Kinetic treatment of oxygen conic formation in the central plasma sheet by broadband waves
Abstract
The acceleration of ions by broadband waves has recently been proposed as an explanation for the simultaneous observation of low-frequency electromagnetic turbulence and oxygen-dominated ion conics within the central plasma sheet. Here we develop a kinetic description for the evolution of a minority (oxygen) ionic species within a hydrogenic plasma. In consideration of some of the properties of the broadband wave spectrum in this plasma, we find that the oxygen heating is described by a quasilinear, velocity space diffusion operator for the oxygen ions. With the aid of suitable approximations, we obtain a simplified kinetic equation for the gyrotropic distribution of ions including the effects of perpendicular velocity space diffusion and the mirror force due to the geomagnetic field. In many cases the spectrum of resonant turbulence is well described as a power law, and one finds that the results are rather independent of the initial conditions imposed on these equations. This is due to the existence of a self-similar solution of the kinetic equation in which the ion distribution relaxes toward a fixed shape in velocity space, with the velocity scaling determined by the altitude. We present a numerical technique for constructing the conic distribution function.
- Publication:
-
Geophysical Monograph Series
- Pub Date:
- 1988
- DOI:
- 10.1029/GM044p0159
- Bibcode:
- 1988GMS....44..159C
- Keywords:
-
- Ion Distribution;
- Oxygen Ions;
- Particle Acceleration;
- Plasma Layers;
- Space Plasmas;
- Conics;
- Kinetic Equations;
- Magnetosphere-Ionosphere Coupling