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Radio Emission from Acceleration Sites of Solar Flares  

Yixuan Li   Submitted: 2010-04-22 12:28

This Letter takes up the question of what radio emission is produced by electrons at the very acceleration site of a solar flare. Specifically, we calculate incoherent radio emission produced within two competing acceleration models?stochastic acceleration by cascading MHD turbulence and regular acceleration in collapsing magnetic traps. Our analysis clearly demonstrates that radio emission from acceleration sites (1) has sufficiently strong intensity to be observed by currently available radio instruments, and (2) has spectra and light curves that are distinctly different in these two competing models, which makes them observationally distinguishable. In particular, we suggest that some of the narrowband microwave and decimeter continuum bursts may be a signature of the stochastic acceleration in solar flares.

Authors: Yixuan Li, Gregory D. Fleishman
Projects: None

Publication Status: Published
Last Modified: 2010-04-23 08:59
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The change of magnetic inclination angles associated with the X3.4 flare on December 13, 2006  

Yixuan Li   Submitted: 2010-04-22 12:23

Recent studies showed a consistent pattern of changes in the sunspot structure associated with major flares: part of the peripheral penumbral regions vanishes during flares, and meanwhile, the umbral cores and/or inner penumbral regions are darkened. To understand the underlying physics of these observations, we compare the magnetic inclination angle in the decayed peripheral and the enhanced inner penumbral regions before and after the 4B/X3.4 flare of 2006 December 13 by using the high-resolution vector magnetograms from Hinode. We find that the mean inclination angle in the decayed penumbra increases after the flare while that in the enhanced penumbra near flaring neutral line decreases. The result confirms the previous idea that two components of a δ sunspot become connected after flares. As a result of new connection, peripheral penumbral fields change from a more inclined to a more vertical configuration and transverse fields in umbral core and inner penumbral regions increase substantially (Liu et al. 2005). The flare-associated changes of Doppler width as well as other parameters (the transverse field strength, continuum intensity and filling factor) are also presented.

Authors: YiXuan Li, Ju Jing, ChangYi Tan and HaiMin Wang
Projects: None

Publication Status: Published
Last Modified: 2010-04-23 08:59
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Radio Emission from Acceleration Sites of Solar Flares
The change of magnetic inclination angles associated with the X3.4 flare on December 13, 2006

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