Magnetic energy dissipation during the 2014 March 29 solar flare

We calculated the time evolution of the free magnetic energy during the 2014 March 29 flare (SOL2014 March 29T17:48), the first X-class flare detected by the Interface Region Imaging Spectrograph (IRIS). The free energy was calculated from the difference between the nonpotential field, constrained by the geometry of observed loop structures, and the potential field. We use Atmospheric Imager Assembly (AIA)/SDO and IRIS images to delineate the geometry of coronal loops in EUV wavelengths, as well as to trace magnetic field directions in UV wavelengths in the chromosphere and transition region. We find an identical evolution of the free energy for both the coronal and chromospheric tracers, as well as agreement between AIA and IRIS results, with a peak free energy of $E_{free}\left(t_{peak}\right)\approx (45\pm 2)\times {10}^{30}$ erg, which decreases by an amount of $\Delta E_{free}\approx (29\pm 3)\times {10}^{30}$ erg during the flare decay phase. The consistency of free energies measured from different EUV and UV wavelengths for the first time here, demonstrates that vertical electric currents (manifested in form of helically twisted loops) can be detected and measured from both chromospheric and coronal tracers.