On the Relation Between Soft Electron Precipitations in the Cusp Region and Solar Wind Coupling Functions

Abstract

In this study, the correlations between the fluxes of precipitating soft electrons in the cusp region and solar wind coupling functions are investigated utilizing the Lyon‐Fedder‐Mobarry global magnetosphere model simulations. We conduct two simulation runs during periods from 20 March 2008 to 16 April 2008 and from 15 to 24 December 2014, which are referred as “Equinox Case” and “Solstice Case,” respectively. The simulation results of Equinox Case show that the plasma number density in the high‐latitude cusp region scales well with the solar wind number density (ncusp/nsw=0.78), which agrees well with the statistical results from the Polar spacecraft measurements. For the Solstice Case, the plasma number density of high‐latitude cusp in both hemispheres increases approximately linearly with upstream solar wind number density with prominent hemispheric asymmetry. Due to the dipole tilt effect, the average number density ratio ncusp/nsw in the Southern (summer) Hemisphere is nearly 3 times that in the Northern (winter) Hemisphere. In addition to the solar wind number density, 20 solar wind coupling functions are tested for the linear correlation with the fluxes of precipitating cusp soft electrons. The statistical results indicate that the solar wind dynamic pressure p exhibits the highest linear correlation with the cusp electron fluxes for both equinox and solstice conditions, with correlation coefficients greater than 0.75. The linear regression relations for equinox and solstice cases may provide an empirical calculation for the fluxes of cusp soft electron precipitation based on the upstream solar wind driving conditions.

A Survey of Dense Low Energy Ions in Earth's Outer Magnetosphere: Relation to Solar Wind Dynamic Pressure, IMF, and Magnetospheric Activity

“…In support of the former, the simulation results of Damiano et al (2010) showed that increases in SW P lead to increased cusp electron precipitation, which effectively enhances the available supply of upflowing ions for outflow. Dang et al (2018) reported simulation results that implicate the solar wind pressure as the most important controlling factor of both the hemispheric precipitation rate and the hemispheric power of precipitating soft electrons in the cusp proper. A strong correlation between densities in the cusp and solar wind density was reported by Walsh et al (2016), which presents indirect observational evidence of a connection with SW P .…”

“…Dang et al. ( 2018 ) reported simulation results that implicate the solar wind pressure as the most important controlling factor of both the hemispheric precipitation rate and the hemispheric power of precipitating soft electrons in the cusp proper. A strong correlation between densities in the cusp and solar wind density was reported by Walsh et al.…”

Recent ionospheric investigations in China (2018–2019)

“…Based on high‐resolution Thermosphere Ionosphere Electrodynamics General Circulation Model (TIEGCM) simulations as well as on DMSP satellite observations,Dang T et al (2019) have reported the occurrence of double Tongues of Ionization (TOIs) (Figure 11) and carried out a comprehensive study of the dynamic evolution and formation mechanism of double TOIs. Predicting the cusp electron precipitation is important in investigating the dayside solar wind‐magnetosphere–ionosphere coupling process and in forecasting space weather phenomena Dang T et al (2018c). used the global MHD simulation to investigate the correlation between the fluxes of precipitating electrons in the cusp and the upstream solar wind conditions.…”