Solar perturbations transits in Mercury exosphere

Abstract

The link existing between the dayside Na exospheric patterns of Mercury and the solar wind-magnetosphere-surface interactions is investigated thanks to the synergy of Earth-based observations with the THEMIS solar telescope and the in-situ measurements of the Interplanetary Magnetic Field (IMF) and proton fluxes at the magnetic cusp regions by MESSENGER. Frequently, two-peak patterns of variable intensity are observed, located at high latitudes in both hemispheres. Occasionally, Na signal is instead diffused above the sub-solar region. In a special case, the Na signal is diffused above the subsolar region, when the MESSENGER data detect the transit of two Coronal Mass Ejections (CMEs). Na emission patterns results to be clearly related to the solar wind conditions at Mercury. Hence, the Na exospheric patterns, observed from ground, could be considered as a natural monitor of solar disturbances when transiting near Mercury.