Wind Interaction Research Articles

The formation and stability of a cold disc made out of stellar winds in the Galactic centre

The reported discovery of a cold (sim 10$^4 K $) disc-like structure within the central $5 $ pc around the super-massive black hole at the centre of the Milk Way, Sagittarius A* (Sgr A*), has challenged our understanding of the gas dynamics and thermodynamic state of the plasma in its immediate vicinity. State-of-the-art simulations do not agree on whether or not such a disc can indeed be a product of the multiple stellar wind interactions of the mass-losing stars in the region. The aims of this study are to constrain the conditions for the formation of a cold disc as a natural outcome of the system of the mass-losing stars orbiting around Sgr A*, to investigate whether the disc is a transient or long-lasting structure, and to assess the validity of the model through direct comparisons with observations. We performed a set of hydrodynamic simulations of the observed Wolf-Rayet (WR) stars feeding Sgr A* using the finite-volume adaptive mesh refinement code Ramses. We focus, for the first time, on the impact of the chemical composition of the plasma emanating from the WR stars. The simulations show that the chemical composition of the plasma affects the radiative cooling to a sufficient degree to impact the properties of the medium, such as density and temperature, and, as a consequence, the rate at which the material inflows onto Sgr A*. We demonstrate that the formation of a cold disc from the stellar winds is possible for certain chemical compositions that are consistent with the current observational constraints. However, even in such cases, it is not possible to reproduce the reported properties of the observed disc-like structure, namely its inclination and the fluxes of its hydrogen recombination lines. We conclude that the stellar winds alone are not sufficient to form the cold disc around Sgr A* inferred from observations. Either relevant ingredients are still missing in the model, or the interpretation of the observed data needs to be revised.

Implementation of an Asymmetric Internal Field in the Comprehensive Inner Magnetosphere‐Ionosphere (CIMI) Model

AbstractA Comprehensive Inner Magnetosphere‐Ionosphere (CIMI) model has been developed to study the dynamics of the cold plasmasphere and the energetic plasmas in the inner magnetosphere, as well as their couplings with each other and with the ionosphere. The CIMI model is able to predict the cold plasma density and energetic electron and ion fluxes in geospace. Furthermore, CIMI is capable of predicting the Region 2 currents, penetration electric field, electron and ion precipitation and magnetospheric heat flux into the ionosphere. The CIMI model includes a realistic magnetic field configuration with a combination of an internal field and an external field imposed by the interaction of the solar wind with the magnetosphere. The internal field has previously been assumed to be a dipole. Recently, the International Geomagnetic Reference Field (IGRF) has been implemented. This new capability enables studies of north‐south and longitudinal dependences in particle precipitation and heat flux, as well as the corresponding asymmetries in ionospheric and thermospheric responses. In this paper, we will briefly review the CIMI equations and model output. Then we will describe the new implementation of the IGRF model into CIMI and how to estimate the north‐south asymmetry in precipitating fluxes from the differences in field strength between magnetic conjugate points. The inclusion of a realistic internal field leads CIMI into a better position to couple with sophisticated ionosphere‐thermosphere models, most of which are using the IGRF model.

Electrostatic Solitary Waves in Electronegative Martian Plasma

The solar wind interacts with planetary magnetospheres, generating plasma waves in both the upstream region and the magnetospheric environment. Mars, lacking an inherent magnetic field, has an induced magnetosphere formed through solar wind interaction with its ionosphere. These waves are crucial for momentum and energy exchange within the planetary plasma environment. This study focuses on the existence and dynamics of electrostatic solitary waves (ESWs) in Martian ionospheric plasma, characterized by various flowing ions. We employ a multifluid plasma model incorporating positive (streaming) ions, negative ions, and two distinct kappa-distributed electron populations to study ESW propagation in the Martian ionosphere from first principles. Linear analysis reveals four distinct modes, including a subsonic mode due to the negative-ion beam. Electrostatic waves may become unstable due to a beam instability excited at long wavelengths. Seeking stationary profile solutions, an energy balance equation is obtained in the moving reference frame, and the shape of the solitary wave can thus be predicted numerically. A meticulous analysis reveals that either positive- or negative-polarity ESWs (or both) may occur (simultaneously) in the Martian environment. In addition to conventional bipolar E-field waveforms, our theoretical model predicts the existence of wiggly bipolar pulses (supersolitary waves) and offset bipolar pulses (flat-top solitary waves) in Martian plasma. Comparison of our model’s predictions with real observational plasma parameters indicates that, like Martian magnetosheath plasma, ionospheric plasma may sustain ESWs measuring several tens of millivolts per meter.

