Hiss or equatorial noise? Ambiguities in analyzing suprathermal ion plasma wave resonance

Lois K. Sarno-Smith, Michael W. Liemohn, Ruth M. Skoug, Ondrej Santolik, Steven K. Morley, Aaron Breneman, Brian A. Larsen, Geoff Reeves, John R. Wygant, George Hospodarsky, Craig Kletzing, Mark B. Moldwin, Roxanne M. Katus, Shasha Zou

Research output: Contribution to journalArticlepeer-review

4 Scopus citations


Previous studies have shown that low-energy ion heating occurs in the magnetosphere due to strong equatorial noise emission. Observations from the Van Allen Probes Helium Oxygen Proton Electron (HOPE) instrument recently determined that there was a depletion in the 1–10 eV ion population in the postmidnight sector of Earth during quiet times at L < 3. The diurnal variation of equatorially mirroring 1–10 eV H+ ions at 2 < L < 3 is connected with similar diurnal variation in the electric field component of plasma waves ranging between 150 and 600 Hz. Measurements from the Van Allen Probes Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) data set are used to analyze waves of this frequency in near-Earth space. However, when we examine the polarization of the waves in the 150 to 600 Hz range in the equatorial plane, the majority are right-hand polarized plasmaspheric hiss waves. The 1–10 eV H+ equatorially mirroring population does not interact with right-hand waves, despite a strong statistical relationship suggesting that the two are linked. We present evidence supporting the relationship, both in our own work and the literature, but we ultimately conclude that the 1–10 eV H+ heating is not related to the strong enhancement of 150 to 600 Hz waves.

Original languageEnglish (US)
Pages (from-to)9619-9631
Number of pages13
JournalJournal of Geophysical Research: Space Physics
Issue number10
StatePublished - Oct 1 2016

Bibliographical note

Funding Information:
The Michigan coauthors would like to thank the University of Michigan Rackham Graduate school, NASA, and the NSF for sponsoring this work under grants NWX11AO60G, NWX144AC02G, AGS-1265651, and AGS-1102863. Work at Los Alamos National Laboratory was performed under the auspices of the U.S. Department of Energy, with support from the NASA Van Allen Probes mission under interagency transfer NNG07EK09I and approved for public release as LA-UR-16-25767. The research at the University of Iowa was supported by JHU/APL contract 921647. Data from HOPE and EMFISIS used to generate figures for this project came from the Van Allen Probes data center at https://emfisis.physics.uiowa.edu/data/index and http://rbsp-ect.lanl.gov/. O. Santolik acknowledges support from grants LH14010, LH15304, and from the Praemium Academiae award.

Publisher Copyright:
©2016. American Geophysical Union. All Rights Reserved.


  • equatorial noise
  • low-energy ions
  • plasma waves
  • plasmasphere
  • plasmaspheric hiss


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