Search

We use the full NASA Van Allen Probes mission (2012–2019) to extract the electron plasma density from the Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) and Electric Field and Waves (EFW) instruments and discuss the evolution of the plasmasphere. We generate new statistics including mean and standard deviations of the plasma density with respect to L‐shell, magnetic local time (MLT), and various geomagnetic indices. These statistics are generated to be applied in radiation belt physics and space weather codes (with fits provided). The mean plasmasphere is circular around Earth with respect to MLT for Kp < 1. The mean 100 cm−3level line is above L = 5 and mean 10 cm−3level expands above the Van Allen Probes apogee for Kp < 1. The outer electron belt lies within the plasmasphere for 60% of all times. As activity increases (Kp > 2), a gradual MLT asymmetry forms with higher mean density in the afternoon sector due to plumes expanding outward. Conversely, the mean density decreases on the dawn and night sectors. The mean density is between ∼500 and ∼50 cm−3between L ∼ 4 and L ∼ 6 during quiet and moderately active times (Kp < 3), representing ∼80% of all times. Statistics in regions of high density below L = 2 are underdefined for intense activity. The highest standard deviation of density represents a factor 2.5 to 3 times the mean above L = 5 and for active times. We find the percent difference between the EFW and EMFISIS densities is bounded by ±20% for quiet and moderate activity (Kp < 5) and goes up to ±100% for extreme activity. The Earth's plasmasphere, discovered in the 1950s, is a region of cold plasma made of ions and electrons of a few electronvolts in energy, originating from upwelling ionized gas from the ionosphere and forming a rotating torus around the Earth. The radial profile of the electron cold plasma density within the plasmasphere decays from 10,000 electrons per cubic centimeter at ∼1,000 km altitude to 10s electrons per cubic centimeter at its outer edge, sometimes exceeding ∼36,000 km in altitude at the equator. The state of the plasmasphere is highly dependent on geomagnetic conditions, with geomagnetic storms and substorms eroding parts of this plasma. Here, we analyze 7 years of NASA Van Allen Probes measurements of the electron plasma density and generate statistics with respect to L‐shell, magnetic local time, and geomagnetic indices. In this way, we show statistical variations of the plasmasphere, a strong magnetic local time dependence, and erosion with increasing geomagnetic activity. New mean electron densities and their standard deviation are generated and fitted with model functions that can be incorporated into space weather codes. This is important because the electron density is a key parameter influencing the strength of wave‐particle interactions that accelerate and scatter energetic particles in the inner magnetosphere. Generation of new statistics of mean and standard deviation of the plasma density from Electric Field and Waves and Electric and Magnetic Field Instrument Suite and Integrated Science of RBSP for the whole missionEmpirical density models made of fits are provided versus L‐shell, magnetic local time (MLT), and geomagnetic indices to be used in radiation belt codesAn extensive analysis of the cold plasma statistics is provided with respect to L‐shell, MLT, and geomagnetic activity Generation of new statistics of mean and standard deviation of the plasma density from Electric Field and Waves and Electric and Magnetic Field Instrument Suite and Integrated Science of RBSP for the whole mission Empirical density models made of fits are provided versus L‐shell, magnetic local time (MLT), and geomagnetic indices to be used in radiation belt codes An extensive analysis of the cold plasma statistics is provided with respect to L‐shell, MLT, and geomagnetic activity

An unusually low density solar wind event was observed in December 2022 moving past both Earth and Mars. The source was traced back to a coronal hole and active region on the Sun's surface. The resulting solar wind lead to the development of a co‐rotating interaction region (CIR) and trailing rarefaction region that lasted for multiple solar rotations. Within this structure, the solar wind conditions, including density, velocity, and magnetic field magnitude and orientation drastically changed. In this study we analyze the response of the Martian ionosphere using MAVEN data to these changing solar wind conditions. The low density solar wind region associated with the December event resulted in the expansion of the Martian ionospheric boundaries. We show that the ion composition boundary (ICB) is located at extreme altitudes that are beyond previously observed locations from the MAVEN mission between 2015 and 2018. Furthermore, the boundary between shocked solar wind and the Martian ionosphere identified using electron and ion data moved together on the dayside of the planet with the changing solar wind conditions. However, at the flank region these boundaries do not move together, and we show here that the decoupling of the two boundaries may be the result of a change in the interplanetary magnetic field azimuthal angle. The Sun constantly emits fast moving charged particles into interplanetary space in what is known as the solar wind. In December 2022, a region of fast moving solar wind overtook a region of slower moving solar wind. The fast solar wind acted as a broom sweeping up and compressing the slower wind preceding it. This interaction of two solar wind speeds is observed to rotate with the Sun. Trailing this interaction region is a region of low density solar wind. In December 2022, this type of interplanetary solar wind structure interacted with Mars' electrically charged atmosphere, or ionosphere. Throughout this period, the ionosphere boundary characterized by a transition from solar wind ions to planetary ions moved up and down relative to the planet near dusk. As the rarefaction region passed through the system, the ionosphere expanded to unusually high heights as it was not compressed by the solar wind. However, the flapping of the ionospheric boundary seems to depend on the orientation that the solar wind interacts with Mars. The disappearing solar wind event observed at Mars in December 2022 was caused by a co‐rotating interaction regionMars' ionosphere expanded further than previously observed locations between 2015 through 2018The flank ion composition boundary experiences large fluctuations in altitude after a change in the interplanetary magnetic field direction The disappearing solar wind event observed at Mars in December 2022 was caused by a co‐rotating interaction region Mars' ionosphere expanded further than previously observed locations between 2015 through 2018 The flank ion composition boundary experiences large fluctuations in altitude after a change in the interplanetary magnetic field direction

