A Nanoflare Heating Model and Comparison with Observations

• Published in: The Astrophysical journal Vol. 703; no. 2; pp. 2118 - 2130
• Main Authors: Sakamoto, Yasushi, Tsuneta, Saku, Vekstein, Grigory
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 01.10.2009; IOP
• Subjects: Astronomy; ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; COMPUTERIZED SIMULATION; Earth, ocean, space; ELECTROMAGNETIC RADIATION; Exact sciences and technology; GAMMA RADIATION; IONIZING RADIATIONS; MAGNETIC FIELDS; MAIN SEQUENCE STARS; RADIATIONS; SIMULATION; SOFT X RADIATION; STARS; SUN; TELESCOPES; X RADIATION; Sun: flares; Gamma radiation; Sun: corona; Models; Sun: X-rays, gamma rays; Sun: activity; Sun
• ISSN: 0004-637X; 1538-4357
• DOI: 10.1088/0004-637X/703/2/2118

A nanoflare-heated coronal loop model is developed based on the model of Vekstein & Katsukawa. We performed numerical simulations based on the model, and then compared the results with the Yohkoh/Soft X-ray Telescope (SXT) and Transition Region and Coronal Explorer (TRACE) observations. We found that the most significant difference between hot (>2 MK) SXT loops and cool (~1 MK) TRACE loops is the energy of nanoflares and the magnetic field strength. Energy of individual nanoflares is 1024-25 erg for SXT loops, and 1023 erg for TRACE loops. This is derived from the observed intensity fluctuations. To observed mean intensities, we require the model SXT loops to have a stronger magnetic field than the TRACE loops, 40 G and 8 G, respectively. The model predicts two characteristic properties of nanoflare-heated coronal loops: (1) the SXT and TRACE light curves of a coronal loop show weak cross-correlation with a lag time corresponding to the cooling timescale. (2) SXT loops have a smaller volumetric filling factor than TRACE loops. We consider that this difference in the filling factor makes SXT loops look more diffuse than TRACE loops.