The solar wind particles reflected by the lunar magnetic field are the major energy source of electromagnetic wave activities, such as the 100 s magnetohydrodynamic waves and the 1 Hz whistler-mode waves generated by protons and the non-monochromatic whistler-mode waves generated by mirror-reflected electrons. Kaguya found a new type of whistler-mode waves at 100 km altitude above the polar regions of the moon with a broad frequency range of 1–16 Hz. The waves appear diffuse in both the time and frequency domains, and their occurrence is less sensitive to the magnetic connection to the lunar surface. The polarization is right-handed with respect to the background magnetic field, and the wave number vector is nearly parallel to the magnetic field perpendicular to the solar wind flow. The diffuse waves are thought to be generated by the solar wind ions reflected by the lunar magnetic field through cyclotron resonance. The resonant ions are expected to have a velocity component parallel to the magnetic field larger than the solar wind bulk speed; however, such ions were not always simultaneously detected by Kaguya. The waves may have been generated above the dayside of the moon and then propagated along the magnetic field being convected by the solar wind to reach the polar regions to be detected by Kaguya.

Ocean worlds have been identified as high-priority astrobiology targets due to the link between life and liquid water. Young surface terrain on many icy bodies indicates they support active geophysical cycles that may facilitate ocean-surface transport that could provide observables for upcoming missions. Accurately interpreting spacecraft observations requires constraining the relationship between ice shell characteristics and interior dynamics. On Earth, the composition, physical characteristics, and bioburden of ocean-derived ices are related to their formation history and parent fluid composition. In such systems the ice-ocean interface, which exists as a multiphase mushy layer, dictates the overlying ice’s properties and evolution. Inclusion of the physics governing these boundaries is a novel strategy in modeling planetary ices, and thus far has been limited to 1D approaches. Here we present results from 2D simulations of an archetypal ice-ocean world. We track the evolution of temperature, salinity, porosity, and brine velocity within a thickening ice shell enabling us to place improved constraints on ice-ocean world properties, including: the composition of planetary ice shells, the thickness and hydraulic connectivity of ice-ocean interfaces, and heterogeneous dynamics/structures in the interfacial mushy layer. We show that stable eutectic horizons are likely a common feature of ice-ocean worlds and that ocean composition plays an important role in governing the structure and dynamics of the interface, including the formation of chemical gradient-rich regions within the mushy layer. We discuss the geophysical and astrobiological implications of our results and highlight how they can be validated by instrument specific measurements.

During its ongoing mission, the Cluster II constellation has provided the first small-scale multipoint measurements of the space environment, and dramatically advanced scientific understanding in numerous regimes. One such region is the Earth’s inner magnetospheric ring current, which could now be computed using the curl of the magnetic field over a spacecraft tetrahedron instead of via plasma moments. While this produced the first 3D current estimates, it also produced different results from prior ring current studies with differing magnitudes and correlations with storm indices/local times. In this analysis, we revisit Cluster ring current data via curlometry, and conduct additional quantitative sensitivity simulations using actual spacecraft position data. During the orbits that observed ring current structure, tetrahedron shape and linearity assumptions can create large errors up to 100% of physical current magnitude in curlometer output that contradict accepted estimated quality parameters. These false currents are directly related to the structure of the current environment, and cannot be distinguished from the actual currents without additional limiting assumptions. The trustworthiness of curlometer output in the ring current is therefore dependent on the linearity of the magnetic structure relative to the tetrahedron orientation, which requires additional characterization. The Cluster curlometer output in the ring current is then explored in light of these new uncertainties, with the computed current magnitude and direction both potentially impacted by the production of false currents.

