Ali Haidar Sulaiman

In this study, we propose a new mechanism to explain the observed particle flux at discrete energies in the flux tubes connecting to the wakes of the Galilean moons, first reported by Sarkango et al. (2024, https://doi.org/10.1029/2023gl107431 ) and referred to as “banded flux.” We demonstrate the proposed mechanism using test particle simulations. Sarkango et al. (2024, https://doi.org/10.1029/2023gl107431 ) propose a bounce resonance mechanism for the formation of the banded flux. However, the mechanism has not been tested numerically or analytically. In contrast, Yang et al. (2025, https://doi.org/10.1029/2024gl112240 ) propose that absorption at the moons' surfaces is responsible for the banded flux observed in the wakes of the moons. In this study, the mechanism proposed by Yang et al. (2025, https://doi.org/10.1029/2024gl112240 ) is tested using test particle simulations for the first time, and the limitations of both mechanisms are discussed. According to our proposed mechanism, the observed banded flux could result from an oscillatory parallel electric field . This is generated by the electron inertial effect in the low density region at high latitudes. The oscillatory nature of arises from multiple secondary reflections at density gradients of the Io plasma torus and the ionosphere. These reflections produce an alternating pattern with longitude and opposite polarity on either side of the M‐shell of the moon's foot point, as seen from the moon's reference frame. At a fixed location in the corotating frame, exhibits a quasi‐periodic temporal pattern.

Low‐altitude measurements above Jupiter's main auroras have shown the presence of persistent auroral density depletions. This low density regime strongly favors auroral acceleration by inertial Alfvén waves to explain the predominance of energetic (100–1,000 keV) broadband electron beams. Well‐constrained auroral density measurements are central to describing the role of inertial Alfvén waves in auroral acceleration. Here we present a refined analysis of auroral electron density measurements in the diffuse and main auroral zones using magnetic field and particle data from the Juno spacecraft. We report densities within the upward current region (Zone‐I) typically ranging from , with depletions to order . Downward current region (Zone‐II) densities are limited but remain on the order of . We provide an improved electron density profile within a few degrees latitude of the auroral oval by accounting for auroral zone dynamics. Waves‐derived polar cap density measurements show that the density remains depleted further poleward of the main auroral oval. These results support the presence of a persistent large‐scale density cavity in Jupiter's polar regions.

Mass and energy fluxes from the solar wind can access a planet's magnetosphere through dayside magnetic reconnection. The plasma and magnetic field conditions on either side of the magnetopause determine whether reconnection is suppressed. However, magnetosheath conditions are sensitive to the shape of the magnetopause, and deviations from axisymmetry manifest in the field and flow patterns. This effect is, therefore, not captured in analytical models that assume axisymmetric boundary shapes. Here we utilize the BATSRUS MHD model to study the extent to which nonaxisymmetry alters the conditions for reconnection at Uranus's dayside magnetopause and how this varies on diurnal and seasonal timescales. Specifically, in this work we study conditions based on plasma and magnetic field parameters near the magnetopause that are known to suppress reconnection, rather than modeling reconnection itself. The magnetopause boundary arises naturally in MHD simulations instead of being prescribed. We demonstrate quantitatively the deviation of Uranus's magnetopause shape from a paraboloid and capture the resulting modification in magnetosheath field and flow patterns. Further, we show that suppression of reconnection is highly diurnal, though reconnection is never suppressed on the entire dayside magnetopause. Finally, we outline the limitations of axisymmetric analytical models and present the various features not captured in those models.

Thermal electrons in Jupiter's magnetodisc have been observed to be anisotropic with higher parallel temperature compared to perpendicular. In this work, we used previously‐derived electron properties (Sarkango et al., 2025, https://doi.org/10.1029/2025gl118209 ) to calculate electron and compared the observed anisotropy with electron temperature‐anisotropy‐driven instability thresholds. For cold electrons, the ratio of perpendicular to parallel temperatures decreased with M‐shell, reached a minimum near M = 20–25, beyond which it increased until the distribution was quasi‐isotropic. In space, this turnover was observed close to the oblique electron firehose instability threshold. Linear dispersion analysis using plasma parameters representative of different M‐shells predicts the onset of the oblique firehose instability arising primarily due to cold electron anisotropy, though growth rates differ based on the cold and hot electron abundances, anisotropies, and . On the basis of these observations, we argue that the cold electron anisotropy in Jupiter's magnetodisc is regulated by the oblique electron firehose instability, which may be a source of plasma waves and could contribute to cyclotron‐resonant heating of the Jovian plasma.

