EDI convection measurements at 5-6 R<sub>E</sub> in the post-midnight region

Abstract

Abstract. We present the ®rst triangulation measurements of electric ®elds with the electron drift instrument (EDI) on Equator-S. We show results from ®ve highdata-rate passes of the satellite through the nearmidnight equatorial region, at geocentric distances of approximately 5±6 R E , during geomagnetically quiet conditions. In a co-rotating frame of reference, the measured electric ®elds have magnitudes of a few tenths of mV/m, with the E Â B drift generally directed sunward but with large variations. Temporal variations of the electric ®eld on time scales of several seconds to minutes are large compared to the average magnitude. Comparisons of the``DC'' baseline of the EDI-measured electric ®elds with the mapped Weimer ionospheric model and the Rowland and Wygant CRRES measurements yield reasonable agreement.

Two types of ion spectral gaps in the quiet inner magnetosphere: Interball-2 observations and modeling

“…Also, the role of particle source location on the model gaps is investigated. It may be concluded that despite the evidence of large amplitude and directional local fluctuations of electric fields in the inner magnetosphere (Quinn et al, 1999), the existence of a stationary average convection pattern is confirmed by this modeling. This fact directly follows from observations of ISGs and from a good agreement of observations with modeled gaps calculated in the frames of adiabatic theory for a stationary (average) convection pattern.…”

“…It should be stressed here that the very existence of stationary convection in quiet times is currently under debate. The existence of a stationary pattern of particle drift motion averaged from large fluctuations of observed electric field, is called into question (Quinn et al, 1999). The observations of ISG which are possible only in a long-term stationary convection can be used to test this issue.…”

Derivation of inner magnetospheric electric field (UNH-IMEF) model using Cluster data set

“…The strength of the electric field at large K p index increases as the distance from the Earth decreases so that the radial dependence is opposite to the usual ionospheric shielding of the magnetospheric electric field. Quinn et al (1999) reported fluctuating electric fields in the inner magnetosphere measured by the Electron Drift Instrument (EDI) on Equator-S. Matsui et al (2003) analyzed the electric field measured by EDI on Cluster. Various types of electric fields exist, such as those originating from solar-wind magnetosphere coupling, subauroral polarization stream (SAPS), and ionospheric dynamo.…”

Cluster EDI convection measurements across the high-latitude plasma sheet boundary at midnight

“…Details of this dependence are given in Quinn et al (1999) and Paschmann et al (1999). The accuracy with which one can determine the drift step through triangulation depends on several factors, including the knowledge of the beam firing direction and the relative magnitude and orientation of the gun-detector baseline b, projected into the B ⊥ plane, with respect to the drift step, d. In general, triangulation is most accurate when the baseline is comparable in magnitude to the drift step.…”

“…Rapid convection variations in the vicinity of the plasma sheet boundary are certainly not unexpected, and often continue to varying degrees into the equatorial regions (e.g. Quinn et al, 1999). Second, due to the flow variability, the ground software that determines the drift step, and thus the flow velocities from all beams within the averaging interval cannot, in many cases, obtain a sharplydefined result.…”