Simulation of solar wind interaction with earth magnetic fiel

Managadze, G. G.

Podgornny, I. M.

English

NASA Technical Reports Server

. 
3 .  - WNGLEY 
National Aeronautics and Space Administration 
Goddard Space Flight Center 
Contract No.NAS-5-12487 
ST - PF - GM - 10749 
SIMULATION OF SOLAR WIND INTERACTION WITH 
THE EARTH’S MAGNETIC FIELD 
G. G. Managadze 
& 
P. M. Podgornyy 
GPO PRICE s 
CSFTI PRICE(S) $ 
Hard copy (He)- 
Microfiche (MF)  
ff 653 July 65 
(USSR) 
11 SEPTEMBER 1968 
https://ntrs.nasa.gov/search.jsp?R=19680024687 2020-03-12T06:20:11+00:00Z
SII4tJIATION OF SOLAR WIND INTERACTION -- 
WITH THE EARTH'S MAGNETIC FIELD 
~ .- --. 
Geomagnetizm i Aeronoii6ya 
Tom 8 ,  No.4, pp 618-623 
I Z ~ - V O  "NAUKA" , MOSCOW I 1 9  6 8 
by 
G . G .  Managadze & 
P .M. Podgornyy 
T h e  p o s s i b i l i t y  i s  i n v e s t i g a t e d  of s imula t ing  t h c  i n t e r -  
a c t i o n  between the s o l a r  wind and the  Earth 's ,magnet ic  f i e l d  
A n  a c c u r a t e  s imua l t ion  of a l l  t h e  processes  occurr ing  i n  t h e  
magnetosphere proves t o  be a c t u a l l y  u n r e a l i z a b l e .  However , 
t h e r e  i s  a p o s s i b i l i t y  of s e l e c t i n g  t h e  experimental  parameters so  
as t o  reproduce under l abora to ry  condi t iol is  the m o s t .  i n t e r e s t i n g  
o u t e r  space  phenonena. The r e s u 1 . t ~  of experiments on t h e  f o r -  
mat ion of t h e  n e u t r a l  sheet  a re  presented  as an example of t h e  
accuracy  of a l i m i t e d  s imula t ion .  
* 
* * 
I t  w a s  r e p o r t e d  e a r l i e i [ l , 2 ]  t h a t  i n  t h e  s imula t ion  of t h e  
i n t e r a c t i o n  between t h e  solar wind and t h e  E a r t h ' s  rnagiiei-ic 
f i e l d  phenomena were d e t e c t e d  which accompany t h e  collisioI)i3 ess 
shock wave i n  t h e  v i c i n i t y  of t h e  magnetosphere. The experi.ments 
were c a r r i e d  o u t  w i t h  a two-dimensional magnetic d i p o l e  i n  a plas-  
ma flow c h a r a c t e r i z e d  by t h e  fol lowing parameters : concen t r a t ion  
n Q 1 0 '  , e l e c t r o n  temperature T, % 15 ev, f l o w  v e l o c i t y  v % 
Q 3=107 cm/sec. The magnetic d i p o l e  was a r e c t a n g u l a r  shaped 
flat copper coil. 4 c m  w i d e  and 30  c1?1 long ( t h e  d.istance between 
the conductor  c e n t e r s  w a s  2 cm). The c o i l  was located i n  t h e  
h o r i z o n t a l  p lane  i n  such a manner t h a t  t h e  d i r ec t ed ,p l a sma  velo- 
c i t y  vector VE.S tu be perpendicular t o  i t s  l a r g e r  si?e and p a r a l l e l  
t o  i t s  smaller s ide .  The magnetic f i e l d  i n t e n s i t y  a t  magnetosphere 
boundary w a s  300-500 oe. The aforementioned va lues  do n o t  corres- 
pond t o  t h e  s imula t ion  of ou te r  space cond i t ions  i n v e s t i g a t e d  by 
Alfven [ 3 ]  b u t  t h e  s e l e c t e d  parameters prove nonethe less  t o  be 
s u i t a b l e  f o r  a l a b o r a t o r y  s imulat ion of solar wind flow arourid t h e  
geomagnetic f i e l d .  