The Rise of Nova V1674 Herculis

Observational constraints on classical novae are heavily biased to phases near optical peak and later because of the simple fact that novae are not typically discovered until they become bright. The earliest phases of brightening, coming before discovery, are typically missed, but this is changing with the proliferation of wide-field optical monitoring systems including the Zwicky Transient Facility, All-Sky Automated Survey for Supernovae, and Evryscope. Here, we report on unprecedented observations of the fast nova V1674 Her beginning >10 mag below its optical peak and including high-cadence (2 minutes) observations that chart a rise of ∼8 mag in just 5 hr. Two clear breaks are identified as the light curve transitions first from rising slowly to rising rapidly, followed by a transition to an even faster, nearly linear rate of increasing flux with time. The depths of the observations allow us to place tight constraints on the size of the photosphere under the assumption of blackbody emission from a white dwarf emitting at its Eddington luminosity. We find that the white dwarf was unlikely to have overflowed its Roche lobe prior to the launch of a fast wind, which poses a challenge for explaining the Fermi γ-ray detections as the interaction of a fast wind with a slow torus of gas stripped from the inflated white dwarf envelope by the companion. High-cadence observations of novae from Evryscope and the planned Argus Array can record the diversity of rising nova light curves and help resolve how the interplay between thermonuclear fusion, binary interaction, and shocks power their earliest light.

Regional modelling of extreme sea levels induced by hurricanes

Abstract. Coastal zones are increasingly threatened by extreme sea level events, with storm surges being among the most hazardous components, especially in regions prone to tropical cyclones. This study aims to explore the factors influencing the performance of numerical models in simulating storm surges in the tropical Atlantic region. The maxima, durations, and time evolutions of extreme storm surge events are evaluated for four historical hurricanes against tide gauge records. The Advanced Circulation (ADCIRC) and Nucleus for European Modelling of the Ocean (NEMO) ocean models are compared using similar configurations in terms of domain, bathymetry, and spatial resolution. These models are then used to perform sensitivity experiments on oceanic and atmospheric forcings, physical parameterizations of wind stress, and baroclinic/barotropic modes. NEMO and ADCIRC demonstrate similar abilities in simulating storm surges induced by hurricanes. Storm surges simulated with ERA5 atmospheric reanalysis forcing are generally more accurate than those simulated with parametric wind models for the simulated hurricanes. The inclusion of baroclinic processes improves storm surge amplitudes at some coastal locations, such as along the southeastern Florida peninsula (USA). However, experiments exploring different implementations of wind stress and interactions among storm surges, tides, and mean sea level have shown minimal impacts on hurricane-induced storm surges.

Arkenstone - II. A model for unresolved cool clouds entrained in galactic winds in cosmological simulations

