Evidence of the Earth's inner radiation belts during the low Solar and geomagnetic activity obtained with the STEP-F instrument

TL;DR

This study used the STEP-F instrument to identify and analyze a new, persistent inner radiation belt in Earth's magnetosphere during a period of low solar activity, revealing complex multi-belt structures.

Contribution

The paper reports the discovery of a new stable inner radiation belt at L≈1.65, alongside known belts, during low solar activity, using data from the STEP-F instrument.

Findings

Identified a new stable radiation belt at L≈1.65.

Observed simultaneous presence of multiple belts in May 2009.

Confirmed belts' presence across wide geographic longitudes.

Abstract

Purpose: The subject of research is the spatio-temporal charged particles in the Earth's magnetosphere outside the South Atlantic magnetic Anomaly during the 11-year cycle of solar activity minimum. The work aims at searching for and clarifying the sustained and unstable new spatial zones of enhanced subrelativistic electron fluxes at the altitudes of the low Earth orbit satellites. Design/methodology/approach: Finding and ascertainment of new radiation belts of the Earth were made by using the data analysis from the D1e channel of recording the electrons of energies of $\Delta E_e =180$-510 keV and protons of energies $\Delta E_p=3.5$-3.7 MeV of the position-sensitive silicon matrix detector and onto the solid angle of view of the detector head of the instrument was used. Findings: A sustained structure of three electron radiation belts in the Earth's magnetosphere was found at the low solar and geomagnetic activity in May 2009. The two belts are known since the beginning of the space age as the Van Allen radiation belts, and an additional permanent layer is formed around the drift shell with the McIlwaine parameter of $L\approx1.65$. On some days in May 2009, the two new inner radiation belts were observed simultaneously, one of those latter being recorded between the investigated sustained belt at $L\approx1.65$ and the Van Allen inner belt at $L\approx2.52$. Conclusions: The new found inner radiation belts are recorded in a wide range of geographic longitudes, both at the ascending and descending nodes of the satellite orbit. Key words: radiation belt, STEP-F instrument, electrons, magnetosphere, drift $L$-shell, particle flux density