Jupiter displays the brightest auroras in the solar system, driven by intensely varying energetic electrons that accelerate into the atmosphere. Here, we provide a comprehensive formalism that accurately describes the bimodality of observed auroral electron acceleration regimes. We demonstrate that the occurrence of the two dominant auroral regimes—broadband and monoenergetic—is dictated by specific characteristic plasma length scales, namely, the relationship between the transverse length scale and the electron inertial length. Furthermore, in contrast to the long-standing acceptance that Alfvén waves responsible for auroral electron acceleration exclusively originate at distant equatorial regions, we demonstrate that they can be locally generated at Jupiter’s low altitudes. From this understanding, we find that locally generated, low-altitude Alfvén waves can be directly responsible for accelerating the most intense auroral electrons at Jupiter. These findings establish that the low-altitude acceleration region can itself become a source of Alfvén waves rather than merely a sink for wave energy, thus altering the standard picture of global magnetospheric energy transfer in strongly magnetized planets.

Low-altitude measurements above Jupiter’s main auroras have shown the presence of persistent auroral density depletions. This low density regime strongly favors auroral acceleration by inertial Alfvén waves to explain the predominance of energetic (100–1000 keV) broadband electron beams. Well-constrained auroral density measurements are central to describing the role of inertial Alfvén waves in auroral acceleration. Here we present a refined analysis of auroral electron density measurements in the diffuse and main auroral zones using magnetic field and particle data from the Juno spacecraft. We report densities within the upward current region (Zone-I) typically ranging from 10 ^-2 —10 ^-1 cm ^-3 , with depletions to order 10 ^-4 cm ^-3 . Downward current region (Zone-II) densities are limited but remain on the order of 10 ^-2 cm ^-3 . We provide an improved electron density profile within a few degrees latitude of the auroral oval by accounting for auroral zone dynamics. Waves-derived polar cap density measurements show that the density remains depleted further poleward of the main auroral oval. These results support the presence of a persistent large-scale density cavity in Jupiter's polar regions.

Thermal electrons in Jupiter's magnetodisc have been observed to be anisotropic with higher parallel temperature compared to perpendicular. In this work, we used previously-derived electron properties (Sarkango et al. 2025) to calculate electron β _∥ and compared the observed anisotropy with electron temperature-anisotropy-driven instability thresholds. For cold electrons, the ratio of perpendicular to parallel temperatures (T _⊥ /T _∥ ) decreased with M-shell, reached a minimum near M=20-25, beyond which it increased until the distribution was quasi-isotropic. In T _⊥ /T _∥ -β _∥ space, this turnover was observed close to the oblique electron firehose instability threshold. Linear dispersion analysis using plasma parameters representative of different M-shells predicts the onset of the oblique firehose instability arising primarily due to cold electron anisotropy, though growth rates differ based on the cold and hot electron abundances, anisotropies, and β _∥ . On the basis of these observations, we argue that the cold electron anisotropy in Jupiter's magnetodisc is regulated by the oblique electron firehose instability, which may be a source of plasma waves and could contribute to cyclotron-resonant heating of the Jovian plasma.

Low-altitude measurements above Jupiter’s main auroras have shown the presence of persistent auroral density depletions. This low density regime strongly favors auroral acceleration by inertial Alfvén waves to explain the predominance of energetic (100–1000 keV) broadband electron beams. Well-constrained auroral density measurements are central to describing the role of inertial Alfvén waves in auroral acceleration. Here we present a refined analysis of auroral electron density measurements in the diffuse and main auroral zones using magnetic field and particle data from the Juno spacecraft. We report densities within the upward current region (Zone-I) typically ranging from 10 ^-2 —10 ^-1 cm ^-3 , with depletions to order 10 ^-4 cm ^-3 . Downward current region (Zone-II) densities are limited but remain on the order of 10 ^-2 cm ^-3 . We provide an improved electron density profile within a few degrees latitude of the auroral oval by accounting for auroral zone dynamics. Waves-derived polar cap density measurements show that the density remains depleted further poleward of the main auroral oval. These results support the presence of a persistent large-scale density cavity in Jupiter's polar regions.

Low-altitude measurements above Jupiter’s main auroras have shown the presence of persistent auroral density depletions. This low density regime strongly favors auroral acceleration by inertial Alfvén waves to explain the predominance of energetic (100–1000 keV) broadband electron beams. Well-constrained auroral density measurements are central to describing the role of inertial Alfvén waves in auroral acceleration. Here we present a refined analysis of auroral electron density measurements in the diffuse and main auroral zones using magnetic field and particle data from the Juno spacecraft. We report densities within the upward current region (Zone-I) typically ranging from 10 ^-2 –10 ^-1 cm ^-3 , with depletions to order 10 ^-4 cm ^-3 . Downward current region (Zone-II) densities remain poorly constrained. We provide an improved electron density profile within a few degrees latitude of the auroral oval by accounting for auroral zone dynamics. These results support the presence of a persistent large-scale density cavity in Jupiter's polar regions.