Science Applications for Soft X-ray Imaging Missions

Reconnection on the dayside magnetopause may be steady or impulsive, patchy or widespread, and occur at subsolar or other locations as predicted by the component, antiparallel, and maximum magnetic shear models. Both solar wind fluctuations and intrinsic magnetopause instabilities may trigger bursty reconnection. Each mode of reconnection generates characteristic plasma signatures. In particular, reconnection erodes the magnetopause either steadily or in a bursty manner, locally or globally, at locations that depend upon solar wind conditions. In situ observations provide evidence for each of the above interaction modes, but determining which mode predominates at any time requires global measurements in conjunction with simultaneous solar wind observations.

Forthcoming soft X-ray missions like CuPID, LEXI, and SMILE will return global observations of the line of sight integrated soft X-rays emitted by the charge exchange of high-state ions with exospheric neutrals in the cusps and magnetosheath from low-altitude, lunar, and high-altitude, high-apogee vantage points. Numerical simulations indicate that the boundaries of the magnetosphere and cusps will be clearly delineated in these observations as will the density structure within the cusps. This presentation describes how the soft X-ray images will be used to distinguish between proposed reconnection models.