This study introduces five linear regression models developed to accurately predict proton intensities in the critical energy range of 92.2 keV to 159.7 keV. To achieve this task we utilized 14 years of data sourced from the Cluster’s RAPID experiment and NASA’s OMNI database. This data was then aligned with the Solar wind-Magnetosphere-Ionosphere Link Explorer (SMILE) mission’s trajectory, to increase model accuracy in the relevant regions. Our approach diverges from existing methodologies by offering a user-friendly model that doesn’t require specialized software, making it accessible for broader applications in satellite mission planning and risk assessment. The research segregates the dataset into four distinct regions, each analyzed for proton intensity dynamics. In the outer regions (|YGSE| ≥ 6 Re) there is a pronounced dependence on radial distance and solar wind speed. In contrast, the inner regions (|YGSE| ≤ 6 Re) demonstrate a significant dependence of proton intensities on the absolute value of the z-coordinate and the magnetic field line topology. Our models achieved a Spearman correlation ranging from 0.57 to 0.72 on the test set, indicating good predictive capabilities. The findings emphasize the role of regional characteristics in space weather prediction and underscore the potential for tailored approaches in future research.

At a low activity comet the plasma is distributed in an asymmetric way. The hybrid simulation code Amitis is used to look at the spatial evolution of ion velocity distribution functions (VDFs), from the upstream solar wind to within the comet magnetosphere where the solar wind is heavily mass-loaded by the cometary plasma. We find that the spatial structures of the ions and fields form a highly asymmetric, half-open induced magnetosphere. The VDFs of solar wind and cometary ions vary drastically for different locations in the comet magnetosphere. The shape of the VDFs differ for different species. The solar wind protons show high anisotropies that occasionally resemble partial rings, in particular at small cometocentric distances. A second, decoupled, proton population is also found. Solar wind alpha particles show similar anisotropies, although less pronounced and at different spatial scales. The VDFs of cometary ions are mostly determined by the structure of the electric field. We perform supplementary dynamic particle backtracing to understand the flow patterns of solar wind ions that lead to these anisotropic distributions. This tracing is needed to understand the origin of cometary ions in a given part of the comet magnetosphere. The particle tracing also aids in interpreting observed VDFs and relating them to spatial features in the electric and magnetic fields of the comet environment.

Fundamental processes in plasmas act to convert energies into different forms, e.g., electromagnetic, kinetic and thermal. Direct derivation from the Valsov-Maxwell equation yields sets of equations that describe the temporal evolution of the magnetic, kinetic and internal energies in either the monofluid or multifluid frameworks. In this work we focus on the main terms that affect the changes in the kinetic energy. These are pressure gradient-related terms and electromagnetic terms. The former account for plasma acceleration or deceleration from a pressure gradient, while the latter from an electric field. The overall balance between these terms is fundamental to ensure the conservation of energy and momentum. We use in-situ observations from the Magnetospheric MultiScale (MMS) mission to study the relationship between these terms. We perform a statistical analysis of those parameters in the context of magnetic reconnection by focusing on small-scale Electron Diffusion Regions and large-scale Flux Transfer Events. The analysis reveals a correlation between the two terms in the monofluid force balance, and in the ion force and energy balance. However, the expected relationship cannot be verified from electron measurements. Generally, the pressure gradient related terms are smaller than their electromagnetic counterparts. We perform an error analysis to quantify the expected underestimation of gradient values as a function of the spacecraft separation compared to the gradient scale. Our findings highlight that MMS is capable of capturing energy and force balance for the ion fluid, but that care should be taken for energy conversion terms based on electron pressure gradients.