The boundary between the solar wind (SW) and the Earths magnetosphere, the magnetopause (MP), is highly dynamic. Its location and shape depend on SW dynamic pressure and interplanetary magnetic field (IMF) orientation. We use a 3D kinetic Particle-In-Cell code (IAPIC) to simulate an event observed by THEMIS spacecraft on July 16, 2007. We investigate the impact of radial (θBx=0◦) and non-radial (θBx=50◦) IMF on the shape and size of Earths MP for a dipole tilt of 31◦ using maximum density gradient and pressure balance methods. Using the Shue model as a reference (MP at 10.3 RE), we find that for non-radial IMF the MP expands by 1.4 and 1.7RE along the the Sun-Earth (OX) and tilted magnetic equatorial (Tilt) axes, respectively, and it expands by 0.5 and 1.6RE for radial IMF along the same respective axes. When the effect of backstreaming ions is removed from the bulk flow, the expansion ranges are 1.0 and 1.3RE and 0.2, and 1.2RE, respectively. It is found that the percentage of backstreaming to bulk flow ions are 16.5% and 20% for radial and non-radial IMF. We also show that when the backstreaming ions are not identified, up to 40% of the observed expansion that is due to backstreaming particles can be inadvertently attributed to a change in the SW upstream properties. Finally, we quantified the temperature anisotropy in the magnetosheath, and observe a strong dawn-dusk asymmetry in the MP location, being more extended on the duskside than on the dawnside.

We utilise Principal Component Analysis to identify and quantify the primary electric potential morphologies during geomagnetic storms. Ordering data from the Super Dual Auroral Radar Network (SuperDARN) by geomagnetic storm phase, we are able to discern changes that occur in association with the development of the storm phases. Along with information on the size of the patterns, the first 6 eigenvectors provide over ~80% of the variability in the morphology, providing us with a robust analysis tool to quantify the main changes in the patterns. Studying the first 6 eigenvectors and their eigenvalues with respect to storm phase shows that the primary changes in the morphologies with respect to storm phase are the convection potential enhancing and the dayside throat rotating from pointing towards the early afternoon sector to being more sunward aligned during the main phase of the storm. We find that the ionospheric electric potential increases through the main phase and then decreases after the end of the main phase is reached. The dayside convection throat points towards the afternoon sector before the main phase and then as the potential increases throughout the main phase, the dayside throat rotates towards magnetic noon. Furthermore, we find that a two cell convection pattern is dominant throughout and that the dusk cell is overall stronger than the dawn cell.

Magnetosheath jets constitute a significant coupling effect between the solar wind (SW) and the magnetosphere of the Earth. In order to investigate the effects and forecasting of these jets, we present the first-ever statistical study of the jet production during large-scale SW structures like coronal mass ejections (CMEs), stream interaction regions (SIRs) and high speed streams (HSSs). Magnetosheath data from Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft between January 2008 to December 2020 serve as measurement source for jet detection. Two different jet definitions were used to rule out statistical biases induced by our jet detection method. For the CME and SIR+HSS lists, we used lists provided by literature and expanded on incomplete lists using OMNI data to cover the time range of May 1996 to December 2020. We find that the number and total time of observed jets decrease when CME-sheaths hit the Earth. The number of jets is lower throughout the passing of the CME-magnetic ejecta (ME) and recovers quickly afterwards. On the other hand, the number of jets increases during SIR and HSS phases. We discuss a few possibilities to explain these statistical results.

We present a new approach for the analysis of high-resolution digital camera photographs taken by photographers who have fortuitously been able to capture rare events such as the glowing sky phenomenon known as STEVE. This method is especially effective with a time lapse series of images of the night sky taken under constant camera settings with a steady pointing. Stars, planets and satellites seen in such images can be used to determine precise and accurate registration of camera pixels to coordinates of angular altitude and azimuth. The location of satellites in the image enables precise and accurate synchronization of the images. We apply these techniques to the series of photographs of STEVE taken on 25 July 2016. We confirm the altitude structure previously found for STEVE. We find it most likely that the green picket fence features often seen during STEVE events are produced by auroral electron precipitation. With the precipitation assumption, we are able to extract novel information about the energy spectrum of the particles responsible for the production of STEVE luminosity in this particular event. Similar analyses of archived digital photographs may constitute a treasure trove of important data for improved understanding of rare and transient events such as STEVE.

