Interaction of Saturn's magnetosphere and its moons: 1. Interaction between corotating plasma and standard obstacles

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95046/1/jgra20170.pd

Astrophysical Unipolar Inductors Powered by Gravitational Wave Emission

We consider the Unipolar Inductor Model (Goldreich & Lynden-Bell 1969) applied to Double Degenerate Binaries (DDBs) with ultrashort periods (Wu et al. 2002). In this model a magnetized primary white dwarf has a slight asynchronism between its spin and orbital motion, so that the (non-magnetic) secondary experiences a motional electric field when moving through the primary field lines. This induces a current flow between the two stars and provides an electric spin-orbit coupling mechanism for the primary. We study the combined effect of Gravitational Wave emission and electric spin-orbit coupling on the evolution of the primary degree of asynchronism and the associated rate of electric current dissipation in such systems, assuming that the primary's spin is not affected by any other mechanisms. In particular, we show that in ultrashort period binaries the emission of GW pumps energy in the electric circuit as to keep it steadily active. This happens despite the fact that spin-orbit coupling can rapidly synchronize the primary, because GW represent a slow desynchronizing mechanism steadily substracting orbital angular momentum to the system. A slightly asynchronous steady-state is thus achieved, determined by the balance between these two competing effects. This can be shown to correspond to a condition where the total available electric energy is conserved, because of GW emission, while dissipation, synchronization and orbital shrinking continue.Comment: INAF - Osservatorio Astronomico di Roma; Accepted for publication on A&

Interaction of Saturn's magnetosphere and its moons: 2. Shape of the Enceladus plume

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95207/1/jgra20314.pd

Periodic plasma escape from the mass‐loaded Kronian magnetosphere

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/94967/1/jgra20364.pd

Response of Jupiter's Aurora to Plasma Mass Loading Rate Monitored by the Hisaki Satellite During Volcanic Eruptions at Io

The production and transport of plasma mass are essential processes in the dynamics of planetary magnetospheres. At Jupiter, it is hypothesized that Io's volcanic plasma carried out of the plasma torus is transported radially outward in the rotating magnetosphere and is recurrently ejected as plasmoid via tail reconnection. The plasmoid ejection is likely associated with particle energization, radial plasma flow, and transient auroral emissions. However, it has not been demonstrated that plasmoid ejection is sensitive to mass loading because of the lack of simultaneous observations of both processes. We report the response of plasmoid ejection to mass loading during large volcanic eruptions at Io in 2015. Response of the transient aurora to the mass loading rate was investigated based on a combination of Hisaki satellite monitoring and a newly developed analytic model. We found that the transient aurora frequently recurred at a 2-6day period in response to a mass loading increase from 0.3 to 0.5t/s. In general, the recurrence of the transient aurora was not significantly correlated with the solar wind, although there was an exceptional event with a maximum emission power of similar to 10TW after the solar wind shock arrival. The recurrence of plasmoid ejection requires the precondition that an amount comparable to the total mass of magnetosphere, similar to 1.5Mt, is accumulated in the magnetosphere. A plasmoid mass of more than 0.1Mt is necessary in case that the plasmoid ejection is the only process for mass release

Enceladus' plasma interaction with Saturn's magnetosphere

International audienc

Enceladus' plasma interaction with Saturn's magnetosphere

International audienc

Enceladus' plasma interaction with Saturn's magnetosphere

International audienc

Model of the Jovian magnetic field topology constrained by the Io auroral emissions

The determination of the internal magnetic field of Jupiter has been the object of many studies and publications. These models have been computed from the Pioneer, Voyager, and Ulysses measurements. Some models also use the position of the Io footprints as a constraint: the magnetic field lines mapping to the footprints must have their origins along Io’s orbit. The use of this latter constraint to determine the internal magnetic field models greatly improved the modeling of the auroral emissions, in particular the radio ones, which strongly depends on the magnetic field geometry. This constraint is, however, not sufficient for allowing a completely accurate modeling. The fact that the footprint field line should map to a longitude close to Io’s was not used, so that the azimuthal component of the magnetic field could not be precisely constrained. Moreover, a recent study showed the presence of a magnetic anomaly in the northern hemisphere, which has never been included in any spherical harmonic decomposition of the internal magnetic field. We compute a decomposition of the Jovian internal magnetic field into spherical harmonics, which allows for a more accurate mapping of the magnetic field lines crossing Io, Europa, and Ganymede orbits to the satellite footprints observed in UV. This model, named VIPAL, is mostly constrained by the Io footprint positions, including the longitudinal constraint, and normalized by the Voyager and Pioneer magnetic field measurements. We show that the surface magnetic fields predicted by our model are more consistent with the observed frequencies of the Jovian radio emissions than those predicted by previous models