The important question of how the solar wind influences Jupiter's magnetosphere is difficult to answer due to the lack of consistent up-stream monitoring of the interplanetary medium (IPM) and the large-scale dynamics internal to the magnetosphere. To compensate for the relative lack of in-situ data, solar wind propagation models are often used to estimate the ambient IPM conditions near Jupiter for comparison to remote observations or in-situ measurements. A statistical analysis of the timescales over which Jupiter's magnetosphere reacts to changes in the IPM would allow the solar wind interaction to be better decoupled from internal dynamics; however, solar wind propagation from near-Earth measurements out to Jupiter introduces uncertainties in both the timing and magnitude of changes in the IPM which are themselves difficult to assess. Here, we present an ensemble modeling framework for the solar wind at Jupiter. A variety of existing solar wind models were compared to in-situ measurements from near-Jupiter spacecraft spanning diverse spacecraft-Sun-Earth alignments and phases of the solar cycle, amounting to more than 23,000 hours over four decades. Typical errors in prediction timing and magnitude, as well as conditions under which the different input models performed better than average, were then characterized as part of this framework. The resulting ensemble model produces the most-probable near-Jupiter IPM conditions for times within the tested epoch and provides the estimated variance in these conditions, allowing for a statistical analysis of the relationship between Jupiter’s magnetosphere and the solar wind. In addition to remote sensing studies, the robust modeling of solar wind conditions near Jupiter is crucial to ongoing and future in-situ studies using Galileo, Juno, JUICE, and Europa Clipper measurements; the compression or expansion of the magnetosphere is crucial to interpreting in-situ measurements of Jupiter’s middle and outer magnetosphere. Finally, we will discuss how the work presented here can be extended towards more robust characterization of solar wind parameters and time-dependent propagation of solar wind conditions at other planetary magnetospheres.

The properties of the first kilometers of the Martian atmospheric Planetary Boundary Layer have until now been measured by only a few instruments and probes. InSight offers an opportunity to investigate this region through seismoacoustics. On six occasions, its seismometers recorded short low-frequency waveforms, with clear dispersion between 0.4 and 4Hz. These signals are the air-to-ground coupling of impact-generated infrasound, which propagated in an low-altitude atmospheric waveguide. Their group velocity depends on the structure of effective sound speed in the boundary layer. Here, we conduct a Bayesian inversion of effective sound speed up to 2000m altitude using the group velocity measured for events S0981c, S0986c and S1034a. The inverted effective sound speed profiles are in good agreement with estimates provided by the Mars Climate Database. Differences between inverted and modeled profiles can be attributed to a local wind variation in the impact → station direction, of amplitude smaller than 2m/s.

Coronal Holes (CH) are large-scale, low-density regions in the solar atmosphere which may expel high-speed solar wind streams that incite hazardous, geomagnetic storms. Segmentation of CH boundaries may aid in validating predictive coronal and solar wind models but has proved difficult due to similar appearances as filaments and the tendency for dense coronal plasmas to block underlying CHs in Extreme Ultraviolet (EUV) imagery. We propose an automated detection algorithm of CHs which revisits ground-observed, chromospheric He I 10830 Å line imagery and underlying photospheric magnetograms as drivers to circumvent these issues and provide a complementary method to the space-observed, coronal EUV emission-driven methods that have been widely adopted in the community. Classical computer vision techniques are applied to imbue the routine with design variables based in radiative and magnetic properties of CHs, as well as produce an ensemble of boundaries with quantified intra-algorithm uncertainty. This method is science-enabling towards future studies of coronal hole formation and variability from a mid-atmospheric perspective.

The relatively unconstrained internal structure of Venus is a missing piece in our understanding of the Solar System formation and evolution. To determine the seismic structure of Venus’ interior, the detection of seismic waves generated by venusquakes is crucial, as recently shown by the new seismic and geodetic constraints on Mars’ interior obtained by the InSight mission. In the next decades multiple missions will fly to Venus to explore its tectonic and volcanic activity, but they will not be able to conclusively report on seismicity or detect actual seismic waves. Looking towards the next fleet of Venus missions in the future, various concepts to measure seismic waves have already been explored in the past decades. These detection methods include typical geophysical ground sensors already deployed on Earth, the Moon, and Mars; pressure sensors on balloons; and airglow imagers on orbiters to detect ground motion, the infrasound signals generated by seismic waves, and the corresponding airglow variations in the upper atmosphere. Here, we provide a first comparison between the detection capabilities of these different measurement techniques and recent estimates of Venus’ seismic activity. In addition, we discuss the performance requirements and measurement durations required to detect seismic waves with the various detection methods. As such, our study clearly presents the advantages and limitations of the different seismic wave detection techniques and can be used to drive the design of future mission concepts aiming to study the seismicity of Venus.

