Multi-frequency electromagnetic sounding of the Galilean moons

Seufert, M.; Saur, Joachim; Neubauer, F. M.

doi:10.1016/j.icarus.2011.03.017

Cited by 55 publications

(113 citation statements)

References 48 publications

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“…Additionally, we use the density model by Bagenal & Delamere (2011) with κ = 1 and κ = 2 and display the resultant Poynting fluxes with the thin blue and the thick black line, respectively. The magnetic field model is based on the composite model including Jupiter's internal field and the plasma sheet contributions assembled in Seufert et al (2011). For the interaction strength α we use (17) and (58) with Σ P,c = 200 S in the center of the plasma sheet (Saur et al 1999;Kivelson et al 2004).…”

Section: Poynting Fluxes: Iomentioning

confidence: 99%

“…We assume an extension of Europa's interaction region of R eff = 1.3 R Europa (Saur et al 1998). The magnetic field is calculated similar to Io with the model by Seufert et al (2011). The dashed curve in Fig.…”

Section: Poynting Fluxes: Iomentioning

confidence: 99%

“…The solid blue and the black lines are calculated with density models from Bagenal & Delamere (2011) and κ = 1 and κ = 2, respectively. The magnetic field model is after Seufert et al (2011). Ganymede possesses an intrinsic magnetic moment and thus a mini-magnetosphere within Jupiter's large magnetosphere (Kivelson et al 1996a;Neubauer 1998).…”

Section: Poynting Fluxes: Iomentioning

confidence: 99%

“…We use in the center of the plasma sheet Σ P,c = 1000 S (Kivelson et al 2004), which corresponds to an interaction strength of α c > 0.99 . The magnetic field model is after Seufert et al (2011). The resulting Poynting fluxes are displayed in the fourth panel of Fig.…”

Section: Poynting Flux: Callistomentioning

confidence: 99%

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Magnetic energy fluxes in sub-Alfvénic planet star and moon planet interactions

Saur

Grambusch

Duling

et al. 2013

A&A

171

332

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Context. Electromagnetic coupling of planetary moons with their host planets is well observed in our solar system. Similar couplings of extrasolar planets with their central stars have been studied observationally on an individual as well as on a statistical basis. Aims. We aim to model and to better understand the energetics of planet star and moon planet interactions on an individual and as well as on a statistical basis. Methods. We derived analytic expressions for the Poynting flux communicating magnetic field energy from the planetary obstacle to the central body for sub-Alfvénic interaction. We additionally present simplified, readily useable approximations for the total Poynting flux for small Alfvén Mach numbers. These energy fluxes were calculated near the obstacles and thus likely present upper limits for the fluxes arriving at the central body. We applied these expressions to satellites of our solar system and to HD 179949 b. We also performed a statistical analysis for 850 extrasolar planets. Results. Our derived Poynting fluxes compare well with the energetics and luminosities of the satellites' footprints observed at Jupiter and Saturn. We find that 295 of 850 extrasolar planets are possibly subject to sub-Alfvénic plasma interactions with their stellar winds, but only 258 can magnetically connect to their central stars due to the orientations of the associated Alfvén wings. The total energy fluxes in the magnetic coupling of extrasolar planets vary by many orders of magnitude and can reach values larger than 10 19 W. Our calculated energy fluxes generated at HD 179949 b can only explain the observed energy fluxes for exotic planetary and stellar magnetic field properties. In this case, additional energy sources triggered by the Alfvén wave energy launched at the extrasolar planet might be necessary. We provide a list of extrasolar planets where we expect planet star coupling to exhibit the largest energy fluxes. As supplementary information we also attach a table of the modeled stellar wind plasma properties and possible Poynting fluxes near all 850 extrasolar planets included in our study. Conclusions. The orders of magnitude variations in the values for the total Poynting fluxes even for close-in extrasolar planets provide a natural explanation why planet star coupling might have been only observable on an individual basis but not on a statistical basis.

