The magnetosheath at high spectral resolution

While we eagerly anticipate SMILE’s (Solar wind Magnetosphere Ionosphere Link Explorer) unprecedented X-ray observations of the Earth’s magnetosheath and the initiation of a new era of magnetospheric research, it seems appropriate to look ahead to the abilities of the next generation of astrophysics missions. Of these, the Line Emission Mapper (LEM), a large aperture micro-calorimeter based mission, is currently planned to be able to observe the magnetosheath at high spectral resolution (~2 eV). With a field of view of ~30′, LEM will allow higher spatial resolution and higher cadence measurement of the motion of a very small portion of the magnetopause over relatively short periods of time (multiple hours), complementing SMILE’s global mapping. LEM’s strength is its spectral resolution. It will be able to measure the abundance of a broad range of elements and ionization states, many of which are inaccessible to current in situ instruments, and will be able to separate the emission from the magnetosheath from the emission from the cosmic X-ray background using the difference in their relative velocities.