The Flare Irradiance Spectral Model (FISM) is an important tool for estimating solar variability for a myriad of space weather research studies and applications, and FISM Version 2 (FISM2) has recently been been released. FISM2 is an empirical model of the solar ultraviolet irradiance created to fill spectral and temporal gaps in the measurements, where these measurements are infrequent as they need to be made from space due to their absorption in the planetary atmospheres. FISM2 estimates solar ultraviolet irradiance variations due to solar cycle, solar rotation, and solar flare variations. The major improvement provided by FISM2 is that it is based on multiple new, more accurate instruments that have now captured almost a full solar cycle and thousands of flares, drastically improving the accuracy of the modeled FISM2 solar irradiance spectra. FISM2 is also improved to 0.1 nm spectral bins across the same 0-190 nm spectral range, and is already being used in research to estimate space weather changes due to solar irradiance variability in planetary thermospheres and ionospheres.

Satellite-atmosphere interactions cause large uncertainties in low-Earth orbit determination and prediction. Thus, knowledge of and the ability to predict the space environment, most notably thermospheric mass density, are essential for operating satellites in this domain. Recent progress has been made toward supplanting the existing empirical, operational methods with physics-based data-assimilative models by accounting for the complex relationship between external drivers such as solar irradiance, Joule, and particle heating, and their response in the upper atmosphere. Simultaneously, a new era of CubeSat constellations is set to provide data with which to calibrate our upper-atmosphere models at higher spatial resolution and temporal cadence. With this in mind, we provide an initial method for converting precision orbit determination (POD) solutions from global navigation satellite system (GNSS) enabled CubeSats into timeseries of thermospheric mass density. This information is then fused with a physics-based, data-assimilative technique to provide calibrated model densities.

In-situ conjugate electromagnetic ion cyclotron (EMIC) waves observed by the Swarm mission in both hemispheres are presented. A complex and unusual pattern of Alfvénic EMIC wave energy is observed, with a mid-latitude peak close to the source at L=3.3, as well as a secondary lower L-peak. A wave propagation model reveals that the secondary peak at L=1.7 may be explained by wave power being redirected equatorward due to the Buchsbaum resonance, crossing and interfering with the same EMIC wave power propagating equatorwards from the opposite hemisphere. This interference creates a coherent equatorial driver for a low-L field line resonance at the secondary peak, and which is associated with strong shear-to-fast mode coupling in the ionosphere. This behavior complicates the interpretation of low-Earth orbit EMIC data for applications assessing radiation belt loss. Combined LEO observations and modelling enable these novel and localized magnetosphere-ionosphere EMIC wave propagation pathways to be identified.

The magnetohydrodynamics with embedded particle-in-cell (MHD-EPIC) model has been successfully applied to global magnetospheric simulations in recent years. However, the PIC region was restricted to be one or more static boxes, which is not always sufficient to cover the whole physical structure of interest efficiently. The FLexible Exascale Kinetic Simulator (FLEKS), which is a new PIC code and allows a dynamic PIC region of any shape, is designed to break this restriction. FLEKS is usually used as the PIC component of the MHD with adaptively embedded particle-in-cell (MHD-AEPIC) model. FLEKS supports dynamically activating or deactivating cells to fit the regions of interest during a simulation. An adaptive time-stepping scheme is also introduced to improve the accuracy and efficiency of a long simulation. The particle number per cell may increase or decrease significantly and lead to load imbalance and large statistical noise in the cells with fewer particles. A particle splitting scheme and a particle merging algorithm are designed to limit the change of the particle number and hence improve the accuracy of the simulation as well as load balancing. Both particle splitting and particle merging conserve the total mass, momentum, and energy. FLEKS also contains a test-particle module to enable tracking particle trajectories due to the time-dependent electromagnetic field that is obtained from a global simulation.

