Behavior of the topside ionosphere during a great magnetic storm

Abstract

L a b o r a t o r y f o r Space S c i e n c e s NASA Goddard Space F l i g h t C e n t e r G r e e n b e l t , Maryland ABSTRACT V a r i a t i o n s i n t h e e l e c t r o n d e n s i t y d i s t r i b u t i o n of t h e t o p s i d e i o n o s p h e r e ( i n c l u d i n g t h e h e i g h t of t h e Fa peak) obt a i n e d from A l o u e t t e I d u r i n g t h e g r e a t m a g n e t i c s t o r m of 17-18 A p r i l 1965 a r e a n a l y z e d . i n g on t h e p h a s e of t h e m a g n e t i c storm. S p e c i f i c a l l y , enhancement is a s s o c i a t e d w i t h t h e p o s i t i v e p h a s e and t h e asymmetric p a r t of t h e main p h a s e , w h i l e d e p l e t i o n of t h e t o p s i d e i o n o s p h e r e o c c u r s d u r i n g t h e s y m m e t r i c p a r t of t h e s t o r m main p h a s e o v e r a l a t i t u d er a n g e c o r r e s p o n d i n g t o L v a l u e s g r e a t e r t h a n 3. A s s o c i a t e d w i t h t h i s d e p l e t i o n is a r e d i s t r i b u t i o n of i o n i z a t i o n i nd i c a t i n g t h a t t h e t o p s i d e i o n o s p h e r e d u r i n g t h e s y m m e t r i c main p h a s e c o n s i s t s p r i m a r i l y of 0 ( w i t h H+ b e i n g d e p l e t e d ) . The + enhancement of t o p s i d e i o n i z a t i o n d u r i n g t h e p o s i t i v e p h a s e of t h e storm a p p e a r s t o b e a s s o c i a t e d w i t h t h e c o m p r e s s i o n of t h e d a y t i m e magnetosphere d u r i n g t h a t p h a s e of t h e storm.The d e p l e t i o n seems t o b e a s s o c i a t e d w i t h t h e e x p a n s i o n of f i e l d t u b e s due t o t h e p r e s e n c e of t h e h i g h e n e r g y -d e n s i t y r i n g c u r r e n t plasma a s o b s e r v e d on s a t e l l i t e s c a u s i n g a n upward f l u

Electron and ion temperatures in the ionosphere

“…Only on-one occasion, at 4 locations near to the S. Atlantic magnetic anomaly was an increase in T e -re corded. Knudsen (1968) which they observed were larger in magnitude, reaching 300 0 K. It seems that this behaviour is typical of rather weak storms, and possibly of the initial phase of more intense storms [Bauer and Krishnamurthy (1968)]. …”

Theoretical models of ionospheric storms

“…Titheridge and Andrews (1967), Mendillo et al (1969) and Taylor and Earnshaw (1969) have investigated variations in Nr during the magnetic storm of June 15, 1965 at Auckland, Hamilton and Jodrell Bank, respectively. Initial increases of electron densities in the topside ionosphere have been reported by King et al (1967b), Bauer and Krishnamurthy (1968) and Katz (1969). Nakata (1966), Goodman (1968) and Jones (1971) have reported increases in Titheridge and Andrews, 1967;Mendillo et al, 1969;and Taylor and Earnshaw, 1969.…”

“…Their results shown in Figure 3 indicate that values of ArT were higher than normal condition for one or two days after the sudden commencement of the magnetic storm and then fell to below normal level. Bauer and Krishnamurthy (1968) have shown increases of electron density from topside N(h) profiles, without appreciable change in plasma scale heights, during the initial phase of a magnetic storm, and suggested a downward diffusion of plasma along magnetic field lines following magnetospheric compression. ) N r at lower mid-latitudes after the commencement of magnetic storms.…”

Ionospheric variations during the 13 September 1967 storm: Incoherent scatter radar results.

“…While earlier workers studied the changes in the peak electron density (NJ2) and its height (hmF2), recently a number of workers have been studying the changes in electron content (NT), electron temperature (Te), and electron density (Ne) profiles (for example, REDDY et al, 1967;RAO, 1968;BAUER and KRISHNAMURTHY, 1968;GOODMAN, 1968;EVANS, 1970;MENDILLO, 1973;GONDHALKAR, 1973;LANZEROTTI et al, 1975). There are also a few reports on changes in ion composition and drift velocity (CHANDRA et al, 1971;MARUBASHI et al, 1976;BLANC et al, 1977;HARPER, 1977).…”