Spatial Distribution of the Pedersen Conductance in the Jovian Aurora From Juno‐UVS Spectral Images

Gérard, Jean‐Claude; Gkouvelis, Leonardos; Bonfond, Bertrand; Grodent, Denis; Gladstone, G. R.; Hue, V.; Greathouse, Thomas; Versteeg, M. H.; Kammer, Joshua A.; Blanc, M.

doi:10.1029/2020ja028142

Cited by 22 publications

(46 citation statements)

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“…These results are in agreement with one‐dimensional models of auroral Pedersen conductance (Hiraki & Tao, 2008; Millward et al., 2002) that have shown that the amount of H 3 + ions is the key quantity controlling the Pedersen conductance. In turn, the H 3 + content in each hemisphere varies nearly proportionally to the square root of the precipitated auroral power (Gérard et al., 2020; Tao et al., 2011).…”

Section: Resultsmentioning

confidence: 99%

“… the ionization rate profile q(z) is calculated versus altitude using the auroral electron energy flux Fe and mean energy E 0 values for each bin from the analytical expressions given by Hiraki and Tao (2008) the q(z) profiles are inputs to an ionosphere model describing the generation and loss of the different ion species (Gérard et al., 2020). The resulting vertical distributions of H 3 + , hydrocarbon ions and electrons are then calculated for each UVS latitude‐longitude bin the altitude‐dependent Pedersen conductivity σ P is obtained by adding the electron and ion contributions based on the classical Pedersen conductivity formulation combining the ion‐neutral and the electron‐neutral contributions: …”

Section: Methodsmentioning

confidence: 99%

“…the q(z) profiles are inputs to an ionosphere model describing the generation and loss of the different ion species (Gérard et al., 2020). The resulting vertical distributions of H 3 + , hydrocarbon ions and electrons are then calculated for each UVS latitude‐longitude bin…”

Section: Methodsmentioning

confidence: 99%

“…Eight examples of Pedersen conductance and H 3 + column density maps have been illustrated in Gérard et al. (2020). They demonstrated the nonuniformity of the auroral conductance, showing local values ranging from less than 0.1 to several mhos.…”

Section: Methodsmentioning

confidence: 99%

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Variability and Hemispheric Symmetry of the Pedersen Conductance in the Jovian Aurora

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The Pedersen conductivity characterizes the ability of ionospheres to carry currents perpendicular to the magnetic field in the presence of an electric field. On Jupiter, it is an important quantity that partly regulates how electric currents can circulate between the magnetosphere and the high-latitude ionosphere. It controls the flow of ionospheric current and the closure of the magnetosphere-ionosphere (M-I) circuit in the ionosphere. It is therefore a key element in the understanding of how and where the Jovian aurora is formed and how currents flow and heat up the neutral atmosphere. Model studies have investigated the magnitude and altitude distribution of Jupiter's ionospheric conductivity (Millward et al., 2002;Singhal, 1996;Strobel & Atreya, 1983). Nichols and Cowley (2004) showed that auroral precipitation can substantially modify the Pedersen vertically integrated conductivity (conductance) and influence the distribution and intensity of the field aligned currents closure in the auroral ionosphere. This interaction was subsequently introduced in 1-D, 2-D, and 3-D models (

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Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Variability and Hemispheric Symmetry of the Pedersen Conductance in the Jovian Aurora

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“…Three main sources of uncertainty affect estimates of the total emitted power by the H 2 molecules in the UV: 1) systematic calibration uncertainties estimated on the order of 16% (Gérard et al., 2020), 2) shot noise uncertainty, which depends on the number of counts in the region of interest and is typically below 5% for the small spots and below 1% for the larger dawn storm features, and 3) the selection uncertainty, which depends on the way the region of interest is defined and which may reach up to 15%. The quadratic sum of all these uncertainties can be rounded to a reasonable value of 25% for power estimates.…”

Section: Image Processingmentioning

confidence: 99%

Are Dawn Storms Jupiter's Auroral Substorms?

