Observations of Magnetospheric Solar Wind Charge Exchange

Abstract

The study of solar wind charge exchange (SWCX) emission is vital to both the X-ray astrophysics and heliophysics communities. SWCX emission contaminates all astrophysical observations in X-rays regardless of the direction. Ignoring this contribution to X-ray spectra can lead to erroneous conclusions regarding the astrophysical plasmas along the line of sight owing to the similar spectral distributions of SWCX and several common types of more distant astrophysical plasmas. Since its discovery, the literature has distinguished between diffuse SWCX emission resulting from solar wind–neutral interactions within Earth’s magnetosphere, called magnetospheric SWCX, and similar interactions occurring more generally throughout the heliosphere, called heliospheric SWCX. Here we build on previous work validating a modeling method for the heliospheric SWCX contribution in X-ray spectra obtained with a medium-resolution CubeSat instrument named HaloSat at low ecliptic latitudes. We now apply this model to a specially designed set of extended observations with the same instrument and successfully separate the spectral contributions of the astrophysical background and the heliospheric SWCX from the remaining contributions. Specifically, we find significant excess emission for four observations in the O vii emission line not explained by other sources, possibly indicative of magnetospheric SWCX. We discuss these results in comparison with simulation results publicly available through the Community Coordinated Modeling Center. We also report an absorbed high-temperature component in 2 of the 12 fields of view analyzed.

Keywords

• Solar wind
• Diffuse x-ray background