Explore the vast range of titles available.

The Juno spacecraft acquired direct observations of the jovian magnetosphere and auroral emissions from a vantage point above the poles. Juno’s capture orbit spanned the jovian magnetosphere from bow shock to the planet, providing magnetic field, charged particle, and wave phenomena context for Juno’s passage over the poles and traverse of Jupiter’s hazardous inner radiation belts. Juno’s 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.

The determination of the internal magnetic field of Jupiter has been the object of many studies and publications. These models have been computed from the Pioneer, Voyager, and Ulysses measurements. Some models also use the position of the Io footprints as a constraint: the magnetic field lines mapping to the footprints must have their origins along Io's orbit. The use of this latter constraint to determine the internal magnetic field models greatly improved the modeling of the auroral emissions, in particular the radio ones, which strongly depends on the magnetic field geometry. This constraint is, however, not sufficient for allowing a completely accurate modeling. The fact that the footprint field line should map to a longitude close to Io's was not used, so that the azimuthal component of the magnetic field could not be precisely constrained. Moreover, a recent study showed the presence of a magnetic anomaly in the northern hemisphere, which has never been included in any spherical harmonic decomposition of the internal magnetic field. We compute a decomposition of the Jovian internal magnetic field into spherical harmonics, which allows for a more accurate mapping of the magnetic field lines crossing Io, Europa, and Ganymede orbits to the satellite footprints observed in UV. This model, named VIPAL, is mostly constrained by the Io footprint positions, including the longitudinal constraint, and normalized by the Voyager and Pioneer magnetic field measurements. We show that the surface magnetic fields predicted by our model are more consistent with the observed frequencies of the Jovian radio emissions than those predicted by previous models. Key Points A more accurate magnetic field model can be computed from the mapping of Io's fo This model is consistent with the magnetometer measurements This model permits a better description of the satellite‐related aurorae

While Jupiter’s magnetosphere is primarily governed by internal processes, variations in solar wind conditions can significantly modulate magnetospheric energy. Assessing solar wind conditions at Jupiter has been a long-standing challenge in the community. In this study, we investigate multiple datasets, including auroral images captured by the Hubble Space Telescope and in situ measurements obtained by the Juno spacecraft, to characterize Jupiter’s magnetosphere during solar wind compression and quiet conditions. The distinct responses demonstrate that auroral morphologies, lobe magnetic fields, ultra-low-frequency waves, and broadband kilometric radio emissions could serve as effective indicators for magnetospheric states. In particular, we statistically analyze the distribution of lobe magnetic fields, which represent the intensities of the cross-field electrical currents in the magnetodisc, and propose the applicability of the lobe magnetic field as a proxy for solar wind conditions. The results from the four individual methods of determining magnetospheric states are generally consistent, providing further evidence of their robustness. These observational proxies for solar wind conditions could therefore be widely applied in both existing spacecraft datasets and those from future missions to Jupiter.

Jupiter's auroral emission is a spectacular phenomenon that provides insight into energy release processes related to the coupling of its magnetosphere and ionosphere. This energy release is influenced by solar wind conditions. Using joint observations from Juno and the Hubble Space Telescope (HST), we statistically investigate the relationship between auroral power and current sheet variations under different solar wind conditions. In this study, we reveal that during global main auroral brightening events that are closely connected to solar wind compressions, the dawn side current sheet is substantially thinner than during times when a quiet auroral morphology is present. Furthermore, the total current intensity in the current sheet is found to increase under solar wind compression conditions compared to the quiet period. These findings provide important observational evidence for how magnetospheric dynamics driven by solar wind behavior affect auroral activity, deepening our understanding of the coupling between Jupiter's magnetosphere and ionosphere. Plain Language Summary Jupiter, the largest planet in our solar system, has a fascinating and powerful auroral emission that can help us understand the interactions between its magnetic field and the charged particles in its atmosphere. These auroral emissions are influenced by solar wind conditions, which are streams of charged particles coming from the Sun. In this study, we used observations from the Juno spacecraft and the Hubble Space Telescope to investigate the relationship between Jupiter's auroral emissions and changes in the planet's magnetic field. We found that during periods of increased solar wind pressure, the magnetic field layer, known as the current sheet, becomes thinner compared to times when the aurora is quiet. These findings offer valuable evidence of how Jupiter's magnetic field is affected by solar wind behavior and improve our understanding of the relationship between the planet's magnetic field and its aurora. This research helps us better comprehend the complex processes occurring in Jupiter's magnetosphere and can potentially enhance our knowledge of similar phenomena occurring on other planets. Key Points The features of the current sheet in Jupiter's dawnside magnetosphere are highly relevant to auroral contexts During a solar wind compression event, the dawnside current sheet becomes substantially thinner than during quiet times The total current intensity of the current sheet is much higher during solar wind compression events than the quiet times

