References of "Radioti, Aikaterini"
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See detailImproved mapping of Jupiter’s auroral features to magnetospheric sources
Vogt, Marissa. F.; Kivelson, Margaret. G.; Khurana, Krishan. K. et al

in Journal of Geophysical Research. Space Physics (2011), 116

The magnetospheric mapping of Jupiter's polar auroral emissions is highly uncertain because global Jovian field models are known to be inaccurate beyond ∼30 RJ. Furthermore, the boundary between open and ... [more ▼]

The magnetospheric mapping of Jupiter's polar auroral emissions is highly uncertain because global Jovian field models are known to be inaccurate beyond ∼30 RJ. Furthermore, the boundary between open and closed flux in the ionosphere is not well defined because, unlike the Earth, the main auroral oval emissions at Jupiter are likely associated with the breakdown of plasma corotation and not the open/closed flux boundary in the polar cap. We have mapped contours of constant radial distance from the magnetic equator to the ionosphere in order to understand how auroral features relate to magnetospheric sources. Instead of following model field lines, we map equatorial regions to the ionosphere by requiring that the magnetic flux in some specified region at the equator equals the magnetic flux in the area to which it maps in the ionosphere. Equating the fluxes in this way allows us to link a given position in the magnetosphere to a position in the ionosphere. We find that the polar auroral active region maps to field lines beyond the dayside magnetopause that can be interpreted as Jupiter's polar cusp; the swirl region maps to lobe field lines on the night side and can be interpreted as Jupiter's polar cap; the dark region spans both open and closed field lines and must be explained by multiple processes. Additionally, we conclude that the flux through most of the area inside the main oval matches the magnetic flux contained in the magnetotail lobes and is probably open to the solar wind. [less ▲]

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See detailJupiter's Aurora as Imaged by the NASA IRTF and Comparison with Hubble Space Telescope Observations in the UV
Lystrup, M.; Radioti, Aikaterini ULg; Bonfond, Bertrand ULg et al

Conference (2011, March)

We investigate Jupiter's infrared aurora using observations from the NASA Infrared Telescope Facility from 1995-2000 as compared with observations in the UV from the Hubble Space Telescope.

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See detailComparative magnetotail flapping: Overview of observations at Earth, Jupiter and Saturn
Volwerk, M.; Andre, N.; Arridge, C. et al

Conference (2011)

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See detailSaturn's aurora seen with the eyes of HST and UVIS
Radioti, Aikaterini ULg

Scientific conference (2011)

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See detailAn overview of the aims and plans of an ISSI Team: Investigating the Dynamics of Planetary Magnetotails
Jackman, C.; Andre, N.; Arridge, C. et al

Poster (2011)

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See detailPeriodic bursts of non-Io DAM and its relationship to Jovian aurora phenomena
Rucker, H.; Panchenko, M.; Grodent, Denis ULg et al

Poster (2011)

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See detailComparative Planetary Magnetotails
Bagenal, F.; Jackman, C.; Slavin, J. et al

Poster (2011)

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See detailSmall-scale structures in Saturn's ultraviolet aurora
Grodent, Denis ULg; Gustin, Jacques ULg; Gérard, Jean-Claude ULg et al

in Journal of Geophysical Research. Space Physics (2011), 116

On 26 August 2008, the Ultraviolet Imaging Spectrograph Subsystem (UVIS) instrument onboard the Cassini spacecraft recorded a series of spatially resolved spectra of the northern auroral region of Saturn ... [more ▼]

On 26 August 2008, the Ultraviolet Imaging Spectrograph Subsystem (UVIS) instrument onboard the Cassini spacecraft recorded a series of spatially resolved spectra of the northern auroral region of Saturn. Near periapsis, the spacecraft was only five Saturn radii (R[SUB]S[/SUB]) from the surface and spatially resolved auroral structures as small as 500 km across (0.5° of latitude). We report the observation of two types of UV auroral substructures at the location of the main ring of emission, bunches of spots and narrow arcs. They are found in the noon and dusk sectors, respectively, at latitudes ranging from 73 to 80° corresponding to equatorial regions located beyond 16 R[SUB]S[/SUB]. Their brightness ranges from 1 to 30 kR and their characteristic size varies from 500 km to several thousands of km. These small-scale substructures are likely associated with patterns of upward field aligned currents resulting from nonuniform plasma flow in the equatorial plane. It is suggested that magnetopause Kelvin-Helmholtz waves trigger localized perturbations in the flow, like vortices, able to give rise to the observed UV auroral substructures. [less ▲]

