Comparison of energies between eruptive phenomena and magnetic field in AR 10930

Abstract

We present a study comparing the energy carried away by a coronal mass ejection (CME) and the radiative energy loss in associated flare plasma, with the decrease in magnetic free energy during a release in active region NOAA 10930 on December 13, 2006 during the declining phase of the solar cycle 23. The ejected CME was fast and directed towards the Earth with a projected speed of ∼1780 km s^{-1} and a de-projected speed of ∼3060 km s^{-1}. We regard these as lower and upper limits for our calculations. It was accompanied by an X3.4 class flare in the active region. The CME carried (1.2-4.5)×10^{32} erg (projected-deprojected) of kinetic and gravitational potential energy. The estimated radiative energy loss during the flare was found to be 9.04×10^{30} erg. The sum of these energies was compared with the decrease in measured free magnetic energy during the flare/CME. The free energy is that above the minimum energy configuration and was estimated using the magnetic virial theorem. The estimated decrease in magnetic free energy is large, 3.11×10^{32} erg after the flare/CME compared to the pre-flare energy. Given the range of possible energies we estimate that 50-100% of the CME energy arose from the active region. The rest of the free magnetic energy was distributed among the radiative energy loss, particle acceleration, plasma and magnetic field reorientation.