High‐Latitude Neutral Density Structures Investigated by Utilizing Multi‐Instrument Satellite Data and NRLMSISE‐00 Simulations

Abstract

AbstractThis study investigates various types of neutral density features developed in the cusp region during magnetically active and quiet times. Multi‐instrument Challenging Minisatellite Payload data provide neutral density, electron temperature, neutral wind speed, and small‐scale field‐aligned current (SS‐FAC) values. Gravity Recovery and Climate Experiment neutral density data are also employed. During active times, cusp densities or density spikes appeared with their underlying flow channels (FCs) and enhanced SS‐FACs implying upwelling, fueled by Joule heating, within/above FCs. Both the moderate nightside cusp enhancements under disturbed conditions and the minor dayside cusp enhancements under quiet conditions developed without any underlying FC and enhanced SS‐FACs implying the role of particle precipitation in their development. Observations demonstrate the relations of FCs, density spikes, and upwelling‐related divergent flows and their connections to the underlying (1) dayside magnetopause reconnection depositing magnetospheric energy into the high‐latitude region and (2) Joule heating‐driven disturbance dynamo effects. Results provide observational evidence that the moderate nightside cusp enhancements and the minor dayside cusp enhancements detected developed due to direct heating by weak particle precipitation. Chemical compositions related to the dayside density spike and low cusp densities are modeled by Naval Research Laboratory Mass Spectrometer Incoherent Scatter Radar Extended 2000. Modeled composition outputs for the dayside density spike's plasma environment depict some characteristic upwelling signatures. Oppositely, in the case of low dayside cusp densities, composition outputs show opposite characteristics due to the absence of upwelling.