Abstract Arkenstone is a new scheme that allows multiphase, stellar feedback-driven winds to be included in coarse resolution cosmological simulations. The evolution of galactic winds and their subsequent impact on the circumgalactic medium are altered by exchanges of mass, energy, momentum, and metals between their component phases. These exchanges are governed by complex, small-scale physical processes that cannot be resolved in cosmological simulations. In this second presentation paper, we describe Arkenstone’s novel cloud particle approach for modelling unresolvable cool clouds entrained in hot, fast winds. This general framework allows models of the cloud–wind interaction, derived from state-of-the-art high-resolution simulations, to be applied in a large-scale context. In this work, we adopt a cloud evolution model that captures simultaneous cloud mass loss to and gain from the ambient hot phase via turbulent mixing and radiative cooling, respectively. We demonstrate the scheme using non-cosmological idealized simulations of a galaxy with a realistic circumgalactic medium component, using the Arepo code. We show that the ability of a high-specific energy wind component to perform preventative feedback may be limited by heavy loading of cool clouds coupled into it. We demonstrate that the diverging evolution of clouds of initially differing masses leads to a complex velocity field for the cool phase and a cloud mass function that varies both spatially and temporally in a non-trivial manner. These latter two phenomena can manifest in the simulation because of our choice of a Lagrangian discretisation of the cloud population, in contrast to other proposed schemes.

Investigation of the nature of the wind interaction in HD 93205 based on multi-epoch X-ray observations

The study of the X-ray emission from massive binaries constitutes a relevant approach to investigate shock physics. The case of short period binaries may turn out to be quite challenging, especially in very asymmetric systems where the primary wind may overwhelm that of the secondary in the wind interaction. Our objective consists in providing an observational diagnostic of the X-ray behavior of HD\,93205, which is a very good candidate with which to investigate these aspects. We analyzed 31 epochs of XMM-Newton X-ray data spanning about two decades to investigate its spectral and timing behavior. The X-ray spectrum is very soft along the full orbit, with a luminosity exclusively from the wind interaction region in the range of 2.3 -- 5.4\,times $. The light curve peaks close to periastron, with a rather wide pre-periastron low state coincident with the secondary's body hiding a part of the X-ray emitting region close to its surface. We determined a variability timescale of 6.0807\,pm \,0.0013\,d, in full agreement with the orbital period. Making use of a one-dimensional approach to deal with mutual radiative effects, our results point to a very likely hybrid wind interaction, with a wind photosphere occurring along most of the orbit, while a brief episode of wind-wind interaction may still develop close to apastron. Besides mutual radiative effects, the radiative nature of the shock that leads to some additional pre-shock obliquity of the primary wind flow certainly explains the very soft emission. HD\,93205 constitutes a relevant target to investigate shock physics in short period, asymmetric massive binary systems, where various mutual radiative effects and radiative shocks concur to display an instructive soft X-ray behavior. HD\,93205 should be considered as a valid, though challenging target for future three-dimensional modeling initiatives.

Global magnetic field properties in the solar wind interaction of Mercury from MESSENGER measurements

The space environment of Mercury is shaped by its proximity to the Sun and by the relatively weak planetary magnetic field, presenting a unique regime of plasmas and shock conditions. We present the global magnetic properties in Mercury's space environment based on more than 4 years of MESSENGER Magnetometer data. We used 20 Hz magnetic field data to examine the magnetic strength, the field configurations, and the fluctuations. We considered both compressional and transverse modes, with frequencies from 5 mHz to 10 Hz, which cover typical ultra-low frequency waves at Mercury. We identified regions of the solar wind, the magnetosheath, and the magnetosphere during over 4\,000 MESSENGER orbits. The solar wind and magnetosheath data were analysed in the solar wind interplanetary magnetic field (IMF) coordinate system, and the magnetosphere data were analysed in the aberrated Mercury solar magnetospheric coordinate system. Each data point was relocated into normalised space using averaged magnetopause and bow-shock models. The magnetic environments for a quasi-parallel and quasi-perpendicular IMF were compared. Under the typical Parker-spiral IMF, the magnetic environment of Mercury features strong fluctuations that are dominated by the transverse mode and stem from interactions at the bow shock and the magnetopause. When they are subjected to a quasi-perpendicular IMF, the magnetic fluctuations diminish, and the magnetic field strength becomes highly compressed throughout the bow shock, magnetosheath, and magnetosphere. Unlike Earth, Mercury exhibits weaker dawn-dusk asymmetries in magnetic field strength and lacks substantial magnetosheath-generated sources of magnetic fluctuations. The magnetic field draping pattern associated with the IMF cone angle at Mercury also differs from that at Earth. Our comparative analysis highlights the critical role of the solar wind Mach number, the radial IMF component, and the system scale size in shaping planetary space environments.

