Power transmission and particle acceleration along the Io flux tube

Abstract

[1] Io's motion relative to the Jovian magnetic field generates a power of about 10 12 W, which is thought to propagate as an Alfvén wave along the magnetic field line. This power is transmitted to the electrons, which will then precipitate and generate the observed auroral phenomena from UV to radio wavelengths. A more detailed look at this hypothesis shows some difficulties: Can the Alfvén waves escape the torus or are they trapped inside? Where and how are the particles accelerated? In which direction? Is there enough power transmitted to the particles to explain the strong brightness of the auroral emissions in UV, IR, visible, and radio? In other words, can we make a global, consistent model of the Io-Jupiter interaction that matches all the observations? To answer these questions, we review the models and studies that have been proposed so far. We show that the Alfvén waves need to be filamented by a turbulent cascade process and accelerate the electrons at high latitude in order to explain the observations and to form a consistent scheme of the Io-Jupiter interaction.

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

“…Part of the wave energy will be reflected/filamented in inhomogeneous plasma densities and magnetic fields or converted into heat and particle acceleration. Similar processes also occur to the Alfvén waves generated at the satellites of Jupiter and Saturn (Wright & Schwartz 1989;Chust et al 2005;Jacobsen et al 2007;Hess et al 2010a).…”

“…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).…”

“…Comparison of the observationally derived energy input fluxes with our Poynting fluxes imply that on the order of ∼10% of the total Poynting flux of Io's Alfvén wave/wing is converted into accelerated electrons to generate Io's main footprint. The rest of the wave energy is (a) partially reflected on its way to Jupiter (Chust et al 2005;Hess et al 2010aHess et al , 2013, is (b) partially distributed over a larger area including multiple spots and the downstream auroral trail, and is (c) partially converted into other forms of plasma energy, such as heating. But succinctly, the overall energy in the Poynting flux originating at Io is sufficient to generate Io's auroral footprint.…”

Characteristics of north jovian aurora from STIS FUV spectral images

“…4) Processes that could lead to such an important upward shift of the hydrocarbon layer with respect to the auroral emission are not well understood. Contrary to the main emission, which is the result of precipitating electrons accelerated by a quasi-static potential, acceleration of electrons by Alfven waves 775 are involved in the IFP emission (Bonfond et al (2008), Hess et al (2010)). This difference could be a clue implying that this uplift of the hydrocarbon layer applies to the IFP region only.…”

Magnetic coupling of planets and small bodies with a pulsar wind

“…Neubauer (1980) derived a nonlinear theory of this interaction. The Alfvén wing connecting Io and Jupiter is the only explored case of such a structure in the universe up to now, and it has been the object of recent studies concerning its overall structure (Chust et al 2005;Hess et al 2010), the possibility of particle acceleration (Hess et al 2007b(Hess et al , 2009b, and its consequences on the radio emissions (Queinnec & Zarka 1998;Hess et al 2007aHess et al , 2009a. In the present paper, we develop a theory that generalizes some of Neubauer's results to highly magnetized (B 2 0 μ 0 ρ 0 γ 0 c 2 ) and relativistic plasma flows with Lorentz factors γ 0 1, when a planet immersed in the magnetized pulsar wind acts as a unipolar inductor and generates two stationary Alfvénic structures that emerge from the planet and extend far into the wind.…”