期刊
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
卷 127, 期 2, 页码 -出版社
AMER GEOPHYSICAL UNION
DOI: 10.1029/2021JA029589
关键词
radial IMF; Heppner-Maynard boundary; IMF Bx; S-M-I coupling
资金
- National Key Research and Development Plan of China [2018YFC1407305, 2018YFC1407304, 2018YFF01013706, 2021YFE0106400]
- National Natural Science Foundation of China [42030203, 41974185, 41974190, 41831072, 42074195, 41674169]
- Foundation of National Key Laboratory of Electromagnetic Environment [201801003]
- Natural Science Foundation of Jiangsu Province [BK20170952]
- Chinese Meridian Project
- International Cooperation Advance Research on Key Scientific Issues of the International Meridian Project [A131901W14]
- Institute of Applied Meteorology
This study presents a statistical analysis of the effect of radial interplanetary magnetic field (IMF BX) on the Heppner-Maynard Boundary (HMB) midnight latitude in the solar wind-magnetosphere-ionosphere (S-M-I) coupling. It is found that the IMF BX plays an important role in determining the HMB midnight latitude, which is negatively correlated with the magnitude of IMF BX and solar wind speed.
The effect of radial interplanetary magnetic field (IMF BX ${\mathrm{B}}_{\mathrm{X}}$) has been ignored in the solar wind-magnetosphere-ionosphere (S-M-I) coupling. We present a statistical study of IMF Bx effects on the Heppner-Maynard Boundary (HMB) midnight latitude calculated from SuperDARN measurements between January 2002 and December 2017. The HMB represents the equatorward extent of the ionospheric convection pattern and can be used as a proxy for the equatorward boundary of the auroral oval. That is, the HMB expands toward lower latitude when the level of S-M-I coupling is enhanced. It is found that the averaged HMB midnight latitudes during both sunward and antisunward radial IMFs are around 64-65 degrees magnetic latitude (MLAT). HMB midnight latitude is negatively correlated with the magnitude of IMF Bx as well as solar wind speed, while no significant trend is found between HMB midnight latitude and IMF Bz or By during radial IMF. For antisunward radial IMF, the relationship between upstream parameters and HMB is more dependent than in sunward radial direction. As the first long-term statistical study focused on HMB during radial IMF conditions, this work provides observational evidence that the IMF Bx plays an important role in the coupling process and the traditional coupling function could not be applicable in the case of radial IMF.
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