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Group on the physics of the solar corona and solar wind

Research Interests

How  is the Sun’s atmosphere heated to multi-million degrees Kelvin? Despite  its long history, this question still remains to be addressed. While  the ultimate energy source is undoubtedly due to mechanical motions in  the convection zone, there is no consensus as to how this energy is  channeled to and then deposited in the solar atmosphere. With the  availability of high-cadence, high-spatial-resolution instruments such  as Hinode/SOT, SDO/AIA and IRIS, there has arisen an idea that  magnetohydrodynamic (MHD) waves are the sought-after energy carrier, and  solar atmospheric heating is then a result of their energy being  transformed into heat. Indeed, observations indicate that the energy  flux density carried by various waves is sufficient from the energy  budget perspective.

 

The  applicability of a wave-heating scenario hinges on a number of things.  First, their energy-carrying capability is sensitive to the physical  parameters of magnetized structures hosting these waves. These  parameters are, however, not easy to directly measure. Second, different  wave modes need to be dissipated in different ways. A pre-requisite is  then to identify the nature of waves in various structures on the Sun.  For this purpose, theories of MHD waves accounting for the highly  inhomogeneous nature of the Sun’s atmosphere are needed but are far from  complete.

 

Our group adopts the following approaches to address the issue of solar atmospheric heating.

l  We  develop MHD wave theories that incorporate such effects as transverse  and longitudinal structuring. This is then followed by applications of  wave theories to the inference of solar atmospheric parameters.

l  We  conduct analytical and numerical studies on MHD waves in the highly  structured solar atmosphere to examine their generation, propagation and  dissipation.

 

With  the solar corona reaching temperatures over a million Kelvin, the solar  atmosphere in open magnetic field regions cannot stay static but will  expand. This coronal expansion, or more precisely the solar wind, is  actually a result of solar atmospheric heating. Nonetheless, the solar  wind itself is also an important subject to work on, given their rich  measurements made both in situ and from remote-sensing. A popular idea  is that while propagating outwards, MHD waves somehow become turbulent,  and their energy is then picked up by solar wind species.

 

Our  group has developed, in collaboration with others, a multi-fluid MHD  code for the solar corona and solar wind. We treat different species on  an equal footing by solving their transport equations. The methodology  is that, with a given description for turbulence, we can then ask  whether our model output can reproduce solar wind measurements. In this  sense, the multi-fluid code can be seen as a quantitative testbed of  turbulence theory.

 

Group Members

Head: Prof. Dr. Bo Li (http://space.wh.sdu.edu.cn/bencandy.php?fid=36&id=558 , where you can find an always up-to-date list of Bo’s publications)

Faculty members: Dr. Shaoxia Chen, Dr. Hui Yu

Postdoctoral Scientists: Dr. Chong Huang

Graduate students: Haixia Xia, Mingzhe Guo, Zhipeng Wangguan

 

Current Research Grants

  1. Properties  and heating efficiencies of fast kink waves in spicules in solar  coronal holes, National Science Foundation of China (NSFC), about CNY  800k, 2017.01-2020.12

  2. Reliability  of seismological tools for deducing solar coronal parameters using  damped transverse waves, NSFC, CNY 900k, 2015.01-2018.12

  3. A  multifluid Magnetohydrodynamic approach for modeling the thermodynamics  of coronal mass ejections, NSFC, CNY 800k,  2013.01-2016.12



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