The Jovian Ionospheric Alfvén Resonator and Auroral Particle Acceleration

R. L. Lysak, Y. Song, S. Elliott, W. Kurth, A. H. Sulaiman, D. Gershman

Research output: Contribution to journalArticlepeer-review

Abstract

The ionospheric Alfvén resonator (IAR) is a structure formed by the rapid decrease in the plasma density above a planetary ionosphere. This results in a corresponding increase in the Alfvén speed that can provide partial reflection of Alfvén waves. At Earth, the IAR on auroral field lines is associated with the broadband acceleration of auroral particles, sometimes termed the Alfvénic aurora. This arises since phase mixing in the IAR reduces the perpendicular wavelength of the Alfvén waves, which enhances the parallel electric field due to electron inertia. This parallel electric field fluctuates at frequencies of 0.1–20.0 Hz, comparable to the electron transit time through the acceleration region, leading to the broadband acceleration. The prevalence of such broadband acceleration at Jupiter suggests that a similar process can occur in the Jovian IAR. A numerical model of Alfvén wave propagation in the Jovian IAR has been developed to investigate these interactions, indicating that the IAR resonant frequencies are in the same range as those at Earth. This model describes the evolution of the electric and magnetic fields in the low-altitude region close to Jupiter that is sampled during Juno's perijove passes. In particular, the model relates measurement of magnetic fields below the ion cyclotron frequency from the MAG and Waves instruments on Juno and electric fields from Waves to the associated parallel electric fields that can accelerate auroral particles.

Original languageEnglish (US)
Article numbere2021JA029886
JournalJournal of Geophysical Research: Space Physics
Volume126
Issue number12
DOIs
StatePublished - Dec 2021

Bibliographical note

Funding Information:
The authors would like to thank Fran Bagenal for useful comments on this work. Work at the University of Minnesota is supported by NASA grant 80NSSC20K1269 and grant AGS‐1840891 from the National Science Foundation. They also acknowledge supercomputer support from the Minnesota Supercomputer Institute. The research conducted at the University of Iowa was supported by NASA through contract 699041X with the Southwest Research Institute.

Publisher Copyright:
© 2021. American Geophysical Union. All Rights Reserved.

Keywords

  • aurora
  • Jupiter
  • kinetic Alfvén waves
  • magnetosphere-ionosphere coupling

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