Spatial structure and temporal evolution of energetic particle injections in the inner magnetosphere during the 14 July 2013 substorm event

TL;DR

This study analyzes a substorm event on 14 July 2013, revealing different types of energetic particle injections in the inner magnetosphere and emphasizing the importance of multipoint observations for understanding their spatial and temporal characteristics.

Contribution

It provides a detailed case study of energetic particle injections during a substorm, highlighting the diversity in injection signatures and the need for combined ground and satellite data.

Findings

Two distinct injection types observed with different signatures

Injections occur at various spatial and temporal scales

Multipoint observations are crucial for understanding injections

Abstract

Recent results by the Van Allen Probes mission showed that the occurrence of energetic ion injections inside geosynchronous orbit could be very frequent throughout the main phase of a geomagnetic storm. Understanding, therefore, the formation and evolution of energetic particle injections is critical in order to quantify their effect in the inner magnetosphere. We present a case study of a substorm event that occurred during a weak storm $\textit{ Dst }$ $\sim$ -40nT on 14 July 2013. Van Allen Probe B, inside geosynchronous orbit, observed two energetic proton injections within 10min, with different dipolarization signatures and duration. The first one is a dispersionless, short-timescale injection pulse accompanied by a sharp dipolarization signature, while the second one is a dispersed, longer-timescale injection pulse accompanied by a gradual dipolarization signature. We combined ground magnetometer data from various stations and in situ particle and magnetic field data from multiple satellites in the inner magnetosphere and near-Earth plasma sheet to determine the spatial extent of these injections, their temporal evolution, and their effects in the inner magnetosphere. Our results indicate that there are different spatial and temporal scales at which injections can occur in the inner magnetosphere and depict the necessity of multipoint observations of both particle and magnetic field data in order to determine these scales.