Outflow of cold dense plasma associated with variation of convection in the outer magnetosphere

Cold dense plasma with the ionospheric origin is often observed in the oute r magnetosphere with L values as large as 10. We have examined the electric field data accompanied by the cold dense plasma. The electric field data a re obtained by the direct measurement of the drift motion of electrons rele ased from electron guns. We get westward components of convection. In addit ion, there is an AC component of electric field in the ULF range larger tha n the DC component. If such a large variation of electric field exists in t he vicinity of the stagnation point, the plasmaspheric plasma is expected t o how away to the outer magnetosphere. Then we have a test particle simulat ion by adding a potential variable in time. There is a particle outflow acc ompanied by the AC variation of electric field in the ULF range. If there a re more complicated variations of electric field, it is possible that parti cles flow out frequently. (C) 2000 Elsevier Science Ltd. All rights reserve d.