An average image of proton plasma pressure and of current systems in the equatorial plane derived from AMPTE/CCE‐CHEM measurements

Abstract

Abstract. The present study attempts to visualize the global equatorial current systems and the proton pressure in the near-Earth magnetosphere based on AMPTE/CCE-CHEM measured proton distributions, which were sorted by the AE index ( "quiet": AE < 100 nT, "active": 100 nT < AE < 600 nT). The data were averaged over 2 years (from January 1985 to June 1987) in order to obtain the necessary spatial resolution with statistical significance. The results provide an average image of proton plasma pressure, proton plasma anisotropy, and current systems as a function of geomagnetic activity. In particular, the changes of pressure anisotropy with local time and the noon-midnight pressure asymmetry are studied and correlated to the current systems out of the equatorial plane that generate the closure circuits. Moreover, we identify and spatially locate two different current systems for the quiet period (the ring current and the inner portion of the quiet thne cross-tail current) and three different current structures for the active period (the ring current, the partial ring current, and the region 2 current).

Azimuthally asymmetric ring current as a function of &lt;i&gt;D&lt;sub&gt;st&lt;/sub&gt;&lt;/i&gt; and solar wind conditions

“…Our results are consistent with those of Iijima et al (1990) and De Michelis et al (1999), who obtained the dayside ring current several times smaller than the nightside one. According to our Fig.…”

“…Lui and Hamilton (1992) obtained plasma pressure radial proCorrespondence to: Y. P. Maltsev (maltsev@pgi.kolasc.net.ru) files from L=2 to L=9 at noon and at midnight for quiet conditions. De Michelis et al (1999), using AMPTE CCE data, have built energetic plasma profiles in four LT sectors for two AE ranges. The profiles appeared to be independent either of LT or AE.…”

3-D Force-balanced Magnetospheric Configurations

“…In this section we present several computed quietand active-time 3-D magnetospheric quasi-equilibria, in which the magnetic fields are in force balance with different observed pressure distributions: the so-called Spence-Kivelson formula [Spence and Kivelson, 1993], plasma sheet pressure from the GEOTAIL satellite, as well as anisotropic pressure profiles observed near Earth by AMPTE/CCE [Lui and Hamilton, 1992;De Michelis et al, 1999]. In all cases presented in this paper, we take the tilt of the Earth's magnetic axis to be zero for simplicity.…”

“…Among plasma sheet pressure measurements at distances |X| > 10 R E , we mention observations using ISEE spacecraft: ISEE1 [Huang and Frank, 1994] and ISEE2 [Spence et al, 1989;Angelopoulos et al, 1993]. Closer to Earth, where plasma pressure is generally bi-Maxwellian, we mention AMPTE/CCE [Lui and Hamilton, 1992;De Michelis et al, 1999] and AMPTE/IRM [Angelopoulos et al, 1993] measurements. Finally, probably the most extensive observations of plasma sheet pressure are those of the GEOTAIL mission [e.g., Hori et al, 2000].…”

“…In the computation we use observation-based pressure profiles and realistic boundary conditions as input. The results we present in this paper are obtained using plasma pressure in the plasma sheet from GEOTAIL observations [e.g., Hori et al, 2000], or along the midnight meridian in the equatorial plane, from the so-called Spence-Kivelson formula [Spence and Kivelson, 1993], as well as anisotropic pressure closer to Earth obtained from AMPTE/CCE measurements [Lui , 1993;Lui et al, 1994;De Michelis et al, 1999]. The computation is performed inside a domain defined by magnetic flux boundaries obtained from Tsyganenko's T96 and T01 empirical field models [Tsyganenko, 1995;Tsyganenko and Stern, 1996;Tsyganenko, 2002].…”