Observations of electron diffusion regions at the subsolar magnetopause.

Electric and magnetic field observations on the Polar satellite at the subsolar magnetopause show that the magnetopause current is often striated. The largest of the resulting current channels are interpreted as electron diffusion regions because their widths are several electron skin depths and the electron flow U(e) within them does not satisfy E-->+U-->(e)xB-->=0. The data suggest that the magnetopause contains many such electron diffusion regions and that they are required because E-->xB-->/B(2) drifting electrons cannot carry the large filamentary currents imposed on the local plasma. The most probable interpretation of E-->+U-->(e)xB--> not equal 0 is that the pressure term on the right side of the generalized Ohm's law balances this inequality.