Kinetic Alfvén waves and auroral particle acceleration: a review

Research output: Contribution to journalReview articlepeer-review

10 Scopus citations

Abstract

Shear mode Alfvén waves are the carriers of field-aligned currents in the auroral zones of Earth and other planets. These waves travel along the magnetic field lines, coupling the outer magnetosphere with the ionosphere. However, in ideal magnetohydrodynamic (MHD) theory, the shear mode Alfvén wave does not carry a parallel electric field that could accelerate auroral particles. This can be modified by including kinetic effects, which lead to a parallel electric field when the perpendicular wavelength becomes comparable to the electron inertial length or the ion acoustic gyroradius. These small perpendicular wavelengths can be formed by phase mixing, ionospheric feedback, or nonlinear effects. Kinetic Alfvén waves are further constrained by their interaction with the ionosphere, which acts as a reflector for these waves. In addition, the strong plasma gradients in the topside ionosphere form an effective resonator that leads to fluctuations on time scales of seconds. These rapidly changing parallel electric fields can lead to broadband acceleration of auroral electrons, often called the Alfvénic aurora. Such interactions do not only take place in Earth’s magnetosphere, but have also been observed in Jupiter’s magnetosphere by the Juno satellite.

Original languageEnglish (US)
Article number6
JournalReviews of Modern Plasma Physics
Volume7
Issue number1
DOIs
StatePublished - Dec 2023

Bibliographical note

Publisher Copyright:
© 2023, The Author(s).

Keywords

  • Auroral particle acceleration
  • Kinetic Alfvén waves
  • Magnetohydrodynamics
  • Planetary magnetospheres

PubMed: MeSH publication types

  • Journal Article
  • Review

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