Adiabatic Invariants Calculations for Cluster Mission: A Long‐Term Product for Radiation Belts Studies

Abstract

The Cluster mission has produced a large data set of electron flux measurements in the Earth's magnetosphere since its launch in late 2000. Electron fluxes are measured using Research with Adaptive Particle Imaging Detector (RAPID)/Imaging Electron Spectrometer (IES) detector as a function of energy, pitch angle, spacecraft position, and time. However, no adiabatic invariants have been calculated for Cluster so far. In this paper we present a step‐by‐step guide to calculations of adiabatic invariants and conversion of the electron flux to phase space density (PSD) in these coordinates. The electron flux is measured in two RAPID/IES energy channels providing pitch angle distribution at energies 39.2–50.5 and 68.1–94.5 keV in nominal mode since 2004. A fitting method allows to expand the conversion of the differential fluxes to the range from 40 to 150 keV. Best data coverage for phase space density in adiabatic invariant coordinates can be obtained for values of second adiabatic invariant, K, ∼10 2, and values of the first adiabatic invariant μ in the range ≈5–20 MeV/G. Furthermore, we describe the production of a new data product “LSTAR,” equivalent to the third adiabatic invariant, available through the Cluster Science Archive for years 2001–2018 with 1‐min resolution. The produced data set adds to the availability of observations in Earth's radiation belts region and can be used for long‐term statistical purposes.

Medium Energy Electron Flux in Earth's Outer Radiation Belt (MERLIN): A Machine Learning Model

“…The same conclusion was drawn in Smirnov et al. (2020) by analyzing the long‐term phase space density (PSD) variations of low‐ μ electrons, indicating the importance of the substorm activity for radiation belts transport processes. For these reasons, we include both Kp and AE indices as inputs.…”

“…Furthermore, Smirnov et al (2019) reported the long-term positive correlation of electron flux at energies up to 400 keV with AE index along the solar cycles 23 and 24. The same conclusion was drawn in Smirnov et al (2020) by analyzing the long-term phase space density (PSD) variations of low-μ electrons, indicating the importance of the substorm activity for radiation belts transport processes. For these reasons, we include both Kp and AE indices as inputs.…”

Preliminary Statistical Comparisons of Spin‐Averaged Electron Data From Arase and Van Allen Probes Instruments

“…A currently active mission is the Exploration of Energization and Radiation in Geospace (ERG/Arase) project, launched in 2016 (Miyoshi, Shinohara, et al., 2018), which provides comparable instrumentation to RBSP and slightly extended sampling in L (discussed in Section 2). This opens up the possibility of direct comparisons between Arase and other long‐term missions in Earth's radiation belts and ring current at higher L, such as the Geostationary Operational Environmental Satellites (GOES: Davis, 2007), the Los Alamos National Laboratory geostationary satellites (LANL‐GEO/GEO: Reeves et al., 1997), and the recently background‐corrected Cluster electron measurements, already cross‐calibrated with the RBSP (Smirnov et al., 2019, 2020).…”

“…background-corrected Cluster electron measurements, already cross-calibrated with the RBSP (Smirnov et al, 2019(Smirnov et al, , 2020.…”

Energetic Charged Particles in the Terrestrial Magnetosphere: Cluster/RAPID Results

“…The method to calculate the adiabatic invariants and convert the RAPID/IES electron flux to PSD in the radiation belts was developed in Smirnov, Kronberg, et al. (2020). Figure 8 shows the long‐term behavior of low‐ electrons along ∼1.5 solar cycles and the 27‐day averaged F10.7 and AE indices.…”