, .. 
2 
The c u r r e n t  a r t ic le  p resen t s  a s u b s t a n t i a t i o n  of t h e  
model experiment and contains  some a d d i t i o n a l  experimental  
d a t e  on t h e  formation of the  n e u t r a l  s h e e t  on t h e  n i g h t  s i d e .  
The Basic  P r i n c i p l e s  of Simulat ion.  A p r e c i s e  s imula t ion  
of t h e  i n t e r a c t i o n  between the  s o l a r  wind  and the geomagnetic 
f i e l d  encounters  v i r t u a l l y  insurmountable d i f f i c u l t i e s .  Thus, 
f o r  i n s t a n c e ,  i n  o r d e r  t o  preserve t h e  magnetic Reynolds number, 
plasma temperature i n  a s imula t ion  experiment should have t h e  
same o r d e r  of magnitude as i n  a thermonuclear reactor. However, 
i n  order t o  determine a number of p e c u l i a r i t i e s  i n  t h e  i n t e r -  
a c t i o n  of a plasma with a magnetic d i p o l e ,  and, i n  p a r t i c u l a r ,  
t o  i n v e s t i g a t e  t h e  shape of a s t eady  shock wave on t h e  ' ' d iurna l"  
s i d e  and t h e  formation of  a n e u t r a l  s h e e t  on t h e  "n igh t "  s i d e ,  
it is n o t  necessary  t o  follow e x a c t l y  t h e  l a w s  of s i m i l a r i t y .  
I t  is s u f f i c i e n t  t h a t  t h e  condi t ions  fo r  t h e  course of t h e  inves t i -  
g a t e d  phenomenon be f u l f i l l e d .  T h i s  means t h a t  the dimensionless  
parameters  c h a r a c t e r i z i n g  t h e  i n t e r a c t i o n  equa l  by o r d e r  of mag- 
n i t u d e  t o  t h e  u n i t y ,  should be a s  f a r  as p o s s i b l e  i d e n t i c a l  i n  
t h e  o u t e r  space and i n  t h e  labora tory .  But when i n  o u t e r  space 
a g iven  dimensionless  parameter i s  by many orde r s  l o w e r  o r  h i g h e r  
t h a n  t h e  u n i t y ,  t h i s  parameter should also be correspondingly 
l o w  o r  high by comparison w i t h  t h e  u n i t y  i n  t h e  model experiment .  
However, i n  any case  when i n v e s t i g a t i n g  t h e  phenomenon i n  a 
f i r s t  approximation, it i s  not necessary  t o  preserve  t h e  same 
o r d e r  of i t s  magnitude. L e t  us i n v e s t i g a t e  s y s t e m a t i c a l l y  t h e  
b a s i c  dimensionless  parameters c h a r a c t e r i z i n g  t h e  i n t e r a c t i o n  
between the plasma f l o w  and a magnetic d ipo le .  
1. The magnetic cav i ty  free of plasma i s  formed under 
cond i t ions  of s u f f i c i e n t l y  high e l e c t r o n  temperature when t h e  
plasma f l u x  cannot p e n e t r a t e  deeply i n t o  t h e  magnetic f i e l d .  
The condi t ion  f o r  a sepa ra t e  e x i s t e n c e  of a plasma and of a mag- 
n e t i c  f i e l d  i s  equ iva len t  t o  t h e  requirement Re, >> 1. H e r e  Re, 
i s  t h e  magnetic Reynolds number 
where CT i s  t h e  plasma conduct iv i ty ,  ? i s  t h e  directed v e l o c i t y ,  
and L is  t h e  magnetosphere dimensions. 
A t  s o l a r  wind i n t e r a c t i o n  w i t h  t h e  geomagnetic f i e l d  Re, 'L 
'L 10". 
'L 15 ev which responds t o  Re, > lo3, i .e .  t h e  cond i t ions  f o r  mag- 
n e t i c  c a v i t y  formation w e r e  f u l f i l l e d .  
