  We calculated the time evolution of the free magnetic energy during the
2014-Mar-29 flare (SOL2014-03-29T17:48), the first X-class flare detected by
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 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 $E_{free}(t_{peak}) \approx (45 \pm 2) \times 10^{30}$
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.
