Long-Term Variability of Jupiter's Magnetodisk and Implications for the Aurora

Marissa F. Vogt; Emma J. Bunce; Jonathan D. Nichols; John T. Clarke; William S. Kurth

doi:10.1002/2017JA024066

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Long-Term Variability of Jupiter's Magnetodisk and Implications for the Aurora

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Long-Term Variability of Jupiter's Magnetodisk and Implications for the Aurora

Marissa F. Vogt, Emma J. Bunce, Jonathan D. Nichols, John T. Clarke and William S. Kurth

Journal of geophysical research. Space physics, Vol.122(12), pp.12090-12110

12/01/2017

DOI: 10.1002/2017JA024066

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Abstract

Observations of Jupiter's UV auroral emissions collected over several years show that the ionospheric positions of the main emission and the Ganymede footprint can vary by as much as 3 degrees in latitude. One explanation for this shift is a change of Jupiter's current sheet current density, which would alter the amount of field line stretching and displace the ionospheric mapping of field lines from a given radial distance in the magnetosphere. In this study we measure the long-term variability of Jupiter's magnetodisk using Galileo magnetometer data collected from 1996 to 2003. Using the Connerney et al. (1981) current sheet model, we calculate the current sheet density parameter that gives the best fit to the data from each orbit and find that the current density parameter varies by about 15% of its average value during the Galileo era. We investigate possible relationships between the observed current sheet variability and quantities such as Io's plasma torus production rate inferred from volcanic activity and external solar wind conditions extrapolated from data at 1 AU but find only a weak correlation. Finally, we trace Khurana (1997) model field lines to show that the observed changes in Jupiter's current sheet are sufficient to shift the ionospheric footprint of Ganymede and main auroral emission by a few degrees of latitude, consistent with the magnitude of auroral variability observed by Hubble Space Telescope (HST). However, we find that the measured auroral shifts in HST images are not consistent with concurrent changes in the current density parameter measured by Galileo.

Astronomy & Astrophysics

Physical Sciences

Science & Technology

Details

Title: Subtitle: Long-Term Variability of Jupiter's Magnetodisk and Implications for the Aurora
Creators: Marissa F. Vogt - Boston University
Emma J. Bunce - University of Leicester
Jonathan D. Nichols - University of Leicester
John T. Clarke - Boston University
William S. Kurth - University of Iowa
Resource Type: Journal article
Publication Details: Journal of geophysical research. Space physics, Vol.122(12), pp.12090-12110
DOI: 10.1002/2017JA024066
ISSN: 2169-9380
eISSN: 2169-9402
Publisher: Amer Geophysical Union
Number of pages: 21
Grant note: ST/N000749/1 / Science and Technology Facilities Council; UK Research & Innovation (UKRI); Science & Technology Facilities Council (STFC) ST/K001000/1 / UK Science and Technology Facilities Council (STFC); UK Research & Innovation (UKRI); Science & Technology Facilities Council (STFC) 1524651 / National Science Foundation; National Science Foundation (NSF) ST/N000749/1 / STFC; UK Research & Innovation (UKRI); Science & Technology Facilities Council (STFC)
Language: English
Date published: 12/01/2017
Academic Unit: Physics and Astronomy
Record Identifier: 9984455659002771

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