Solar radio bursts, and astrophysical radio emissions in general, are observed either in space or on the ground by measuring their fluctuating electric field. Here, we report the first measurement of the magnetic component of a solar radio wave, observed simultaneously by the Solar Orbiter and Parker Solar Probe missions. The observations were made during the type III radio burst on 2021 October 28. The analysis of the wave polarization and magnetic and electric field amplitudes allows us to estimate the refractive index and put constraints on the direction of the wave. The wave is found to be consistent with an ordinary-mode wave and with a source near the southeast limb of the Sun. These results pave the way for future observations and analyses of the magnetic field of radio waves, in particular, for solar radio bursts.

Solar Orbiter entered the topside ionosphere of Venus for the first time when performing its 4th flyby of the planet, reaching an altitude of 378 km on 18 Feb 2025. High-cadence electron density measurements showed previously unresolved fine-structuring within plasma regions and boundaries, particularly at the ionopause. During the rapid flyby, a rare snapshot of the entire induced magnetosphere was captured during calm solar wind conditions around solar maximum. A well-structured and a relatively steady plasma environment was observed. Assuming an electron temperature of 0.5 eV, pressure balance was found across the ionopause, while at the same time quasi-periodic density and magnetic field variations suggest boundary oscillations. Near closest approach, non-force free magnetic flux ropes were observed. Small-scale perturbations in both magnetic field strength and density across them indicate them being dynamically evolving, rather than in a stationary state.

At the magnetopause, the boundary between the magnetosphere and the shocked solar-wind-dominated region, a fundamental process takes place: magnetic reconnection, which allows part of the solar wind plasma to enter the magnetosphere. In order to investigate this process at the scale of electron dynamics, within a region known as the electron diffusion region (EDR), the Magnetospheric Multiscale (MMS) mission was launched in 2015.Our work focuses on the analysis of a magnetic reconnection event at the magnetopause observed by MMS. This event was initially reported as a crossing of the EDR (Webster et al., 2018).We carried out a detailed investigation of this event to determine the spacecraft trajectories within the reconnection region. The signatures of the electric and magnetic fields, particle velocities and energies, energy dissipation, current analysis, as well as the presence of highly structured whistler and lower-hybrid waves, suggest that the EDR may have been confused with another adjacent region: the magnetospheric separatrix. This region corresponds to the boundary between electrons moving toward the reconnection site and those moving away from it. Both the EDR and the magnetospheric separatrix are electron-scale regions that exhibit a number of similar observational signatures.Our results raise an important question: could some previously reported EDR crossings actually correspond to magnetospheric separatrices? What are the differences in terms of energy conversion and partitioning, wave activity, plasma acceleration and heating between the near-EDR magnetospheric separatrix and the EDR?

Magnetic reconnection is a fundamental process that is ubiquitous in the universe. It converts magnetic field energy into heating and acceleration of plasma. On the dayside of the Earth’s magnetosphere, it is responsible for the dominant transport of plasma, momentum, and energy across the magnetopause from the solar wind into the Earth’s magnetosphere. The present study reports on a magnetic reconnection event with a guide field (BM=0.5 B) detected by the Magnetospheric Multiscale mission (MMS) on October 21, 2015, around 04:39:24 UT. The MMS traversed the compressed magnetospheric separatrix and the reconnection jet far from the diffusion regions and in specific conditions: observing magnetospheric cold ions and a large magnetosheath density of up to 150 p/cc. We investigate the generalized Ohm’s law and the energy conversion process in the spacecraft frame (J.E) and in the fluid frame (J.E`) associated with the separatrix crossing under such conditions. We further validate and compare our results using 2D fully kinetic simulation.

Nonlinear kinetic structures, called electron phase-space holes (EHs), are regularly observed in space and experimental magnetized plasmas. The existence of EHs is conditioned and varies according to the ambient magnetic field and the parameters of the electron beam(s) that may generate them. The objective of this paper is to extend the 3D Bernstein–Greene–Kruskal model with cylindrical geometry developed by L.-J. Chen et al. [“Bernstein–Greene–Kruskal solitary waves in three-dimensional magnetized plasma,” Phys. Rev. E 69, 055401 (2004)] and L.-J. Chen et al., [“On the width-amplitude inequality of electron phase space holes,” J. Geophys. Res. 110, A09211 (2005)] to include simultaneously finite effects due to (i) the strength of the ambient magnetic field B0, by modifying the Poisson equation with a term derived from the electron polarization current, and (ii) the drift velocity ue of the background plasma electrons with respect to the EH, by considering velocity-shifted Maxwellian distributions for the boundary conditions. This allows us to more realistically determine the distributions of trapped and passing particles forming the EHs, as well as the width-amplitude relationships for their existence.

