The Low Energy Particle (LEP) Experlment onboard the GEOTAIL Satellite.

Abstract

The low energy particle (LEP) instrument onboard GEOTAIL is designed to make comprehensive observations of plasma and energetic electrons and ions with fine temporal resolution in the terrestrial magnetosphere (mainly magnetotail) and in the interplanetary medium. It consists of three units of sensors (LEP-EA, LEP-SW and LEP-MS) and a common electronics (LEP-E). The Energy-per-charge Analyzers (EA) measure three-dimensional velocity distributions of electrons (with EA-e) and ions (with EA-i), simultaneously and separately, over the. energy-per-charge range of several eV/q to 43 keV/q. Emphasis in the EA design is laid on the large geometrical factor to measure tenuous plasma in the magnetotail with sufficient counting statistics in the high-time-resolution measurement. On the other hand, the Solar Wind ion analyzer (SW) has smaller geometrical factor, but fine angular and energy resolutions, to measure energy-per-charge spectra of the solar wind ions. In both EA and S W sensors, the complete three-dimensional velocity distributions can only be obtained in a period of four spins, while the velocity moments up to the third order are calculated onboard every spin period (nominally, 3 sec). The energetic-ion Mass Spectrometer (MS) can provide three-dimensional determinations of the ion composition. In this paper, we describe the instrumentation and present some examples of the inflight measurements.

Waves on the dusk flank boundary layer during very northward interplanetary magnetic field conditions: Observations and simulation

“…Figure 3a repeats the solar wind kinetic pressure of Figure 2 shifted 23 min to its Earth arrival time. The red traces in Figures 3b, 3c, 3d, 3f, 3g, and 3i correspond to plasma density, temperature, velocity, solar magnetospheric flow direction angles q and f, and plasma pressure, all measured by the Geotail LEP plasma experiment [Mukai et al, 1994] and shown at 12 s resolution. This experiment has separate instruments to measure the solar wind and the hot plasmas of the magnetosphere.…”

X lines in the magnetotail for southward and northward IMF conditions

“…The 12 s resolution data from Geotail magnetometer [Kokubun et al, 1994] and the low-energy particle (LEP) experiment [Mukai et al, 1994] have been collected from 1998 to 2005. The LEP data on Geotail are over the energy range of several eV to 43 keV.…”

Compressional Pc5 type pulsations in the morningside plasma sheet

“…From Geotail we use 12-sec averaged data from the Geotail magnetic field (Kokubun et al, 1994) and low energy particle experiment (Mukai et al, 1994).…”