Implications for MI coupling from a subcorotation-driven System IV model
Abstract
Jupiter exhibits a fundamental rotational periodicity known as System IV that has no widely-accepted explanation, yet is easily observed in ultraviolet emission from the Io plasma torus. To attack this problem we model the response of the Io plasma torus to superthermal electron modulation and volcanic eruptions using a two-dimensional (radial and azimuthal) physical chemistry model [Copper et al., 2016]. In particular, we investigate the torus response to a prescribed System III superthermal electron modulation following Steffl et al. [2008] and an additional hot electron modulation governed by the radial flux tube content gradient per Hess et al., 2011, and generate a radially independent beat periodicity consistent with System IV. We demonstrate that variation of the subcorotation velocity profile is sufficient to explain observed shifts by a factor of two of the System IV period [Ryo et al., 2018]. We also investigate observations by the Hisaki spacecraft [Ryo] that eruptions return the torus towards full corotation, counter to previous models of mass loading [Pontius et al., 1982]. Instead, we argue the return to corotation implies improved MI coupling due to a transport-related increase in hot electrons following the eruption. We also provide limits for Io-localized plasma production based on an observed Io phase-related periodicity.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMSM23E3229C
- Keywords:
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- 2731 Magnetosphere: outer;
- MAGNETOSPHERIC PHYSICSDE: 5737 Magnetospheres;
- PLANETARY SCIENCES: FLUID PLANETSDE: 6222 Ganymede;
- PLANETARY SCIENCES: SOLAR SYSTEM OBJECTSDE: 7899 General or miscellaneous;
- SPACE PLASMA PHYSICS