The High Accuracy Satellite Drag Model (HASDM) is the operational thermospheric density model used by the US Space Force (USSF) Combined Space Operations Center (CSpOC). By using real-time data assimilation, HASDM can provide density estimates with increased accuracy over empirical models. With historical HASDM density data being released publicly for the first time, we can analyze the data to identify dominant modes of variations in the upper atmosphere. As HASDM is a close relative to the Jacchia-Bowman 2008 Empirical Thermospheric Density Model (JB2008), we look at time-matched density data to better understand the models’ characteristics. This model comparison is conducted through the use of Principal Component Analysis (PCA). We then compare both datasets to the CHAllenging Minisatellie Payload (CHAMP) and Gravity Recovery and Climate Experiment (GRACE) accelerometer-derived density estimates. By looking at the principal components and PCA scores from the two models, we confirm the increased complexity of the HASDM dataset while the CHAMP and GRACE comparisons show that HASDM more closely matches the accelerometer-derived densities with mean absolute differences of 23.81% and 30.84% compared to CHAMP and GRACE-A, respectively.

The present atmosphere of Venus contains almost no water, but recent measurements indicate that in its early history Venus had an Earth-like ocean. Understanding how the Venusian atmosphere evolved is important not only for Venus itself, but also for understanding the evolution of other planetary atmospheres. In this study, we quantify the escape rates of oxygen ions from the present Venus to infer the past of the Venusian atmosphere. We show that an extrapolation of the current escape rates back in time leads to the total escape of 0.02-0.6 m of a global equivalent layer of water. This implies that the loss of ions to space, inferred from the present state, cannot account for the loss of an historical Earth-like ocean. We find that the O+ escape rate increases with solar wind energy flux, where more energy available leads to a higher escape rate. Oppositely, the escape rate decrease slightly with increased EUV flux, though the small variation of EUV flux over the measured solar cycle may explain the weak dependency. These results indicate that there isn’t enough energy transferred from the solar wind to Venus’ upper atmosphere that can lead to the escape of the atmosphere over the past 3.9 billion years. This means that the Venusian atmosphere didn’t have as much water in its atmosphere as previously assumed or the present-day escape rates don’t represent the historical escape rates at Venus. Otherwise, some other mechanisms have acted to more effectively remove the water from the Venusian atmosphere.

We present multi-instrument Juno observations on day-of-year 86, 2017 that link particles and fields in Jupiter’s polar magnetosphere to transient UV emissions in Jupiter’s northern auroral region known as dawn storms. Juno ranged from 42ºN - 51ºN in magnetic latitude and 5.8 – 7.8 jovian radii (1 RJ = 71,492 km) during this period. These dawn storm emissions consisted of two separate, elongated structures which extended into the nightside, rotated with the planet, had enhanced brightness (up to at least 1.4 megaRayleigh) and high color ratios. The color ratio is a proxy for the atmospheric penetration depth and therefore the energy of the electrons that produce the UV emissions. Juno observed electrons and ions on magnetic field lines mapping to these emissions. The electrons were primarily field-aligned, bi-directional, and, at times, exhibited sudden intensity decreases below ~10 keV coincident with intensity enhancements up to energies of ~1000 keV, consistent with the high color ratio observations. The more energetic electron distributions had characteristic energies of ~160 – 280 keV and downward energy fluxes (~70 – 135 mW/m2) that were a significant fraction needed to produce the UV emissions for this event. Magnetic field perturbations up to ~0.7% of the local magnetic field showing evidence of upward and downward field-aligned currents, whistler mode waves, and broadband kilometric radio emissions were also observed along Juno’s trajectory during this timeframe. These high latitude observations show similarities to those in the equatorial magnetosphere associated with dynamics processes such as interchange events, plasma injections, and/or tail reconnection.

