Missing Links between the Solar Photospheric Magnetic Field and the Upper Atmosphere
Technical Report,17 Sep 2015,16 Sep 2017
SOLAR PHYSICS RESEARCH INC Aichi Japan
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To uncover missing links between the photosphere and the upper atmosphere, two approaches were taken-observational and theoretical. As the observational approach, full disk chromospheric magnetic field maps were synthesized using the 17 GHz image data taken by the Nobeyama Radioheliograph. It was found that extended enhanced magnetic field regions in the chromosphere are associated with radio brightness enhancement even outside active regions. Generally, association between magnetic enhancements at the photosphere and at the chromosphere associated with enhanced radio brightness is good but not always. To understand these relations, we need to understand mechanisms for radio brightness enhancement and magnetic field strength. As the theoretical approach, the magnetohydrodynamic theory MHD is revisited. The solar chromosphere is in the transition from the low to high plasma beta condition, or the gas pressure is not negligible relative to the magnetic pressure. However, the existing MHD theory is based on the assumption of low-beta. It is necessary to modify the existing MHD to be applicable to the high-beta plasma. For this purpose, magnetic moment of thermal plasma was calculated and added to the MHD equation. It has been believed that the magnetic moment is negligible in the thermal plasma due to the frequent collisions among particles and the random velocity distribution. However, it is shown that even under the highly collisional conditions and the random velocity distribution, the magnetic moment does exist and plays important roles in the solar atmosphere. By adding the magnetic moment to MHD, we can understand the lifting of hot plasma into the upper atmosphere against the gravity. Generally the magnetic field is weaker upwards, hence the magnetic Kelvin force acting on the magnetic moment is directed upward.
- Electricity and Magnetism