The Magnetic Electron Ion Spectrometer (MagEIS) Instruments Aboard the Radiation Belt Storm Probes (RBSP) Spacecraft

Abstract

This paper describes the Magnetic Electron Ion Spectrometer (MagEIS) instruments aboard the RBSP spacecraft from an instrumentation and engineering point of view. There are four magnetic spectrometers aboard each of the two spacecraft, one low-energy unit (20-240 keV), two medium-energy units (80-1200 keV), and a high-energy unit (800-4800 keV). The high unit also contains a proton telescope (55 keV-20 MeV).The magnetic spectrometers focus electrons within a selected energy pass band upon a focal plane of several silicon detectors where pulse-height analysis is used to determine if the energy of the incident electron is appropriate for the electron momentum selected by the magnet. Thus each event is a two-parameter analysis, an approach leading to a greatly reduced background.The physics of these instruments are described in detail followed by the engineering implementation. The data outputs are described, and examples of the calibration results and early flight data presented.

Prompt energization of relativistic and highly relativistic electrons during a substorm interval: Van Allen Probes observations

“…In Figure 4, we present electron flux observations measured by the REPT and magnetic electron ion spectrometer (MagEIS) [Blake et al, 2012] instruments, both from the RBSP-B energetic particle, composition, and thermal plasma (ECT) instrument suite [Spence et al, 2013]. These clearly indicate the timing and extent of electron energization associated with the substorm onset.…”

Investigation of EMIC wave scattering as the cause for the BARREL 17 January 2013 relativistic electron precipitation event: A quantitative comparison of simulation with observations

“…Probes A and B observed very similar features, due to the proximity of the two spacecraft during this day. We analyze the electron flux measurements from the Relativistic Electron Proton Telescope (REPT) [Baker et al, 2013] and the Magnetic Electron Ion Spectrometer (MagEIS) [Blake et al, 2013] of the Energetic Particle, Composition, and Thermal Plasma suite [Spence et al, 2013]. Since the calibration efforts on REPT remain ongoing, we use a simple linear adjustment factor in the instrument overlap region to match the flux observed by REPT with MagEIS and plot in Figure 3a both electron fluxes as a function of pitch angle.…”

Relativistic electron response to the combined magnetospheric impact of a coronal mass ejection overlapping with a high‐speed stream: Van Allen Probes observations

“…On board each spacecraft (probes A and B), the Relativistic Electron Proton Telescope (REPT) measures electrons in the range ≈1.5-20 MeV and the medium-and high-energy units of the Magnetic Electron and Ion Sensor (MagEIS) instrument cover electrons from ≈80-4800 keV [Blake et al, 2013]. The two instruments are part of the Energetic Particle, Composition, and Thermal Plasma suite [Spence et al, 2013].…”

“…MagEIS and REPT measure particle count rates and direction of arrival, which are then converted into particle fluxes and pitch angles using the known instrument characteristics such as geometry factors and the local direction of the geomagnetic field Blake et al, 2013]. In order to differentiate between the physical processes of radial transport and in situ energization, it is necessary to transform the flux and pitch angle measurements into phase space density (PSD), f , defined as f (W, , r) = j(W, , r)∕p 2 , where j is the measured differential directional flux and is a function of the particle energy W, pitch angle , spatial location r, and particle momentum p. In order to understand the physical process of electron energization, the electron PSD must be transformed and expressed in terms of the three adiabatic invariants of particle motion in the geomagnetic field, viz., , K, and L * [Schulz and Lanzerotti, 1974] which correspond to gyrational motion about the magnetic field, bounce motion along the field lines, and drift motion around the Earth, respectively.…”