Articles | Volume 23, issue 3
Ann. Geophys., 23, 723–732, 2005
Ann. Geophys., 23, 723–732, 2005

  30 Mar 2005

30 Mar 2005

LHR band emissions at mid-latitude and their relationship to ionospheric ELF hiss and relativistic electrons

A. Morioka1, H. Oya2, T. Obara3, Y. S. Miyoshi4, K. Nagata5, K.-I. Oyama6, and T. Abe6 A. Morioka et al.
  • 1Planetary Plasma and Atmospheric Research Center, Tohoku University, Aoba-ku, Sendai, 980-8578, Japan
  • 2Fukui University of Technology, 3-6-1, Gakuen, Fukui, 910-8505, Japan
  • 3National Institute of Information and Communications Technology, 4-2-1, Nukiikitamachi, Koganei, 184-8795, Japan
  • 4Solar-Terrestrial Environment Laboratory, Nagoya University, Honohara, Toyokawa, 422-8507, Japan
  • 5Faculty of Engineering, Tamagawa University, 6-1-1, Tamagawagakuen, Machida, Tokyo, 194-8610, Japan
  • 6Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Sagamihara, 229-8510, Japan

Abstract. LHR band emissions observed at mid-latitude were investigated using data from the EXOS-C (Ohzora) satellite. A typical feature of the LHR band emissions is a continuous banded structure without burst-like and cut-off features whose center frequency decreases as the satellite moves to higher latitudes. A statistical analysis of the occurrence characteristics of the phenomena showed that mid-latitude LHR emissions are distributed inside the plasmapause during magnetically quiet periods, and the poleward boundary of the emission region moves to lower latitudes as the magnetic activity increases. The altitude distribution of the waves suggests that the propagation in the LHR duct formed horizontally in the mid-latitude upper-ionosphere. The emission is closely related to the occurrence of ionospheric ELF hiss. It is also shown that LHR emissions are commonly observed in the slot region of the radiation belt, and they sometimes accompany the enhancement of the ionospheric electron temperature. The generation of the LHR band emissions is discussed based on the observed characteristics.