Average profile of ion flow and convection electric field in the near-Earth plasma sheet

Two-dimensional distribution of ion flow and convection electric field in t he near-Earth plasma sheet (9 < R < 30 R-E) is investigated on the basis of GEOTAIL measurements. Our statistics confirms that the observed ion flow i n the plasma sheet is generally earthward, being accompanied by a significa nt dawn-to-dusk component which is distributed asymmetrically about the noo n-midnight meridian. On the other hand, the convection electric field deduc ed from the V X B term after excluding the effects of ion pressure gradient drift shows much better symmetry about the noon-midnight meridian. Existen ce of significant difference between the ion and magnetic flux convection p atterns suggests that the frozen-in condition does not hold in the near-Ear th plasma sheet.