Dominance of Bursty over Steady Heating of the 4–8 MK Coronal Plasma in a Solar Active Region: Quantification Using Maps of Minimum, Maximum, and Average Brightness

A challenge in characterizing active region (AR) coronal heating is separating transient (bursty) loop from the diffuse background (steady) heating. We present a method of quantifying heating's bursty and steady components ARs, applying it to FeXVIII (hot94) emission an AR observed by SDO/AIA. The maximum, minimum, average brightness values for each pixel, over 24 hour period, yield maximum-brightness map, minimum-brightness average-brightness map AR. Running sets such three maps come repeating this process time step running windows 20, 16, 12, 8, 5, 3, 1 0.5 hours. From window's set maps, we obtain AR's corresponding luminosity light curves. find: (1) time-averaged ratio minimum-brightness-map average-brightness-map increases as window decreases, maximum-brightness-map decreases decreases. (2) For 24-hour window, map's 5% luminosity, indicating that at most hot94 (3) This upper limit on fraction 33% 30-minute window. requires 4--8 MK plasma mostly bursts lasting less than 30 minutes: third minutes.