I n  the p r e s e n t  experiment t h e  plasma temperature w a s  
2. T o  form a shock wave i n  t h e  v i c i n i t y  of t h e  plasma-f ie ld  
i n t e r f a c e ,  plasma flow must be supersonic .  I n  t h e  s o l a r  wind t h e  
d i r e c t e d  v e l o c i t y  exceeds t h a t  of i o n  sound by a f a c t o r  of 5-10 
I .  
3 
[ 4 , 5 ] .  
and a temperature  Q, 1 5  ev, t h i s  va lue  amounts t o  7-8, i . e .  t h e  
s e l e c t e d  v e l o c i t y  and temperature f u l f i l l  t h e  cond i t ions  f o r  
shock wave formation. S imi la r  cons ide ra t ions  w i t h  r e s p e c t  t o  
a d i s tu rbance  propagat ing a t  a v e l o c i t y  of t h e  magnetic sound 
r e s u l t  i n  t h e  n e c e s s i t y  of having i n  t h e  plasma a frozen-in 
f i e l d  of % 30 o e r s t e d .  
A t  a flow v e l o c i t y  i n  t h e  model experiment of 3 0 1 0 ~  cm/sec 
3.  To form a c o l l i s i o n l e s s  shock wave t h e  l eng th  of t h e  
f r e e  pa th  must exceed t h e  c h a r a c t e r i s t i c  dimensions of t h e  sys-  
t e m .  I n  t h e  so la r  wind t h e  r a t i o  between t h e  l eng th  of t h e  free 
pa th  and t h e  magnetosphere dimensions i s  l o 3 .  I n  t h e  p r e s e n t  
work, a t  a concen t r a t ion  of 10' t h i s  r a t i o  i s  Q 1 0 .  There-  
f o r e  h e r e ,  as i n  o u t e r  space,  t h e  onse t  of t h e  shock wave cannot 
occur  a t  t h e  expense of Coulomb c o l l i s i o n s .  
4 .  I n  t h e  boundary l a y e r  "plasma-f ie ld"  t h e  i o n  and e l e c t r o n  
cu rva tu re  r a d i u s  is  much smal le r  than t h e  dimensions of t h e  l a y e r .  
I n  t h e  p r e s e n t  experiment t h i s  condi t ion  i s  v a l i d  only f o r  elec- 
t r o n s .  However, t h e  s m a l l  Debye r a d i u s  of plasma does no t  permi t  
i o n s  t o  de tach  themselves from e l e c t r o n s .  Consequently, t h e  con- 
d i t i o n s  can b e a r  comparison i n  t h i s  r e s p e c t  too .  
I t  i s  i n t e r e s t i n g  t o  note t h a t  i n  t h e  experiments c u r r e n t l y  
planned a t  t h e  Royal I n s t i t u t e  of Technology (Stockholm) [ 6 ] ,  
plasma parameters  v i r t u a l l y  co inc ide  wi th  t h e  parameters of our  
own experiments ,  whose r e s u l t s  w e r e  d i scussed  f o r  t h e  f i r s t  t i m e  
a t  t h e  I n t e r n a t i o n a l  Conference on shock waves i n  a plasma ( N o -  
v o s i b i r s k ,  August 1 9 6 7 ) .  A t  t h a t  Conference Sh ind le r  has  noted 
i n  h i s  r e p o r t  t h a t  t h e  i n d i c a t e d  parameters  a r e  close t o  opt imal .  
The Neu t ra l  Sheet .  When organiz ing  experiments on s imula t ion  
of t h e  geomagnetic f i e l d  shape on t h e  n i g h t  side,  it w a s  assumed 
t h a t  plasma flow p e n e t r a t e s  through t h e  boundary of t h e  magneto- 
sphere .  The p e n e t r a t i o n  takes p lace  most probably e i the r  through 
t h e  n e u t r a l  p o i n t s ,  which i n  a two-dimensional case  degenerate  
i n t o  n e u t r a l  l i n e s ,  o r  i s  due t o  t h e  i n s t a b i l i t y  of t h e  plasma- 
magnetic f i e l d  i n t e r f a c e .  