On the effect of a tangential intake on the performance of natural dry draft cooling towers in crosswind conditions

Crosswind has a negative effect on the performance of natural draft dry cooling towers, NDDCTs, serving thermal power plants. This, in turn, lowers the efficiency of the thermal power plant as less heat can be rejected to the ambient air through the tower. This occurs due to interaction of cross wind and cooling tower structure. This phenomenon leads to generation of primary and secondary vortices inside the tower which located in leeward side (downwind side) and windward side (upwind side) of the tower, respectively. In an innovative interpretation of the challenge, this paper aims at directing the crosswind flow through the tower shell above the heat exchangers to assist the buoyancy-induced plume. In particular, the intake of the crosswind through the tower is utilized as a tangentially-induced swirl source to help the upward draft, and its penetration in the ambient air, enhancing the tower performance which otherwise would have been significantly deteriorated. Two independent approaches are presented to assess the proposed design quantitatively. CFD simulation of a small scale tower model has revealed significant performance improvement (in terms of natural draft blockage and outlet flow velocity) when the crosswind is allowed to penetrate the tower shell, through an opening on the tower side-wall, above the heat exchangers. Results of the simulations have been validated against the experimental data collected using the tests ran on an identical model, with and without the side opening, in a wind tunnel.

Heavy Ion Escape at Mars during the Disappearing Solar Wind Event in 2022 December

A unique event known as the disappearing solar wind (DSW), characterized by an extremely low-density solar wind stream, occurred at Mars on 2022 December 26–27. As this stream flowed past Mars, several properties of the Mars–solar wind interaction changed in response to the density drop. We utilize in situ plasma measurements from the Mars Atmosphere and Volatile EvolutioN spacecraft to examine heavy ion escape during this event. We find that escaping ions with energies above and below 30 eV responded differently to the reduction in solar wind density. High-energy ions experienced a decrease in flux, whereas low-energy ions experienced an increase, regardless of whether they were escaping through the plume or tailward channel. Furthermore, we observe a net reduction in the flux of plume escaping ions during the DSW period, primarily due to a considerable reduction in the high-energy component, which typically dominates plume escape. In contrast, the overall flux of tailward escaping ions increased during this period. These variations in heavy ion escape are mainly attributed to substantial reductions in solar wind dynamic pressure and momentum density. This paper provides new insights into the dynamics of heavy ion escape under an exceptional state of the Mars–solar wind interaction.

Energy performance and wind exposure of windward, lateral, and leeward high-rise photovoltaic facades

The growing demand for sustainable energy solutions leads to the integration of photovoltaic/thermal (PV/T) modules into building facades. This study evaluates and compares the energy potential, wind load, and environmental benefits of PV/T modules installed on different facades of high-rise buildings. Using advanced computational techniques, including Computational Fluid Dynamics (CFD), the wind interaction with PV/T modules on windward, lateral, and leeward facades is modeled and analyzed. Each computational process requires over two weeks to complete due to the complexity of the simulations. The results demonstrate that the leeward facade is more effective for electricity generation, while the windward and sideward facades perform better for thermal energy storage. Maximum energy outputs of 217 kW for thermal energy and 73 kW for electrical energy are recorded, depending on wind conditions. Additionally, energetic and exergetic efficiencies reach 55.2 % and 17.7 %, respectively. The study also finds that the leeward facade has the greatest impact on reducing CO2 emissions. These findings provide valuable insights into designing optimal PV/T facades for high-rise structures, expanding the range of structural designs and offering opportunities for implementing mitigation measures to enhance system durability and efficiency. The novelty of this research lies in the detailed comparative analysis of PV/T performance across multiple facades, offering a practical framework for future sustainable building designs.