Magnetic reconnection is a fundamental process that is ubiquitous in the universe and allows the conversion of magnetic field energy into heating and acceleration of plasma. It is responsible for the dominant transport of plasma, momentum, and energy across the magnetopause from the solar wind into the Earth's magnetosphere. The present study reports on a magnetic reconnection event detected by the Magnetospheric Multiscale mission (MMS) on 21 October 2015 around 04:40 UT far from the diffusion regions and related to a large-scale solar wind (SW) perturbation impacting the Earth’s magnetosphere. Based on OMNI data, the event impacting the Earth’s magnetosphere is ahead of weak Stream Interacting Region (SIR) (SW beta≈7 and Alfvénic Mach number≈15) where the averaged density of solar wind is about ~20 cm-3 (compared with average SW density ~3-10 cm-3). On one hand, the magnetosheath (MSH) density measured by MMS just after the crossing of the magnetosphere separatrix layer (identified by the large decrease of energetic electrons fluxes) is very large ~95 cm-3 (compared with average MSH density ~20 cm-3). In such a condition, we show that the current density at this separatrix is dominated by the ion diamagnetic current. On the other hand, cold ions are detected close to the magnetic reconnection separatrix layer on the magnetosphere side. Their origin and impact on the ongoing reconnection process are investigated/discussed. The drifting cold ions and the presence of a guide field have significant effects on the orientation of the electric field normal to the magnetopause.

Ion-acoustic waves are often observed in the solar wind along the Solar Orbiter’s orbit. These electrostatic waves are generated via ion-ion or current-driven instabilities below the local proton plasma frequency. Due to the Doppler shift, they are typically observed in the frequency range between the local electron and proton plasma frequency in the spacecraft frame. Ion-acoustic waves often accompany large-scale solar wind structures and play a role in the energy dissipation in the propagating solar wind. Time Domain Sampler (TDS) receiver, a part of the Radio and Plasma Waves (RPW) instrument, is sampling wave emissions at frequencies below 200 kHz almost continuously from the beginning of the mission. Almost three years of observations allow us to perform a detailed study of ion-acoustic waves in the solar wind under variable plasma conditions. The emission tends to be observed when proton density and temperature are highly perturbed. A detailed analysis of the proton velocity distribution and wave generation using solar wind data from a Proton and Alpha particle Sensor (PAS) of the Solar Wind Analyzer (SWA) is shown.

The JUpiter ICy moons Explorer (JUICE) mission is the first large-class (L1) mission of ESA Cosmic Vision. JUICE will be launched in April 2023 with an arrival at Jupiter in 2031 and at least four years making detailed observations of Jupiter’s magnetosphere and of three of its largest moons (Ganymede, Callisto and Europa). The Radio and Plasma Wave Investigation (RPWI) consortium will carry the most advanced set of electric and magnetic fields sensors ever flown in Jupiter’s magnetosphere, which will allow to characterize the radio emission and plasma wave environment of Jupiter and its icy moons. Here we present the scientific objectives and the technical features of the Search Coil Magnetometer (SCM) of RPWI. SCM will provide for the first time three-dimensional measurements of magnetic field fluctuations in the frequency range 0.1 Hz – 20 kHz within Jupiter’s magnetosphere. High sensitivity (~10 fT / √Hz at 1 kHz) will be assured by combining an optimized (20 cm long) magnetic transducer with a low-noise (4 nV / √Hz) ASIC pre-amplifier. Perturbations by the spacecraft are strongly reduced by accommodating SCM at about 10 m away from the spacecraft on the JUICE magnetometer boom. The combination of high sensitivity and high cleanliness of SCM measurements will allow unpreceded studies of electromagnetic fluctuations down to plasma kinetic scales, in particular in key regions such as the magnetopause, the auroral region and the magnetotail current sheet of Ganymede’s own magnetosphere which JUICE will orbit for many months. This will lead to important advances in understanding how fundamental plasma processes such as magnetic reconnection, turbulence and particle energization occur in Jupiter’s plasma environment.