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Section: Poynting Fluxes: Iomentioning

confidence: 99%

Section: Poynting Fluxes: Iomentioning

confidence: 99%

Section: Poynting Fluxes: Iomentioning

confidence: 99%

Section: Poynting Flux: Callistomentioning

confidence: 99%

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Magnetic energy fluxes in sub-Alfvénic planet star and moon planet interactions

Saur

Grambusch

Duling

et al. 2013

A&A

171

332

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“…In consequence, as Io passes through the tilted plasma torus from one edge to the other, it experiences changes in plasma density, magnetic field magnitude, and its orientation. Specifically, local variation of the magnetic field in Io's orbital plane at the synodic period of Jupiter is elliptically polarized with the radial (toward Jupiter) component reaching values ≈±750 nT and the azimuthal component reaching values ≈ ± 400 nT (e.g., Seufert et al, ). The tilt of Jovian dipole field is the main source of periodicity in the magnetic field at the Galilean satellites.…”

Section: Introductionmentioning

confidence: 99%

Dynamic Plasma Interaction at Io: Multispecies Hybrid Simulations

et al. 2019

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The interaction between the Io plasma torus and Io exhibits significant dynamics resulting from temporal variations of both external conditions in the plasma torus and local conditions in Io's environment. We present analysis of an extensive simulation campaign of the Io plasma interaction under varying interaction conditions performed by using a hybrid multispecies simulation model. We test two models of electron impact ionization, one resulting in plasma production constrained to the upstream hemisphere of Io and the other producing a more symmetric distribution of the plasma with nonnegligible plasma production on the downstream side of Io. In the latter case, the simulation model provides high level of agreement with Galileo measurements of magnetic field obtained during the I0 flyby, where the model captures even smaller‐scale features of the magnetic field profile. Our simulated results provide strong support for the existence of Io's induced dipole field. In this model we assume that induced dipole field moment is antiparallel to the direction of the inducing magnetic field, equivalent to induction in a highly conductive Io. Our results further support the idea that Io's atmosphere collapsed during the Galileo I27 flyby, which manifests itself in the lack of ion heating due to pickup processes in the extended atmosphere. Our results show that the dominant torus species, O+ and S++, are depleted around Io and may exhibit temperature anisotropy, T⊥/T‖ < 1, resulting from merging of ion populations coming from opposite sides of Io along the magnetic field.

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Consistent boundary conditions at nonconducting surfaces of planetary bodies: Applications in a new Ganymede MHD model

2014

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The interaction of planetary bodies with their surrounding magnetized plasma can often be described with the magnetohydrodynamic (MHD) equations, which are commonly solved by numerical models. For these models it is necessary to define physically correct boundary conditions for the plasma mass and energy density, the plasma velocity, and the magnetic field. Many planetary bodies have surfaces whose electrical conductivity is negligibly small and thus no electric current penetrates their surfaces. Magnetic boundary conditions, which consider that the associated radial electric current at the planetary surface is zero, are difficult to implement because they include the curl of the magnetic field. Here we derive new boundary conditions by a decomposition of the magnetic field in poloidal and toroidal parts. We find that the toroidal part of the magnetic field needs to vanish at the surface of the insulator. For the spherical harmonics coefficients of the poloidal part, we derive a Cauchy boundary condition, which also matches a possible intrinsic field by including its Gauss coefficients. Thus, we can additionally include planetary dynamo fields as well as time-variable induction fields within electrically conductive subsurface layers. We implement the nonconducting boundary condition in the MHD simulation code ZEUS-MP using spherical geometry and provide a numerical implementation in Fortran 90 as supporting information on the JGR website. We apply it to a model for Ganymede's plasma environment. Our model also includes a consistent set of boundary conditions for the other MHD variables density, velocity, and energy. With this model we can describe Galileo spacecraft observations in and around Ganymede's minimagnetosphere very well.

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Multi-frequency electromagnetic sounding of the Galilean moons

Cited by 55 publications

References 48 publications

Magnetic energy fluxes in sub-Alfvénic planet star and moon planet interactions

Magnetic energy fluxes in sub-Alfvénic planet star and moon planet interactions

Dynamic Plasma Interaction at Io: Multispecies Hybrid Simulations

Consistent boundary conditions at nonconducting surfaces of planetary bodies: Applications in a new Ganymede MHD model

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