References of "Paranicas, C"
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See detailA radiation belt of energetic protons located between Saturn and its rings
Roussos, E.; Kollmann, P.; Krupp, N. et al

in Science (2018), 362

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See detailPrecipitating electron energy flux and characteristic energies in Jupiter's main auroral region as measured by Juno/JEDI
Clark, G.; Tao, C.; Mauk, B. H. et al

in Journal of Geophysical Research. Space Physics (2018), 113(ja),

Abstract The relationship between electron energy flux and the characteristic energy of electron distributions in the main auroral loss cone bridges the gap between predictions made by theory and ... [more ▼]

Abstract The relationship between electron energy flux and the characteristic energy of electron distributions in the main auroral loss cone bridges the gap between predictions made by theory and measurements just recently available from Juno. For decades such relationships have been inferred from remote sensing observations of the Jovian aurora, primarily from the Hubble Space Telescope (HST), but also more recently from Hisaki. However, to infer these quantities, remote sensing techniques had to assume properties of the Jovian atmospheric structure – leading to uncertainties in their profile. Juno's arrival and subsequent auroral passes have allowed us to obtain these relationships unambiguously for the first time, when the spacecraft passes through the auroral acceleration region. Using Juno/JEDI, an energetic particle instrument, we present these relationships for the 30 keV to 1 MeV electron population. Observations presented here show that the electron energy flux in the loss cone is a non-linear function of the characteristic or mean electron energy and supports both the predictions from Knight [1973] and MHD turbulence acceleration theories [e.g.,Saur et al., 2003]. Finally, we compare the in situ analyses of Juno with remote Hisaki observations and use them to help constrain Jupiter's atmospheric profile. We find a possible solution that provides the best agreement between these datasets is an atmospheric profile that more efficiently transports the hydrocarbons to higher altitudes. If this is correct, it supports the previously published idea [e.g., Parkinson et al. 2006] that precipitating electrons increase the hydrocarbon eddy diffusion coefficients in the auroral regions. [less ▲]

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See detailJuno's Investigation of Jupiter's Magnetosphere
Clark, G.; Gurnett, D.; Haggerty, D. et al

in 42nd COSPAR Scientific Assembly (2018, July)

Since its arrival in July of 2016, NASA's Juno spacecraft continues to return invaluable observations regarding Jupiter's dynamic magnetosphere. The polar orbiting spacecraft has an orbital period of 53.5 ... [more ▼]

Since its arrival in July of 2016, NASA's Juno spacecraft continues to return invaluable observations regarding Jupiter's dynamic magnetosphere. The polar orbiting spacecraft has an orbital period of 53.5 days, which takes it from just a few thousand kilometers above Jupiter's one-bar "surface" outward to over 100 jovian radii - cutting through Jupiter's polar region as well as its equatorial region. Although these regions are inherently coupled, in this talk we compartmentalize Juno's observations into the auroral and magnetospheric regions and briefly discuss their connections. One of Juno's primary science goals is to investigate the nature of Jupiter's aurora - the most powerful aurora in the solar system. Outfitted on the spacecraft are a suite of instruments dedicated to measuring the in situ plasma waves and magnetic fields, charged particles as well as remote sensing the ultraviolet and infrared signatures of the aurora. In concert, these observations have and continue to paint a fundamentally different view of the mechanisms producing the Jovian auroras. Juno's instruments are also sending back new and compelling observations of Jupiter's magnetospheric regions. Examples include: the discovery of a belt of heavy ions residing inside the main ring, new details regarding the magnetopause structure and dynamics, and a more comprehensive survey of the plasma sheet particle populations and dynamics. In this presentation we will briefly summarize some of the major findings from both the auroral and magnetospheric regions and discuss new mysteries and future anticipated observations from Juno. [less ▲]

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See detailHeliospheric conditions at Saturn during Cassini's Ring-Grazing and Proximal Orbits
Roussos, E.; Krupp, N.; Paranicas, C. et al

in Geophysical Research Letters (2018), 45

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See detailIntervals of intense energetic electron beams over Jupiter's poles
Paranicas, C.; Mauk, B. H.; Haggerty, D. K. et al

in Journal of Geophysical Research. Space Physics (2018), 123

Juno's Jupiter Energetic particle Detector Instrument (JEDI) often detects energetic electron beams over Jupiter's polar regions. In this paper, we document a subset of intense magnetic field-aligned ... [more ▼]