On 28th of August 2018 at 5:30 UT, MMS and Cluster were located in the magnetotail at about 16 earth radii (RE). They both suddenly crossed plasma interfaces. Located near the post midnight sector, Cluster transitioned from a cold plasma sheet to a hot plasma sheet associated with a quasi-parallel earthward flow 800 km/s whereas MMS, located at 4 RE duskward of Cluster, transitioned from a similar cold plasma sheet to the lobe region via a very short period in a hot plasma sheet associated with a vortex-like signature. At 05:50 UT MMS returned to a hot plasma sheet and also detected a quasi-parallel earthward flow ~ 400 km/s and increased energetic ion and electron fluxes. We use measurements from both missions during this conjunction to describe the possible large scale dynamics of the magnetotail as well as some associated kinetic processes. Energetic particle (>50keV) measurements from the two missions are compared. Furthermore, at ion scales, we investigate the possible role of ion fire-hose instability in the plasma flow reduction. At electron scales, we analyze fast and slow non linear electrostatic waves propagating tailward which are detected in the so called electron boundary layer as well as in the hot plasma sheet. We discuss their possible generation mechanisms and link with the large scale dynamics of the magnetotail.

<p>Magnetic reconnection is a fundamental process that is ubiquitous in the universe and allows the conversion of the magnetic field energy into heating and acceleration of plasma. It’s also very important as it is responsible for the dominant transport of plasma, momentum, and energy across the magnetopause from the solar wind into the Earth magnetosphere. Coronal Mass Ejections (CMEs) and Corotating Interaction Regions (CIRs) are the primary large-scale propagating structures and important drivers of unusual space weather disturbances causing magnetospheric activity. The present study reports on a magnetic reconnection event detected by the Magnetospheric Multiscale mission (MMS) on 21 October 2015 around 04:40 UT and related to a large-scale solar wind (SW) perturbation impacting the Earth’s magnetopause. Based on OMNI data, the event impacting the Earth’s magnetosphere is ahead of weak CIR (SW beta=~7 and Alfvénic Mach number~15) where the density of solar wind is about ~20 cm <sup>-3 </sup>(compared with average SW density ~3-10 cm <sup>-3</sup>). Furthermore, the magnetosheath (MSH) density measured by MMS just after the crossing of the magnetopause is about ~95 cm <sup>-3</sup> (compared with average MSH density ~20 cm <sup>-3</sup>). Reconnection signatures such as ion and electron jets, Hall field, and energy conversion are compared with a “classical” reconnection event observed during quiet solar wind conditions.</p>

In the present work, we consider 49 dipolarization fronts (DF) detected by the Magnetospheric Multiscale (MMS) mission on 2017, near the Earth’s magnetotail equator (Bx<5nT). Criteria for selecting DF using an AIDApy routine are based on difference of maximum and minimum values computed with a 306 s sliding window. They request a Bz increase, an ion velocity increase and a density decrease. This first automatic selection is then ajusted manually with the following criteria : Bz increase larger than 5 nT, ion velocity larger than 150 km/s, density decrease and both ion and electron temperature increases. All these events belong to the most common category (A) defined by Schmid et al., 2015 in term of density decrease and temperature increase at the DF. However, based on a superposed epoch analysis of DF basic properties (magnetic field, density, velocity, ...) we distinguish two subcategories of events depending on the shape of the DF. The first subcategory (55.1%) corresponds to a slow decrease of the magnetic field after the DF and is associated with smaller ion velocity and hotter plasma. The second subcategory (44.9%) has the same time scale for the rising and the falling of the magnetic field (a bump) associated with a decrease of ion and electron pressures and faster velocity as shown in Alqeeq et al. 2021. For both categories we found that ions are mostly decoupled from the magnetic field by the Hall fields. The electron pressure gradient term is also contributing to the ion decoupling and likely responsible for an electron decoupling at DF. We also analyzed the energy conversion process. For the first subcategory we found that the energy in the spacecraft frame is transferred from the electromagnetic field to the plasma (J·E>0) ahead or at the DF. For the second subcategory, we found the same behavior ahead or at the DF whereas it is the opposite (J·E<0) behind the front. In the fluid frame, we found that the energy is mostly transferred from the plasma to the electromagnetic field (J·E ′ <0) ahead or at the DF for both subcategories but energy dissipation (J·E ′ >0) only occurs behind the front for the second subcategory. The possible origin of these two subcategories is discussed.

