Spatial Distribution of Fine-Structured and Unstructured EMIC Waves Observed by the Arase Satellite

S. Matsuda, Y. Kasahara, Y. Miyoshi, R. Nomura, M. Shoji, A. Matsuoka, Y. Kasaba, S. Kurita, M. Teramoto, K. Ishisaka

Research output: Contribution to journalArticlepeer-review

13 Citations (Scopus)


We surveyed 378 electromagnetic ion cyclotron (EMIC) wave events using Arase during the first 12 months. We discriminated the observed EMIC waves into two types (fine-structured EMIC waves and unstructured EMIC waves), according to whether or not they exhibited clear periodic amplitude modulations. We found a clear afternoon peak in the occurrence probability of unstructured EMIC waves in the region of L = 5–9. Fine-structured EMIC waves were mainly distributed in the off-equatorial region, and their occurrence probability was clearly high around the noon sector. Such noon sector EMIC wave peaks had not been found in the THEMIS, AMPTE, or Cluster measurements, due to their limited L shell coverages. The Van Allen probes, too, were not able to measure the major region of fine-structured EMIC waves because of their limited latitudinal coverage. Our unique statistical results demonstrate the importance of discriminating the wave structures as well as of performing observations over a wide range of latitudes.

Original languageEnglish
Pages (from-to)11,530-11,538
JournalGeophysical Research Letters
Issue number21
Publication statusPublished - 2018 Nov 16


  • Arase satellite
  • EMIC wave
  • inner magnetosphere
  • spatial distribution


Dive into the research topics of 'Spatial Distribution of Fine-Structured and Unstructured EMIC Waves Observed by the Arase Satellite'. Together they form a unique fingerprint.

Cite this