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. The solar wind is often associated with Coronal Mass Ejections (CMEs), solar flares and coronal holes.

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. Like every other radioactive radiation it causes damage to material and health.

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).

I suppose that sounds and semlls just about right.

Counter Measures

Artificial magnetic field

The threat from solar wind can be managed through the generation of local magnetic fields. Recent research has shown that the size of the field need only be several hundred meters wide to provide protection to humans in space. This magnetic shield could be scaled up to protect an entire settlement on the surface.

Shielding

While shielding a space ship increases its mass and fuel consumption, the shielding of a Martian colony is much easier, since the mass is only limited by structural stability constraints.