Solar Wind Charge Exchange Process Research Articles

The SMILE Soft X-ray Imager (SXI) CCD design and development

SMILE, the Solar wind Magnetosphere Ionosphere Link Explorer, is a joint science mission between the European Space Agency and the Chinese Academy of Sciences. The spacecraft will be uniquely equipped to study the interaction between the Earth's magnetosphere-ionosphere system and the solar wind on a global scale. SMILE's instruments will explore this science through imaging of the solar wind charge exchange soft X-ray emission from the dayside magnetosheath, simultaneous imaging of the UV northern aurora and in-situ monitoring of the solar wind and magnetosheath plasma and magnetic field conditions. The Soft X-ray Imager (SXI) is the instrument being designed to observe X-ray photons emitted by the solar wind charge exchange process at photon energies between 200 eV and 2000 eV . X-rays will be collected using a focal plane array of two custom-designed CCDs, each consisting of 18 μm square pixels in a 4510 by 4510 array. SMILE will be placed in a highly elliptical polar orbit, passing in and out of the Earth's radiation belts every 48 hours. Radiation damage accumulated in the CCDs during the mission's nominal 3-year lifetime will degrade their performance (such as through decreases in charge transfer efficiency), negatively impacting the instrument's ability to detect low energy X-rays incident on the regions of the CCD image area furthest from the detector outputs. The design of the SMILE-SXI CCDs is presented here, including features and operating methods for mitigating the effects of radiation damage and expected end of life CCD performance. Measurements with a PLATO device that has not been designed for soft X-ray signal levels indicate a temperature-dependent transfer efficiency performance varying between 5×10−5 and 9×10−4 at expected End of Life for 5.9 keV photons, giving an initial set of measurements from which to extrapolate the performance of the SXI CCDs.

Simulations of solar wind charge exchange X‐ray emissions at Venus

A hybrid simulation of the solar wind‐Venus interaction and a test particle simulation of heavy ion trajectories near Venus are used to compute the contribution from solar wind charge exchange processes to the X‐ray emission from Venus. It is found that the X‐ray halo caused by the solar wind charge exchange process at Venus is confined to lower altitudes than at Mars, and that the structure on the ion gyro radius scale that is seen in X‐ray images of Mars is absent at Venus.

Simulations of X-rays from solar wind charge exchange at Mars: Parameter dependence

A hybrid simulation of the solar wind–Mars interaction and a test particle simulation of heavy ion trajectories near Mars are used to compute the contribution from solar wind charge exchange processes to the X-ray emission from Mars. Here, we study how the simulated X-ray emissions depend on the parameters of the simulation model. Solar wind parameters are estimated using a ballistic model based on data from the WIND satellite and using an MHD model that uses inputs from interplanetary scintillation measurements. These two models produce X-ray images with significantly different structure. The intensity of the X-ray emissions and the size of the X-ray halo are also found to increase with an increasing exobase neutral temperature.

X rays from solar wind charge exchange at Mars: A comparison of simulations and observations

A hybrid simulation of the solar wind‐Mars interaction and a test particle simulation of heavy ion trajectories near Mars are used to compute the contribution from solar wind charge exchange processes to the X‐ray emission from Mars. It is found that the X‐ray halo observed by the Chandra X‐ray observatory can be explained by emissions from heavy, highly charged, ions in the solar wind undergoing charge exchange collisions in the upper atmosphere of Mars.