Having pene t r a t ed  i n t o  t h e  magnetic c a v i t y ,  t h e  plasma flow 
must c a r r y  along t h e  l i n e s  of f o r c e  t o  t h e  n i g h t  s i d e  and t h e r e -  
by b r i n g  about t h e  formation of a n e u t r a l  sheet,  which has been 
r e c e n t l y  d e t e c t e d  by means of a r t i f i c i a l  Ear th  sa te l l i t es  [ 7 ] .  
The en t ra inment  of t h e  l i n e s  of f o r c e  by t h e  plasma flow having 
p e n e t r a t e d  i n t o  t h e  magnetic f i e l d  w a s  p rev ious ly  d e t e c t e d  under 
l a b o r a t o r y  cond i t ions  during plasma i n j e c t i o n  along t h e  a x i s  of 
a s h o r t  coi l  [ 8 1 .  The f i e l d  i n t e n s i t y  i n  t h e  n e u t r a l  s h e e t  i s  
zero. The l i n e s  of fo rce  i n  t h e  v i c i n i t y  of t h e  median p lane  
are p a r a l l e l  t o  t h e  n e u t r a l  s h e e t  and have oppos i t e  d i r e c t i o n s  
i n  t h e  no r the rn  and southern hemisphere. Fig.  l a  shows t h a t  t h e  
4 
b!) 
shape of t h e  E a r t h ' s  magne t i c  f i e l d  l i n e s  of f o r c e  i n  t h e  p lane  
pass ing  through t h e  magnetic a x i s  and t h e  Earth-Sun l i n e  accor- 
d ing  t o  t h e  d a t a  of t h e  a r t i f i c i a l  s a t e l l i t e s .  For t h e  s a k e  of 
comparison, Fig.  l b  shows t h e  conf igu ra t ion  of  an unperturbed 
from t h e  d i p o l e  c e n t e r .  However, t h e  
good coincindence of t h i s  experimental  
- curve wi th  t h e  curve t ak ing  p l ace  a t  
- 
S 0% 
W* .'/I R E  
-. -_ 
211 
RE 
5 
F i g .  3 
Fig. 4 
b 
b 
6 
Previous ly ,  a s i m i l a r  curve was experimental ly  obta ined  
i n  [9] befo re  the d a t a  on the  e x i s t e n c e  of t h e  n e u t r a l  s h e e t  
i n  t h e  geomagnetic f i e l d  were available. However, t h e  lack i n  
t h i s  work of d e t a i l e d  data on d i p o l e  f i e l d  conf igu ra t ion  i n  
t h e  plasma flow had n o t  made it p o s s i b l e  t o  detect the n e u t r a l  
s h e e t  under l abora to ry  condi t ions  before  it w a s  detected by 
m e a n s  of a r t i f i c i a l  E a r t h  s a t e l l i t e s .  Bes ides ,  i naccurac i e s  
i n  the alignment of magnetic probes i n  t h e  median plane of t h e  
d i p o l e  and t h e  p o s s i b i l i t y  of a s l i g h t  asymmetry of plasma flow 
do n o t  make it p o s s i b l e  to  e a s t a b l i s h  whether t h e  component Hy 
i n  t h i s  p lane  is  a c t u a l l y  exac t ly  zero.  
A cons iderably  more ex tens ive  information i s  provided by 
t h e  experiment i n  which both components of magnetic f i e l d  i n -  
t e n s i t y  are measured simultaneously n e a r  t h e  median plane.  
Such measurements w e r e  c a r r i e d  o u t  f o r  several f i x e d  va lues  of 
t h e  coord ina te  Z .  I n  each series of measurements t h e  magnetic 
probe w a s  moved i n  t h e  ver t ica l  d i r e c t i o n  i n t e r s e c t i n g  t h e  equa- 
t o r i a l  p lane ,  and a t  each po in t  components Hy and H, w e r e  m e a -  
s u r e d  s imultaneously.  The r e s u l t s  of measurements provide t h e  
p o s s i b i l i t y  of determining not  only t h e  d i r e c t i o n  and va lue  of 
f i e l d  i n t e n s i t y  vec to r ,  b u t  a l s o  t o  trace t h e  g radua l  t r a n s i -  
t i o n  from feebly-d is turbed  f i e l d  conf igu ra t ion  i n  t h e  v i c i n i t y  
of t h e  d i p o l e  c e n t e r  t o  t h e  n e u t r a l  sheet conf igu ra t ion  a t  long 
d i s t a n c e s .  F igs .  3,4 and 5 show t h e  d i s t r i b u t i o n  of  t h e  magne- 
t i c  f i e l d  r e s p e c t i v e l y  f o r  t h r e e  f i x e d  va lues  of t h e  coord ina te  2 ,  
i . e .13 ,  18 and 23 an. 
