Finding Magnetopause Standoff Distance using a Soft X-ray Imager - Part
2: Methods to Analyze 2-D X-ray Images
Abstract
The Earth’s magnetosheath and cusps are the sources of soft X-rays. In
the accompanying paper (Part 1) and this paper, we discuss the methods
of finding the magnetopause position by analyzing the X-ray images. We
use the software developed for the Soft X-ray Imager (SXI) on board the
forthcoming Solar wind - Magnetosphere - Ionosphere Link Explorer
(SMILE) mission. We show how to find the maximum SXI count rate in noisy
count maps. We verify the assumption that the maximum of the X-ray
emissivity integrated along the Line-of-Sight (Ix) is tangent to
the magnetopause. We consider two cases using two MHD models and apply
different methods of magnetospheric masking. Overall, the magnetopause
is located close to the maximum Ix gradient or between the
maximum Ix gradient and the maximum Ix depending on the
method used. But since the angular distance between the maximum
Ix gradient and the maximum Ix is relatively small (about
3{degree sign}), the maximum Ix might be used as an indicator
of the outer boundary of a wide magnetopause layer usually obtained in
MHD simulations.