During the solar minimum, when the Sun is at its least active, the solar wind1,2is observed at high latitudes as a predominantly fast (more than 500 kilometres per second), highly Alfvénic rarefied stream of plasma originating from deep within coronal holes. Closer to the ecliptic plane, the solar wind is interspersed with a more variable slow wind3of less than 500 kilometres per second. The precise origins of the slow wind streams are less certain4; theories and observations suggest that they may originate at the tips of helmet streamers5,6, from interchange reconnection near coronal hole boundaries7,8, or within coronal holes with highly diverging magnetic fields9,10. The heating mechanism required to drive the solar wind is also unresolved, although candidate mechanisms include Alfvén-wave turbulence11,12, heating by reconnection in nanoflares13, ion cyclotron wave heating14and acceleration by thermal gradients1. At a distance of one astronomical unit, the wind is mixed and evolved, and therefore much of the diagnostic structure of these sources and processes has been lost. Here we present observations from the Parker Solar Probe15at 36 to 54 solar radii that show evidence of slow Alfvénic solar wind emerging from a small equatorial coronal hole. The measured magnetic field exhibits patches of large, intermittent reversals that are associated with jets of plasma and enhanced Poynting flux and that are interspersed in a smoother and less turbulent flow with a near-radial magnetic field. Furthermore, plasma-wave measurements suggest the existence of electron and ion velocity-space micro-instabilities10,16that are associated with plasma heating and thermalization processes. Our measurements suggest that there is an impulsive mechanism associated with solar-wind energization and that micro-instabilities play a part in heating, and we provide evidence that low-latitude coronal holes are a key source of the slow solar wind.

Results obtained in the Martian ionosphere by the Langmuir Probe and Waves instrument aboard the Mars Atmosphere and Volatile EvolutioN Mission spacecraft are presented. The results include ionospheric electron densities determined from the frequency of Langmuir waves. Since the amplitude of thermal Langmuir waves is often below the instrument's detection level, Langmuir Probe and Waves excites these waves by injecting into the plasma a 3.3‐V white noise signal. Electric field spectral measurements obtained shortly after the excitation show a resonance line at frequencies slightly below the local plasma frequency. The observed resonance line is interpreted to originate from plasma waves excited in the wake behind the spacecraft. These results reveal an important phenomenon in electron density estimation from stimulated Langmuir waves. The observed phenomenon, not previously reported by earlier missions, may be a common process in active sounding that can affect in situ electron density measurements. Electric field spectra in active sounding show an anomalous resonance line at frequencies below the local electron plasma frequencyThe observed resonance line is interpreted as the signature of the plasma waves excited within the spacecraft wakeThe observed phenomenon may have affected results in similar active missions that were incapable of identifying this process

We present a statistical analysis with 100% duty cycle and non‐time‐averaged amplitudes of the prevalence and distribution of high‐amplitude >50‐pT whistler mode waves in the outer radiation belt using 5 years of Van Allen Probes data. Whistler mode waves with high magnetic field amplitudes are most common above L=4.5 and between magnetic local time of 0–14 where they are present approximately 1–6% of the time. During high geomagnetic activity, high‐amplitude whistler mode wave occurrence rises above 25% in some regions. The dayside population are more common during quiet or moderate geomagnetic activity and occur primarily >5° from the magnetic equator, while the night‐to‐dawn population are enhanced during active times and are primarily within 5° of the magnetic equator. These results are different from the distribution of electric field peaks discussed in our previous paper covering the same time period and spatial range. Our previous study found large‐amplitude electric field peaks were common down to L=3.5 and were largely absent from afternoon and near noon. The different distribution of large electric and magnetic field amplitudes implies that the low‐Lcomponent of whistler mode waves observed previously are primarily highly oblique, while the dayside and high‐Lpopulations are primarily field aligned. These results have important implications for modeling radiation belt particle interactions with chorus, as large‐amplitude waves interact nonlinearly with electrons, resulting in rapid energization, de‐energization, or pitch angle scattering. This also may provide clues regarding the mechanisms which can cause significant whistler mode wave growth up to more than 100 times the average wave amplitude. Whistler mode waves greater than 50 pT are present from night to afternoon sectorA significant dayside and field‐aligned population occurs during both quiet and active timesLow Lhigh‐amplitude waves are primarily electrostatic and oblique

We present the first statistical analysis with continuous data coverage and nonaveraged amplitudes of the prevalence and distribution of high‐amplitude (>5 mV/m) whistler mode waves in the outer radiation belt using 5 years of Van Allen Probes data. These waves are most common above L= 3.5 and between magnetic local time of 0–7 where they are present 1–4% of the time. During high geomagnetic activity, high‐amplitude whistler mode wave occurrence rises above 30% in some regions. During these active times the plasmasphere erodes to lower Land high‐amplitude waves are observed at all Loutside of it, with the highest occurrence at low L(3.5–4) in the predawn sector. These results have important implications for modeling radiation belt particle interactions with chorus, as large‐amplitude waves interact nonlinearly with electrons. Results also may provide clues regarding the mechanisms which result in growth to large amplitudes. Our Earth is surrounded by a ring of high‐energy electrons, known as the outer radiation belt, which can cause damage to satellites in orbit. These electrons gain such high energy because of a type of electromagnetic waves called “whistler waves,” which exist in the space around Earth. Satellites have recently discovered whistler waves that are tens or hundreds of times as large as the average waves. Such large whistler waves can energize electrons very quickly and also cause electrons to be knocked into our atmosphere, creating aurora. Because these large waves are hard to measure, scientists have not been able to say how often they occur, where they occur, or even how exactly they form. This study uses a unique data set gathered by the Van Allen Probes to find out when and where these very large whistler waves occur. We found that these waves appear mostly in the nightside and morning side of the Earth, and they tend to appear much closer to Earth than smaller whistler waves do. This information offers us clues about how these monster waves form and what impact they might have on the radiation belt and the Earth. High‐amplitude whistler mode waves are most prevalent between midnight and dawn and above Lof 3.5During active times, high‐amplitude waves are present over 30% of the time in some regionsWaves greater than 20 mV/m preferentially occur at low Lshell in the predawn sector

