A stream of charged particles
The solar wind is a plasma, a stream of charged particles (ions and electrons) which are continuously escaping from the Sun into the interplanetary medium. The particles can escape from the hold of the Sun because the solar corona consists of a very hot plasma of which the temperature exceeds millions of degrees.
Solar wind – magnetosphere interaction
To understand the perturbations of the magnetosphere by the solar wind, we need to know the properties of the solar wind itself. By the way, this solar wind also affects the other bodies in our Solar System.
At the BIRA-IASB, we have developed detailed models that describe the behaviour of the solar wind.
With those models we try to understand why the solar wind (which is, in fact, the outermost part of the solar atmosphere) is so hot, and why it is flowing so fast (up to 800 km/s and more).
The solar wind collides head-on with the magnetosphere. The collision zone constitutes the outermost boundary of the magnetosphere.
At the BIRA-IASB, we use spacecraft observations, especially by the four Cluster satellites of the European Space Agency, to study the behaviour of that boundary. It is indeed important to know how much matter and energy can penetrate from the solar wind through that boundary into the magnetosphere.
At times of strong perturbations of the solar wind (during periods of strong solar activity) such transfers of mass and energy can cause magnetic storms, dramatic temporary changes in the structure of the magnetosphere.