- Email: [email protected]
The first suggestion of an ionosphere
J carnal of Atmospheric and Terrestrial Physics, 1962, Vol. 26, pp. 219 to 221. Pergamon Press Ltd. Printed in Northern Ireland
RESEARCH
NOTES
The first suggestion o~ an ionosphere (Received 13 December 1961) T g E i m p o r t a n c e o f a c o n d u c t i n g region in t h e h i g h e r a t m o s p h e r e , u s u a l l y t e r m e d t h e i o n o s p h e r e , e a n b e c o n s i d e r e d u n d e r t h r e e h e a d s : (a) t h e r e f l e x i o n o f r a d i o w a v e s , (b) a t m o s p h e r i c electricity, a n d (c) v a r i a t i o n s o f t e r r e s t r i a l m a g n e t i s m . I t is g e n e r a l l y t h o u g h t t h a t t h e idea of a c o n d u c t i n g region i n t h e u p p e r a t m o s p h e r e was first i n t r o d u c e d b y BAr~'OUR STEWART (1878) in c o n n e x i o n w i t h (c), t h e n in c o n n e x i o n w i t h (a) in 1902 b y HEAVISIDE (1902) a n d KENNELLY (1902) w i t h t h e a p p l i c a t i o n t o (b) m u c h later. B u t , i n fact, t h e idea of a c o n d u c t i n g r e g i o n h i g h u p in t h e a t m o s p h e r e was t h o u g h t of m u c h earlier b y TI~OMSO~, l a t e r L o r d KELVI>r, in 1860, a n d u s e d in discussing a t m o s p h e r i c electricity. T~tOMSON'S e s t i m a t e o f t h e height, of s u c h a region, s t a r t i n g a t a b o u t 100 miles, is c o n s i d e r a b l y n e a r e r t h e t r u t h t h a n BALFOUR STEWART'S e s t i m a t e o f u p p e r cloud level, i.e. 5 - 1 0 miles. TIIOMSON'S a r g u m e n t s are of s u c h i n t e r e s t t h a t it seems w o r t h while to r e p r o d u c e a p o r t i o n of his lecture. " I n r e a l i t y we k n o w t h a t air h i g h l y r a r e f i e d b y t h e a i r - p u m p , or b y o t h e r processes, as in t h e c o n s t r u c t i o n of t h e " v a c u u m t u b e s " b y w h i c h s u c h a d m i r a b l e p h e n o m e n a o f electric light, h a v e r e c e n t l y b e e n s e e n in t h i s place, b e c o m e s e x t r e m e l y w e a k in its r e s i s t a n c e to t h e t r a n s f e r e n c e o f e l e c t r i c i t y t h r o u g h it, a n d b e g i n s t o a p p e a r r a t h e r as a c o n d u c t o r t h a n a n i n s u l a t o r . One h u n d r e d miles or u p w a r d s f r o m t h e e a r t h ' s surface, t h e a i r in space c a n n o t in all p r o b a b i l i t y h a v e r e s i s t i n g p o w e r e n o u g h to b e a r a n y s u c h electric forces as t h o s e w h i c h we g e n e r a l l y find e v e n in serene w e a t h e r i n t h e lower s t r a t a . I-[enee we c a n n o t , w i t h P e l t i e r , r e g a r d t h e e a r t h as a r e s i n o u s l y c h a r g e d c o n d u c t o r , i n s u l a t e d in space, a n d s u b j e c t o n l y to a c c i d e n t a l influences f r o m t e m p o r a r y electric d e p o s i t s in clouds, or air r o u n d it; but, we m u s t s u p p o s e t h a t t h e r e is a l w a y s essentially in t h e h i g h e r a e r i a l regions a d i s t r i b u t i o n a r i s i n g f r o m t h e self-relief of t h e o u t e r h i g h l y r a r e f i e d air b y d i s r u p t i v e d i s c h a r g e . T h i s electric s t r a t u m m u s t c o n s t i t u t e v e r y n e a r l y t h e e l e c t r o - p o l a r c o m p l e m e n t t o all t h e e