Evolving Outer Heliosphere: Tracking Solar Wind Transients from 1 au to the VLISM with IBEX and Voyager 1

Interstellar Boundary Explorer (IBEX) observations of energetic neutral atom (ENA) fluxes from the heliosphere have greatly enriched our understanding of the interaction of the solar wind (SW) with the local interstellar medium (LISM). However, there has been recent controversy surrounding the inability of most ENA models to produce as high an intensity of ∼0.5–6 keV ENAs as IBEX observes at 1 au, especially as a function of time. In our previous study (E. J. Zirnstein et al.), we introduced a new model that utilizes a data-driven magnetohydrodynamic simulation of the SW–LISM interaction to propagate pickup ions through the heliosheath (HS) after they are nonadiabatically heated at the heliospheric termination shock. E. J. Zirnstein et al. only simulated and analyzed IBEX observations from the direction of Voyager 2. In this study, we expand our model to include fluxes from the direction of Voyager 1, as well as in the low-latitude part (middle) of the ribbon (10° below the ecliptic plane). We show that the model results at Voyager 1 are consistent with E. J. Zirnstein et al.’s results at Voyager 2 in terms of a secondary ENA source contribution of ≲20% from both directions. Our results in the middle of the ribbon also reproduce the data, when including a time-dependent secondary ENA source. Finally, we demonstrate with our simulation that three large pressure waves likely merged in the VLISM and were observed by Voyager 1 as “pf2,” while at least one of the wave’s effects in the HS was observed by IBEX as a brief enhancement in ENA flux in early 2016.

Sunward Oxygen Ion Fluxes and the Magnetic Field Topology at Mars From Hybrid Simulations

AbstractIt is commonly believed that because of the direct solar wind interaction with the Martian atmosphere/ionosphere, the planet could have lost a significant part of its atmosphere. Closed field lines of the crustal magnetic field can weaken a transport of the ionospheric ions to the tail. Reconnection of the interplanetary magnetic field lines draping around Mars and the crustal magnetic field can also lead to a presense of sunward fluxes of planetary ions that might affect the total ion loss. The LatHyS (LATMOS Hybrid Simulation) three‐dimensional multispecies hybrid model is used here to characterize sunward fluxes of O+ ions and the magnetic field topology at Mars. It is shown that although reconnection between the interplanetary magnetic field (IMF) and the crustal magnetic fields strongly modifies the field topology, then sunward ion fluxes are rather small and do not significantly change the total ion loss.

Theory and Observation of Winds from Star-Forming Galaxies

Galactic winds shape the stellar, gas, and metal content of galaxies. To quantify their impact, we must understand their physics. We review potential wind-driving mechanisms and observed wind properties, with a focus on the warm ionized and hot X-ray-emitting gas. Energy and momentum injection by supernovae (SNe), cosmic rays, radiation pressure, and magnetic fields are considered in the light of observations: ▪Emission and absorption line measurements of cool/warm gas provide our best physical diagnostics of galactic outflows.▪The critical unsolved problem is how to accelerate cool gas to the high velocities observed. Although conclusive evidence for no one mechanism exists, the momentum, energy, and mass-loading budgets observed compare well with theory.▪A model in which star formation provides a force ∼L/c, where L is the bolometric luminosity, and cool gas is pushed out of the galaxy's gravitational potential, compares well with available data. The wind power is ∼0.1 of that provided by SNe.▪The very hot X-ray-emitting phase may be a (or the) prime mover. Momentum and energy exchange between the hot and cooler phases is critical to the gas dynamics.▪Gaps in our observational knowledge include the hot gas kinematics and the size and structure of the outflows probed with UV absorption lines. Simulations are needed to more fully understand mixing, cloud–radiation, cloud–cosmic ray, andcloud–hot wind interactions, the collective effects of star clusters, and both distributed andclustered SNe. Observational works should seek secondary correlations in the wind data thatprovide evidence for specific mechanisms and compare spectroscopy with the column density–velocity results from theory.

