Pitch Angle Measurement Method based on Detector Counts Distribution. -I. Basic conception

TL;DR

This paper introduces a new detector counts distribution method for measuring the pitch angle of charged particles using GECAM-style instruments, demonstrated through simulations and a specific electron precipitation event.

Contribution

A novel method based on detector counts distribution for pitch angle measurement with GECAM instruments is proposed and validated through simulation and a real event.

Findings

Feasibility demonstrated by a 90° pitch angle measurement

Method applicable to space particle event studies

Potential to study TEBs and LEPs

Abstract

As an X-ray and gamma-ray all-sky monitor aiming for high energy astrophysical transients, Gravitational-wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM) has also made a series of observational discoveries on burst events of gamma-rays and particles in the low Earth orbit. Pitch angle is one of the key parameters of charged particles traveling around geomagnetic field. However, the usage of the GECAM-style instruments to measure the pitch angle of charged particles is still lacking. Here we propose a novel method for GECAM and similar instruments to measure the pitch angle of charged particles based on detector counts distribution. The basic conception of this method and simulation studies are described. With this method, the pitch angle of a peculiar electron precipitation event detected by GECAM-C is derived to be about 90$^\circ$, demonstrating the feasibility of our method. We note that the application of this method on GECAM-style instruments may open a new window for studying space particle events, such as Terrestrial Electron Beams (TEBs) and Lightning-induced Electron Precipitations (LEPs).