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Regions of ECH occurrence in different planetary magnetospheres. Two distinct regions of ECH waves are present in Saturn and Jupiter. ECH waves are seen in the equatorial regions outside the high density plasmasphere / plasma torus and also at intermediate latitude in the magnetospheres, where plasma is confined in a thin disc near centrifugal equator.

Whistler-mode waves propagating in the Earth’s inner magnetosphere sometimes appear as a set of nearly constant frequency elements separated by a fixed frequency. Such events are typically called line radiation, and they can have two distinct origins. First, events with narrow spectral lines and the frequency spacing corresponding to the base power system frequency (50/100 or 60/120 Hz) are generated by electromagnetic radiation from electric power systems on the ground (power line harmonic radiation, PLHR). Second, waves with broader spectral lines, whose frequency spacing does not correspond to the power system frequency, are believed to be generated by plasma instabilities in the magnetosphere (magnetospheric line radiation, MLR).Frequencies of line radiation events are typically on the order of a few kHz, while their frequency spacing is on the order of a hundred Hz. Relevant spacecraft observations at larger radial distances are thus very sparse due to the typically low frequency resolution of available measurements, not sufficient to distinguish the line structure. We use high-resolution multicomponent wave measurements performed by the EMFISIS instrument on board the Van Allen Probes during the burst mode to fill this observational gap. We systematically identify the line radiation events and analyze their occurrence and properties. Detailed wave propagation analysis allows us to reveal wave propagation throughout the magnetosphere. We further show that the frequency spacing of MLR events appears to be related to an electrostatic wave observed at the corresponding frequency (≈100 Hz). Finally, conjugate observations performed by the Kannuslehto station in Finland are used to estimate the spatial extent of the events.

We define the spatial clustering of X-rays within Jupiter’s northern auroral regions by classifying their distributions into ‘X-ray auroral structures’. Using data from Chandra during Juno’s main mission observations (24 May 2016 – 8 September 2019), we define five X-ray structures based on their ionospheric location and calculate the distribution of auroral photons. The morphology and ionospheric location of these structures allow us to explore the possibility of numerous X-ray auroral magnetospheric drivers. We compare these distributions to Hubble Space Telescope (HST)and Juno (Waves and MAG) data, and a 1D solar wind propagation model to infer the state of Jupiter’s magnetosphere. Our results suggest that the five sub-classes of ‘X-ray structures’ fall under two broad morphologies: fully polar and low latitude emissions. Visibility modelling of each structure suggests the non-uniformity of the photon distributions across the Chandra intervals are likely associated with the switching on/off of magnetospheric drivers as opposed to geometrical effects. The combination of ultraviolet (UV) and X-ray morphological structures is a powerful tool to elucidate the behaviour of both electrons and ions and their link to solar wind/magnetospheric conditions in the absence of an upstream solar monitor.

On June 7th, 2021 the Juno spacecraft visited Ganymede and provided the first in situ observations since Galileo's last flyby in 2000. The measurements obtained along a one-dimensional trajectory can be brought into global context with the help of three-dimensional magnetospheric models. Here we apply the magnetohydrodynamic model of Duling et al. (2014) to conditions during the Juno flyby. In addition to the global distribution of plasma variables we provide mapping of Juno's position along magnetic field lines, Juno's distance from closed field lines and detailed information about the magnetic field's topology. We find that Juno did not enter the closed field line region and that the boundary between open and closed field lines on the surface matches the poleward edges of the observed auroral ovals. To estimate the sensitivity of the model results, we carry out a parameter study with different upstream plasma conditions and other model parameters.

The Juno Waves instrument measured plasma waves associated with Ganymede's magnetosphere during its flyby on 7 June, day 158, 2021. Three distinct regions were identified including a magnetotail/wake, and nightside and dayside regions in the main magnetosphere distinguished by their electron densities and associated variability. The main magnetosphere includes electron cyclotron harmonic emissions including a band at the upper hybrid frequency, as well as whistler-mode chorus and hiss. These waves likely interact with energetic electrons in Ganymede’s magnetosphere by pitch angle scattering and/or accelerating the electrons. The magnetotail/wake is accentuated by low-frequency turbulence and electrostatic solitary waves. Radio emissions observed before and after the flyby likely have their source in Ganymede’s magnetosphere.

