The Solar Wind

The solar wind is a flow of particles that comes from the Sun in every direction.  Because the Sun has such a high temperature, it has high pressure.  This high pressure pushes the particles out, creating the solar wind.

How does gravity fit into this?  Without gravity, all of the particles that make up the Sun would just fly out into space.  Gravity pulls the particles in while the pressure from the Sun tries to push them out.  But because the pressure is greater than the gravity, we have the solar wind.  You might think of it as a "leak" in gravity's force.

As the wind moves out from the Sun, it accelerates and gets less dense.  It covers more volume and cools as the particles hit each other less often.  This process is called adiabatic expansion because no energy is gained or lost.

There are two kinds of solar wind, the fast and the slow.   The difference in speed depends on where on the Sun the wind comes from.  The fast solar wind comes from coronal holes and extends toward the poles of the Sun, while the slow solar wind comes from the solar equator.

Another subject of recent interest in our research are pick-up ions.  Pick-up ions come about when neutral particles become ionized and are then swept into the heliosphere by the solar wind. The interstellar medium is the main source of these neutrals.  They can also be knocked off of interplanetary dust grains (and are then called inner source pick-up ions).