Ion-scale Electromagnetic Waves in the Inner Heliosphere

Academic Article


  • Understanding the physical processes in the solar wind and corona which actively contribute to heating, acceleration, and dissipation is a primary objective of NASA's Parker Solar Probe (PSP) mission. Observations of coherent electromagnetic waves at ion scales suggests that linear cyclotron resonance and non-linear processes are dynamically relevant in the inner heliosphere. A wavelet-based statistical study of coherent waves in the first perihelion encounter of PSP demonstrates the presence of transverse electromagnetic waves at ion resonant scales which 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 of order 20 seconds; however long duration wave events can exist without interruption on hour-long timescales. 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 quasi-parallel 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 strong radial scaling of characteristic wave amplitudes and duration suggests that the waves are generated {\em{in-situ}} through plasma instabilities. Additionally, observations of proton distribution functions indicate that temperature anisotropy may drive the observed ion-scale waves.
  • Authors

  • Bowen, Trevor A
  • Mallet, Alfred
  • Huang, Jia
  • Klein, Kristopher G
  • Malaspina, David M
  • Stevens, Michael
  • Bale, Stuart D
  • Bonnell, JW
  • Case, Anthony W
  • Chandran, Benjamin
  • Chaston, CC
  • Chen, Christopher HK
  • de Wit, Thierry Dudok
  • Goetz, Keith
  • Harvey, Peter R
  • Howes, Gregory G
  • Kasper, JC
  • Korreck, Kelly E
  • Larson, Davin
  • Livi, Roberto
  • MacDowall, Robert J
  • McManus, Michael D
  • Pulupa, Marc
  • Verniero, JL
  • Whittlesey, Phyllis
  • Team, PSPSWEAP
  • Status

    Publication Date

  • February 2020
  • Has Subject Area


  • astro-ph.SR
  • Digital Object Identifier (doi)

    Start Page

  • 66
  • End Page

  • 66
  • Volume

  • 246
  • Issue

  • 2