Exploring the dynamics of the heavy magnetized dusty plasma in laboratory experiments and solar wind interaction with lunar terminator: Theoretical predictions into the role of polarization force

This study is motivated by the lack of research that connects the dynamics of space dusty plasma (DP) with the existing experimental findings and the role of the magnetic field in the case of massive DP. For that purpose, we presented a theoretical interpretation of the dynamics of strongly (experimental) and weakly (space) magnetized DP, including the influence of the polarization force (PF). We used the multifluid model to describe the dynamics of dust particles while the hot plasma of electrons and ions is described by the Boltzmann distribution. We derived the dispersion relation to investigate the behavior of the compressive dust-acoustic waves (DAWs). To get a full picture of the mechanism of dust particles, we used the reductive perturbation technique to obtain the periodic solution for the Zakharov–Kuznetsov equation (ZK), which is coincidental with the observed wave profiles. In the case of the experimental application, we observed that the non-propagating instability starts at a small value of the polarization parameter (R), which is 0.02. Therefore, for values of R less than 0.02, the linear analysis revealed that increasing the value of the polarization parameter is not significant in distinguishing the growth rates. Moreover, we noted that both R and the applied magnetic field enhance the strength of the wave electric field. Interestingly, calculating the value of the electric field required to levitate the dust particles that are subject to a high magnetic field agrees with our theoretical findings. The current model has also been applied to DP observed in the lunar terminator. Our results reveal no role for the PF in the lunar terminator. The analysis conducted using the New Hampshire Dispersion Relation Solver (NHDS) confirms the dominance of electrostatic modes in response to the solar wind interaction with the lunar terminator. Moreover, at certain values of plasma parameters such as the temperature of solar wind electrons and ions and the density of dust particles and solar wind electrons, there is a cutoff in the fluid dispersion curve corresponding to certain values of the normalized wavenumber. Such electrostatic profiles could contribute to the observed glow in the horizontal direction of the lunar terminator.

Observational Overview of the May 2024 G5-Level Geomagnetic Storm: From Solar Eruptions to Terrestrial Consequences

This study reports comprehensive observations for the G5-level geomagnetic storm that occurred from May 10 to 12, 2024, the most intense event since the 2003 Halloween storm. The storm was triggered by a series of coronal mass ejections (CMEs) originating from the merging of two active regions 13664/13668, which formed a large and complex photospheric magnetic configuration and produced X-class flares in early May 2024. Among the events, the most significant CME, driven by an X2.2 flare on May 9, caught up with and merged with a preceding slower CME associated with an X-class flare on May 8. These combined CMEs reached 1 AU simultaneously, resulting in an extreme geomagnetic storm. Geostationary satellite observations revealed changes in Earth’s magnetosphere due to solar wind impacts, increased fluxes of high-energy particles, and periodic magnetic field fluctuations accompanied by particle injections. Extreme geomagnetic storms resulting from the interaction of the solar wind with the Earth’s magnetosphere caused significant energy influx into Earth’s upper atmosphere over the polar regions, leading to thermospheric heating and changes in the global atmospheric composition and ionosphere. As part of this global disturbance, significant disruptions were also observed in the East Asian sector, including the Korean Peninsula. Ground-based observations show strong negative storm effects in the ionosphere, which are associated with thermospheric heating and resulting in decreases in the oxygen-to-nitrogen ratio (O/N2) in high-latitude regions. Global responses of storm-time prompt penetration electric fields were also observed from magnetometers over the East-Asian longitudinal sector. We also briefly report storm-time responses of aurora and cosmic rays using all-sky cameras and neutron monitors operated by the Korea Astronomy and Space Science Institute (KASI). The extensive observations of the G5-level storm offer crucial insights into Sun-Earth interactions during extreme space weather events and may help establish better preparation for future space weather challenges.

Numerical simulation of wind–snow flow on a roof considering time-varying snow phase boundaries

Large-span roofs can be damaged by uneven snow loads caused by snow drifting. To predict wind-induced snow loads more accurately, this paper proposes a numerical simulation method. The method considers the interaction of wind and snow, the changing characteristics of snow phase boundaries over time, and corrects for snow deposition and erosion flux. The effectiveness of the method was confirmed by simulating wind–snow flow on a three-centered cylindrical shell and comparing the results with wind tunnel measurements. The simulation considered different snowfall conditions and time-varying snow phase boundaries on a large-span shell-shaped roof. The study investigated the influence of snowfall conditions and dynamic changes in snow phase boundaries on snow cover distribution by comparing simulation results.

