Electron intensity measurements by the Cluster/RAPID/IES instrument in Earths radiation belts and ring current

TL;DR

This paper develops and validates background correction algorithms for electron flux data from the Cluster/RAPID/IES instrument, enabling more accurate analysis of Earth's radiation belts and ring current over solar cycles.

Contribution

It introduces two novel background correction algorithms for IES electron data, improving data accuracy for inner-magnetospheric science.

Findings

Corrected IES data closely match Van Allen Probes measurements.

Yearly IES electron intensities correlate with AE index and solar wind pressure.

Derived a linear-log relationship between solar wind pressure and electron fluxes.

Abstract

The Cluster mission, launched in 2000, has produced a large database of electron flux intensity measurements in the Earths magnetosphere by the Research with Adaptive Particle Imaging Detector (RAPID)/ Imaging Electron Spectrometer (IES) instrument. However, due to background contamination of the data with high-energy electrons (>400 keV) and inner- zone protons (230-630 keV) in the radiation belts and ring current, the data have been rarely used for inner-magnetospheric science. The current paper presents two algorithms for background correction. The first algorithm is based on the empirical contamination percentages by both protons and electrons. The second algorithm uses simultaneous proton observations. The efficiencies of these algorithms are demonstrated by comparison of the corrected Cluster/RAPID/IES data with Van Allen Probes/Magnetic Electron Ion Spectrometer (MagEIS) measurements for 2012-2015. Both techniques improved the IES electron data in the radiation belts and ring current.Yearly averaged flux intensities of the two missions show the ratio of measurements close to 1. IES corrected measurements were also compared with Arase Medium-Energy Particle Experiments-Electron Analyzer (MEP-e) electron data during two conjunction periods in 2017 and also exhibited ratio close to 1. We demonstrate a scientific application of the corrected IES electron data analyzing its evolution during solar cycle. Spin-averaged yearly mean IES electron intensities in the outer belt for energies 40-400 keV at L-shell between 4 and 6 showed high positive correlation with AE index and solar wind dynamic pressure during 2001- 2016. Relationship between solar wind dynamic pressure and IES electron measurements in the outer radiation belt was derived as a uniform linear-logarithmic equation.