Universität zu Köln

Schlegel, Stephan ORCID: 0000-0002-4779-2813 and Saur, Joachim ORCID: 0000-0003-1413-1231 (2022). Alternating Emission Features in Io's Footprint Tail: Magnetohydrodynamical Simulations of Possible Causes. J. Geophys. Res-Space Phys., 127 (5). WASHINGTON: AMER GEOPHYSICAL UNION. ISSN 2169-9402

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Abstract

Io's movement relative to the plasma in Jupiter's magnetosphere creates Alfven waves propagating along the magnetic field lines which are partially reflected along their path. These waves are the root cause for auroral emission, which is subdivided into the Io Footprint (IFP), its tail and leading spot. New observations of the Juno spacecraft by Mura et al. (2018, ) have shown puzzling substructure of the footprint and its tail. In these observations, the symmetry between the poleward and equatorward part of the footprint tail is broken and the tail spots are alternatingly displaced. We show that the location of these bright spots in the tail are consistent with Alfven waves reflected at the boundary of the Io torus and Jupiter's ionosphere. Then, we investigate three different mechanisms to explain this phenomenon: (a) The Hall effect in Io's ionosphere, (b) travel time differences of Alfven waves between Io's Jupiter facing and its opposing side and (c) asymmetries in Io's atmosphere. For that, we use magnetohydrodynamic simulations within an idealized geometry of the system. We use the Poynting flux near the Jovian ionosphere as a proxy for the morphology of the generated footprint and its tail. We find that the Hall effect is the most important mechanism under consideration to break the symmetry causing the Alternating Alfven spot street. The travel time differences contributes to enhance this effect. We find no evidence that the inhomogeneities in Io's atmosphere contribute significantly to the location or shape of the tail spots.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Schlegel, Stephan UNSPECIFIED orcid.org/0000-0002-4779-2813 UNSPECIFIED Saur, Joachim UNSPECIFIED orcid.org/0000-0003-1413-1231 UNSPECIFIED
URN:	urn:nbn:de:hbz:38-658608
DOI:	10.1029/2021JA030243
Journal or Publication Title:	J. Geophys. Res-Space Phys.
Volume:	127
Number:	5
Date:	2022
Publisher:	AMER GEOPHYSICAL UNION
Place of Publication:	WASHINGTON
ISSN:	2169-9402
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language ALFVEN-WAVE PROPAGATION; PLASMA TORUS; AURORA; MAGNETOSPHERE; HST Multiple languages Astronomy & Astrophysics Multiple languages
URI:	http://kups.ub.uni-koeln.de/id/eprint/65860