Comparative study of the power transferred from satellite-magnetosphere interactions to auroral emissions

Hess, S.; Delamere, P. A.; Dols, V.; Ray, L. C.

doi:10.1029/2010ja015807

Cited by 42 publications

(63 citation statements)

References 53 publications

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“…The power transferred to the electrons by an Alfvén wave packet can be estimated by assuming that, for each Alfvén wavelength, the electrons are accelerated by the Alfvén wave parallel electric field during a half‐period of the wave. Hess et al [2010, 2011b] showed that in this case, an Alfvén wave packet carrying a power P w transfers to the electrons a power P e given by: where a ( k ) is the phase velocity of a Alfvén wave packet component with a wavenumber k in the equatorial plane (and perpendicular wavenumber ). The electrons to be accelerated are described by a thermal velocity v th and an inertial length λ e .…”

Section: Generation Of Hot Electronsmentioning

confidence: 99%

“…The calculations of Hess et al [2010, 2011b] showed that the transmission function depends mostly on the parallel component of the Alfvén wave vector, whereas the acceleration of the electrons depends only on the perpendicular component. Thus can be re‐written separating the propagation effects which depend on the parallel wavelength () and the electron acceleration itself which depends on the perpendicular wavelength (): The power generate by the Io interaction and put into the Alfvén wave packet ( P w ) varies considerably with time, since Io's orbit and the plasma torus are oriented in different planes, thus introducing a longitudinal modulation of the interaction.…”

Section: Generation Of Hot Electronsmentioning

confidence: 99%

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Longitudinal modulation of hot electrons in the Io plasma torus

et al. 2011

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[1] The longitudinal modulation in the Io torus has been an open question for decades. A major clue was provided by the discovery of the key modulation of the hot electron population, at both the System III and System IV periods. However, very little progress has been made in explaining the origin of these hot electron modulations. We propose that the hot electrons population is powered by the inward motion of empty flux tubes (i.e. related to the outward transport of the Iogenic plasma), which has been observed in the torus. We propose that the System IV and System III modulation of the hot electron population corresponds to modulation of the intensity of the current system and of the efficiency of the electron acceleration, respectively. We build on the latest models of the Io current system to describe the current system associated with the motion of the empty flux tubes, and the associated electron acceleration. The System III modulation of the hot electron population, due to the modulation of the efficiency of the electron acceleration, can then be related to the topology of the magnetic field. We show through calculation and simulation that the electron acceleration related to the inward motion of the empty flux tube may explain the observations. We discuss the energy budget and show that it is in favor of our hypothesis.

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Section: Generation Of Hot Electronsmentioning

confidence: 99%

Section: Generation Of Hot Electronsmentioning

confidence: 99%

Longitudinal modulation of hot electrons in the Io plasma torus

et al. 2011

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“…When Io is in the center of the torus, the leading spot will overlap with Io's main spot and thus will enhance its brightness as well. A fraction of the wave energy at Io will be partly reflected and filamented while traveling along the inhomogeneous plasma densities and magnetic fields (Wright & Schwartz 1989;Chust et al 2005;Jacobsen et al 2007;Hess et al 2010aHess et al , 2011a. The strength of the wave reflection, transmission and filamentation also depends on Io's position in the torus and will contribute to the variably of the brightness (Hess et al 2013).…”

Section: Poynting Fluxes: Iomentioning

confidence: 99%

“…Zarka (2007) and Hess et al (2011a) estimate values for the energies in the interaction of the satellites with Jupiter's magnetosphere. Our derived values for the Poynting flux are on the same order but somewhat smaller than those in Zarka (2007) since the expressions in Zarka (2007) consider the energy flux into the satellites' ionospheres or the energies dissipated within the satellites' ionospheres, which are generally larger than the energy radiated away from the satellites, which we calculate here.…”

Section: Comparison and Commentsmentioning

confidence: 99%

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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“…The chosen width corresponds to ∼3 • of latitude, which encompasses the typical day-to-day variability in the main emission location but avoids the selection of significant portions of outer or polar emissions. The longitudinal boundaries of the ROIs correspond to the mapping of boundaries of the equatorial local time sectors at a radial distance of 30 R J using the mapping model from Vogt et al (2015) based on the VIPAL model (Hess et al, 2011). As a consequence, the two ROIs do not cover an equal area on the planet because of the asymmetry of the magnetic field on the surface of the planet.…”

Section: Dawn-dusk Variations In the Main Emission Brightnessmentioning

confidence: 99%

The far-ultraviolet main auroral emission at Jupiter – Part 1: Dawn–dusk brightness asymmetries

Bonfond¹,

Gustin²,

Gérard³

et al. 2015

Ann. Geophys.

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Abstract. The main auroral emission at Jupiter generally appears as a quasi-closed curtain centered around the magnetic pole. This auroral feature, which accounts for approximately half of the total power emitted by the aurorae in the ultraviolet range, is related to corotation enforcement currents in the middle magnetosphere. Early models for these currents assumed axisymmetry, but significant local time variability is obvious on any image of the Jovian aurorae. Here we use far-UV images from the Hubble Space Telescope to further characterize these variations on a statistical basis. We show that the dusk side sector is ∼ 3 times brighter than the dawn side in the southern hemisphere and ∼ 1.1 brighter in the northern hemisphere, where the magnetic anomaly complicates the interpretation of the measurements. We suggest that such an asymmetry between the dawn and the dusk sectors could be the result of a partial ring current in the nightside magnetosphere.

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Comparative study of the power transferred from satellite-magnetosphere interactions to auroral emissions

Cited by 42 publications

References 53 publications

Longitudinal modulation of hot electrons in the Io plasma torus

Longitudinal modulation of hot electrons in the Io plasma torus

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

The far-ultraviolet main auroral emission at Jupiter – Part 1: Dawn–dusk brightness asymmetries

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