Electromagnetic waves radiated by powerful military very low frequency transmitters can efficiently interact with energetic electrons trapped in the radiation belts and result in their precipitation. However, such interactions ultimately depend on the wave normal angles of propagating emissions. In the equatorial interaction region, these can be either very low (ducted propagation) or comparatively large (unducted propagation). It is thus important to be able to distinguish between the two propagation types and to quantify what portion of the wave energy propagates ducted/unducted. Unfortunately, spacecraft multicomponent wave measurements which would allow to directly experimentally tackle this issue typically do not extend to high enough frequencies with a sufficient frequency resolution. One exception that we exploit are signals from Alpha navigation transmitters, which radiate at frequencies as low as about 11.9 kHz. Such frequencies are readily detectable by the EMFISIS instrument onboard the Van Allen Probes spacecraft operating close to the geomagnetic equator at L-shells between about 1.1 and 6.5. We use respective multicomponent burst mode measurements to distinguish between the ducted and unducted modes of propagation and to evaluate their relative importance under different conditions. We show that while the unducted waves are detected more often, the ducted waves tend to have larger Poynting fluxes, so that the total power propagating in the two modes is roughly comparable.

We expand on previous observations of magnetic reconnection in Jupiter's magnetosphere by constructing a survey of ion-inertial scale plasmoids in the Jovian magnetotail. We developed an automated detection algorithm to identify reversals in the

The RBSP and the Arase satellites have different inclinations and sometimes they fly both near the equator and off the equator on the same magnetic field line, simultaneously. Such conjunction even...

The ionospheric Alfven resonator (IAR) is a structure formed by the rapid decrease in the plasma density above a planetary ionosphere. This results in a corresponding increase in the Alfv&ea...

We present simultaneous observations of aurorae at Jupiter from the Hubble Space Telescope and Hisaki, in combination with the in situ measurements of magnetic field, particles, and radio waves from the Juno Spacecraft in the outer magnetosphere, from ~ 80RJ to 60RJ during 17 to 22 March 2017. Two cycles of accumulation and release of magnetic flux, named magnetic loading/unloading, were identified during this period, which correlate well with electron energization and auroral intensifications. Magnetic reconnection events are identified during both the loading and unloading periods, indicating that reconnection and unloading are independent processes. These results show that the dynamics in the middle magnetosphere are coupled with auroral variability.

The heliopause is the boundary between the hot heliospheric (solar wind) plasma and the relatively cold interstellar plasma. Pressure balance considerations show that there should be a large (factor of 20 to 50) density increase across the heliopause. Here we report electron density measurements from the Voyager 1 and 2 plasma wave instruments near and beyond the heliopause. The plasma density in the outer heliosphere is typically about 0.002 cm−3. The first electron density measured by the Voyager 2 plasma wave instrument in the interstellar medium, 0.039 cm−3 ± 15%, was on 30 January 2019 at a heliocentric radial distance of 119.7 au. The density jump, about a factor of 20, confirms that Voyager 2 crossed the heliopause. The new density is very similar to the first density measured in the interstellar medium by the Voyager 1 plasma wave instrument, 0.055 cm−3, on 23 October 2013 at a radial distance of 122.6 au. These small differences in the densities and radial distances are probably due to the relative locations of the spacecraft in the boundary layer that forms in the interstellar plasma just beyond the heliopause. This Article reports measurements from the plasma wave instruments of the Voyager spacecraft as they passed from the heliosphere into interstellar space. The Voyager 2 instrument recorded an electron density jump of a factor of 20, similar to that from Voyager 1 several years previously.

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Naturally occurring chorus emissions are a class of electromagnetic waves found in the space environments of the Earth and other magnetized planets. They play an essential role in accelerating high-energy electrons forming the hazardous radiation belt environment. Chorus typically occurs in two distinct frequency bands separated by a gap. The origin of this two-band structure remains a 50-year old question. Here we report, using NASA’s Van Allen Probe measurements, that banded chorus waves are commonly accompanied by two separate anisotropic electron components. Using numerical simulations, we show that the initially excited single-band chorus waves alter the electron distribution immediately via Landau resonance, and suppress the electron anisotropy at medium energies. This naturally divides the electron anisotropy into a low and a high energy components which excite the upper-band and lower-band chorus waves, respectively. This mechanism may also apply to the generation of chorus waves in other magnetized planetary magnetospheres., Chorus waves are crucial on radiation belt dynamics in the space of magnetized planets. Here, the authors show that initially excited single-band chorus waves can quickly accelerate medium energy electrons, and divide the anisotropic electrons into low and high energy components, which subsequently excite two-band chorus waves.