We compare Hubble Space Telescope observations of Jupiter's FUV auroras with contemporaneous conjugate Juno in situ observations in the equatorial middle magnetosphere of Jupiter. We show that bright patches on and equatorward of the main emission are associated with hot plasma injections driven by ongoing active magnetospheric convection. During the interval that Juno crossed the magnetic field lines threading the complex of auroral patches, a series of energetic particle injection signatures were observed, and immediately prior, the plasma data exhibited flux tube interchange events indicating ongoing convection. This presents the first direct evidence that auroral morphology previously termed “strong injections” is indeed a manifestation of magnetospheric injections, and that this morphology indicates that Jupiter's magnetosphere is undergoing an interval of active iogenic plasma outflow. Plain Language Summary Auroras, known as the “Northern (or Southern) Lights” on Earth, are spectacular manifestations of energetic processes occurring in the space environment of a planet. The behavior of Jupiter's magnetosphere is dominated by the planet's rapid rotation, along with the centrifugally‐driven outflow of plasma (ionized gas) originating from active volcanoes on the moon Io. A prominent auroral feature on Jupiter has for many years been interpreted as a sign that Jupiter's magnetosphere is undergoing active convection, in which plasma from Io “falls” away from the planet, to be replaced by hot, relatively empty “bubbles” known as injections, moving inward. This feature comprises prominent patches of bright emission that are often observed in Jupiter's auroras, though the evidence associating them with injections has been largely circumstantial. Here we show that the NASA Juno spacecraft flew through such injections in the equatorial magnetosphere on magnetic field lines mapping to a cluster of auroral patches as observed by HST. The Juno data also indicated the interval was characterized by signatures of convection and outflow of plasma originating from Io. This demonstrates that auroral patches are signatures of injections, and that auroral emissions are an important tool for diagnosing the behavior of planetary magnetospheres. Key Points Bright FUV auroral patches on Jupiter are associated with magnetospheric injections and magnetospheric convection Hubble Space Telescope and Juno equatorial data show a cluster of patches is magnetically conjugate with energetic particle injections The interval also exhibits flux tube interchange and lagging magnetic field associated with plasma mass outflow

Contrary to the case of the Earth, the main auroral oval on Jupiter is related to the breakdown of plasma corotation in the middle magnetosphere. Even if the root causes for the main auroral emissions are Io's volcanism and Jupiter's fast rotation, changes in the aurora could be attributed either to these internal factors or to fluctuations of the solar wind. Here we show multiple lines of evidence from the aurora for a major internally‐controlled magnetospheric reconfiguration that took place in Spring 2007. Hubble Space Telescope far‐UV images show that the main oval continuously expanded over a few months, engulfing the Ganymede footprint on its way. Simultaneously, there was an increased occurrence rate of large equatorward isolated auroral features attributed to injection of depleted flux tubes. Furthermore, the unique disappearance of the Io footprint on 6 June appears to be related to the exceptional equatorward migration of such a feature. The contemporary observation of the spectacular Tvashtar volcanic plume by the New‐Horizons probe as well as direct measurement of increased Io plasma torus emissions suggest that these dramatic changes were triggered by Io's volcanic activity. Key Points The Ganymede footprint can be engulfed into the Jovian main emissions The main oval expanded and the outer emissions brightened from 02 to 06/2007 The Io auroral footprint momentarily disappeared on June 7th 2007

