Электродинамические процессы в высоких широтах: материалы междунарордного симпозиума «Полярные геомагнитные явления», 25-31 мая 1986 г., Суздаль, СССР / Междунар. геодез. и геофиз. союз, Междунар. ассоц. геомагнетизма и аэрономии ; Акад. наук СССР, Кол. фил. им. С. М. Кирова, Поляр. геофиз. ин-т ; [редкол.: О. М. Распопов (отв. ред.). и др.]. - Апатиты : Кольский филиал АН СССР, 1988.

K.SCHLEGEL, T.R.ROBINSON R EСЕНТ P R O G RE S S IM THE STUDY- OF THE T WO STREAM PLASMA I NSTABILITY I N THE HI G H LATITUDE E-REGIOM INTRODUCTION. The two s tream plasma instability is the most frequently- excited plasma instability in the h i g h latitude E - r eg i o n a n d it h as a very profound influence on the thermodynamics a nd the electrodynamics of this region. It is a. so-oalled "micro-instability" which means that it is a micro scopic attribute of the plasma, the particle velocity d istribution function, wh i c h leads to an instabi l i ty un d e r certain circumstances. It should be expl ained w i t h the help of Figure 1. O n the left han d side we have a particle veloc i t y d i s tribution funct io n of a plasma in thermal equilibrium, the normd. Maxwell-distribution. There are always w e a k oscillations in a plasma. If they httve a f r equency oj 0 , the wave energy of this oscillations will be equivalent to the energy of the plasma p a rticles wi t h a velo c it y v Q = ш0/ к , к being the wave nu m b e r of the oscillations. Particles w i t h velocities v > v Q will then feed energy into the waves, w he reas particles w i t h velocitis v < v Q will receive energy fro m the waves. But since there are always more particles w i t h v c vQ than particles w i t h v > v Q , more particles will take energy away fro m the waves than feed energy to the waves. The result is a damping of these oscillations i n the plasma that means the plasma will re m a in stable. If the particle v e l oc i t y h as a so called "bump in the tail" the situa tion is quite different. Such a "bump" occurs if there is a difference in ы*К-ѵ<, waves dumped .staBte" Ш ‘ К'Ѵо waves amplified „unsta&te" Figure 1. Particle v e l o c it y distr ib u t io n func t io n (number of particles with a v e l o c it y be t w e e n v and v+dv) of a stable (left) a nd of a n unstable (right) plasma. 78