The occurrence of Venusian lighting has been debated for decades. Terrestrial lightning generates whistler waves, and many whistlers have been observed in Venus's ionosphere and induced magnetosphere. Venusian lightning occurrence rates derived from these whistler observations are relatively high. However, optical flashes on Venus are exceedingly rare and Venus encounters by multiple spacecrafts have not detected lightning. These non‐detections and rare optical observations are consistent with low Venusian lightning occurrence rates, which is incompatible with the high whistler‐derived rates. We present observations of whistlers during a Parker Solar Probe Venus gravity assist and eliminate lightning as a possible source. These waves are observed at an altitude of 0.39 Venus radii on Venus' nightside with planetward propagation and are simultaneous with Langmuir waves. This provides a mechanism for whistler generation near Venus that does not require lightning, and suggests that whistler‐based lightning occurrence rates may be overestimated. Whistler waves are a type of plasma wave. These waves can be generated in several ways, including by lightning. Every lightning strike on Earth generates a whistler wave, but only some of the whistler waves in near‐Earth space are generated by lightning. Many whistler waves have been detected near Venus and have been used to argue that lightning likely occurs on Venus at a relatively high rate. However, other signatures of lightning (including flashes of light in the sky) on Venus are very rare, which indicates that Venusian lightning must occur at a very low rate. The discrepancy between these different signatures of lightning on Venus means that we do not know how often Venus actually experiences lightning. We use data from Parker Solar Probe during a Venus gravity assist to study whistler waves that occurred on the nightside of Venus, very close to the planet. We observe that these waves are traveling toward Venus, which means they could not have been generated by lightning. This shows that whistler waves can occur near Venus without being generated by lightning and indicates that the occurrence rates of Venusian lightning based on whistler wave observations might be overestimated. Whistler waves were observed at an altitude of 0.39 Venus radii on Venus's nightside with planetward Poynting vectorLangmuir waves occurred simultaneously with the whistlers, suggesting electron beam driving with magnetotail originsLightning is eliminated as a possible generation mechanism for these whistler waves Whistler waves were observed at an altitude of 0.39 Venus radii on Venus's nightside with planetward Poynting vector Langmuir waves occurred simultaneously with the whistlers, suggesting electron beam driving with magnetotail origins Lightning is eliminated as a possible generation mechanism for these whistler waves

The search‐coil magnetometer (SCM) aboard Parker Solar Probe (PSP) measures the 3 Hz to 1 MHz magnetic field fluctuations. During Encounter 1, the SCM operated as expected; however, in March 2019, technical issues limited subsequent encounters to two components for frequencies below 1 kHz. Detrimentally, most whistler waves are observed in the affected frequency band where established techniques cannot extract the wave polarization properties under these conditions. Fortunately, the Electric Field Instrument aboard PSP measures two electric field components and covers the affected bandwidth. We propose a technique using the available electromagnetic fields to reconstruct the missing components by neglecting the electric field parallel to the background magnetic field. This technique is applicable with the assumptions of (a) low‐frequency whistlers in the plasma frame relative to the electron cyclotron frequency; (b) a small propagation angle with respect to the background magnetic field; and (c) a large wave phase speed relative to the cross‐field solar wind velocity. Critically, the method cannot be applied if the background magnetic field is aligned with the affected SCM coil. We have validated our method using burst mode measurements made before March 2019. The reconstruction conditions are satisfied for 80% of the burst mode whistlers detected during Encounter 1. We apply the method to determine the polarization of a whistler event observed after March 2019 during Encounter 2. Our novel method is an encouraging step toward analyzing whistler properties in affected encounters and improving our understanding of wave‐particle interactions in the young solar wind. We present a method to determine whistler wave polarization without a magnetic field component (Parker Solar Probe regime after March 2019)This allows us to expand whistler wave statistical databases; this is an essential step to better understanding wave‐particle interactionsWe demonstrate that this method applies to 80% of whistler waves observed in burst‐mode data from the first encounter We present a method to determine whistler wave polarization without a magnetic field component (Parker Solar Probe regime after March 2019) This allows us to expand whistler wave statistical databases; this is an essential step to better understanding wave‐particle interactions We demonstrate that this method applies to 80% of whistler waves observed in burst‐mode data from the first encounter

Harmonically related electromagnetic ion cyclotron waves with the fundamental frequency near the double oxygen cyclotron frequency were observed by the MMS spacecraft on 18–20 May 2016. The wave activity lasted for three days, detected by the spacecraft on their consecutive inbound passages through the Earth's plasma sheet boundary layer. The waves were seen in both magnetic and electric fields, formed by over 10 higher order harmonics. Simultaneous ion flux measurements show the presence of ion ring distributions suggesting the energy source for the observed waves. The ion cyclotron harmonics were observed together with broadband waves extending from ~Hz to ~kHz frequency range, ion and electron phase space holes, and chorus waves. During some intervals, there is a clear modulation of chorus wave packets at the ion cyclotron fundamental harmonic frequency. These observations are particularly interesting since they suggest cross‐frequency and cross‐species coupling between processes happening on ion and electron scales. We presented an example oxygen harmonic wave event observed by the MMS spacecraft in the morning magnetosphere. The observed harmonic waves are transverse electromagnetic and propagate almost parallel to the background magnetic field at lower harmonics and become electrostatic at higher harmonics. Energetic ion measurements show enhanced approximately a few keV H+and O+fluxes and the presence of H+and O+ring distributions suggesting that the wave energy source for the observed waves is provided by these distributions. Harmonics were accompanied by higher frequency broadband waves extending from ~Hz to ~kHz frequency range, ~ms spikes in the electric field and chorus waves. The latter were modulated at the fundamental frequency of the ion cyclotron harmonic wave. These observations are particularly interesting since they suggest cross‐frequency and cross‐species coupling between kinetic plasma processes happening on ion and electron scales. Harmonic ion cyclotron waves with the fundamental frequency near the double oxygen cyclotron frequency were observed in the plasma sheet boundary layerThe presence of H+and O+ring distributions suggests that the wave energy source for the observed waves is provided by these distributionsThere is a clear modulation of simultaneously observed chorus wave packets at the ion cyclotron fundamental harmonic frequency