et al. 2021

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The specificity of the dawn storms among the various auroral morphologies at Jupiter was recognized as soon as the first high resolution ultraviolet (UV) images of the aurorae on Jupiter became available (Gérard et al., 1994). As observed from the Hubble Space Telescope (HST), having only access to the Earth-facing side of the aurora, they consist of a thickening and a major enhancement of the brightness of the dawn arc of the main auroral emission (main oval). They seem to last for at least 1-2 h (Ballester et al., 1996), but given the typical length of HST sequences is ∼45 min, HST could not provide a complete and uninterrupted view of the process. Dawn storms are also characterized by clear signatures of methane absorption, indicating that the charged particles causing them can precipitate deep below the methane homopause, with energies up to 460 keV (Gustin et al., 2006) in the case of electrons. Based on the large HST observation campaign carried out in 2007, dawn storms appeared rare (3 cases out of 54 observations) and occurred independently from the state of the solar wind (Nichols et al., 2009). However, the dawn storm observed Abstract Dawn storms are among the brightest events in the Jovian aurorae. Up to now, they had only been observed from Earth-based observatories, only showing the Sun-facing side of the planet. Here, we show for the first time global views of the phenomenon, from its initiation to its end and from the nightside of the aurora onto the dayside. Based on Juno's first 20 orbits, some patterns now emerge. Small short-lived spots are often seen a couple of hours before the main emission starts to brighten and evolve from a straight arc to a more irregular one in the midnight sector. As the whole feature rotates dawnward, the arc then separates into two arcs with a central initially void region that is progressively filled with emissions. A gap in longitude then often forms before the whole feature dims. Finally, it transforms into an equatorward-moving patch of auroral emissions associated with plasma injection signatures. Some dawn storms remain weak and never fully develop. We also found cases of successive dawn storms within a few hours. Dawn storms thus share many fundamental features with the auroral signatures of the substorms at Earth, despite the substantial differences between the dynamics of the magnetosphere at the two planets. Plain Language Summary Polar aurorae are a direct consequence of the dynamics of the plasma in the magnetosphere. The sources of mass and energy differ between the Earth's and Jupiter's magnetospheres, leading to fundamentally distinct auroral morphologies and very different responses to solar wind variations. Here, we report on the imaging of all development stages of spectacular auroral events at Jupiter, called dawn storms, including, for the first time, their initiation on the nightside. Our results reveal surprising similarities with auroral substorms at Earth, which are auroral events stemming from explosive magnetospheric reconfigurations. These...

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Morphology of Jupiter's Polar Auroral Bright Spot Emissions via Juno-UVS Observations

Haewsantati

Bonfond

Wannawichian

et al. 2020

Preprint

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Jupiter's very bright ultraviolet (UV) auroras result from the collision between precipitating energetic particles and the atmospheric constituents in the planet's upper atmosphere. The auroras are generally divided into four components: The main emissions, the equatorward emissions, the polar emissions, and the satellites' footprints. The location, morphology and behavior of each component indicates that they are related to specific processes in different parts of the magnetosphere. The ever-present main emissions are the easiest feature to identify. They appear as a discontinuous contour around the magnetic pole. The northern hemisphere is subjected to a magnetic anomaly leading to regions of very strong and very weak magnetic field strength, which distorts the shape of the northern main emissions (Grodent et al., 2008). The main emissions are driven by internal processes in the middle magnetosphere at a radial distance of 20-60 Jovian radii (R J ) in the magnetosphere (Clarke et al., 2004;Vogt et al., 2011). The second component of Jupiter's aurora, the equatorward emissions, appear between the main emissions and Io's footpath and are mostly associated with magnetospheric injections (Dumont et al., 2014;Mauk et al., 2002). The multiple components of the satellite magnetic footprints are connected to the satellites of Jupiter via magnetic field lines (Bonfond, 2012). Lastly, polar auroras are characterized by the large variability of the auroral emissions in the entire region located poleward of the main emissions. The polar auroras are related to the dynamics of the outer magnetosphere, but the detailed mechanisms are still unclear. The UV polar emissions are divided into three subregions, the dark region, the swirl region, and the active region (Grodent et al., 2003). The

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Spatial Distribution of the Pedersen Conductance in the Jovian Aurora From Juno‐UVS Spectral Images

Cited by 22 publications

References 43 publications

Variability and Hemispheric Symmetry of the Pedersen Conductance in the Jovian Aurora

Variability and Hemispheric Symmetry of the Pedersen Conductance in the Jovian Aurora

Are Dawn Storms Jupiter's Auroral Substorms?

Morphology of Jupiter's Polar Auroral Bright Spot Emissions via Juno-UVS Observations

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