The Magnetic Properties of Heating Events on High-temperature Active-region Loops

Understanding the relationship between the magnetic field and coronal heating is one of the central problems of solar physics. However, studies of the magnetic properties of impulsively heated loops have been rare. We present results from a study of 34 evolving coronal loops observed in the Fe XVIII line component of 94 angstrom filter images obtained by the Atmospheric Imaging Assembly (AIA)/Solar Dynamics Observatory (SDO) from three active regions with different magnetic conditions. We show that the peak intensity per unit cross section of the loops depends on their individual magnetic and geometric properties. The intensity scales proportionally to the average field strength along the loop (B-avg) and inversely with the loop length (L) for a combined dependence of (B-avg/L)(0.52 +/- 0.13). These loop properties are inferred from magnetic extrapolations of the photospheric Helioseismic and Magnetic Imager (HMI)/SDO line-of-sight and vector magnetic field in three approximations: potential and two nonlinear force-free (NLFF) methods. Through hydrodynamic modeling (enthalpy-based thermal evolution loop (EBTEL) model) we show that this behavior is compatible with impulsively heated loops with a volumetric heating rate that scales as epsilon(H )similar to B-avg(0.)3 +/- 0.2 / L-0.(2 +/- 0.1 0.2).