l e c t r i c i t y t h a t exists o n t h e e a r t h ' s surface, a n d in t h e lower s t r a t a of t h e a t m o s p h e r e - - i n o t h e r words, t h e t o t a l q u a n t i t y of electricity, r e c k o n e d as excess of p o s i t i v e a b o v e n e g a t i v e , or of n e g a t i v e a b o v e positive, in a n y large p o r t i o n of t h e a t m o s p h e r e , or o n t h e p o r t i o n of t h e e a r t h ' s s u r f a c e b e l o w it, m u s t b e v e r y n e a r l y zero. T h e q u a l i t y of n o n - r e s i s t a n c e to electric force o f t h e t h i n i n t e r p l a n e t a r y air b e i n g d u l y c o n s i d e r e d , we m i g h t r e g a r d t h e e a r t h , its a t m o s p h e r e , a n d t h e sin.rounding m e d i u m as c o n s t i t u t i n g respect,ively t h e i n n e r c o a t i n g , t h e di-electric (as it were glass), a n d t h e o u t e r c o a t i n g of a g r e a t L e y d e n phial, c h a r g e d n e g a t i v e l y ; a n d e v e n if we were to neglect t h e c o n s i d e r a t i o n of possible d e p o s i t s of e l e c t r i c i t y t h r o u g h t h e b o d y of t h e di-electrie itself, we s h o u l d a r r i v e a t a correct view of t h e electric i n d i c a t i o n s d i s c o v e r a b l e a t a n y one t i m e a n d place o f t h e e a r t h ' s s u r f a c e . "
Department of l'hysics Durham Colleges in the University of Durham
J . A . (~HALMER8
I~EFERENCES HEAVISIDE O. KEN-NELLY A . E . STEWART B. TgOMSON ~V.
1902 1902 1878 1860
Encyclopaedia Britannica ( 1 0 t h Ed.), Vol. 33, p p . 213-218. Elect. World, N . Y . 39, 473. Encyclopaedia Britannica ( 9 t h Ed.), Vol. 16, p p . 181-184. Papers on Electrostatics and 3lagnetism, pp. 217-218. M a c m i l l a n , L o n d o n (1884). 219
RESEARCH
NOTES
The first suggestion o~ an ionosphere (Received 13 December 1961) T g E i m p o r t a n c e o f a c o n d u c t i n g region in t h e h i g h e r a t m o s p h e r e , u s u a l l y t e r m e d t h e i o n o s p h e r e , e a n b e c o n s i d e r e d u n d e r t h r e e h e a d s : (a) t h e r e f l e x i o n o f r a d i o w a v e s , (b) a t m o s p h e r i c electricity, a n d (c) v a r i a t i o n s o f t e r r e s t r i a l m a g n e t i s m . I t is g e n e r a l l y t h o u g h t t h a t t h e idea of a c o n d u c t i n g region i n t h e u p p e r a t m o s p h e r e was first i n t r o d u c e d b y BAr~'OUR STEWART (1878) in c o n n e x i o n w i t h (c), t h e n in c o n n e x i o n w i t h (a) in 1902 b y HEAVISIDE (1902) a n d KENNELLY (1902) w i t h t h e a p p l i c a t i o n t o (b) m u c h later. B u t , i n fact, t h e idea of a c o n d u c t i n g r e g i o n h i g h u p in t h e a t m o s p h e r e was t h o u g h t of m u c h earlier b y TI~OMSO~, l a t e r L o r d KELVI>r, in 1860, a n d u s e d in discussing a t m o s p h e r i c electricity. T~tOMSON'S e s t i m a t e o f t h e height, of s u c h a region, s t a r t i n g a t a b o u t 100 miles, is c o n s i d e r a b l y n e a r e r t h e t r u t h t h a n BALFOUR STEWART'S e s t i m a t e o f u p p e r cloud level, i.e. 5 - 1 0 miles. TIIOMSON'S a r g u m e n t s are of s u c h i n t e r e s t t h a t it seems w o r t h while to r e p r o d u c e a p o r t i o n of his lecture. " I n r e a l i t y we k n o w t h a t air h i g h l y r a r e f i e d b y t h