Magnetospheric convection observed between 0600 and 2100 LT: Solar wind and IMF dependence

Abstract

Using data from the GEOS 2 electron gun experiment, we have analyzed the dependence of the dayside convection electric field at L = 6.6 (averaged into 3‐hour LT bins) on solar wind and interplanetary magnetic field conditions. The convection electric field does not correlate at all with the solar wind momentum flux density (correlation coefficients of <0.25). Hence viscous interaction plays only a minor role for equatorial magnetospheric convection at L = 6.6. The correlation coefficients for convection electric field versus merging electric field are of the order of 0.5–0.6, thus indicating that dayside convection is predominantly driven by dayside merging. The regression coefficients, describing the (LT‐dependent) transfer of the merging electric field to synchronous orbit, are of the order of 0.1–0.2. Their LT dependence follows approximately that described by a Volland‐Stern model with γ = 2, except that the regression analysis yields a dawn‐dusk asymmetry with the dusk sector electric fields being about twice as strong as those in the dawn sector. For the above shielding factor (γ = 2) the regression coefficients are consistent with a merging efficiency of about 20%. The regression constants (of the order of 0.05 mV/m) apparently describe an electric field stemming from the ionospheric wind dynamo. A comparison of the electric field described by the regression constants and two empirical models of quiet day electric fields implies that these models still include a substantial dawn‐to‐dusk electric field, thus indicating the presence of solar wind dynamo action even during quiet intervals.

Electrodynamics in the duskside inner magnetosphere and plasmasphere during a super magnetic storm on March 13–15, 1989

“…Furthermore, due to the very long orbital period (57 hours) of the ISEE-1 satellite, Maynard et al (1983) could not discuss the description of the electric field variations in the inner magnetosphere associated with the evolution of a magnetic storm. Baumjohann et al (1985) and Baumjohann and Haerendel (1985) presented observation results from the GEOS-2 electron gun experiment at geosynchronous orbit. The electric field at this radial position (L = 6.6) within a magnetic local time range from 06:00 to 21:00 scaled both with K p index and with the solar wind electric field.…”

“…Several reports on the electric field phenomena in the inner magnetosphere during a geomagnetic storm have been made, based on the in-situ observations (e.g., Heelis et al, 1976;Spiro et al, 1979;Maynard et al, 1980Maynard et al, , 1983Baumjohann et al, 1985;Baumjohann and Haerendel, 1985). A statistical analysis result of the electric field in the inner magnetosphere (2.0 < L < 6.0) measured by the ISEE-1 satellite within a period of one year was made by Maynard et al (1983), who showed that the magnitude of the electric field depends on K p and AE indices and the typical magnitude in the equatorial plane (L = 2.5-5.0) is in a range between 0.2 and 0.8 mV/m in a frame co-rotating with the earth.…”

IMF &lt;i&gt;B&lt;sub&gt;Y&lt;/sub&gt;&lt;/i&gt; and the seasonal dependences of the electric field in the inner magnetosphere

“…Another reason is that the IMF B Z component is a more important parameter controlling the electric field in the inner magnetosphere than the IMF B Y component and season, so that the IMF B Z component is often chosen for studies (e.g. Baumjohann and Haerendel, 1985;Goldstein et al, 2002). However, one work by Baumjohann et al (1986) investigated the dependence of the strength of the inner magnetospheric electric field on IMF B Y polarity by using data from a geosynchronous satellite GEOS-2 located in the Northern Hemisphere and slightly off the equator.…”

Solar wind—magnetosphere–ionosphere coupling: an event study based on Freja data

“…Whether this hypothesis represents reality will be the subject of future studies. Baumjohann and Haerendel (1985) studied the dependence on the solar wind and IMF of the convection electric ÿeld at geosynchronous orbit on the dayside. They found no correlation to the solar wind momentum ux, and thus, concluded that the dayside convection ÿeld does not arise from a viscous process.…”