University of Leicester
Browse
2021JA029544.pdf (1.24 MB)

Magnetic reconnection near the planet as a possible driver of Jupiter’s mysterious polar auroras

Download (1.24 MB)
journal contribution
posted on 2021-08-10, 15:26 authored by A Masters, WR Dunn, TS Stallard, H Manners, J Stawarz
Auroral emissions have been extensively observed at the Earth, Jupiter, and Saturn. These planets all have appreciable atmospheres and strong magnetic fields, and their auroras predominantly originate from a region encircling each magnetic pole. However, Jupiter’s auroras poleward of these “main” emissions are brighter and more dynamic, and the drivers responsible for much of these mysterious polar auroras have eluded identification to date. We propose that part of the solution may stem from Jupiter’s stronger magnetic field. We model large-scale Alfvénic perturbations propagating through the polar magnetosphere toward Jupiter, showing that the resulting <0.1° deflections of the magnetic field closest to the planet could trigger magnetic reconnection as near as ∼0.2 Jupiter radii above the cloud tops. At Earth and Saturn this physics should be negligible, but reconnection electric field strengths above Jupiter’s poles can approach ∼1 V m−1, typical of the solar corona. We suggest this near-planet reconnection could generate beams of high-energy electrons capable of explaining some of Jupiter’s polar auroras.

Plain Language Summary
When energetic particles from space hit a planet’s upper atmosphere the resulting chemistry can produce light, leading to spectacular “auroras.” Jupiter is the largest planet in the Solar System, with the strongest magnetic field generated in its interior, and with the brightest auroras. We understand why Jupiter’s auroras are so bright to a large extent, but a long-standing mystery is what causes the swirling auroras around Jupiter’s poles, which we do not see at other planets. We present a new idea that might lead to a solution to this problem. We show that under certain conditions in space just above Jupiter’s polar atmosphere some of the energy stored in the planet’s magnetic field can be released, possibly accelerating particles and producing auroras below. If this idea is supported by future research it would imply that Jupiter’s bright polar auroras are due to the planet’s very strong magnetic field, with implications for similarly strongly magnetized planets in orbit around distant stars.

Funding

Royal Society

Science and Technology Facilities Council

University College London

European Space Agency

History

Citation

Journal of Geophysical Research: Space Physics, Volume 126, Issue 8, August 2021, e2021JA029544

Author affiliation

Department of Physics and Astronomy

Version

  • VoR (Version of Record)

Published in

Journal of Geophysical Research: Space Physics

Volume

126

Issue

8

Publisher

Wiley for American Geophysical Union (AGU)

issn

2169-9380

eissn

2169-9402

Acceptance date

2021-06-28

Copyright date

2021

Available date

2022-01-14

Language

en

Usage metrics

    University of Leicester Publications

    Categories

    Exports

    RefWorks
    BibTeX
    Ref. manager
    Endnote
    DataCite
    NLM
    DC