Cusp radiation belts on quiet and disturbed dayside magnetosphere
Abstract
The possibility of quasi-stable trapping of charged particles of hundreds keV to MeV energy on the front side Earth magnetosphere in high latitudes is explored by numerical modeling of the single particle orbits in the geomagnetic field utilizing empirical Tsyganenko model. On the dayside magnetosphere the remote equatorial magnetic field lines are compressed by the solar wind pressure and exhibit two minima in the geomagnetic field strength along the field line in high latitudes on both sides of the equator. It results in stable confinement structures in the north or/and the south hemispheres, providing energetic particle trapping for times from several minutes to durations of seasonal scale. Simulation the energetic charged particle orbits passing through the regions of the magnetic field minima with different disturbance level shows when and where these trapped radiation zones could situate. It is noted that the existence of this adiabatic confinement zones depends on the tilt. As a result the northern polar cap (cusp) confinement zone appears mostly during a summer solstice and similarly the southern hemisphere capture zone appears only during a winter solstice. During equinox times the confinement zones exist in both hemispheres in the disturbed magnetospheric conditions, however, they are less pronounced. The zones are essentially restricted to the sunlit side of the magnetosphere. They form a kind of cusp radiation belt/ring, where a particle drifts with a period of the several minutes around the cusp region, conserving its 1st and the 2nd adiabatic invariants. The latitudinal width of the ring is very thin, about 2-5 latitudinal degrees. The particles orbits passing through opposite off-equatorial field minimum reveal another interesting effect: a bound/deflection of the particle drift plane from geomagnetic equatorial plane in the day sector. These and other features of the confinement zones in the two minima off-equatorial magnetic field regions are discussed.
- Publication:
-
35th COSPAR Scientific Assembly
- Pub Date:
- 2004
- Bibcode:
- 2004cosp...35..360P