The spacecraft potential is often used to infer rapid changes in the thermal plasma density. The variations in spacecraft potential associated with large‐amplitude Langmuir and upper hybrid waves are investigated with the Magnetospheric Multiscale (MMS) mission. When large‐amplitude Langmuir and upper hybrid waves are observed, the spacecraft potential increases. The changes in spacecraft potential are shown to be due to enhanced photoelectron escape from the spacecraft when the wave electric fields reach large amplitude. The fluctuations in spacecraft potential follow the envelope function of the Langmuir and upper hybrid waves. Comparison with the high‐resolution electron moments shows that the changes in spacecraft potential associated with the waves are not due to density perturbations. Indeed, using the spacecraft potential as a density probe leads to unphysically large density fluctuations. In addition, the changes in spacecraft potential are shown to increase as density decreases: larger spacecraft potential changes are observed in the magnetosphere, than in the magnetosheath and solar wind. These results show that external electric fields can lead to unphysical results when the spacecraft potential is used as a density probe. The results suggest that fluctuations in the spacecraft potential alone cannot be used to determine whether nonlinear processes associated with Langmuir and upper hybrid waves, such as the ponderomotive force and three‐wave decay, are occurring. The electric field of Langmuir and upper hybrid waves increases the spacecraft potential due to enhanced photoelectron escapeIncreased spacecraft potentials associated with Langmuir and upper hybrid waves are not due to density depletions or ponderomotive forceThe magnitude of the changes in spacecraft potential due to Langmuir and upper hybrid waves becomes larger as density decreases

The Magnetospheric Multiscale mission has observed electron whistler waves at the center and at the edges of magnetic holes in the dayside magnetosheath. The magnetic holes are nonlinear mirror structures since their magnitude is anticorrelated with particle density. In this article, we examine the growth mechanisms of these whistler waves and their interaction with the host magnetic hole. In the observations, as magnetic holes develop and get deeper, an electron population gets trapped and develops a temperature anisotropy favorable for whistler waves to be generated. In addition, the decrease in magnetic field magnitude and the increase in density reduce the electron resonance energy, which promotes the electron cyclotron resonance. To investigate this process, we used expanding box particle‐in‐cell simulations to produce the mirror instability, which then evolve into magnetic holes. The simulation shows that whistler waves can be generated at the center and edges of magnetic holes, which reproduces the primary features of the MMS observations. The simulation shows that the electron temperature anisotropy develops in the center of the magnetic hole once the mirror instability reaches its nonlinear stage of evolution. The plasma is then unstable to whistler waves at the minimum of the magnetic field structures. In the saturation regime of mirror instability, when magnetic holes are developed, the electron temperature anisotropy appears at the edges of the holes and electron distributions become more isotropic at the magnetic field minimum. At the edges, the expansion of magnetic holes decelerates the electrons, which leads to temperature anisotropies. Electron whistler waves are generated at mirror mode magnetic holes in the magnetosheathElectron temperature anisotropy is enhanced at the center of magnetic holes by trapping and at the edges by Fermi acceleration or deceleration of electronsIn deep magnetic holes, low energy electrons resonate with the electron whistler waves and are isotropized, while higher energy electrons remain anisotropic inside the magnetic holes

Large‐amplitude waves near the electron plasma frequency are found by the Magnetospheric Multiscale (MMS) mission near Earth's magnetopause. The waves are identified as Langmuir and upper hybrid (UH) waves, with wave vectors either close to parallel or close to perpendicular to the background magnetic field. The waves are found all along the magnetopause equatorial plane, including both flanks and close to the subsolar point. The waves reach very large amplitudes, up to 1 V m−1, and are thus among the most intense electric fields observed at Earth's magnetopause. In the magnetosphere and on the magnetospheric side of the magnetopause the waves are predominantly UH waves although Langmuir waves are also found. When the plasma is very weakly magnetized only Langmuir waves are likely to be found. Both Langmuir and UH waves are shown to have electromagnetic components, which are consistent with predictions from kinetic wave theory. These results show that the magnetopause and magnetosphere are often unstable to intense wave activity near the electron plasma frequency. These waves provide a possible source of radio emission at the magnetopause. Large‐amplitude upper hybrid and Langmuir waves frequently occur at Earth's magnetopause, reaching a maximum amplitude of 1 V m−1The waves are quasi‐electrostatic but electromagnetic properties are observedThe upper hybrid and Langmuir wave properties are consistent with predictions from linear kinetic theory

Structured diffuse auroras are often observed near magnetic local noon (MLN), but their generation mechanisms are poorly understood. We have found that two types of structured diffuse auroras with obviously different dynamical properties often coexist near MLN. One type usually drifts from low to high latitude with higher speed and shows pulsation. The other type is always adjacent to the discrete aurora oval and drifts together with nearby discrete aurora with much lower speed. Using coordinated observations from MMS and ground all‐sky imagers, we found that the two types of diffuse auroras are well correlated with number density increase of O+(from the ionosphere) and of He2+(from magnetosheath) ions, respectively. These observations indicate that mangetosheath particles penetrated into the magnetosphere also can play an important role for producing the dayside diffuse aurora. In addition, for the first time, electron cyclotron harmonic waves are observed associated with dayside diffuse aurora. Two types of structured diffuse auroras observed near magnetic local noon with obviously different dynamical properties are identifiedTypes 1 and 2 are associated with number density increase of O+from the magnetosphere and of He2+from the magnetosheath, respectivelyFor the first time, ECH waves, but no whistler mode chorus waves, were observed associated with dayside diffuse auroras