On November 27, 2021, Solar Orbiter completed its only flyby of Earth on its way to the following Sun’s encounter in March 2022. Although this fast flyby was performed primarily to decrease the spacecraft’s velocity and change orbit to get closer to the Sun, the Radio and Plasma Wave (RPW) instrument had the opportunity to perform high cadence measurements in the Earth’s magnetosphere. We review the main observation of the Time Domain Sampler (TDS) receiver, a part of the RPW instrument, made during this flyby at frequencies below 200 kHz. The TDS receiver operated in a high cadence mode providing us with the regular waveform snapshot with 62 ms length every ten seconds for two electric components. Besides the regular captures, we have got more than five hundred onboard classified snapshots and the statistical products with a sixteen-second cadence. Before entering the terrestrial magnetosphere around 02:30UT, the spacecraft wandered through the foreshock region, registering intense bursts of Langmuir waves. After the bowshock crossing, Solar Orbiter was for more than two hours in the morning sector of the magnetosphere, recording various plasma wave modes. The closest approach was reached at 04:30UT above North Africa at an altitude of 460 km. Then the spacecraft continued into the Earth’s tail and entered the magnetosheath around 13:00UT. After 15:00UT, the Solar Orbiter crossed the bowshock, and bursts of Langmuir waves were detected again pointing out to the deep downstream foreshock region. Further from the Earth, intense Auroral Kilometric Radiation (AKR) at frequencies above 100 kHz was also detected.

&lt;p&gt;We investigate the polarization of Langmuir waves observed by the Time Domain Sampler (TDS) module of the Radio and Plasma Waves instrument on Solar Orbiter during several extensive Type III burst events. During its two-year-long cruise phase, Solar orbiter often crossed the source region of the Type III radio emission and observed the Langmuir waves generated by solar energetic electrons. The waves are known to exhibit complex modulation and often non-trivial elliptical polarization which sometimes rapidly changes on the timescales of tens of milliseconds. We show that the observed waveforms are typically composed of multiple sub-packets with a relatively short coherence length. We investigate the correlation between the polarization of the waves, simultaneously observed energetic electrons beams and other plasma properties.&lt;/p&gt;

In July 2017, the MMS constellation was evolving in the magnetotail with an apogee of 25 Earth radii and an average inter-satellite distance of 10 km (i.e. at electron scales). On 23 rd of July around 16:19 UT, MMS was located at the edge of the current sheet which was in a quasi-static state. Then, MMS suddenly entered in the central plasma sheet and detected the local onset of a small substorm as indicated by the AE index (~400 nT). Fast earthward plasma flows were measured for about 1 hour starting with a period of quasi-steady flow and followed by a saw-tooth like series of plasma jets (“bursty bulk flows”). In the present study, we focus on a short sequence related to an ion scale current sheet crossing embedded in a fast earthward flow. We analyse in detail two other kinetic structures in the vicinity of this current sheet: an ion-scale flux rope and an electron vortex magnetic hole and discuss the Ohm’s law and conversion energy processes.

Nonlinear kinetic structures are regularly observed in space and experimental magnetized plasmas, called electron phase-space holes (EH). The existence of EH is conditioned and varies according to the ambient magnetic field and the parameters of the electron beam that may generate them. The objective of this paper is to extend the 3D Bernstein-Greene-Kruskal (BGK) model with cylindrical geometry to include finite effects due to (i) the strength of the ambient magnetic field $\vec{B}_0$, by modifying the Poisson equation with a term derived from the electron polarization current, and (ii) the drift velocity $u_e$ of the background plasma with respect to the EH, by considering velocity-shifted Maxwellian distributions for the boundary conditions. This allows us to more realistically determine the distributions of trapped and passing particles interacting with the EH, as well as the width-amplitude relationships for their existence.

