JpGU-AGU Joint Meeting 2017

Presentation information

[EE] Oral

P (Space and Planetary Sciences) » P-EM Solar-Terrestrial Sciences, Space Electromagnetism & Space Environment

[P-EM16] [EE] Physics of Inner Magnetosphere Coupling

Tue. May 23, 2017 3:30 PM - 5:00 PM A02 (Tokyo Bay Makuhari Hall)

convener:Danny Summers(Memorial University of Newfoundland), Jichun Zhang(University of New Hampshire Main Campus), Yusuke Ebihara(Research Institute for Sustainable Humanosphere, Kyoto University), Kunihiro Keika(Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo ), Aleksandr Y Ukhorskiy(Johns Hopkins University Applied Physics Laboratory), Dae-Young Lee(Chungbuk Natl Univ), Yiqun Yu(Beihang University), Yoshizumi Miyoshi(Institute for Space-Earth Environmental Research, Nagoya University), Chairperson:Aleksandr Ukhorskiy(Johns Hopkins University Applied Physics Laboratory)

3:45 PM - 4:00 PM

[PEM16-14] Occurrence of EMIC waves and plasmaspheric plasmas derived from THEMIS
observations in the outer magnetosphere

★Invited papers

*Khan-Hyuk Kim1, Gi-Jeong Kim1, Dong-Hun Lee1 (1.School of Space Research, Kyung Hee University)

Keywords:EMIC waves, Plasmaspheric plasma

We have statistically studied the relationship between electromagnetic ion cyclotron (EMIC)
waves and cold plasmaspheric plasma (Nsp) in the L range of 6-12 using the Time History of
Events and Macroscale Interactions during Substorms (THEMIS) data for 2008-2011. The
important observational results are as follows: (1) Under quiet geomagnetic conditions (Kp =
0-1), the maximum occurrence rate of the hydrogen (H) band EMIC waves appears in the early
morning sector (0600-0900 MLT) at the outermost region (L = 10-12). (2) Under moderate and
disturbed conditions (Kp > 2), the H-band occurrence rate is higher in the morning-to-early
afternoon sector for L > 10. (3) The high occurrence region of helium (He) band waves for Kp =
0-1 varies from L = 7 to 12 in radial distances along the local time (i.e., at L ~ 7 near noon and
at L = 8-12 near late afternoon). (4) The He-band waves for Kp > 2 are mainly localized
between 1200 and 1800 MLT with a peak around 1500-1600 MLT at L = 8-10. (5) Nsp is much
higher for the He-band intervals than for the H-band intervals by a factor of 10 or more. The He-band
high occurrence appears at a steep Nsp gradient region. (6) The morning-afternoon
asymmetry of the normalized frequency seen both in H and He bands is similar to the
asymmetric distribution of Nsp along the local time. These observations indicate that the cold
plasma density plays a significant role in determining the spectral properties of EMIC waves.
We discuss whether a morning-afternoon asymmetry of the EMIC wave properties can be
explained by the spatial distribution of cold plasmaspheric plasma.