We show observations of whistler mode waves in both the low‐latitude boundary layer (LLBL) and on closed magnetospheric field lines during a crossing of the dayside reconnecting magnetopause by the Magnetospheric Multiscale (MMS) mission on 11 October 2015. The whistlers in the LLBL were on the electron edge of the magnetospheric separatrix and exhibited high propagation angles with respect to the background field, approaching 40°, with bursty and nonlinear parallel electric field signatures. The whistlers in the closed magnetosphere had Poynting flux that was more field aligned. Comparing the reduced electron distributions for each event, the magnetospheric whistlers appear to be consistent with anisotropy‐driven waves, while the distribution in the LLBL case includes anisotropic backward resonant electrons and a forward resonant beam at near half the electron‐Alfvén speed. Results are compared with the previously published observations by MMS on 19 September 2015 of LLBL whistler waves. The observations suggest that whistlers in the LLBL can be both beam and anisotropy driven, and the relative contribution of each might depend on the distance from the X line. Whilstlers in both LLBL and magnetosphere observed during magnetopause crossingLLBL whistlers have large parallel electric field and more oblique propagation anglesThe presence of electron beam and anisotropy suggests two simultaneous generation mechanisms for whistlers in LLBL

The Van Allen Probes have reported frequent flux enhancements of 100s keV electrons in the slot region, with lower energy electrons exhibiting more dynamic behavior at lower L shells. Also, in situ electric field measurements from the Combined Release and Radiation Effects Satellite, Time History of Events and Macroscale Interactions during Substorms (THEMIS), and the Van Allen Probes have provided evidence for large‐scale electric fields at low L shells during active times. We study an event on 19 February 2014 where hundreds of keV electron fluxes were enhanced by orders of magnitude in the slot region and electric fields of 1–2 mV/m were observed below L= 3. Using a 2‐D guiding center particle tracer and a simple large‐scale convection electric field model, we demonstrate that the measured electric fields can account for energization of electrons up to at least 500 keV in the slot region through inward radial transport. We connect in situ electric field measurements to slot region flux enhancements for 100s keV electronsAn increase in convection can explain enhancements for electrons up to 500 keV near L= 3 through inward radial transportOur convection model does not match higher‐energy flux observations, indicating a transition point where other mechanisms are required

A new empirical density model is developed for the inner zone between 1 < L< 3 using plasma densities inferred from the upper hybrid resonance on Arase, and hiss‐inferred density values from Van Allen Probes. The Van Allen Probes hiss‐inferred densities are first recalibrated and validated against Arase observations, using both a conjunction event and statistical analyses. The newly developed density model includes dependencies on L, magnetic latitude, and magnetic local time (MLT). Between 1.5 < L< 3.0, the equatorial density variation with Lis shown to be equivalent to that of the Ozhogin et al. (2012, https://doi.org/10.1029/2011JA017330) model. However, for L< 1.5, this dependence changes as the plasma density increases at a faster rate with decreasing L. The latitudinal dependence of the plasma density is shown to present a flatter profile than previous models, meaning lower densities extend to higher latitudes. This dependence is well‐modeled by updated fitting coefficients. A clear MLT dependence of the plasma density is identified, which was not found or included in some previous models. This variation is consistent with the diurnal variation of the ionosphere, peaking near MLT = 14 and becoming larger in amplitude with decreasing L. A function describing this MLT dependence is presented. Overall, the new L, latitude, and MLT‐dependent empirical model can provide density values in areas outside the validity region of many previous models, making it a useful resource for accurately determining diffusion coefficients and predicting electron dynamics and their lifetimes in the inner radiation belt. Radiation Belt Storm Probes and Arase data are used to build a new empirical plasma density model for the inner zone, including L, latitude, and magnetic local time (MLT) dependenciesMLT dependence consistent with diurnal variation of ionosphere. Variation is largest in amplitude at low L, but persists out to L= 3New model provides density in areas outside previous model bounds, making it a useful resource for modeling inner radiation belt dynamics Radiation Belt Storm Probes and Arase data are used to build a new empirical plasma density model for the inner zone, including L, latitude, and magnetic local time (MLT) dependencies MLT dependence consistent with diurnal variation of ionosphere. Variation is largest in amplitude at low L, but persists out to L= 3 New model provides density in areas outside previous model bounds, making it a useful resource for modeling inner radiation belt dynamics

Transmission of HIV across mucosal barriers accounts for the majority of HIV infections worldwide. Thus, efforts aimed at enhancing protective immunity at these sites are a top priority, including increasing virus-specific antibodies (Abs) and antiviral activity at mucosal sites. Mucin proteins, including the largest cell-associated mucin, mucin 16 (MUC16), help form mucus to provide a physical barrier to incoming pathogens. Here, we describe a natural interaction between Abs and MUC16 that is enhanced in specific disease settings such as chronic HIV infection. Binding to MUC16 was independent of IgG subclass, but strongly associated with shorter Ab glycan profiles, with agalactosylated (G0) Abs demonstrating the highest binding to MUC16. Binding of Abs to epithelial cells was diminished following MUC16 knockdown, and the MUC16 N-linked glycans were critical for binding. Further, agalactosylated VRC01 captured HIV more efficiently in MUC16. These data point to a novel opportunity to enrich Abs at mucosal sites by targeting Abs to MUC16 through changes in Fc glycosylation, potentially blocking viral movement and sequestering the virus far from the epithelial border. Thus, next-generation vaccines or monoclonal therapeutics may enhance protective immunity by tuning Ab glycosylation to promote the enrichment of Abs at mucosal barriers.

