Deriving the magnetopause position from wide field-of-view soft x-ray imager simulation

Imaging techniques provide essential information in astronomical and space physics studies. The Soft X-ray imager (SXI) will obtain images of the Earth’s magnetosphere from solar wind charge exchange emission in a global view. However, it is a challenge to reconstruct its 3-D structures from the observed 2-D image(s). Solar wind Magnetosphere Ionosphere Link Explorer (SMILE) will have a Soft X-ray Imager (SXI) onboard, which is a powerful tool to study the geo-space environment under various solar wind conditions. SMILE will be launched around the year 2024 and operate in a highly inclined elliptical orbit. This orbit is ~20 R_E at apogee and will allow SMILE to make clear and quasi-continuous observations of key regions in near-Earth space with remote sensing instrument. As one of the four payloads, SXI will provide macro-scale magnetopause images near subsolar region (field of view is 16°×27°).

So far, several approaches had been developed to reconstruct the 3-D magnetopause from such 2-D images. Each method has its own applicable situation. Recently, Sun et al. (2020) proposed the Tangent Fitting Approach (TFA). It enables the reconstruction of the 3-D magnetopause from a single X-ray image by finding the optimum match of the tangent directions. We apply TFA to SXI photon count images by using instrument simulation, considering the effects of instrument and X-ray background noises. It validates the capability of TFA to reconstruct magnetopause under different solar wind conditions and various viewing geometries.

Researchers validated the efficiency of TFA to reconstruct the 3-D magnetopause, especially the subsolar magnetopause position, in some typical solar wind conditions and vantage viewing geometries by using SXI simulation data. Based on the SXI simulation of the X-ray photon images, the series scatter diagram of max photon counts for each line in SXI simulation result can be used to reconstruct the position of magnetopause.

Reference：

Sun T R, Wang C, Connor H K, Jorgensen A M, Sembay S. 2020. Deriving the magnetopause position from the soft X-ray image by using the tangent fitting approach. J Geophys Res-Space Phys, 125: e28169

See the article:

Guo Y, Sun T, Wang C, Sembay S. 2022. Deriving the magnetopause position from wide field-of-view soft X-ray imager simulation. Science China Earth Sciences,  65: 1601–1611(2022), https://doi.org/10.1007/s11430-021-9937-y