Non-thermal radio emission in Sakurai's Object

The very late thermal pulse (VLTP) affects the evolution of sim 20<!PCT!> of 1--8\,$ M_ stars, repeating the last red giant phases within a few years and leading to the formation of a new, but hydrogen-poor, nebula within the old planetary nebula. The strong dust formation in the latter obscures the optical and near-infrared radiation of the star. We aimed to determine the reheating timescale of the central star in Sakurai's Object, which is an important constraint for the poorly understood VLTP evolution. We observed the radio continuum emission of Sakurai's Object for almost 20 years, from 2004 to 2023. Continuous, multi-frequency observations proved to be essential for distinguishing between phases dominated by photoionization and shock ionization. The flux density fluctuates by more than a factor of 40 within months to years. The spectral index remained negative between 2006 and 2017 and has been close to zero since 2019. The emission region has been only barely resolved since 2021. Non-thermal radio emission observed from 2004 to 2017 traces shocks induced by wind interactions due to discrete mass-loss events. Thermal emission dominates from 2019 to 2023 and may indicate photoionization of the nebula by the central star.

Characterizing the Solar Wind‐Magnetosphere Viscous Interaction at Uranus and Neptune

AbstractThe solar wind interaction with planetary magnetospheres dictates the mechanism through which energy is transported across planetary systems. The magnetohydrodynamic plasma description suggests that solar wind conditions in the outer solar system encourage the magnetopause boundaries at Uranus and Neptune to be more Kelvin‐Helmholtz unstable, however, no quantitative assessment has been performed. To characterize the viscous solar wind interaction at Uranus and Neptune, we create an analytical model to determine where Kelvin‐Helmholtz Instabilities (KHIs) may form along their magnetopauses by searching for regions where the minimum condition for KHI formation is satisfied. We run the model at solstice and equinox for a range of Interplanetary Magnetic Field (IMF) strengths, and rotation phases. We find minimal seasonal variation for low IMF strengths (B = 0.01 nT), with ∼70% of the magnetopause surface at Uranus and ∼80% at Neptune, enabling KHI formation. For periods of stronger IMF strength (B > 0.3 nT), KHIs were significantly suppressed. While KHIs depend on both the conditions inside the magnetopause boundary and the shocked solar wind IMF strength, we find that the IMF strength is the most significant criterion in determining whether or not KHIs are allowed to form at the magnetopause boundaries.

Investigating Boundary Layer Properties at Jupiter's Dawn Magnetopause

AbstractWe survey crossings of Jupiter's dawn magnetopause during the Juno prime mission to identify and characterize Jupiter's magnetopause boundary layer. Using plasma and magnetic field observations from Jovian Auroral Distributions Experiment and Juno Magnetic Field investigation, we identify 53 boundary layer events from the 62 magnetopause crossings studied here. We find that the boundary layer generally exhibits mixed properties of magnetosheath and magnetosphere electron distributions, including lower characteristic electron energies and denser ion populations than in the magnetosphere, but higher characteristic electron energies and less dense ion populations than in the magnetosheath. Boundary layer proton speeds are on average slower than both the magnetosheath and magnetosphere. Other proton parameters in the boundary layer have intermediate values between the magnetosheath and magnetosphere. Through ion composition analysis in regions adjacent to the magnetopause, we find evidence of solar wind and magnetospheric plasma in the boundary layer that suggests plasma is transported across the magnetopause in both directions. This mass and energy transport may be the result of solar wind interactions such as magnetic reconnection and Kelvin‐Helmholtz instabilities. However, many boundary layer events do not exhibit local signatures of these solar wind interactions and plasma may be transported by a non‐local process or diffusively transported.