[This post participates in the Carnival of Space #190 at Centauri Dreams]

In the plasma the ions move in opposite direction to the electrons. The total I current is the sum of the positive and negative currents. As the electrons and ions have opposite charge, the gas is neutral and its behavior is like a fluid.
It is called magnetic pressure to the pressure that acts in a magnetic field in all directions.
In the Sun, plasma Beta (β) is the ratio of gas pressure to magnetic pressure:

– β > 1 : Gas pressure is greater than magnetic pressure, and magnetic field follows the motion of the plasma. These values can be found in the Photosphere at base of field lines, in the upper corona and in the solar wind acceleration region.
– β < 1 : Magnetic pressure is greater than gas pressure and plasma follows the motion of magnetic field. These values can be found in mid corona.
– β = 1 : Neither magnitude field nor plasma dominates de motion. This value can be found in upper corona, super corona and in the chromosphere.
Starting at β >1 in the photosphere, it decreases towards mid corona, and at this point it changes the tendency, increasing again the value.
More information in the post about CMEs and solar flares.