The dynamics of the Jovian magnetosphere are controlled by the interplay of the planet's fast rotation, its main iogenic plasma source and its interaction with the solar wind. Magnetosphere‐Ionosphere‐Thermosphere (MIT) coupling processes controlling this interplay are significantly different from their Earth and Saturn counterparts. At the ionospheric level, they can be characterized by a set of key parameters: ionospheric conductances, electric currents and fields, exchanges of particles along field lines, Joule heating and particle energy deposition. From these parameters, one can determine (a) how magnetospheric currents close into the ionosphere, and (b) the net deposition/extraction of energy into/out of the upper atmosphere associated to MIT coupling. We present a new method combining Juno multi‐instrument data (MAG, JADE, JEDI, UVS, JIRAM and Waves) and modeling tools to estimate these key parameters along Juno's trajectories. We first apply this method to two southern hemisphere main auroral oval crossings to illustrate how the coupling parameters are derived. We then present a preliminary statistical analysis of the morphology and amplitudes of these key parameters for eight among the first nine southern perijoves. We aim to extend our method to more Juno orbits to progressively build a comprehensive view of Jovian MIT coupling at the level of the main auroral oval.
Ionospheric conductivity perpendicular to the magnetic field plays a crucial role in the electrical coupling between planetary magnetospheres and ionospheres. At Jupiter, it controls the flow of ionospheric current from above and the closure of the magnetosphere‐ionosphere circuit in the ionosphere. We use multispectral images collected with the Ultraviolet Spectral (UVS) imager on board Juno to estimate the two‐dimensional distribution of the electron energy flux and characteristic energy. These values are fed to an ionospheric model describing the generation and loss of different ion species, to calculate the auroral Pedersen conductivity. The vertical distributions of H3+, hydrocarbon ions, and electrons are calculated at steady state for each UVS pixel to characterize the spatial distribution of electrical conductance in the auroral region. We find that the main contribution to the Pedersen conductance stems from collisions of H3+and heavier ions with H2. However, hydrocarbon ions contribute as much as 50% to Σp when the auroral electrons penetrate below the homopause. The largest values are usually associated with the bright main emission, the Io auroral footprint and occasional bright emissions at high latitude. We present examples of maps for both hemispheres based on Juno‐UVS images, with Pedersen conductance ranging from less than 0.1 to a few mhos.
Jupiter, the fifth planet from the sun, has the strongest intrinsic magnetic field among planets in the solar system. The interplay between this magnetic field and the solar wind results in a magnetosphere extending from the topside of Jupiter's atmosphere/ionosphere to beyond 𝐴𝐴 𝐴𝐴∼ 100 𝐴𝐴 R𝐽𝐽 (1 𝐴𝐴 R𝐽𝐽 = 𝐴𝐴 ∼ 71,400 km, Jupiter radii; hereinafter, 𝐴𝐴 𝐴𝐴 represents the radial distance to the Jupiter) (Bagenal et al., 2007). Jupiter's magnetosphere is filled with plasma originating from various sources, including the solar wind, Jupiter's atmosphere/ionosphere, and Jupiter's moons. Among these sources, the moon Io, which supplies 𝐴𝐴 ∼ 1 ton plasma per second to the magnetosphere (e.g., Thomas et al., 2004), serves as the dominant one (e.g., Bolton et al., 2015). After entering the magnetosphere, plasma from Io (and other sources) is picked up by the magnetospheric corotating electric fields and corotates with Jupiter with a period of 9.92 hr. The corotation, in turn, induces a centrifugal force on plasma. This force tends to pull plasma radially outward against the magnetic forces, leading to the deformation of Jupiter's dipole-like magnetic fields (e.g., Hill et al., 1974). The deformation is reinforced by the plasma pressure gradient and anisotropy, which, as suggested by later observational and modeling work (e.g., Caudal, 1986;Mauk & Krimigis, 1987;Paranicas et al., 1991), even play a dominant role in balancing the magnetic forces. As a final result of the force balance, a current sheet is formed in Jupiter's middle and outer magnetosphere (Vasyliunas, 1983).Because of Jupiter's dipole tilts ( ∼10 • ), Jupiter's current sheet is generally displaced from Jupiter's rotational equator (Khurana, 1992;Khurana & Schwarzl, 2005;Connerney et al., 1981). As a result of this displacement and Jupiter rotation, a spacecraft in Jupiter's magnetosphere would periodically cross the current sheet. These periodical crossings manifest as a series of magnetic field reversals in magnetic field data (e.g., Connerney et al., 1981;Khurana & Schwarzl, 2005). According to previous observations, magnetic field reversals can be detected from 𝐴𝐴 𝐴𝐴∼ 10 𝐴𝐴 R𝐽𝐽 to almost the magnetopause (e.g., Connerney et al., 1981;Khurana & Schwarzl, 2005), suggesting the existence of the current sheet in the most of the equatorial regions of Jupiter's magnetosphere. Besides its huge size and notability in observations, the current sheet plays a Abstract Jupiter's magnetosphere contains a current sheet of huge size near its equator. The current sheet not only mediates the global mass and energy cycles of Jupiter's magnetosphere, but also provides a site for many localized dynamic processes, such as reconnection and wave-particle interaction. To correctly evaluate its role in these processes, a statistical description of the current sheet is required. To this end, here we conduct statistics on Jupiter's current sheet, by using four-year Juno data obtained in the 20-100 Jupiter radius, 0-6 local time magnetosphere. The statistics show the thickness of th...
We analyze the first 30 orbits of Juno to retrieve the properties of current systems and plasma flows associated with Jovian main auroras.• Southern hemisphere results are consistent with ionospheric plasma sub-corotation.• The two opposite patterns, sub-corotation and super-corotation, are observed in the northern hemisphere.
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