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Journal Articles The Astrophysical Journal Supplement Year : 2020

Ion-scale Electromagnetic Waves in the Inner Heliosphere

Jia Huang
Kristopher Klein
  • Function : Author
David Malaspina
Michael Stevens
Stuart Bale
J. Bonnell
Anthony Case
Benjamin Chandran
  • Function : Author
Christopher Chen
  • Function : Author
Keith Goetz
Peter Harvey
Gregory Howes
  • Function : Author
J. Kasper
Kelly Korreck
Davin Larson
Roberto Livi
Robert Macdowall
Marc Pulupa
J. Verniero
Phyllis Whittlesey


Understanding the physical processes in the solar wind and corona that actively contribute to heating, acceleration, and dissipation is a primary objective of NASA's Parker Solar Probe (PSP) mission. Observations of circularly polarized electromagnetic waves at ion scales suggest that cyclotron resonance and wave-particle interactions are dynamically relevant in the inner heliosphere. A wavelet-based statistical study of circularly polarized events in the first perihelion encounter of PSP demonstrates that transverse electromagnetic waves at ion resonant scales are observed in 30-50% of radial field intervals. Average wave amplitudes of approximately 4 nT are measured, while the mean duration of wave events is on the order of 20 s; however, long-duration wave events can exist without interruption on hour-long timescales. Determination of wave vectors suggests propagation parallel/antiparallel to the mean magnetic field. Though ion-scale waves are preferentially observed during intervals with a radial mean magnetic field, we show that measurement constraints, associated with single spacecraft sampling of quasi-parallel waves superposed with anisotropic turbulence, render the measured coherent ion-wave spectrum unobservable when the mean magnetic field is oblique to the solar wind flow; these results imply that the occurrence of coherent ion-scale waves is not limited to a radial field configuration. The lack of radial scaling of characteristic wave amplitudes and duration suggests that the waves are generated in situ through plasma instabilities. Additionally, observations of proton distribution functions indicate that temperature anisotropy may drive the observed ion-scaley
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Dates and versions

insu-02937801 , version 1 (18-09-2020)



Trevor Bowen, Alfred Mallet, Jia Huang, Kristopher Klein, David Malaspina, et al.. Ion-scale Electromagnetic Waves in the Inner Heliosphere. The Astrophysical Journal Supplement, 2020, Early Results from Parker Solar Probe: Ushering a New Frontier in Space Exploration, 246 (2), pp.66. ⟨10.3847/1538-4365/ab6c65⟩. ⟨insu-02937801⟩
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