A t  a d i s t a n c e  of 13 cm from t h e  d i p o l e  c e n t e r  the n e u t r a l  
s h e e t  i s  n o t  y e t  formed b u t  the tendency i s  already p e r c e p t i b l e  
t o  t h e  decrease of t h e  component Hy and i n c r e a s e  of t h e  component 
HZ 
The curves taken down a t  d i s t a n c e s  of 1 8  and 23 cm f r o m  t h e  
c e n t e r  are evidence of  the  vanishing of t h e  magnetic f i e l d  i n t e n -  
s i t y  on the a x i s  Z ,  whereupon the component perpendicular  t o  t h e  
a x i s  i s  zero  w i t h i n  a c e r t a i n  i n t e r v a l  above and below t h e  a x i s ,  
measured a t  2 - 3 cm. As regards the component H,, it i s  also 
z e r o  on t h e  a x i s  Z ,  and i t s  abso lu te  va lue  smoothly increases 
on both s i d e s  o f  t h e  a x i s .  I n  other  words, t h e  observed con-  
f i g u r a t i o n  i s  p r e c i s e l y  t h a t  which responds t o  t h e  conf igu ra t ion  
of the n e u t r a l  sheet. 
Another i n t e r e s t i n g  p e c u l i a r i t y  of the experimental  r e s u l t s  
is  t h e  v a r i a t i o n  i n  t h e  d i r e c t i o n  of t h e  Hy component a t  a d i s -  
t a n c e  of 2r 20 mi from t h e  d ipole  c e n t e r  i n  t h e  reg ion  ad jacen t  
t o  t h e  n e u t r a l  shee t .  A t  a d i s t a n c e  of 2 5  - 30 cm t h e  ve r t i ca l  
component i n  t h e  e q u a t o r i a l  p lane  i s  aga in  nonzero and has  a 
d i r e c t i o n  oppos i te  t o  t h a t  of t h e  unperturbed d i p o l e  f i e l d .  
a behavior  of t h e  i n t e n s i t y  vector during the ormation of t h e  
n e u t r a l  s h e e t  may be l inked  wi th  t h e  development of i t s  i n s t a b i -  
Such 
. .I e 
7 
l i t y  [lO,ll]. I n  t h i s  connection, t h e  p o s s i b i l i t y  of an e f f e c t  
of chamber w a l l s  is  n o t  excluded. 
Discussion of t h e  Resul ts .  The magnetic f i e l d  conf igu ra t ion  
on t h e  " n i g h t  s i d e "  observed i n  t h e  p r e s e n t  work is  i n  complete 
agreement w i t h  t h e  concept of n e u t r a l  sheet formation on account 
of t h e  entrainment  of t h e  magnetic f i e l d  l i n e s  by the plasma 
f l o w  p e n e t r a t i n g  through the magnetosphere boundary. 
between the gas k i n e t i c  pressure  of t h e  plasma flow and t h e  mag- 
n e t i c  f i e l d  p re s su re  i s  t h e  condi t ion  of e x i s t e n c e  of t h e  neut-  
r a l  s h e e t .  A f i n a l  cor robora t ion  of t h e  v a l i d i t y  of ou r  assump- 
t i o n  can be made only through an experimental  v e r i f i c a t i o n  of 
t h e  presence of plasma i n  t he  reg ion  of ze ro  va lues  of t h e  mag- 
n e t i c  f i e l d .  
