Thermodynamic description of the dynamics of CMEs

We present a Thermodynamic analytical model that describes the dynamics of CMEs. Unlike the hydrodynamic treatment, the thermodynamic approach deals with the energy involved and one may calculate the work done by the different forces separately and sum all contributions to determine the changes in speed, which simplifies the problem and allows us to obtain fully rigorous results.

Our model considers the drag force, which dominates the dynamics of CMEs and the solar gravitational force, which has a much smaller effect, but it is, still, relevant enough to be considered.

We obtain explicit analytical expressions for the speed and temperatures of CMEs. The model is evaluated with a CME observed at three different heliocentric distances with three different spacecraft (SOHO, ACE an Ulysses), also, with a set of 11 CMEs observed with the SOHO, Wind and ACE spacecraft and with two events observed with the STEREO spacecraft. In all cases, we have a consistent agreement between the theoretical and the observed speeds and transit times. Additionally, for the set of 11 events, we estimate their temperatures at their departure position from their temperatures measured near the orbit of the Earth.