Neutral Atom Imaging of the Solar Wind-Magnetosphere-Exosphere Interaction Near the Subsolar Magnetopause.

S A Fuselier,A Galli,M A Dayeh,S Toledo‐Redondo,D J Mccomas,K J Trattner,H O Funsten,J L Burch,N A Schwadron,S M Petrinec,R J Strangeway,J R Szalay

doi:10.1029/2020gl089362

Abstract

Energetic neutral atoms (ENAs) created by charge‐exchange of ions with the Earth's hydrogen exosphere near the subsolar magnetopause yield information on the distribution of plasma in the outer magnetosphere and magnetosheath. ENA observations from the Interstellar Boundary Explorer (IBEX) are used to image magnetosheath plasma and, for the first time, low‐energy magnetospheric plasma near the magnetopause. These images show that magnetosheath plasma is distributed fairly evenly near the subsolar magnetopause; however, low‐energy magnetospheric plasma is not distributed evenly in the outer magnetosphere. Simultaneous images and in situ observations from the Magnetospheric Multiscale (MMS) spacecraft from November 2015 (during the solar cycle declining phase) are used to derive the exospheric density. The ~11–17 cm−3 density at 10 RE is similar to that obtained previously for solar minimum. Thus, these combined results indicate that the exospheric density 10 RE from the Earth may have a weak dependence on solar cycle.

Highlights

In November‐December 2015, the spacecraft apogee was near the subsolar point, providing many opportunities for conjunctions with Interstellar Boundary Explorer (IBEX) remotely imaging the subsolar magnetopause while Magnetospheric Multiscale (MMS) observed the plasma in situ
JENA(E, x, z) is the column integrated Energetic neutral atoms (ENAs) flux that depends on energy and the x,z Geocentric Solar Ecliptic (GSE) coordinates, Jion(E, x, y, z) is the magnetosheath/boundary layer ion flux that depends on GSE coordinates, σ(E) is the energy‐dependent charge‐exchange cross section
Plasma fluxes below 0.1 keV derived from ENA imaging must be considerably higher than average fluxes measured in situ at a single point and time by MMS

Summary

Introduction—The Subsolar Magnetopause

The Earth's magnetopause separates magnetospheric and shocked solar wind plasmas. It is approximately a paraboloid of revolution around the Earth‐Sun line with a subsolar standoff distance of ~10 Earth Radii (RE) for 1.5 nPa solar wind dynamic pressure. One of these is a ~10s to 100s of eV population of H+ and higher energy O+ called the warm plasma cloak (Chappell et al, 2008) This population originates in the high‐latitude ionosphere and is often found near the noon/duskside magnetopause (Fuselier et al, 2017). H+ is a magnetospheric or magnetosheath proton, H0 is an exospheric hydrogen atom, HENA is a (neutral) ENA, and H+* is a newly created, very cold (

IBEX and MMS Observations

Observations on 4 November 2015

Combined ENA and In Situ Observations

Discussion and Conclusions

Findings

Data Availability Statement