Like Earth, Jupiter has aurorae generated by energetic particles hitting its atmosphere. Those incoming particles can come from Jupiter's moons Io and Ganymede. Mura et al. used infrared observations from the Juno spacecraft to image the moon-generated aurorae. The pattern induced by Io showed an alternating series of spots, reminiscent of vortices, and sometimes split into two arcs. Aurorae related to Ganymede could also show a double structure. Although the cause of these unexpected features remains unknown, they may provide a way to examine how the moons produce energetic particles or how the particles propagate to Jupiter. Science , this issue p. 774 Auroral features induced on Jupiter by the moons Io and Ganymede have complex spatial structures. Jupiter’s aurorae are produced in its upper atmosphere when incoming high-energy electrons precipitate along the planet’s magnetic field lines. A northern and a southern main auroral oval are visible, surrounded by small emission features associated with the Galilean moons. We present infrared observations, obtained with the Juno spacecraft, showing that in the case of Io, this emission exhibits a swirling pattern that is similar in appearance to a von Kármán vortex street. Well downstream of the main auroral spots, the extended tail is split in two. Both of Ganymede’s footprints also appear as a pair of emission features, which may provide a remote measure of Ganymede’s magnetosphere. These features suggest that the magnetohydrodynamic interaction between Jupiter and its moon is more complex than previously anticipated.

While the terrestrial aurorae are known to be driven primarily by the interaction of the Earth's magnetosphere with the solar wind, there is considerable evidence that auroral emissions on Jupiter and Saturn are driven primarily by internal processes, with the main energy source being the planets' rapid rotation. Prior observations have suggested there might be some influence of the solar wind on Jupiter's aurorae and indicated that auroral storms on Saturn can occur at times of solar wind pressure increases. To investigate in detail the dependence of auroral processes on solar wind conditions, a large campaign of observations of these planets has been undertaken using the Hubble Space Telescope, in association with measurements from planetary spacecraft and solar wind conditions both propagated from 1 AU and measured near each planet. The data indicate a brightening of both the auroral emissions and Saturn kilometric radiation at Saturn close in time to the arrival of solar wind shocks and pressure increases, consistent with a direct physical relationship between Saturnian auroral processes and solar wind conditions. At Jupiter the correlation is less strong, with increases in total auroral power seen near the arrival of solar wind forward shocks but little increase observed near reverse shocks. In addition, auroral dawn storms have been observed when there was little change in solar wind conditions. The data are consistent with some solar wind influence on some Jovian auroral processes, while the auroral activity also varies independently of the solar wind. This extensive data set will serve to constrain theoretical models for the interaction of the solar wind with the magnetospheres of Jupiter and Saturn.

The Hubble Space Telescope (HST) data set obtained over two campaigns in 2007 is used to determine the long‐term variability of the different components of Jupiter's auroras. Three regions on the planet's disc are defined: the main oval, the low‐latitude auroras, and the high‐latitude auroras. The UV auroral power emitted from these regions is extracted and compared to estimated solar wind conditions projected to Jupiter's orbit from Earth. In the first campaign the emitted power originated mainly from the main oval and the high‐latitude regions, and in the second campaign the high‐latitude and main oval auroras were dimmer and less variable, while the low‐latitude region exhibited bright, patchy emission. We show that, apart from during specific enhancement events, the power emitted from the poleward auroras is generally uncorrelated with that of the main oval. The exception events are dawn storms and compression region enhancements. It is shown that the former events, typically associated with intense dawnside main oval auroras, also result in the brightening of the high‐latitude auroras. The latter events associated with compression regions exhibit a particular auroral morphology; that is, where it is narrow and well defined, the main oval is bright and located ∼1° poleward of its previous location, and elsewhere it is faint. Instead there is bright emission in the poleward region in the postnoon sector where distinct, bright, sometimes multiple arcs form.

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. Key Points First observations on bifurcations of the main auroral ring at Saturn The bifurcations could be the ionospheric signature of reconnection events The auroral bifurcations represent the amount of newly open flux