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Evidence of thermal conduction suppression in hot coronal loops: supplementary results

Published online by Cambridge University Press:  09 September 2016

Tongjiang Wang ,
Leon Ofman ,
Xudong Sun ,
Elena Provornikova  and
Joseph M. Davila
Tongjiang Wang
Affiliation:
Dept. of Physics, Catholic University of America, 620 Michigan Avenue NE, Washington, DC 20064, USA; email: [email protected] NASA Goddard Space Flight Center, Code 671, Greenbelt, MD 20770, USA
Leon Ofman
Affiliation:
Dept. of Physics, Catholic University of America, 620 Michigan Avenue NE, Washington, DC 20064, USA; email: [email protected] NASA Goddard Space Flight Center, Code 671, Greenbelt, MD 20770, USA
Xudong Sun
Affiliation:
W. W. Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA 94305, USA
Elena Provornikova
Affiliation:
Space Science Division, Naval Research Laboratory, Washington, DC 20375, USA
Joseph M. Davila
Affiliation:
NASA Goddard Space Flight Center, Code 671, Greenbelt, MD 20770, USA
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Abstract

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Slow magnetoacoustic waves were first detected in hot (>6 MK) flare loops by the SOHO/SUMER spectrometer as Doppler shift oscillations in Fe xix and Fe xxi lines. Recently, such longitudinal waves have been found by SDO/AIA in the 94 and 131 Å channels. Wang et al. (2015) reported the first AIA event revealing signatures in agreement with a fundamental standing slow-mode wave, and found quantitative evidence for thermal conduction suppression from the temperature and density perturbations in the hot loop plasma of ≳ 9 MK. The present study extends the work of Wang et al. (2015) by using an alternative approach. We determine the polytropic index directly based on the polytropic assumption instead of invoking the linear approximation. The same results are obtained as in the linear approximation, indicating that the nonlinearity effect is negligible. We find that the flare loop cools slower (by a factor of 2–4) than expected from the classical Spitzer conductive cooling, approximately consistent with the result of conduction suppression obtained from the wave analysis. The modified Spitzer cooling timescales based on the nonlocal conduction approximation are consistent with the observed, suggesting that nonlocal conduction may account for the observed conduction suppression in this event. In addition, the conduction suppression mechanism predicts that larger flares may tend to be hotter than expected by the EM-T relation derived by Shibata & Yokoyama (2002).

Keywords

Sun: Flares –- Sun: corona –- Sun: oscillations –- waves –- Sun: UV radiation
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 11 , Symposium S320: Solar and Stellar Flares and their Effects on Planets , August 2015 , pp. 202 - 208
Copyright
Copyright © International Astronomical Union 2016 

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