The effective ion and electron temperatures of dust impact generated plasma clouds are measured experimentally as a function of impact speed in the range of 4–20 km/s. The measurements are performed in an experimental setup that resembles the detection of dust particles by electric field or plasma wave antennas on spacecraft. The spacecraft is modeled as a conductive plate and a cylindrical antenna connected to voltage follower electronics is used to measure the collected charge. The setup is bombarded with dust particles using the University of Colorado IMPACT dust accelerator facility. The effective ion and electron temperatures are determined from the variation of the impact signals with an applied bias voltage. The results show that the temperatures of the electrons remain at around or below 5 eV over the investigated impact speed range. The characteristic ion temperature is about 5 eV at 4 km/s; however, it increases with increasing impact speed to > 10 eV at 20 km/s. Given that the floating potentials of spacecraft and antennas are on the order of a few volts, the findings suggest that any model for the interpretation of dust impact signals should take into account the effects of a finite temperatures. The effective temperature of dust impact plasmas is measured experimentallyThe electron temperature remains below 5 eV for impact velocities below 20 km/sThe ion temperature increases with impact velocity

Ideally, the sources of type III solar radio bursts, which are produced mainly by flare-accelerated electron beams, trace the magnetic field lines along which the beams propagate from the Sun to interplanetary space. A recently developed 2-D approach for large-scale mapping of magnetic field lines between the Sun and Earth in the solar equatorial plane is applied to the sources of the 7 April 1995 type III radio burst imaged by Ulysses and Wind. The approach uses near-Earth solar wind data and a solar wind model with intrinsic nonradial magnetic field at the source surface of the solar wind. Quantitative agreement is found between the mapped field lines, the observed path of the radio source centroids, and the field configurations inferred from solar wind suprathermal electrons observed by Wind. Moreover, the mapped field lines are consistent with Wind not observing the in situ type III electron beam, Langmuir waves, and local radio emission for this type III event. Large-scale magnetic field lines are mapped in the solar equatorial plane for the 7 April 1995 type III solar radio burstMapped field lines are consistent with the field configuration traced by the radio source centroidsMapped field lines are also consistent with observations of suprathermal and energetic electrons and waves

We show observations from the Magnetospheric Multiscale (MMS) mission of whistler mode waves in the Earth's low‐latitude boundary layer (LLBL) during a magnetic reconnection event. The waves propagated obliquely to the magnetic field toward the X line and were confined to the edge of a southward jet in the LLBL. Bipolar parallel electric fields interpreted as electrostatic solitary waves (ESW) are observed intermittently and appear to be in phase with the parallel component of the whistler oscillations. The polarity of the ESWs suggests that if they propagate with the waves, they are electron enhancements as opposed to electron holes. The reduced electron distribution shows a shoulder in the distribution for parallel velocities between 17,000 and 22,000 km/s, which persisted during the interval when ESWs were observed, and is near the phase velocity of the whistlers. This shoulder can drive Langmuir waves, which were observed in the high‐frequency parallel electric field data. Whistler mode waves are observed on the magnetic reconnection separatrixThese waves are propagating toward the X lineSolitary bipolar parallel electric fields appear to be in phase with the wave and may correspond with electron enhancements

We report observations from the Magnetospheric Multiscale satellites of large-amplitude, parallel, electrostatic waves associated with magnetic reconnection at the Earth's magnetopause. The observed waves have parallel electric fields (E||) with amplitudes on the order of 100?mV/m and display nonlinear characteristics that suggest a possible net E||. These waves are observed within the ion diffusion region and adjacent to (within several electron skin depths) the electron diffusion region. They are in or near the magnetosphere side current layer. Simulation results support that the strong electrostatic linear and nonlinear wave activities appear to be driven by a two stream instability, which is a consequence of mixing cold (<10?eV) plasma in the magnetosphere with warm (~100?eV) plasma from the magnetosheath on a freshly reconnected magnetic field line. The frequent observation of these waves suggests that cold plasma is often present near the magnetopause. Magnetospheric Multiscale observations of large-amplitude, parallel, electrostatic waves associated with magnetic reconnectionSimulations support that the strong electrostatic linear and nonlinear wave activities appear to be driven by a two-stream instabilityThe frequent observation of these waves suggests that cold plasma is often present near the magnetopause

The subauroral polarization stream (SAPS) is an important magnetosphere-ionosphere (MI) coupling phenomenon that impacts a range of particle populations in the inner magnetosphere. SAPS studies often emphasize ionospheric signatures of fast westward flows, but the equatorial magnetosphere is also affected through strong radial electric fields in the dusk sector. This study focuses on a period of steady southward interplanetary magnetic field (IMF) during the 29 June 2013 geomagnetic storm where the Van Allen Probes observe a region of intense electric fields near the plasmapause over multiple consecutive outbound duskside passes. We show that the large-amplitude electric fields near the equatorial plane are consistent with SAPS by investigating the relationship between plasma sheet ion and electron boundaries, associated field-aligned currents, and the spatial location of the electric fields. By incorporating high-inclination DMSP data we demonstrate the spatial and temporal variability of the SAPS region, and we suggest that discrete, earthward propagating injections are driving the observed strong electric fields at low L shells in the equatorial magnetosphere. We also show the relationship between SAPS and plasmasphere erosion, as well as a possible correlation with flux enhancements for 100s keV electrons. SAPS electric fields are shown in relation to equatorial magnetospheric particle boundariesRBSP and DMSP observations suggest that SAPS region is composed of numerous earthward propagating spatial structuresSAPS electric fields are correlated with plasmasphere erosion

