Observation of flow of low-energy ions at synchronous altitude and implications for magnetospheric convection

The Rice University suprathermal ion detector aboard the ATS 1 synchronous orbit satellite has established the existence of occasional bulk motion of the magnetospheric thermal ions. This conclusion is based on the observation of a highly directional flux of positive ions, moving with a flow velocity of approximately 30 km/sec with a thermal energy substantially less than the flow velocity energy. The flow direction and magnitude observed are generally consistent with present theories of magnetospheric convection. The electric field required to account for the observed flow velocity is 5 millivolts/meter, and the electric field direction is across the magnetosphere from the dawn to dusk side. A gross pattern of magnetospheric convection that is consistent with this, as well as previously reported ATS 1 data, is presented. Implications of the requisite electric field for the energetic trapped radiation in the outer portion of the outer zone of the Van Allen radiation belt are briefly discussed.