Remote sensing of mercury sodium exospheric patterns in relation to particle precipitation and interplanetary magnetic field.

The ground-based solar telescope THEMIS performed several observations of Mercury's sodium exosphere in years 2011-2013, when the MESSENGER spacecraft was orbiting around the planet. Typical two-peak exospheric patterns were frequently identified. In previous studies, some specific cases of THEMIS Na two-peak observations were characterized and related to IMF conditions, during specific extreme cases, in the occasion of CME arrival.

Mercury sodium exospheric emission as a proxy for solar perturbations transit.

The first evidence at Mercury of direct relation between ICME transit and Na exosphere dynamics is presented, suggesting that Na emission, observed from ground, could be a proxy of planetary space weather at Mercury. The link existing between the dayside exosphere Na patterns and the solar wind-magnetosphere-surface interactions is investigated. This goal is pursued by analyzing the Na intensity hourly images, as observed by the ground-based THEMIS solar telescope during 10 selected periods between 2012 and 2013 (with seeing, σ < = 2″), when also MESSENGER data were available.