Recent MMS observations (e.g. [Holmes et al, 2018, Steinvall et al., 2019]) exploring various regions of the magnetosphere have found solitary potential structures call Electron phase-space Hole (EH). These structures have kinetic scale (dozens of Debye lengths) and persist during long time (dozens of plasma frequency periods). EH are characterized by a bipolar electric field parallel to ambient magnetic field and fastly propagate along this latter (a few tenths of speed light). We have created a 3D Bernstein-Greene-Kruskal (BGK) model (as [Chen et al, 2004]) adapted to various magnetospheric ambient magnetic fields. BGK model results depend on choice of potential shape and passing distribution function at infinity (before EH potential interaction). 2D-3V Particle-In-Cell simulations have been developed with the fully kinetic code Smilei [Derouillat et al, 2017], using real magnetosphere plasma parameters. Solitary waves in the magnetotail are three-dimensional potentials which can be generated through nonlinear evolution of an electron beam instability (or bump on tail). The simulated EH are comparable to the EH observed in the magnetosphere with the same parameters. We have also investigated the EH formation with density inhomogeneities using a BGK stability model we have developed. Indeed, density inhomogeneities exist notably in interplanetary plasmas. As a result taking into account the background density inhomogeneities, significantly alters the stability criteria. We have performed 2D-3V PIC simulations with realistic inhomogeneous density background (smaller than 10% of mean density) to understand such a type of EH formation. References: Holmes et al., J. Geophys. Res. Space Phys. 123, 9963, 2018 Steinvall et al., Phys. Rev. Lett. 123, 255101, 2019 Chen et al., Phys. Rev. E 69, 055401, 2004 Derouillat et al., Comput. Phys. Commun. 222, 351, 2017

Plasma waves can play an important role in the evolution of the solar wind and the particle velocity distribution functions in particular. We analyzed the electromagnetic waves observed above a few Hz by the Radio Plasma Waves (RPW) instrument suite onboard Solar Orbiter, during its first orbit, which covered a distance from the Sun between 1 AU and 0.5 AU. We identified the majority of the detected waves as whistler waves with frequency around 0.1 f_ce and right handed circular polarisation. We found these waves to be mostly aligned or anti aligned with the ambient magnetic field, and rarely oblique. We also present and discuss their direction of propagation and the variation of the waves' properties with heliocentric distance.

Thin current sheets are routinely observed in the solar wind. Here we report observations of thin current sheets and the associated plasma waves using the Solar Orbiter spacecraft. The Radio and Plasma Waves (RPW) instrument provides high-resolution measurements of the electric field, number density perturbations, and magnetic field fluctuations, which we use to identify and characterise the observed waves, while the magnetic field provided by the MAG instrument is used to characterise the current sheets. We discuss the role of current sheets in the generation of the observed waves and the effects of the waves on the current sheets.

In the present work, we consider four dipolarization front (DF) events detected by MMS spacecraft in the Earth’s magnetotail during a substorm on 23rd of July 2017 between 16:05 and 17:19 UT. From their ion scale properties, we show that these four DF events embedded in fast Earthward plasma flows have classical signatures with increases of Bz, velocity and temperature and a decrease of density across the DF. We compute and compare current densities obtained from magnetic and particle measurements and analyse the Ohm’s law. Then we describe the wave activity related to these DFs. We investigate energy conversion processes via J.E calculations and estimate the importance of the electromagnetic energy flow by computing the divergence of the Poynting vector. Finally we discuss the electromagnetic energy conservation in the context of these DFs.

A large-amplitude impact-induced like electric field signal is often observed by the Radio and Plasma Wave (RPW) Instrument onboard Solar Orbiter. The signal has a sharp increase followed by an exponential decay, typically observed when spacecraft experiences a dust impact. The amplitude can reach several V/m. The impact dust size can be estimated from the electric field amplitude and is similar to the characteristic dust size near the sun expected from the zodiacal-light observations. On the other hand, the signal's decay time is the order of second, unusually long compared to the dust impact signals previously reported by the other spacecraft. We will show the characteristics of these signals and discuss the origin.