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See detailBifurcations of the main auroral ring at Saturn: ionospheric signatures of consecutive reconnection events at the magnetopause
Radioti, Aikaterini ULg; Grodent, Denis ULg; Gérard, Jean-Claude ULg et al

in Journal of Geophysical Research. Space Physics (2011), 116

This work reports for the first time on bifurcations of the main auroral ring at Saturn observed with the UVIS instrument onboard Cassini. The observation sequence starts with an intensification on the ... [more ▼]

This work reports for the first time on bifurcations of the main auroral ring at Saturn observed with the UVIS instrument onboard Cassini. The observation sequence starts with an intensification on the main oval, close to noon, which is possibly associated with dayside reconnection. Consecutive bifurcations appear with the onset of dayside reconnection, between 11 and 18 magnetic local time, while the area poleward of the main emission expands to lower latitudes. The bifurcations depart with time from the main ring of emission, which is related to the open-closed field line boundary. The augmentation of the area poleward of the main emission following its expansion is balanced by the area occupied by the bifurcations, suggesting that these auroral features represent the amount of newly open flux and could be related to consecutive reconnection events at the flank of the magnetopause. The observations show that the open flux along the sequence increases when bifurcations appear. Magnetopause reconnection can lead to significant augmentation of the open flux within a couple of days and each reconnection event opens ∼10% of the flux contained within the polar cap. Additionally, the observations imply an overall length of the reconnection line of ∼4 hours of local time and suggest that dayside reconnection at Saturn can occur at several positions on the magnetopause consecutively or simultaneously. [less ▲]

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See detailQuasi-periodic polar flares at Jupiter: A signature of pulsed dayside reconnections?
Bonfond, Bertrand ULg; Vogt, M. F.; Gérard, Jean-Claude ULg et al

in Geophysical Research Letters (2011), 38

The most dynamic part of the Jovian UV aurora is located inside the main auroral oval. This region is known to regularly show localized but dramatic enhancements on timescales of several tens of seconds ... [more ▼]

The most dynamic part of the Jovian UV aurora is located inside the main auroral oval. This region is known to regularly show localized but dramatic enhancements on timescales of several tens of seconds, called polar flares. They have often been associated with the polar cusp, based on their location in the polar cap. The present study is based on the longest high-time resolution image sequences ever acquired by the Space Telescope Imaging Spectrograph aboard the Hubble Space Telescope. We report the first observations of a regularity in the occurrence of these flares, with a timescale of 2-3 minutes. We use a magnetic flux mapping model to identify the region corresponding to these emissions in the equatorial plane: the radial distance ranges from 55 to 120 Jovian radii and the local times are between 10: 00 and 18: 00. The analogy with similar phenomena observed at Earth suggests that these quasi-periodic auroral flares could be related to pulsed reconnections at the dayside magnetopause. Indeed, the flares' projected location in the equatorial plane and their rate of re-occurrence show some similarities with the properties of the flux transfer events observed by the Pioneer and Voyager probes. [less ▲]

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See detailNightside reconnection at Jupiter: Auroral and magnetic field observations from 26 July 1998
Radioti, Aikaterini ULg; Grodent, Denis ULg; Gérard, Jean-Claude ULg et al

in Journal of Geophysical Research. Space Physics (2011), 116

In this study we present ultraviolet and infrared auroral data from 26 July 1998, and we show the presence of transient auroral polar spots observed throughout the postdusk to predawn local time sector ... [more ▼]

In this study we present ultraviolet and infrared auroral data from 26 July 1998, and we show the presence of transient auroral polar spots observed throughout the postdusk to predawn local time sector. The polar dawn spots, which are transient polar features observed in the dawn sector poleward of the main emission, were previously associated with the inward moving flow resulting from tail reconnection. In the present study we suggest that nightside spots, which are polar features observed close to the midnight sector, are related to inward moving flow, like the polar dawn spots. We base our conclusions on the near-simultaneous set of Hubble Space Telescope (HST) and Galileo observations of 26 July 1998, during which HST observed a nightside spot magnetically mapped close to the location of an inward moving flow detected by Galileo on the same day. We derive the emitted power from magnetic field measurements along the observed plasma flow bubble, and we show that it matches the emitted power inferred from HST. Additionally, this study reports for the first time a bright polar spot in the infrared, which could be a possible signature of tail reconnection. The spot appears within an interval of 30 min from the ultraviolet, poleward of the main emission on the ionosphere and in the postdusk sector planetward of the tail reconnection x line on the equatorial plane. Finally, the present work demonstrates that ionospheric signatures of flow bursts released during tail reconnection are instantaneously detected over a wide local time sector. [less ▲]