Using Magnetospheric Multiscale (MMS) data, we find, classify and analyze transient dynamic pressure enhancements in the magnetosheath (jets) from May 2015 until May 2019. A classification algorithm is presented, using in-situ MMS data to classify jets (n = 8499) into different categories according to their associated angle between IMF and the bow shock normal vector ( θ ). Jets appearing for θ < 45° are referred to as quasi-parallel, while jets appearing for θ > 45° as quasi-perpendicular jets. Furthermore, we define those jets that occur at the boundaries between quasi-parallel and quasi-perpendicular magnetosheath as boundary jets. Finally, encapsulated jets are jet-like structures with similar characteristics to quasi-parallel jets while the surrounding plasma is of quasi-perpendicular nature. We present the first statistical results of such a classification and provide comparative statistics for each class. Furthermore, we investigate correlations between jet quantities. Quasi-parallel jets have the highest dynamic pressure while occurring more often than quasi-perpendicular jets. The infrequent quasi-perpendicular jets, have a much smaller duration, velocity, and density and are therefore relatively weaker. We conclude that quasi-parallel and boundary jets have similar properties and are unlikely to originate from different generation mechanisms. Regarding the encapsulated jets, we suggest that they are a special subset of quasi-parallel jets originating from the flanks of the bow shock, for large IMF cone angles although a relation to FTEs and magnetospheric plasma is also possible. Our results support existing generation theories, such as the bow shock ripple and SLAMS-associated mechanisms while indicating that other factors may contribute as well.

The Earth’s upper atmosphere is a dynamic environment that is continuously affected by space weather from above and atmospheric processes from below. An effective way to observe this interface region is the monitoring of airglow. Since the 1950s, airglow emissions have been systematically measured by ground-based photometers in specific wavelength bands during the nighttime. The availability of the calibrated data from over 30 years of photometric airglow measurements at Abastumani in Georgia (41.75 N, 42.82 E), at wavelengths of 557.7 nm and 630.0 nm, enable us to investigate if a data-driven model based on advanced machine learning techniques can be successfully employed for modeling airglow intensities. A regression task was performed using the time series of space weather indices and thermosphere-ionosphere parameters. We have found that the developed data-driven model has good consistency with the commonly used GLOW airglow model and also captures airglow variations caused by cycles of solar activity and changes of the seasons. This enables us to visualize the green and red airglow variations over a period of three solar cycles with a one-hour time resolution.

It has been recently advocated that Mars has excellent conditions for oxygen and fuel production directly from atmospheric CO2 using non-equilibrium plasmas. The Martian conditions would be favorable for vibrational excitation and/or enhanced dissociation by electron impact, two important pathways for CO2 plasma dissociation. Herein we confirm these theoretical predictions by measuring, for the first time, the vibrational temperatures of CO2 and the CO and CO2 concentrations in realistic Martian conditions. In situ Fourier transform infrared spectroscopy (FTIR) measurements are performed in experiments conducted in DC glow discharges operating at pressures p=1-5 Torr, discharge currents I=10-50 mA, initial gas temperatures of 220 K and 300 K, both in pure CO2 and in the synthetic Martian atmosphere 96%CO2-2%Ar-2%N2. To analyse and interpret the experimental results, we develop a detailed self-consistent kinetic model for pure CO2 plasmas, describing the coupled electron and heavy-particle kinetics. The simulation results are in very good agreement with the experimental data. It is shown that the low-temperature conditions may enhance the degree of vibrational non-equilibrium and that the Martian atmospheric composition has a positive effect on CO2 decomposition. Accordingly, the present investigation confirms the potential of plasma technologies for in-situ resource utilization (ISRU) on Mars.

