摘要： For decades, unusual locations of the magnetopause under radial interplanetary magnetic field (IMF) have been reported in many studies using in situ satellite observations. These studies have shown that the magnetopause is expanded either over all magnetic local times (MLTs) on the dayside (global expansion) or just near the noon (bullet‐like expansion) during radial IMF conditions. With limited observations near the magnetopause, the type of the magnetopause expansion is still undetermined. In this study, 19 years of dayside geosynchronous magnetic field data obtained from Geostationary Operational Environmental Satellites (GOES) are statistically processed to infer the shape of the dayside magnetopause under radial IMF conditions. The MLT distributions of geosynchronous magnetic fields for radial IMF are compared with those for northward IMF with the correction of solar wind dynamic pressure distributions between two different IMF conditions. After removal of the solar wind dynamic pressure effect, we have found that the geosynchronous magnetic field for radial IMF is smaller than that for northward IMF over almost all MLTs on the dayside regardless of magnetic latitudes and seasons. The difference between geosynchronous magnetic fields for the northward and radial IMFs supports the suggestion that the dayside magnetopause is globally expanded during the radial IMF conditions. Key Points First MLT distribution of the magnetic field at geosynchronous orbit for radial IMF Smaller dayside geostationary magnetic field for radial than for northward IMF Globally expanded magnetopause on the dayside for radial IMF 出版者： Washington: Blackwell Publishing Ltd 出版日期： 2016-07 出處： Journal of geophysical research : Space physics (2013 - Present), 2016-07, Vol.121 (7), p.6480-6492 資源來源： Wiley Online Library 版權： 2016. American Geophysical Union. All Rights Reserved. 識別號： ISSN: 2169-9380 識別號： EISSN: 2169-9402 識別號： DOI: 10.1002/2016JA022772
