On forbidden high-energy electrons as a source of background in X-ray and gamma-ray observations

TL;DR

This paper investigates how high-energy electrons in forbidden zones significantly contaminate X-ray and gamma-ray measurements on low-orbiting satellites, especially during geomagnetic storms.

Contribution

It provides the first detailed analysis of electron flux enhancements in the forbidden zone and their impact on astrophysical measurements.

Findings

Electron fluxes in the 100-300 keV range can increase by several orders of magnitude during geomagnetic storms.

Enhancements occur at any local time and are linked to high substorm activity.

Forbidden zone electrons are a significant source of background contamination for space-based X-ray and gamma-ray observations.

Abstract

The study is devoted to a problem of electron-induced contaminant to X-ray and gamma-ray astrophysical measurements on board low-orbiting satellites. We analyzed enhancements of electron fluxes in energy range 100 - 300 keV observed at equatorial and low latitudes by a fleet of NOAA/POES low-orbiting satellites over the time period from 2003 to 2005. It was found that 100-300 keV electron fluxes in the forbidden zone below the inner radiation belt enhanced by several orders of magnitude during geomagnetic storms and/or under strong compressions of the magnetosphere. The enhancements are related to high substorm activity and occurred at any local time. Intense fluxes of the energetic electrons in the forbidden zone can be considered as an essential contaminant to X-ray and gamma-ray measurements at low-latitude and low-altitude orbits.