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Simultaneous Observations of Electromagnetic Ion Cyclotron Waves and Longer-Period Ultra Low Frequency Waves by the GOES-16 Magnetometer
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  • Paul T. M. Loto'aniu,
  • Robert Joseph Redmon,
  • Maria E. Usanova,
  • Samuel T Califf
Paul T. M. Loto'aniu
National Oceanic and Atmospheric Administration (NOAA)

Corresponding Author:[email protected]

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Robert Joseph Redmon
National Oceanic and Atmospheric Administration (NOAA)
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Maria E. Usanova
Laboratory for Atmospheric and Space Physics, University of Colorado Boulder
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Samuel T Califf
Cooperative Institute for Research in Environmental Sciences
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Simultaneous bursts of EMIC and longer-period ULF waves were observed by the GOES-16 magnetometer on the 11 January and the 7 September 2017. No correlation was found between the repeat times of EMIC wavepackets and Pc4 ULF wave periods. However, the repetition times visually correlated with variations in solar wind dynamic pressure (Pdyn). EMIC wavepackets are composed of short duration subpackets and when subpackets last >1/2 the ULF wave period, correlation with the ULF wave cycle was strong, R=0.6. On 11 Jan., observations suggest the Pc5 ULF waves were in-part directly driven by Pdyn. The observed Pc4-5 ULF waves were predominately poloidal. Assuming high azimuthal m-numbers, the observations as a whole imply that the simultaneous repeating EMIC and Pc4-5 wave bursts were formed by mode cross-coupling through a common wave generation free energy source of anisotropic ion distributions created by repetitive magnetospheric compressions driven by small Pdyn fluctuations.