Ionospheric conductance is a crucial factor in regulating the closure of magnetospheric field-aligned currents through the ionosphere as Hall and Pedersen currents. Despite its importance in predictive investigations of the magnetosphere - ionosphere coupling, the estimation of ionospheric conductance in the auroral region is precarious in most global first-principles based models. This impreciseness in estimating the auroral conductance impedes both our understanding and predictive capabilities of the magnetosphere-ionosphere system during extreme space weather events. In this article, we address this concern, with the development of an advanced Conductance Model for Extreme Events (CMEE) that estimates the auroral conductance from field aligned current values. CMEE has been developed using nonlinear regression over a year’s worth of one-minute resolution output from assimilative maps, specifically including times of extreme driving of the solar wind-magnetosphere-ionosphere system. The model also includes provisions to enhance the conductance in the aurora using additional adjustments to refine the auroral oval. CMEE has been incorporated within the Ridley Ionosphere Model (RIM) of the Space Weather Modeling Framework (SWMF) for usage in space weather simulations. This paper compares performance of CMEE against the existing conductance model in RIM, through a validation process for six space weather events. The performance analysis indicates overall improvement in the ionospheric feedback to ground-based space weather forecasts. Specifically, the model is able to improve the prediction of ionospheric currents which impact the simulated dB/dt and ΔB, resulting in substantial improvements in dB/dt predictive skill.

Rubble pile asteroids such as (162173) Ryugu have large bulk porosities, which are believed to result from void spaces in between the constituent boulders (macroporosity) as well as void spaces within the boulders themselves (microporosity). In general, both macroporosity and microporosity are estimated based on comparisons between the asteroid bulk density and both the bulk and grain density of meteorite analogues, and relatively large macroporosities are usually obtained. Here we use semi-empirical models for the macroporosity of multi-component mixtures to determine Ryugu’s macroporosity based on the observed size-frequency distribution of boulders on the surface. We find that Ryugu’s macroporosity can be significantly smaller than usually assumed, as the observed size-frequency distribution allows for an efficient packing of boulders, resulting in a macroporosity of $16 \pm 3$~\%. Therefore, { we confirm that} Ryugu’s high bulk porosity is a direct consequence of a very large boulder microporosity. Furthermore, using estimates of boulder microporosity of around { 50~\%} as derived from in-situ measurements, the average grain density in boulders is { $2848 \pm 152$ kg m$^{-3}$, similar to values obtained for CM and the Tagish lake meteorites}. Ryugu’s bulk porosity corresponding to the above values is { 58~\%.} { Thus, the macroporosity of rubble pile asteroids may have been systematically overestimated in the past.}

Collisionless shocks in astrophysical plasmas are important thermalizers, converting some of the incident flow energy into thermal energy, and non-thermalizers, partitioning that energy in unequal ways to different particle species, sub-populations thereof, and field components. This partition problem, or equivalently the shock equation of state, lies at the heart of shock physics. Here we employ systematically a framework to capture all the incident and downstream energy fluxes at two example traversals of the Earth's bow shock by the Magnetospheric Multiscale Mission. Here and traditionally such data has to be augmented by information from other spacecraft, e.g., to provide more accurate measurements of the cold solar wind beam. With some care and fortuitous choices, the energy fluxes are constant, including instantaneous measurements through the shock layer. The dominant incident proton ram energy is converted primarily into downstream proton enthalpy flux, the majority of which is actually carried by a small fraction of suprathermal protons. Fluctuations include both real and instrumental effects. Separating these, resolving the solar wind beam, and other considerations point the way to a dedicated mission to solve this energy partition problem across a full range of plasma and shock conditions.

