Heating Mechanisms for Intermittent Loops in Active Region Cores from AIA/SDO EUV Observations
Abstract
We investigate intensity variations and energy deposition in five coronal loops in active region cores. These were selected for their strong variability in the AIA/SDO 94 Å intensity channel. We isolate the hot Fe XVIII and Fe XXI components of the 94 Å and 131 Å by modeling and subtracting the "warm" contributions to the emission. HMI/SDO data allow us to focus on "inter-moss" regions in the loops. The detailed evolution of the inter-moss intensity time series reveals loops that are impulsively heated in a mode compatible with a nanoflare storm, with a spike in the hot 131 Å signals leading and the other five EUV emission channels following in progressive cooling order. A sharp increase in electron temperature tends to follow closely after the hot 131 Å signal confirming the impulsive nature of the process. A cooler process of growing emission measure follows more slowly. The Fourier power spectra of the hot 131 Å signals, when averaged over the five loops, present three scaling regimes with break frequencies near 0.1 min-1 and 0.7 min-1. The low frequency regime corresponds to 1/f noise; the intermediate indicates a persistent scaling process and the high frequencies show white noise. Very similar results are found for the energy dissipation in a 2D "hybrid" shell model of loop magneto-turbulence, based on reduced magnetohydrodynamics, that is compatible with nanoflare statistics. We suggest that such turbulent dissipation is the energy source for our loops.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- November 2014
- DOI:
- 10.1088/0004-637X/795/1/48
- arXiv:
- arXiv:1404.7824
- Bibcode:
- 2014ApJ...795...48C
- Keywords:
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- Sun: corona;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- 22 pages, 8 figures