Characteristic dimension of electromagnetic ion cyclotron wave activity in the magnetosphere

Jeongwoo Lee, Kyungguk Min, Kap Sung Kim

Research output: Contribution to journalArticlepeer-review

14 Scopus citations


In this paper, we estimate the size of coherent activity of electromagnetic ion cyclotron (EMIC) waves using the multi-spacecraft observations made during the Time History of Events and Macroscale Interactions during Substorms (THEMIS) mission. We calculate the cross-correlations between EMIC wave powers measured by different THEMIS spacecraft, plot them over the separation distances between pairs of observing spacecraft, and determine the 1/e folding distance of the correlations as the characteristic dimension of the coherent wave activity. The characteristic radius in the direction transverse to the local magnetic field is found to lie in rather a wide range of 1500-8600 km varying from the AM to PM sectors and also from hydrogen to helium bands. However, the characteristic dimensions normalized by either gyroradius or wavelength fall into narrower ranges almost independent of the emission band and event location. Specifically, the coherent dimension is found to be 10-16 times gyroradius of 100 keV protons and 2-3 times local wavelength. The former may give a useful scale for the source dimension, and the latter suggests that the EMIC wave activity maintains coherency only up to a couple of wavelengths. Key PointsFirst time estimation of the dimension of coherent EMIC wave activityThe typical size is found to be 10-16 times local gyroradius of 100 keV protonsThe EMIC wave activity maintains coherency only up to 2-3 wavelengths

Original languageEnglish (US)
Pages (from-to)1651-1658
Number of pages8
JournalJournal of Geophysical Research: Space Physics
Issue number4
StatePublished - Apr 2013

All Science Journal Classification (ASJC) codes

  • Space and Planetary Science
  • Geophysics


  • Magnetospheric physics: plasma waves and instabilities


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