Prior analyses of oceanic magnetic induction within Jupiter’s large icy moons have assumed uniform electrical conductivity. However, the phase and amplitude responses of the induced fields will be influenced by the natural depth-dependence of the electrical conductivity. Here, we examine the amplitudes and phase delays for magnetic diffusion in modeled oceans of Europa, Ganymede, and Callisto. For spherically symmetric configurations, we consider thermodynamically consistent interior structures that include realistic electrical conductivity along the oceans’ adiabatic temperature profiles. Conductances depend strongly on salinity, especially in the large moons. The induction responses of the adiabatic profiles differ from those of oceans with uniform conductivity set to values at the ice–ocean interface, or to the mean values of the adiabatic profile, by more than 10\% for some signals. We also consider motionally induced magnetic fields generated by convective fluid motions within the oceans, which might optimistically be used to infer ocean flows or, pessimistically, act to bias the ocean conductivity inversions. Our upper-bound scaling estimates suggest this effect may be important at Europa and Ganymede, with a negligible contribution at Callisto. Based on end-member ocean compositions, we quantify the magnetic induction signals that might be used to infer the oxidation state of Europa’s ocean and to investigate stable liquids under high-pressure ices in Ganymede and Callisto. Fully exploring this parameter space for the sake of planned missions requires thermodynamic and electrical conductivity measurements in fluids at low temperature and to high salinity and pressure as well as modeling of motional induction responses.

The plumes of Enceladus produce a cloud of neutral H2O molecules and, via dissociation, OH and O. These neutrals are ionized by charge exchange, solar UV, and electron impacts, producing the thermal water group ions W+ (O+, OH+, H2O+, and H3O+) which become energized in Saturn’s magnetosphere. We first separate the components of energetic (~96 keV) W+ using Cassini Charge-Energy-Mass Spectrometer (CHEMS) data from 78 near equatorial main ring current passes (dipole L = 7-16, ±10° in latitude) in 2004-2010. We find ~53% O+, ~22% OH+, ~22% H2O+, and ~3% H3O+ when averaged over L = 7-16, resulting in a mean water group mass of 16.7 amu. At 7 < L < 21, we find abundance ratios for O+/W+, OH+/W+, and H2O+/W+ that vary little with L. However, while H3O+/W+ is nearly constant at L > 13, H3O+/W+ tends to increase persistently at L < ~10. The large O+ abundance qualitatively agrees with the broad atomic O cloud observed by Cassini and predicted by some models. Our observation of H2O+/W+ > ~20% out to L ~ 21 suggests that neutral H2O spreads throughout the magnetosphere rather than being confined to a narrow H2O torus centered on Enceladus’ orbit.

We present space and ground-based multi-instrument observations demonstrating the impact of the 2022 Tonga volcanic eruption on dayside equatorial electrodynamics. A strong counter electrojet (CEJ) was observed by Swarm and ground-based magnetometers on 15 January after the Tonga eruption and during the recovery phase of a moderate geomagnetic storm. Swarm also observed an enhanced equatorial electrojet (EEJ) preceding the CEJ in the previous orbit. The observed EEJ and CEJ exhibited complex spatiotemporal variations. We combine them with the Ionospheric Connection Explorer (ICON) neutral wind measurements to disentangle the potential mechanisms. Our analysis indicates that the geomagnetic storm had minimal impact; instead, a large-scale atmospheric disturbance propagating eastward from the Tonga eruption site was the most likely driver for the observed intensification and directional reversal of the equatorial electrojet. The CEJ was associated with strong eastward zonal winds in the E-region ionosphere, as a direct response to the lower atmosphere forcing.

The Parker Solar Probe (PSP) spacecraft completed its second Venus gravity assist maneuver (VGA2) on 26 December 2019. For a 20 minute interval surrounding closest approach, the PSP/FIELDS Radio Frequency Spectrometer (RFS) was set to ‘burst mode’, recording radio spectra from 1.3–19.2 MHz at sub-second cadence. We analyze this burst mode data, searching for signatures of radio frequency ‘sferic’ emission from lightning discharges. During the burst mode interval, only 4 spectra were observed with strong impulsive signals, and all 4 could be attributed to saturation of the RFS high gain stage by \emph{in situ} electrostatic plasma waves. These RFS measurements during VGA2 are consistent with previous non-detection of radio frequency lightning signals from Venus reported by Gurnett et al. (2001).