学术讲座公告--- IMF BZ dependence of EMIC wave occurrence in the magnetosphere: THEMIS observations

  • 发布时间:[2017-06-22] 来源:[学院] 点击量:[2636]

报告时间:2017年6月26日(周一)下午15:00 
报告地点:学院303会议室 
报告题目:IMF BZ dependence of EMIC wave occurrence in the magnetosphere: THEMIS observations
报告人:Dr. Jong-Sun Park
报告主题简介:
We investigate the L-MLT (i.e., L-shall versus magnetic local time) distributions of electromagnetic ion cyclotron (EMIC) waves, using the Time History of Events and Macroscale Interactions during Substorms (THEMIS) data from 2009 to 2014, under the prolonged (more than four hours) intervals of northward and southward interplanetary magnetic fields (IMFs). In H-band EMIC waves, the high occurrence region is located in the dawn-to-postnoon sector (0400-1600 MLT) at L > ~7 for northward IMFs. For southward IMFs, on the other hand, H-band EMIC waves occur in the morning-to-afternoon sector (0700-1500 MLT), and no strong wave activity is found in the dawn sector (0400-0700 MLT). The preferential location for H-band EMIC wave activities is shown to be located in the region where the ambient temperature anisotropy for the low portion of the energetic ions (< 25 keV) is high. In He-band EMIC waves, the high occurrence region is located in the noon dusk sector for both IMF BZ conditions. In the dusk sector, however, the high occurrence region is shifted into the inner L-shell (L < 8) for southward IMFs in comparison with that for northward IMFs (L < 10). He-band EMIC waves are shown to be generated in the region where the cold plasma density is high (especially near the plasmapause). Overall, EMIC waves in both frequency bands are lower for southward IMFs than those for northward IMFs. We suggest that this result is likely associated with the increase of O+ ion concentration, which leads to the reduction of the wave growth rate above O+ ion gyrofrequency, for southward IMFs.

 报告人简介:
‧2011-2015 Ph.D, Kyung-Hee University, Korea
–Magnetospheric current systems, ULF waves
‧2015- Postdoc, National Central University, Taiwan
–Magnetopause, EMIC Waves, Solar Wind Thermodynamics

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