Maintaining accurate real-time hindcast and forecast specification of the radiation environment is essential for operators to monitor and mitigate the effects of hazardous radiation on satellite components. The Radiation Belt Forecasting Model and Framework (RBFMF) provides real-time forecasts and hindcasts of the electron radiation belt environment, which are used as inputs for the Satellite Charging Assessment Tool (SatCAT). We evaluated the long-term statistical error and bias of the RBFMF by comparing the 10-hour hindcast of electron phase space densities (PSD) to a multi-mission dataset of PSD observations. We found that, between the years 2016-2018, the RBFMF reproduced the radiation belt environment to within a factor of 1.5. While the error and bias of assimilated observations were found to influence the error and bias of the hindcast, data assimilation resulted in more accurate specification of the radiation belt state than real-time Van Allen Probe observations alone. Furthermore, when real time Van Allen Probe observations were no longer available, the hindcast errors increased by an order of magnitude. This highlights two needs; (i) the development of physics-based modelling incorporated into this framework, and (ii) the need for real-time observations which span the entire outer radiation belt.

Coronal mass ejections (CMEs) directed toward Earth can modulate cosmic ray fluxes detected on the ground. We provide definitive evidence that even moderately fast CMEs produce small-scale Forbush decreases (FDs) - brief ≤ 3% cosmic ray exclusions over a day. Tracking fronted halo CMEs with coordinated solar imaging and in situ monitoring reveals timing and efficiency signatures statistically linking intensity drops with transient shock passages at ejecta fronts. The reductions originate in weak sheath scattering zones featuring elliptical cross-sections preferentially oriented edge-on to Earth. Connecting properties of these subtle effects to remote CME structure and kinematics elucidates inner heliospheric shock physics below major FDs detection thresholds (CR ≥ 3%). This reveals an entirely overlooked category of minor interplanetary perturbations by common solar eruptions insufficient to spark major storms.

Previous simulations have suggested that O+ outflow plays a role in driving the sawtooth oscillations. This study investigates the role of O+ by identifying the differences in ionospheric outflow between sawtooth and non-sawtooth storms using 11 years of FAST/Time of flight Energy Angle Mass Spectrograph (TEAMS) ion composition data from 1996 through 2007 during storms driven by coronal mass ejections (CMEs). We find that the storm’s initial phase shows larger O+ outflow during non-sawtooth storms, and the main and recovery phases revealed differences in the location of ionospheric outflow. On the pre-midnight sector, a larger O+ outflow was observed during the main phase of sawtooth storms, while non-sawtooth storms exhibited stronger O+ outflow during the recovery phase. On the dayside, the peak outflow shifts significantly towards dawn during sawtooth storms. This strong dawnside sector outflow during sawtooth storms warrants consideration.

We present an application of the latest UCL-AGA magnetodisc model (MDISC) to the study of the magnetic and plasma conditions in the near-Ganymede space. By doing this, we provide a comparison with measurements from Juno’s most recent flyby of the Jovian moon, perijove 34 (PJ34). We find good agreement between the model results and the magnetometer data, pointing towards a hot plasma index value $K_h = \SI{2.719(24)e7}{\pascal\,\meter\,\tesla^{-1}}$ and an effective magnetodisc radius $r_{\text{max}} = \SI{79.5(11)}{}$ Jupiter radii for the Jovian magnetosphere, for the duration of the trajectory, suggesting a configuration with middling levels of expansion. We also predict the plasma conditions observed by Juno during the same flight-path, as well as the typical conditions over the orbit of Ganymede, with the magnetic and hot plasma pressures assuming dominant roles. Finally, these results are compared with functional fits of a compilation of Galileo flyby data obtained in the vicinity of Ganymede’s orbit, suggesting Juno experienced somewhat similar conditions, despite a systematic overestimation in magnetic field intensity in the near-Ganymede space.

We performed 2D PIC simulations of Kelvin Helmholtz instability (KHI) with symmetric and asymmetric density and temperature profiles along the flow shear with a northward interplanetary magnetic field. The Magnetic Flux Transport method, field topology and magnetic field minimums are used to identify the reconnection X-lines. We start to observe the reconnection signatures such as magnetic field and flow reversals at the vortex edges in the nonlinear phase of the KHI when the vortices are rolling up. The number of reconnection regions increases at the turbulence phase. The signatures eventually decrease and finally disappear at very turbulent stages of KHI developments. Our results qualitatively agree with MMS observations of reconnection signatures at KHI along the magnetospheric flanks.