Magnetospheric ions from the ring current, warm plasma cloak, and the plasmaspheric drainage plume all interact with the dusk flank magnetopause. During periods of strong magnetospheric convection, these ions may contribute significantly to the magnetospheric mass density at the magnetopause. Observations from the Magnetospheric Multiscale mission Hot Plasma Composition Analyzer at the duskside magnetopause near reconnection X lines show that ions from the ring current and warm plasma cloak may have high mass densities. However, these mass densities are not as large as the mass density in the magnetosheath. The results suggest that except for possible influence from the plasmaspheric drainage plume, the other major magnetospheric ion populations do not greatly influence asymmetric reconnection at the duskside magnetopause. Magnetospheric ions have significant density at the magnetopauseMagnetospheric ions do not influence reconnection significantly at the duskside magnetopause

Plasmaspheric hiss waves are a dominant source of scattering for keV‐MeV radiation belt electrons within the plasmasphere. Previous simulation and modeling work concerning hiss waves has often incorporated them via particle‐based parameterizations (e.g., L‐shell). However, recent work has shown that not only is hiss wave power loosely dependent on L‐shell, but that proximity to the plasmapause may yield more accurate wave power distributions as it pertains to the modeling and scattering of electrons. This work serves to expand upon those previous studies by creating a low frequency (20–150 Hz) hiss wave model and incorporating a previously crafted high frequency (>150 Hz) hiss wave model based on plasmapause location, proximity to the plasmapause, and Kp activity level. Diffusion coefficients created using this method produced shorter lifetimes for electrons between ∼300 keV and 4 MeV than their L‐sorted counterparts. Furthermore, 3D‐simulations using and comparing the different hiss wave models (plasmapause sorting vs. L‐sorting) find that the plasmapause‐based approach yields more accurate results when compared to Van Allen Probe‐A observations. Earth's radiation belts are composed of two highly dynamic regions consisting of very energetic charged particles (electrons and protons). These particles may become accelerated or scattered through a series of wave‐particle interactions. For this paper, we examined and tested various parametrizations of plasmapheric hiss waves to identify which parametrization scattered electrons more effectively and which best reproduced Van Allen Probe‐A observations. This study derived a new plasmapsheric hiss wave model, which incorporates the entire frequency range where hiss wave activity is observed (∼10–∼2,000 Hz). Furthermore, hiss wave activity was modeled with respect to plasmapause location instead of a purely L‐based parametrization. To test our model, we performed simulations with the versatile electron radiation belt‐3D code and compared our hiss wave model, a higher frequency (150–2,000 Hz) hiss wave model parametrized by plasmapause location, an L‐based plasmapause model, and a simulation with hiss wave activity excluded with the Van Allen Probe‐A electron (0.3–4.4 MeV) observations for the year 2013. Low frequency (20–150 Hz) plasmaspheric hiss waves are modeled with respect to plasmapause location and distance from the plasmapauseThe plasmapause location‐based hiss wave modeling produces smaller lifetimes for ∼300 keV–4 MeV electrons3D simulations performed with this method yield more accurate results than L‐based hiss wave modeling Low frequency (20–150 Hz) plasmaspheric hiss waves are modeled with respect to plasmapause location and distance from the plasmapause The plasmapause location‐based hiss wave modeling produces smaller lifetimes for ∼300 keV–4 MeV electrons 3D simulations performed with this method yield more accurate results than L‐based hiss wave modeling

We describe laboratory experiments which reproduce characteristic signals observed on spacecraft, believed to be caused by dust impact. A simulated spacecraft, including an antenna system using a facsimile of the preamplifier electronics from the STEREO/WAVES instrument, was bombarded by 10 km/s submicron‐sized dust at the University of Colorado Institute for Modeling Plasma, Atmospheres, and Cosmic Dust accelerator facility. Signal variation was investigated as a function of the DC potentials of both the spacecraft and the antennas. We observed (1) signals corresponding to modification of the spacecraft body potential, an important process believed to be responsible for the so‐called “triple hit” antenna signals on STEREO, (2) a few‐eV energy distribution for the electrons and ions released in the impact leading to (3) signals corresponding to direct recollection of a substantial fraction of the impact charge by the spacecraft antennas, even at modest antenna bias potentials. We also observe (4) an unexpected class of fast antenna signals, which do not appear to be caused by charge recollection by either the spacecraft or the antennas and may be induced by charge separation in the expanding plasma cloud. Similar signals are also commonly observed by the STEREO/WAVES instrument but have not previously been analyzed. We observe fast electrostatically induced signals also seen in the STEREO data

We use 4 years of Time History of Events and Macroscale Interactions during Substorms (THEMIS) double‐probe measurements to offer, for the first time, a complete picture of the dawn‐dusk electric field covering all local times and radial distances in the inner magnetosphere based on in situ equatorial observations. This study is motivated by the results from the CRRES mission, which revealed a local maximum in the electric field developing near Earth during storm times, rather than the expected enhancement at higher L shells that is shielded near Earth as suggested by the Volland‐Stern model. The CRRES observations were limited to the duskside, while THEMIS provides complete local time coverage. We show strong agreement with the CRRES results on the duskside, with a local maximum near L= 4 for moderate levels of geomagnetic activity and evidence of strong electric fields inside L= 3 during the most active times. The extensive data set from THEMIS also confirms the day/night asymmetry on the duskside, where the enhancement is closest to Earth in the dusk‐midnight sector, and is farther away closer to noon. A similar, but smaller in magnitude, local maximum is observed on the dawnside near L= 4. The noon sector shows the smallest average electric fields, and for more active times, the enhancement develops near L= 7 rather than L= 4. We also investigate the impact of the uncertain boom‐shorting factor on the results and show that while the absolute magnitude of the electric field may be underestimated, the trends with geomagnetic activity remain intact. We show full local time coverage of the equatorial electric field from THEMISLocal maximum occurs near L= 4 during active times in dawn and dusk sectorsNo clear increased electric field with Kpnear midnight at high L