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See detailRelating Jupiter's auroral features to magnetospheric sources
Vogt, Marissa F.; Kivelson, Margaret G.; Khurana, Krishan K. et al

Poster (2010, December)

In order to understand the physical processes that produce the various auroral features we must first understand how the auroral emissions are linked to magnetospheric sources. However, magnetic mapping ... [more ▼]

In order to understand the physical processes that produce the various auroral features we must first understand how the auroral emissions are linked to magnetospheric sources. However, magnetic mapping of Jupiter’s polar auroral emissions to equatorial regions in which source currents are plausibly generated is highly uncertain because the available field models are inaccurate beyond ~30 Jovian radii. We have related auroral features to their magnetospheric sources through a flux equivalence calculation, where we require that the magnetic flux in some specified region at the equator equals the magnetic flux in the area to which it links in the ionosphere. This approach is preferred to tracing model field lines for mapping the auroral polar regions, because the latter method is inaccurate at large distances. Here we present our results, highlighting new mappings for the southern hemisphere, and will compare our mapping to auroral observations from both hemispheres. In particular we relate equatorial regions in which reconnection events have been identified with the locations of polar dawn spots and other possible auroral signatures of tail reconnection. We find that the mapping reproduces several other key auroral features. The polar auroral active region maps to just outside the dayside magnetopause, a region that we identify as the Jovian polar cusp. The polar auroral swirl region maps to open tail field lines and is interpreted as the Jovian polar cap. These interpretations are consistent with some earlier predictions based on auroral observations. We identify the boundary between open and closed flux in the ionosphere, which previously was not well defined. We show that the magnetic flux through the regions interpreted as the polar caps in both hemispheres closely matches the estimated flux through the tail lobe, consistent with the suggestion that this area maps to open field lines. [less ▲]

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See detailDiscovery of pulsed polar flares in the Jovian aurorae
Bonfond, Bertrand ULg; Vogt, M~F; Grodent, Denis ULg et al

Poster (2010, December)

The most active part of the aurora at Jupiter is certainly the polar region, i.e. the emissions located poleward of the main auroral oval. This region is known to occasionally show localized but dramatic ... [more ▼]

The most active part of the aurora at Jupiter is certainly the polar region, i.e. the emissions located poleward of the main auroral oval. This region is known to occasionally show localized but dramatic enhancements of its brightness, referred to as polar flares. These emissions have been associated with the polar cusp, based on their location in the polar cap. In summer 2009, right after the refurbishment of the Space Telescope Imaging Spectrograph camera, the Hubble Space Telescope acquired the longest high-time resolution sequence ever of images of the Jovian aurora. We report the first observations of a quasi-periodicity in the occurrence of these flares, with a timescale of ~2-3 minutes. By using a magnetic flux mapping model, we show that these features originate from a region located at a radial distance ranging from 80 to 100 Jovian radii and local times between 10:00 and 15:00. As a consequence, by analogy with similar behaviors observed in the Earth aurora, we suggest that these emissions could be attributed to pulsed reconnections in the dayside magnetopause. [less ▲]

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See detailComparison Of Jupiter's Infrared And Uv Aurorae With Simultaneous And Near-simultaneous HST And Ground-based Observations
Lystrup, Makenzie B; Radioti, Aikaterini ULg; Bonfond, Bertrand ULg et al

Conference (2010, October)

Jupiter's UV aurorae have been observed extensively for the last twenty years using the Hubble Space Telescope and the infrared aurorae have been investigated using ground-based telescope observations ... [more ▼]

Jupiter's UV aurorae have been observed extensively for the last twenty years using the Hubble Space Telescope and the infrared aurorae have been investigated using ground-based telescope observations. The two wavelength regimes complement each other; the UV is a tracer of inputs from the magnetosphere while the infrared emissions from the H3+ molecular ion show how the ionosphere responds to those inputs. Between 1995 and 2000 Spectroscopic, J.E.P Connerney & T. Satoh carried out observations with the NSFCAM imaging instrument at the NASA Infrared Telescope Facility. Results from this data set have been published, although the entire data set has not been examined and there has been only limited comparison with the UV. We reanalyze this data set in order to statistically characterize the infrared aurora and compare with the UV. Here we present a detailed study of simultaneous and near-simultaneous observations of the UV (STIS instrument on HST) and infrared northern aurorae made on July 26, 1998 and December 16, 2000. The comparative study addresses the main oval emissions, satellite footprints, and polar aurorae. M. Lystrup is supported by an NSF Astronomy and Astrophysics Postdoctoral Fellowship under award AST-0802021. [less ▲]

