I(2D,,,,s,a

-

'P, ,)/I('Su

-

^{'P, ,) =}

1(1f28.3~)/1(815.0h and R, = 1('D2

,,

- 'P ) / I ( Z S u

-

^{,P3 ,) =}

1 ( 1 1 2 h . ~ ~ ~ ~ 1 ( 8 1 8 ~ ~ ~ ) p l o t t e d a s function of electron temperature.

0.7

-

0

5

-

^-

I I I I I

1.1

1.6 1.8 5.0 5-2

Log Te

f r a c t i o n a l abundance i n i o n i s a t i o n e q u i l i b r i u m 4 , l o g T- = 4.8. This provides support f o r t h e

atcanic

d a t a adopted i n t h e c a l c u l a t i o n s . and f u r t h e r m o r e i m p l i e s t h a t t h e 1128.3A l i n e i s unblended

in

c o n t r a s t t o t h e findings of Keenan

e t

al.l who s u g g e s t e d b l e n d i n g t o explain

a

discrepancy between theory

and

observation f o r t h e

r a t i o

R, = 1(112~.3A)/1(1393.~A). A

more

l i k e l y

cause

of t h i s is

an

e r r o r i n t h e 13 93.8a l i n e f l u x . The R, r a t i o analysed by Keenan e t al. was determined by Dupree and ~ e e v e s l O from

a la

resolution EW

s~ectrum

covering t h e wavelength range 300-1400L obtained by

a

s F e c t r m e t e r on board t h e Orbiting Astronanical Observatory (OSO) IV

satellite.

A s t h e 1 3 93.8A l i n e therefore occurred near t h e edge of t h e i n s t r u m e n t a l s p e c t r a l c o v e r a g e it

i s

p o s s i b l e t h a t

its

i n t e n s i t y was n o t w e l l determimd.

The t e m p e r a t u r e d e d u c e d f o r t h e a c t i v e r e g i o n from

R,

i n T a b l e 1

is

approximately 0 -4 dex l e s s t h a n l o g T-. A probable

cause

of t h i s disagreenent

is

blending i n t h e 1122.5A feature,

as

suggested previously

&

Flaver and ~ u s s b a u m e r l ~ . To s u p p o r t t h i s . we n o t e t h a t t h e t h e o r e t i c a l r a t i o R = 1(1122.5~)/1(1128.3~)

is

0.5. w h i c h i s i n d e p e n d e n t of e l e c t r o n t e m p e r a t u r e and d e n s i t y . However a n i n s p c t i o n of

W e

1 s h a i s

that

f o r the s o l a r f e a t u r e s analysed R

>

0.69. The f a c t t h a t t h e R r a t i o s determined £ran f l a r e s p e c t r a a r e

closer

t o theory than t h a t f o r t h e a c t i v e region i n d i c a t e s t h a t any blending

is

probably due t o l i n e s of s p e c i e s w i t h r e l a t i v e l y law i o n i s a t i o n p o t e n t i a l s , such

as

t h e Fe I11 3d6 'D,

-

3dVp IP,

t r a n s i t i o n a t 1122.53A12113

.

I n t h e

case

of t h e s u n s p o t observations t h e e l e c t r o n t e m p r a t u r e s derived from R, and R, a r e

i n

s l i g h t l y b e t t e r agreement than those f o r t h e a c t i v e region.

a l t h o u g h they

are

a b u t a f a c t o r of two smaller than T-. W e s

e t

61.9 note t h a t f o r t h i s s u n s p o t t h e i n t e n s i t i e s of t h e l i n e s formed near l o g Te = 5.0 a r e up t o

-

⁴⁰ t i m e s l a r g e r t h a n t h e a v e r a g e q u i e t

sun

v a l u e s o f Vernazza and ~ e e v e s l ~ . a l t h o u g h 1 i n e s formed n e a r 1 og Te = 4.3 and 6.0

are

only enhanced by

a

f a c t o r of two. Hence t h e blending s p e c i e s i n t h e 1122.58 l i n e probably c o n t r i h t e

a

Smaller amount t o t h e t o t a l f l u x i n this case. Furthermore, Dcyle

e t

61.15

pint

out t h a t t e m p e r a t u r e d i a g n o s t i c s f o r s e v e r a l o t h e r ions i n t h i s

sunspt,

such

as

S IV and 0 V, l e a d t o v a l u e s of Te s i g n i f i c a n t l y l a v e r than T-. which probably i n d i c a t e s a c o o l i n g f l o w 1 6 . The

s i m i l a r

e f f e c t f o u n d h e r e f o r S i IV is t h e r e f o r e n o t surprising.

J i c k n c w l t + ~ Q : We a r e g r a t e f u l t o Professor A. E. Kingston

and

D r P. L. Dufton f o r t h e provision of S i

IV

a t o m i c d a t a i n advance of publication. Additiondlly,

we

would like to thank P r o f e s s o r H.B. Gilbody and D r R.W.P. M w h i r t e r f o r t h e i r continued i n t e r e s t i n t h e work.

FPK

is g r a t e f u l t o t h e SERC f o r f i m n c i a l support.

-

1. Keenan, F.P., D u f t o n , P.L., K i n g t o n , A.E. 1986. A s t r . Ap.

169,

319.

2. Dufton, P.L., Kingston. A. E. 1987. J. Piys. B

(in

p r e s s ) . 3. Doschek, G.A., Feldman, U. 1987. Ap. J.

315,

M7.

4. A r n a u d , M . . R o t h e n f l u g . R. 1 9 8 5 .

A s t r .

Ap. S u p p l . 60. 4 2 5 . 5. Reeves. E.M., Huber, M.C.E., Timothy. J . G . 1977. Appl. Opt.

16,

837.

6. Reeves, E.M.

e t

61. 1977. Appl. Qk. & 849.

7. Doyle, J.G. 1983. Solar Plys. &!. 115.

8. Doyle, J . G . , Mason, H.E., V e r n a z z a , J . E . 1 9 8 5 . A s t r . Ap.

156,

69.

9. Noyes, R.W.

et

dl. 1985. Ap. J. 297, 805.

lo.

Dupree, A.K., Reeves, E.M. 1971. Ap. J.

165.

599.

11. Flaver, D.R.. Nussbamer. H. 1975.

M r .

Ap. 42. 265.

12. Burton, W.M.. R i d g e l y , A. 1970. Solar Plys.

M,

^3.

13. Fel- U., Doschek, G.A. 1977. Astr. Ap. 61. 295.

14. Vernazza, J.E., Reeves, E.M. 1978. Ap. J. Suppl.

a

485.

15. Doyle, J.G. e t dl. 1985. Ap. J. 297. 816.

16.

Raymond,

J.C.. Foukal. P.V. 1982. Ap. J. 293. 323.