e a i r - p u m p , or b y o t h e r processes, as in t h e c o n s t r u c t i o n of t h e " v a c u u m t u b e s " b y w h i c h s u c h a d m i r a b l e p h e n o m e n a o f electric light, h a v e r e c e n t l y b e e n s e e n in t h i s place, b e c o m e s e x t r e m e l y w e a k in its r e s i s t a n c e to t h e t r a n s f e r e n c e o f e l e c t r i c i t y t h r o u g h it, a n d b e g i n s t o a p p e a r r a t h e r as a c o n d u c t o r t h a n a n i n s u l a t o r . One h u n d r e d miles or u p w a r d s f r o m t h e e a r t h ' s surface, t h e a i r in space c a n n o t in all p r o b a b i l i t y h a v e r e s i s t i n g p o w e r e n o u g h to b e a r a n y s u c h electric forces as t h o s e w h i c h we g e n e r a l l y find e v e n in serene w e a t h e r i n t h e lower s t r a t a . I-[enee we c a n n o t , w i t h P e l t i e r , r e g a r d t h e e a r t h as a r e s i n o u s l y c h a r g e d c o n d u c t o r , i n s u l a t e d in space, a n d s u b j e c t o n l y to a c c i d e n t a l influences f r o m t e m p o r a r y electric d e p o s i t s in clouds, or air r o u n d it; but, we m u s t s u p p o s e t h a t t h e r e is a l w a y s essentially in t h e h i g h e r a e r i a l regions a d i s t r i b u t i o n a r i s i n g f r o m t h e self-relief of t h e o u t e r h i g h l y r a r e f i e d air b y d i s r u p t i v e d i s c h a r g e . T h i s electric s t r a t u m m u s t c o n s t i t u t e v e r y n e a r l y t h e e l e c t r o - p o l a r c o m p l e m e n t t o all t h e e l e c t r i c i t y t h a t exists o n t h e e a r t h ' s surface, a n d in t h e lower s t r a t a of t h e a t m o s p h e r e - - i n o t h e r words, t h e t o t a l q u a n t i t y of electricity, r e c k o n e d as excess of p o s i t i v e a b o v e n e g a t i v e , or of n e g a t i v e a b o v e positive, in a n y large p o r t i o n of t h e a t m o s p h e r e , or o n t h e p o r t i o n of t h e e a r t h ' s s u r f a c e b e l o w it, m u s t b e v e r y n e a r l y zero. T h e q u a l i t y of n o n - r e s i s t a n c e to electric force o f t h e t h i n i n t e r p l a n e t a r y air b e i n g d u l y c o n s i d e r e d , we m i g h t r e g a r d t h e e a r t h , its a t m o s p h e r e , a n d t h e sin.rounding m e d i u m as c o n s t i t u t i n g respect,ively t h e i n n e r c o a t i n g , t h e di-electric (as it were glass), a n d t h e o u t e r c o a t i n g of a g r e a t L e y d e n phial, c h a r g e d n e g a t i v e l y ; a n d e v e n if we were to neglect t h e c o n s i d e r a t i o n of possible d e p o s i t s of e l e c t r i c i t y t h r o u g h t h e b o d y of t h e di-electrie itself, we s h o u l d a r r i v e a t a correct view of t h e electric i n d i c a t i o n s d i s c o v e r a b l e a t a n y one t i m e a n d place o f t h e e a r t h ' s s u r f a c e . "
Department of l'hysics Durham Colleges in the University of Durham
J . A . (~HALMER8
I~EFERENCES HEAVISIDE O. KEN-NELLY A . E . STEWART B. TgOMSON ~V.
1902 1902 1878 1860
Encyclopaedia Britannica ( 1 0 t h Ed.), Vol. 33, p p . 213-218. Elect. World, N . Y . 39, 473. Encyclopaedia Britannica ( 9 t h Ed.), Vol. 16, p p . 181-184. Papers on Electrostatics and 3lagnetism, pp. 217-218. M a c m i l l a n , L o n d o n (1884). 219