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See detailJupiter's ultraviolet polar emission: a statistical study
Coumans, Valérie ULg; Bonfond, Bertrand ULg; Grodent, Denis ULg et al

Conference (2010, September)

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See detailSaturn's polar auroral emissions
Radioti, Aikaterini ULg; Grodent, Denis ULg; Gérard, Jean-Claude ULg et al

Conference (2010, June 07)

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See detailSaturn's aurora seen by HST and UVIS
Grodent, Denis ULg; Radioti, Aikaterini ULg; Bonfond, Bertrand ULg et al

Conference (2010, June 07)

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See detailAuroral footprints; everywhere
Grodent, Denis ULg; Bonfond, Bertrand ULg; Radioti, Aikaterini ULg et al

Conference (2010, May 06)

Jupiter’s moons Io, Europa and Ganymede are continuously interacting with the Jovian magnetic field and with the sheet of plasma flowing near its equatorial plane. The interaction between these moons and ... [more ▼]

Jupiter’s moons Io, Europa and Ganymede are continuously interacting with the Jovian magnetic field and with the sheet of plasma flowing near its equatorial plane. The interaction between these moons and the Jovian magnetosphere causes strong Alfvénic perturbations which propagate along the magnetic field lines. On their way towards Jupiter’s polar regions, these perturbations accelerate charged particles which then interact with Jupiter’s ionosphere where they loose a fraction of their energy in the form of auroral emissions. Each of the three moons leaves an auroral footprint around the poles of Jupiter which departs from the bulk of the auroral emission. Their location is mainly controlled by the topology of the field lines and thus analysis of the auroral footprints provides information on the magnetic field itself. In that regard, the satellites auroral footpaths were used to highlight the presence of a strong magnetic anomaly in the northern hemisphere of Jupiter. Detailed inspection of the footprints’ brightness and morphology as a function of time reveals fundamental information on the interaction mechanisms near the moons, on the particles acceleration mechanisms as well as on the Jovian ionosphere. For example, it was suggested that the Io footprint actually consists of several spots resulting from successive steps in the perturbation propagation process. Another example is the finding of three different timescales in the variations of Ganymede’s footprint; each of them is pointing to a different part of the electromagnetic interaction between the moon’s mini-magnetosphere and the Jovian plasma. Several recent images of Saturn’s auroral regions obtained with Cassini/UVIS at high latitude show an obvious auroral spot at the predicted location of Enceladus’ footprint. This major finding demonstrates that the electromagnetic interaction between a moon and its parent planet is not unique to Jupiter but appears to be a common feature in planetary systems. [less ▲]

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See detailAuroral footprints of tail reconnection at Jupiter and Saturn
Radioti, Aikaterini ULg; Grodent, Denis ULg; Gérard, Jean-Claude ULg et al

Conference (2010, May 03)

Tail reconnection at Jupiter’s magnetosphere, has recently been shown to leave its signature in the aurora. The Hubble Space Telescope observed transient polar dawn spots on the Jovian aurora, with a ... [more ▼]

Tail reconnection at Jupiter’s magnetosphere, has recently been shown to leave its signature in the aurora. The Hubble Space Telescope observed transient polar dawn spots on the Jovian aurora, with a characteristic recurrence period of 2-3 days. Because of their periodic occurrence cycle and observed location, it is suggested that the transient auroral features are related to the precipitated, heated plasma during reconnection processes taking place in the Jovian magnetotail. Particularly, it is proposed that the transient auroral spots are triggered by the planetward moving flow bursts released during the process. A comparison of their properties with those of the <br />auroral spots strengthen the conclusion that they are signatures of tail reconnection. <br />Cassini recently revealed magnetotail reconnection events at Saturn similar to those observed at Jupiter. Based on the UVIS dataset we present transient features at Saturn’s polar auroral region, which are possible signatures of tail reconnection. We study their size, power, duration and duty cycle and we suggest possible triggering mechanisms associated with magnetotail dynamics. We compare these auroral emissions with those at Jupiter and we discuss how energy is transferred to the ionosphere during tail reconnection. [less ▲]

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