Statistical study of EMIC Pc1-Pc2 waves observed at subauroral latitudes

Jong Woo Kwon, Khan Hyuk Kim, Ho Jin, Hyuck Jin Kwon, Geonhwa Jee, Kazuo Shiokawa, Martin Connors

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6 Citations (Scopus)


Although the occurrence rate of electromagnetic ion cyclotron (EMIC) waves is high in the outer magnetosphere (L > 7), it has been suggested in the past that a steep plasma density gradient region of the plasmapause is a preferred location for the generation of EMIC waves. To examine spectral properties of the EMIC waves occurred near the nominal location of the plasmapause (L = 4–5), we focus on Pc1-Pc2 waves observed at subauroral latitude Athabasca station (magnetic latitude: ~62°, and L ~ 4.6). A statistical study of 10,494 wave samples identified from Athabasca data for 2007–2008 reveals the following wave characteristics. (1) Wave frequencies are higher in the postmidnight-to-dawn sector and lower in the late afternoon sector. (2) They mostly appear to be in frequency band between helium and oxygen gyrofrequencies (i.e., He-band) calculated from the dipole field model magnetic field intensity at L = 4.6. (3) The occurrence rate of Pc1-Pc2 waves has a peak in the prenoon sector at 0900–1100 LT under quiet geomagnetic conditions (Kp ≤ 1), but is peaked in the afternoon sector under moderate and disturbed geomagnetic conditions (Kp ≥ 2). (4) The Pc1-Pc2 waves observed at Athabasca were composed of a mixture of left-hand, right-hand, and linearly polarized waves. By comparing previous and recent studies with these observations, we suggest that the subauroral latitude Pc1-Pc2 waves are associated with EMIC waves generated near the plasmapause and discuss the EMIC wave properties in a region of cold and dense plasmas containing heavy ions in the inner magnetosphere.

Original languageEnglish
Article number105292
JournalJournal of Atmospheric and Solar-Terrestrial Physics
Publication statusPublished - 1 Sep. 2020


  • He-band
  • Pc1-Pc2 waves
  • Plasmapause
  • Subauroral latitude


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