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Is It Small-scale Weak Magnetic Activity That Effectively Heats the Upper Solar Atmosphere?  

K.J. Li   Submitted: 2018-07-09 18:59

Solar chromosphere and coronal heating is a big question for astrophysics. Daily measurement of 985 solar spectral irradiances (SSIs) at the spectral intervals 1-39 nm and 116-2416 nm during March 1 2003 to October 28 2017 is utilized to investigate phase relation respectively with daily sunspot number, the Mount Wilson Sunspot Index, and the Magnetic Plage Strength Index. All SSIs which form in the whole abnormally heated layer: the upper photosphere, chromosphere, transition region, and corona are found to be significantly more correlated to weak magnetic activity than to strong magnetic activity, and to dance in step with weak magnetic activity. All SSIs which form in the low photosphere, which indicate the ``energy" leaked from the solar subsurface are found to be more related to strong magnetic activity instead and in anti-phase with weak magnetic activity. In the upper photosphere and chromosphere, strong magnetic activity should lead SSI by about a solar rotation, also displaying that weak magnetic activity should take effect on heating there. It is thus small-scale weak magnetic activity that effectively heats the upper solar atmosphere.

Authors: K.J. Li, J.C. Xu, W. Feng
Projects: None

Publication Status: In press by ApJSS
Last Modified: 2018-07-11 15:23
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Solar-cycle related variation of solar differential rotation  

K.J. Li   Submitted: 2013-05-21 02:58

Solar-cycle related variation of differential rotation is investigated through analyzing the rotation rates of magnetic fields, distributed along latitudes and varying with time at the time interval of August 1976 to April 2008. More pronounced differentiation of rotation rates is found to appear at the ascending part of a Schwabe cycle than at the descending part on an average. The coefficient B in the standard form of differential rotation, which represents the latitudinal gradient of rotation, may be divided into three parts within a Schwabe cycle. Part one spans from the start to the 4th year of a Schwabe cycle, within which the absolute B is approximately a constant or slightly fluctuates. Part two spans from the 4th to the 7th year, within which the absolute B decreases. Part three spans from the 7th year to the end, within which the absolute B increases. Strong magnetic fields repress differentiation of rotation rates, so that rotation rates show less pronounced differentiation, but weak magnetic fields seem to just reflect differentiation of rotation rates. The solar-cycle related variation of solar differential rotation is inferred to the result of both the latitudinal migration of the surface torsional pattern and the repression of strong magnetic activity to differentiation of rotation rates.

Authors: K. J. Li, X. J. Shi, J. L. Xie, P. X. Gao, H. F. Liang, L. S. Zhan, W. Feng
Projects: None

Publication Status: accepted by MNRAS
Last Modified: 2013-05-22 08:52
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Internal-cycle variation of solar differential rotation  

K.J. Li   Submitted: 2013-05-19 19:34

The latitudinal distributions of the yearly mean rotation rates measured respectively by Suzuki in 1998 and 2012 and Pulkkinen & Tuominen in 1998 are utilized to investigate internal-cycle variation of solar differential rotation. The rotation rate at the solar Equator seems to decrease since cycle 10 onwards. The coefficient B of solar differential rotation, which represents the latitudinal gradient of rotation, is found smaller in the several years after the minimum of a solar cycle than in the several years after the maximum time of the cycle, and it peaks several years after the maximum time of the solar cycle. The internal-cycle variation of the solar rotation rates looks similar in profile to that of the coefficient B. A new explanation is proposed to address such a solar-cycle related variation of the solar rotation rates. Weak magnetic fields may more effectively reflect differentiation at low latitudes with high rotation rates than at high latitudes with low rotation rates, and strong magnetic fields may more effectively repress differentiation at relatively low latitudes than at high latitudes. The internal-cycle variation is inferred to the result of both the latitudinal migration of the surface torsional pattern and the repression of strong magnetic activity to differentiation.

Authors: K. J. Li, J. L. Xie, X. J. Shi
Projects: None

Publication Status: In press at ApJ Supplement Series, 206:1 (6pp), 2013
Last Modified: 2013-05-20 09:40
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Is It Small-scale Weak Magnetic Activity That Effectively Heats the Upper Solar Atmosphere?
Solar-cycle related variation of solar differential rotation
Internal-cycle variation of solar differential rotation

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