SPACE-CHARGE ENHANCED, PLASMA GRADIENT INDUCED ERROR IN SATELLITE ELECTRIC-FIELD MEASUREMENTS

In magnetospheric plasmas it is possible for plasma gradients to cause error in electric field measurements made by satellite double probes. The space charge enhanced plasma gradient induced error is discussed in general terms, the results of a laboratory experiment designed to i llustrate this error are presented, and a simple expression that quant ifies this error in a form that is readily applicable to satellite dat a is derived. The simple expression indicates that for a given probe b ias current there is less error for cylindrical probes than for Spheri cal probes. The expression also suggests that for Viking data the erro r is negligible.