Magnetospheric plasma regimes identified using Geotail measurements: 2. Statistics, spatial distribution, and geomagnetic dependence

Abstract

Abstract. We investigate the spatial distribution, solar-terrestrial correlation, and basic statistics of a long sequence of plasma regime identifications through the probability of observation P at downtail distances of-30 < Xagsm < 210 RE, in an aberrated GSM coordinate system. The data are from Geotail spacecraft measurements obtained from October 1992 through October 1994. Earth's local plasma environment has been classified into five principal plasma regimes: PS, the plasma sheet, LB, the lobe (vacuum lobe, with only trace plasma content), and BL, the magnetospheric boundary layer, which together comprise the magnetosphere proper, and MS, the magnetosheath, and SW, the nearby solar wind. Eastman et al.

<title>Charged particle environment for NGST: model development</title>

“…Many of the distinctions between components of individual regions (i.e., the central plasma sheet, plasma sheet, and plasma sheet boundary layer) are difficult to assign to the L2 plasma environment. However, the main magnetotail regions identified in the near Earth magnetotail shown in Figure lb are clearly identifiable at L2 [2,3,4]. These include the boundary layer (including the plasma mantle, lobe, low latitude boundary layer), plasma sheet (including the central plasma sheet, boundary plasma sheet, and neutral sheet).…”

“…Greater variations in orientation of the magnetotail (Figures 2b and 2c) can occur due to changes in the solar wind flow. At downtail distances greater than 125 RE from the Earth, the magnetosheath is frequently observed near the XGSE axis [4,5]. One cannot simply assume, therefore, that L2 is located in the magnetotail because the motion of the tail regularly moves the magnetotail far from the Sun-Earth line.…”

“…Second, the original determination of the number density, velocity, and temperatures from the IMP-8 and Geotail data are obtained by implementing a numerical integration of the velocity moments < v >= vf1 (vk )iv (4) where the distribution function f1(vk ) is the velocity distribution function for the i species obtained by the instrument at a discrete set of Vk velocities. The observed distribution function need not necessarily be a Maxwellian to implement this algorithm.…”

What Controls the Structure and Dynamics of Earth’s Magnetosphere?

“…The overall structure of the distant magnetotail has been mapped out by Geotail and ISEE-3 with the basic structure extending to at least 240R E (Fairfield 1992;Christon et al 1998). Further observations far downstream of the Earth in the solar wind indicate that signatures of the magnetotail may persist and extend to 3100R E from the Earth (Intriligator et al 1979).…”

“…The plasma sheet is predominantly a hydrogen plasma (e.g., Haaland et al 2010), but can contain oxygen, especially during active times (e.g., Moore and Horwitz 2007). The locations of these regions have been mapped out by several different satellites (e.g., Christon et al 1998).…”