Juno's Jupiter Energetic particle Detector Instrument (JEDI) often detects energetic electron beams over Jupiter's polar regions. In this paper, we document a subset of intense magnetic field-aligned beams of energetic electrons moving away from Jupiter at high magnetic latitudes both north and south of the planet. The number fluxes of these beams are often dominated by electrons with energies above about 1 MeV. These very narrow beams can create broad angular responses in JEDI with unique signatures in the detector count rates, probably because of >10 MeV electrons. We use these signatures to identify the most intense beams. These beams occur primarily above the swirl region of the polar cap aurora. This polar region is described as being of low brightness and high absorption and the most magnetically "open" at Jupiter. [less ▲]

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See detailEvolution of the Auroral Signatures of Jupiter's Magnetospheric Injections
Dumont, Maïté ULiege; Grodent, Denis ULiege; Radioti, Aikaterini ULiege et al

in Journal of Geophysical Research. Space Physics (2018), 123(10),

Auroral emissions equatorward of the main emission at Jupiter are suggested to reflect the dynamics of the plasma in the middle magnetosphere. Here, we examine the motion of the auroral signatures of ... [more ▼]

Auroral emissions equatorward of the main emission at Jupiter are suggested to reflect the dynamics of the plasma in the middle magnetosphere. Here, we examine the motion of the auroral signatures of magnetospheric injections appearing in Hubble Space Telescope (HST) images. Our results suggest that the injected plasma moves planetward and lags behind corotation. We then compare the characteristics of the observed signatures with simulations of the auroral precipitation related to injections due to pitch angle scattering. These results indicate that the lifetime of the auroral structures lies between a half and a full rotation of Jupiter. Ultraviolet (UV) spectrally resolved images acquired with HST are then used to highlight the energy-dependent drift of the electrons in auroral injection signatures. Comparison of these observations with simulations of the energy-dependent drift of injected particles suggests that these structures are 3 hours old. Finally, we extend our investigations towards larger and less structured outer emissions possibly associated with younger plasma injections. The motion and evolution of these features are similar to those of the small and compact ones considered in the first part of the study. [less ▲]

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See detailDiscrete and broadband electron acceleration in Jupiter's powerful aurora
Mauk, B. H.; Haggerty, D. K.; Paranicas, C. et al

in Nature (2017), 549

The most intense auroral emissions from Earth's polar regions, called discrete for their sharply defined spatial configurations, are generated by a process involving coherent acceleration of electrons by ... [more ▼]

The most intense auroral emissions from Earth's polar regions, called discrete for their sharply defined spatial configurations, are generated by a process involving coherent acceleration of electrons by slowly evolving, powerful electric fields directed along the magnetic field lines that connect Earth's space environment to its polar regions. In contrast, Earth's less intense auroras are generally caused by wave scattering of magnetically trapped populations of hot electrons (in the case of diffuse aurora) or by the turbulent or stochastic downward acceleration of electrons along magnetic field lines by waves during transitory periods (in the case of broadband or Alfvénic aurora). Jupiter's relatively steady main aurora has a power density that is so much larger than Earth's that it has been taken for granted that it must be generated primarily by the discrete auroral process. However, preliminary in situ measurements of Jupiter's auroral regions yielded no evidence of such a process. Here we report observations of distinct, high-energy, downward, discrete electron acceleration in Jupiter's auroral polar regions. We also infer upward magnetic-field-aligned electric potentials of up to 400 kiloelectronvolts, an order of magnitude larger than the largest potentials observed at Earth. Despite the magnitude of these upward electric potentials and the expectations from observations at Earth, the downward energy flux from discrete acceleration is less at Jupiter than that caused by broadband or stochastic processes, with broadband and stochastic characteristics that are substantially different from those at Earth. [less ▲]

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See detailJupiter's magnetosphere and aurorae observed by the Juno spacecraft during its first polar orbits
Connerney, J. E. P.; Adriani, A.; Allegrini, F. et al

in Science (2017), 356(6340), 826--832

Jupiter is the largest and most massive planet in our solar system. NASA\textquoterights Juno spacecraft arrived at Jupiter on 4 July 2016 and made its first close pass on 27 August 2016. Bolton et al ... [more ▼]