Equi l ibr ium 
The d e t e c t i o n  and t h e  measurement of plasma concent ra t ion  
i n  t h i s  reg ion  w a s  c a r r i e d  out by means of a double Langmuir 
probe,  as t h e  s e n s i t i v i t y  of t h e  laser i n t e r f e r o m e t e r  [ l l  pre-  
v i o u s l y  used f o r  determining t h e  concent ra t ion  a t  t h e  shock wave 
f r o n t  w a s  i n s u f f i c i e n t  f o r  such measurements. Measurements ca r -  
ried o u t  w i t h  a double Langmuir probe have shown t h a t  plasma 
concen t r a t ion  on t h e  n i g h t  s i d e  i s  Q 5*1012cm'3 up t o  the  reg ion  
i n  which t h e  t a i l  of t h e  magnetic f i e l d  may have been d i s t o r t e d  
by chamber w a l l  e f f e c t .  The d i s t r i b u t i o n  of concent ra t ion  i n  
t h e  n e u t r a l  s h e e t ,  ob ta ined  by t h e  double probe, i s  p l o t t e d  i n  
Fig.6.  
Thus, t h e  combination of t h e  obtained experimental  d a t a  
makes it p o s s i b l e  t o  conclude that  t h e  model experiments have 
d e t e c t e d  t h e  n e u t r a l  sheet, whose formation i s  l inked  w i t h  the  
p e n e t r a t i o n  of plasma i n  the magnetosphere. The c u r r e n t  d e n s i t y  
through t h e  plasma i n  t h e  region of t h e  n e u t r a l  sheet i s  'L 5 a/cm2. 
The au thors  expres s  t h e i r  g r a t i t u d e  t o  E.M. Dubinin, B . I .  
Pa t rushev  and D.A. Frank-Kamenetskiy. 
* * * THE END * * * 
Contrac t  NO .NAS-5-12 4 8 7  Trans l a t ed  by 
Vo l t  Information Sciences Inc . ,  Mr. Daniel Wolkonsky 
1145 19th  Street ,  N.W. Sept .  3, 1 9 6 8  
Washington, D.C. 20036 Revised by 
Telephone: [ 2 0 2 ]  223-6700 X 36 6 37 D r .  Andre L. Brichant  
Sept .9 ,  1 9 6 8 .  
. . . . . . ./ 
8 
R E F E R E N C E S  
1. 
2. 
3. 
4. 
5. 
6 .  
7. 
G.G. MAGANADZE, I . M .  PODGORNYY, V.D. RUSANOV: 
G.G. MAGANADZE, B . I .  PETRUSHEV, I . M .  PODGORNYY, V.D. RUSANOV: 
G e o m a g n .  i aeronom., 1 9 6 8 ,  8 ,  5 4 5 .  
V I 1 1  I n t e r n a t .  C o n f e r e n c e  on Ionised  G a s e s .  
V i e n n a ,  Izd-vo MAGATE, 1 9 6 4 ,  465 .  
11. 1 9 5 2 .  
G e o p h y s .  R e s . ,  1 9 6 7 ,  7 2 ,  1 9 .  
and A R o s e n ,  t ranslated from E n g l i s h ) .  
C .  ALFVEN:- - Kosmicheskaya e l ek t rod inamika ,  
J . M .  WILCOX, K.H.  SCHATTEN: 
--------------- Kosmicheskaya F i z i k a  ( e d i t e d  by D.P .  L e  H e l l i  
Izd-vo "MIR" , 1 9 6 6  
U. FAHLESON, L. BLOK, L. LINDBERG, I?. BOSTROM: 
P r e p r i n t  R o y a l  I n s t i t u t e  of Technology, No.66-09 
Stockholm, 1967 .  
N.F. MESS: - - J. G e o p h y s .  R e s . ,  1965 ,  7 0 ,  2989. 
8. I . M .  PODGORNY, V.N.  SUMAROKOV: 
Nuclear  F u s i o n ,  1 9 6 2 ,  Suppl. 1, 87. 
1 0 .  H . P .  FURTH: - A d v a n c e s  P l a s m a  Theory,  
New Y o r k ,  1 9 6 4 .  
11. B.  COPPY, G .  LAVAL, R. PELLAT: 
Phys. R e v .  Letters, 1 9 6 6 ,  1 6 ,  1 2 0 7 .  
Manuscript  received 
2 5  January ,  1968.  


Simulation of Solar Wind Interaction with the Earth's Magnetic Field

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server