To study the contributions of cusp outflow coming through the lobes and nightside auroral outflow to the O+ in the plasma sheet, we performed a statistical study of tailward streaming O+ in the lobes, the plasma sheet boundary layer (PSBL) and the plasma sheet (PS), using MMS/HPCA data. Similar spatial distributions demonstrate the entry of cusp-origin O+ from the lobes to the plasma sheet through the PSBL. There is an energy dependence in the lobe O+ spatial distribution, with low-energy O+ streaming near the center in YGSM while high energy (1-3 keV) O+ streams near the flanks. Low energy (< 100 eV) O+ from the nightside auroral oval can be identified in the near-Earth PSBL/PS with high-density (> 0.03 cm-3), and energetic (> 3 keV) streaming O+ with similar density (~0.02 cm-3) is seen further out on the duskside of the PSBL/PS. The rest of the nightside auroral O+ in the PSBL is mixed with O+ coming in from the lobe, and difficult to distinguish. We estimated the inflow and outflow of ions in the plasma sheet between 7-17 RE, using data extracted from previous studies and this work. Comparisons between the estimated fluence suggest that the majority of near-Earth plasma sheet H+ are from cusps and Earthward convection from the distant tail. The O+ in the same region, on the other hand, has a mixed source, with auroral outflow giving the highest contribution.

The strip-like bulge is a storm-time conjugate ionospheric plasma density enhancement that extends widely (over 150° in longitude) in the zonal dimension but occupies only 1°~5° in latitude. Based on in-situ measurements of 11 low earth orbit (LEO) satellites, this study statistically investigates the bulge structures of geomagnetic storms driven by 136 interplanetary coronal mass ejections (ICMEs) during 2000~2021. The statistical results show that the strip-like bulges are initiated at the end of the storm main phase and can persist for more than 60 hours. The spatial and temporal coverage of the strip-like bulge varies from storm to storm. However, the bulges do exhibit occurrence preferences: stronger storms, the Asian-Pacific sector (with eastward magnetic declination), the nightside of the dawn-dusk terminator, and solar minimum periods. A quiet time density enhancement called midlatitude extra peaks could be recognized as a precursor of the strip-like bulge. The plasmaspheric compression shares some similar occurrence features with the strip-like bulge, indicating a field-aligned downward and cross-L inward intrusion of the plasmaspheric ions. The local net ion drifts partly support this scenario with downward/inward being the most dominant but not unique pattern, other diverse net ion drift configurations exist but their impact on the strip-like bulges remains unclear.

The spatial distribution of whistler-mode wave emissions in the Jovian magnetosphere measured during the first 45 perijove orbits of Juno is investigated. A double-belt structure in whistler-mode wave intensity is revealed. Between the two whistler-mode belts, there exists a region devoid of 100s keV electrons near the magnetic equator at 9 < M < 16. Insufficient source electron population in such an electron “slot” region is a possible explanation for the relatively lower wave activity compared to the whistler-mode belts. The wave intensity of the outer whistler-mode belt measured in the dusk-premidnight sector is significantly stronger than in the postmidnight-dawn sector. We suggest that the inherent dawn-dusk asymmetries in source electron distribution and/or auroral hiss emission rather than the modulation of solar cycle are more likely to result in the azimuthal variation of outer whistler-mode belt intensity during the first 45 Juno perijove orbits.

A document by Jérémie Vasseur. Click on the document to view its contents.

A document by Jason M H Beedle. Click on the document to view its contents.

The generation and propagation of Ultra Low Frequency (ULF) waves are intrinsically coupled to the cold plasma population in the terrestrial magnetosphere. During geomagnetic storms, extreme reconfigurations of the cold plasma creates a complex and dynamic system that drastically modifies this coupling. The extent and manner in which this coupling is affected remains an open question. In this report, we assess the coupling between ULF waves and cold plasmaspheric plumes during geomagnetic storms, and investigate the implications for ULF wave-driven radial transport of the outer radiation belt population. We present a series of event studies of Van Allen Probes observations. For each event, we use inferred measurements of the cold plasma density during plume crossings, in combination with magnetic and electric field observations of ULF waves. The event studies show very different, and at times contrasting, wave behaviour. This includes events where ULF waves appear to be spatially confined within plume structures. Initial estimates show that the localised patches of ULF wave power have significant implications for radial diffusion processes, and highlights the need for caution in estimating radial diffusion coefficients. We suggest that the cold plasma dynamics is an important source of uncertainty in radial diffusion models, and understanding cold plasma-ULF wave coupling is a critical area of future investigations.