Jupiter is the largest and most massive planet in our solar system. NASA\textquoterights Juno spacecraft arrived at Jupiter on 4 July 2016 and made its first close pass on 27 August 2016. Bolton et al. present results from Juno\textquoterights flight just above the cloud tops, including images of weather in the polar regions and measurements of the magnetic and gravitational fields. Juno also used microwaves to peer below the visible surface, spotting gas welling up from the deep interior. Connerney et al. measured Jupiter\textquoterights aurorae and plasma environment, both as Juno approached the planet and during its first close orbit.Science, this issue p. 821, p. 826The Juno spacecraft acquired direct observations of the jovian magnetosphere and auroral emissions from a vantage point above the poles. Juno\textquoterights capture orbit spanned the jovian magnetosphere from bow shock to the planet, providing magnetic field, charged particle, and wave phenomena context for Juno\textquoterights passage over the poles and traverse of Jupiter\textquoterights hazardous inner radiation belts. Juno\textquoterights energetic particle and plasma detectors measured electrons precipitating in the polar regions, exciting intense aurorae, observed simultaneously by the ultraviolet and infrared imaging spectrographs. Juno transited beneath the most intense parts of the radiation belts, passed about 4000 kilometers above the cloud tops at closest approach, well inside the jovian rings, and recorded the electrical signatures of high-velocity impacts with small particles as it traversed the equator. [less ▲]

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See detailQuasi-periodic injections of relativistic electrons in Saturn's outer magnetosphere
Roussos, E.; Krupp, N.; Mitchell, D. G. et al

in Icarus (2016), 263

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See detailRecurrent energization of plasma in the midnight-to-dawn quadrant of Saturn's magnetosphere, and its relationship to auroral UV and radio emissions
Mitchell, D. G.; Krimigis, S. M.; Paranicas, C. et al

in Planetary and Space Science (2009), 57

We demonstrate that under some magnetospheric conditions protons and oxygen ions are accelerated once per Saturn magnetosphere rotation, at a preferred local time between midnight and dawn. Although ... [more ▼]

We demonstrate that under some magnetospheric conditions protons and oxygen ions are accelerated once per Saturn magnetosphere rotation, at a preferred local time between midnight and dawn. Although enhancements in energetic neutral atom (ENA) emission may in general occur at any local time and at any time in a Saturn rotation, those enhancements that exhibit a recurrence at a period very close to Saturn's rotation period usually recur in the same magnetospheric location. We suggest that these events result from current sheet acceleration in the 15-20 Rs range, probably associated with reconnection and plasmoid formation in Saturn's magnetotail. Simultaneous auroral observations by the Hubble Space Telescope (HST) and the Cassini Ultraviolet Imaging Spectrometer (UVIS) suggest a close correlation between these dynamical magnetospheric events and dawn-side transient auroral brightenings. Likewise, many of the recurrent ENA enhancements coincide closely with bursts of Saturn kilometric radiation, again pointing to possible linkage with high latitude auroral processes. We argue that the rotating azimuthal asymmetry of the ring current pressure revealed in the ENA images creates an associated rotating field aligned current system linking to the ionosphere and driving the correlated auroral processes. [less ▲]

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See detailRecurrent Energization of Plasma in the Midnight-to-Dawn Quadrant of Saturn's Magnetosphere, and its Relationship to Auroral UV and Radio Emissions
Mitchell, D.; Krimigis, S.; Paranicas, C. et al

Poster (2009, August 11)

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See detailTransient auroral features at Saturn: Signatures of energetic particle injections in the magnetosphere
Radioti, Aikaterini ULiege; Grodent, Denis ULiege; Gérard, Jean-Claude ULiege et al

in Journal of Geophysical Research. Space Physics (2009), 114

We report for the first time transient isolated auroral spots at Saturn's southern polar region, based on Hubble Space Telescope (HST) FUV images. The spots last several minutes and appear distinct from ... [more ▼]

We report for the first time transient isolated auroral spots at Saturn's southern polar region, based on Hubble Space Telescope (HST) FUV images. The spots last several minutes and appear distinct from the rest of the auroral emissions. We study two sets of HST and Cassini observations during which Cassini instrumentation detected signatures of energetic particle injections close to the region where, on the same day, HST observed transient auroral spots. On the basis of the simultaneous remote and in situ observations, we discuss the possibility that the transient features are associated with the dynamical processes taking place in the Kronian magnetosphere. Given the limitations in the available observations, we suggest the following possible explanations for the transient aurora. The injection region could directly be coupled to Saturn's ionosphere by pitch angle diffusion and electron scattering by whistler waves, or by the electric current flowing along the boundary of the injected cloud. The energy contained in the injection region indicates that electron scattering could account for the transient aurora process. [less ▲]

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