Solar wind

The solar wind is the continuous stream of energetic and ionized particles from the Sun that extends far into interplanetary space following the interplanetary magnetic field (IMF). The solar wind strongly interacts with magnetic fields of the planets and will often manifest itself as aurorae in the upper atmospheres of planets with magnetic fields. In the case of Mars, with a weak (often considered to be non-existent) global magnetic field, solar wind particles have greater penetration into the atmosphere creating a hazard to any future human settlements on the surface. The solar wind is often associated with Coronal Mass Ejections (CMEs), solar flares and coronal holes.

Characteristics

The solar wind is characterised as a constant flow of plasma from the chromosphere into interplanetary space. Understood to be bi-modal, the solar wind consists of two distinct streams. The fast solar wind travels at velocities of between 700-900 km/s and is associated with open magnetic flux (i.e. coronal holes located in solar polar regions). The slow solar wind travels at velocities of between 300-400 km/s and is located above equatorial closed magnetic flux regions (i.e. the streamer belt).

Effect on Mars

It is believed that the solar wind is responsible for stripping around one third of Mars' atmosphere away and into space. Partly due to the Martian atmosphere's inability to retain its atmospheric gases due to the lack of a planetary magnetic field and the sheer voracity of the flow of ionizing solar wind particles, the solar wind is a major culprit for the low atmospheric pressure measured at the surface.