A new plasma regime in the distant geomagnetic tail

Abstract

The three Rice Suprathermal Ion Detector Experiments have detected an extensive region of low energy plasma flow antisunward along the ordered field lines in the lobes of the geomagnetic tail at lunar distances. This particle regime resembles the “boundary layer” and “plasma mantle” observed at smaller geocentric distances and an interior flow region parallel to the magnetopause in the dayside magnetosphere. It possesses plasma characteristics uniquely different from the plasma sheet and magnetosheath. Spatially the particle regime is found exterior to the plasma sheet across essentially the entire tail and adjacent to the magnetopause on both the dawn and dusk sides of the magnetosphere. The integral flux varies from 105 to 108 ions/cm² sec ster with the differential flux peak between 50 and 250 eV/q. Temperatures range from 4 × 104 to 5 × 105 °K and number densities from .1 to 5/cm³.