The pitch angle distribution (PAD) of energetic electrons in the slot region and inner radiation belt received little attention in the past decades due to the lack of quality measurements. Using the state‐of‐the‐art pitch angle‐resolved data from the Magnetic Electron Ion Spectrometer instrument onboard the Van Allen Probes, a detailed analysis of hundreds of keV electron PADs below L= 4 is performed, in which the PADs are categorized into three types: normal (flux peaking at 90°), cap (exceedingly peaking narrowly around 90°), and 90° minimum (lower flux at 90°) PADs. By examining the characteristics of the PADs of ∼460 keV electrons for over a year, we find that the 90° minimum PADs are generally present in the inner belt (L<2), while normal PADs dominate at L∼3.5–4. In the region between, 90° minimum PADs dominate during injection times and normal PADs dominate during quiet times. Cap PADs appear mostly at the decay phase of storms in the slot region and are likely caused by the pitch angle scattering of hiss waves. Fitting the normal PADs into sinnαform, the parameter nis much higher below L= 3 than that in the outer belt and relatively constant in the inner belt but changes significantly in the slot region (2 < L< 3) during injection times. As for the 90° minimum PADs, by performing a detailed case study, we find in the slot region this type of PAD is likely caused by chorus wave heating, but this mechanism can hardly explain the formation of 90° minimum PADs at the center of inner belt. Pitch angle distribution (PAD) of hundreds of keV electrons in low L region is studiedThe formation of three PAD types in low L region is investigatedNinety degrees minimum PAD is the most prevalent PAD type in low L region

The impact ionization charge yield is experimentally measured from four common materials used in space and specifically on the two STEREO spacecraft (germanium‐coated black Kapton, beryllium copper, multilayer insulation, and solar cells). Cosmic dust particle impacts on spacecraft have been detected by electric field and plasma and radio wave instruments. The accurate interpretation of these signals is complicated by many factors, including the details of the spacecraft antenna system, the local spacecraft plasma environment, and our understanding of the physics of the impact process. The most basic quantity, the amount of charge liberated upon impact, is generally considered poorly constrained and is suspected to depend on the target material. Here we show that for common materials used on spacecraft this variability is small for impacts around 10 km/s, and the impact charge yield can be approximated by 80 fC for a 1 pg projectile. At higher speeds (∼50 km/s), variation of up to a factor of 5 is observed. The measured yields in the 10–50 km/s range are compared to measurements and predictions from the literature and are found to be lower than predicted by at least a factor of 12 at 10 km/s and at least a factor of 1.7 at 50 km/s. Impact charge is also found to depend on angle of incidence; the data suggest a maximum at 45°. Impact ionization was measured for spacecraft‐relevant materialsYields are smaller than predicted by certain published lawsYields do not differ strongly between materials tested at 10 km/s

We present a detailed outline and discussion of the analysis techniques used to compare the relevance of different energy dissipation mechanisms at collisionless shock waves. We show that the low‐frequency, quasi‐static fields contribute less to ohmic energy dissipation, (−j·E), than their high‐frequency counterparts. In fact, we found that high‐frequency, large‐amplitude (>100 mV/m and/or >1 nT) waves are ubiquitous in the transition region of collisionless shocks. We quantitatively show that their fields, through wave‐particle interactions, cause enough energy dissipation to regulate the global structure of collisionless shocks. The purpose of this paper, part one of two, is to outline and describe in detail the background, analysis techniques, and theoretical motivation for our new results presented in the companion paper. The companion paper presents the results of our quantitative energy dissipation rate estimates and discusses the implications. Together, the two manuscripts present the first study quantifying the contribution that high‐frequency waves provide, through wave‐particle interactions, to the total energy dissipation budget of collisionless shock waves. High‐frequency electric fields are much larger than quasi‐static fieldsThey produce more energy dissipation than the quasi‐static fieldsMost energy dissipation pathways end with wave‐particle interactions

We present the first quantified measure of the energy dissipation rates, due to wave‐particle interactions, in the transition region of the Earth's collisionless bow shock using data from the Time History of Events and Macroscale Interactions during Substorms spacecraft. Our results show that wave‐particle interactions can regulate the global structure and dominate the energy dissipation of collisionless shocks. In every bow shock crossing examined, we observed both low‐frequency (<10 Hz) and high‐frequency (≳10 Hz) electromagnetic waves throughout the entire transition region and into the magnetosheath. The low‐frequency waves were consistent with magnetosonic‐whistler waves. The high‐frequency waves were combinations of ion‐acoustic waves, electron cyclotron drift instability driven waves, electrostatic solitary waves, and whistler mode waves. The high‐frequency waves had the following: (1) peak amplitudes exceeding δB∼ 10 nT and δE∼ 300 mV/m, though more typical values were δB∼ 0.1–1.0 nT and δE∼ 10–50 mV/m; (2) Poynting fluxes in excess of 2000 μW m−2(typical values were ∼1–10 μW m−2); (3) resistivities > 9000 Ωm; and (4) associated energy dissipation rates >10 μW m−3. The dissipation rates due to wave‐particle interactions exceeded rates necessary to explain the increase in entropy across the shock ramps for ∼90% of the wave burst durations. For ∼22% of these times, the wave‐particle interactions needed to only be ≤ 0.1% efficient to balance the nonlinear wave steepening that produced the shock waves. These results show that wave‐particle interactions have the capacity to regulate the global structure and dominate the energy dissipation of collisionless shocks. Microscopic wave‐particle interactions can regulate macroscopic shock structureHigh‐frequency large‐amplitude waves are ubiquitous in collisionless shocksWave‐particle interactions are the end result of nearly all dissipation pathways

In type II and type III solar radio bursts and planetary foreshocks, the processes which convert Langmuir waves (LWs) to transverse waves are not well understood. One of the proposed mechanisms for generating transverse waves involves electrostatic (ES) decay followed by coalescence of two LWs. One of the tests used to identify this process is bicoherence analysis. Bicoherence has been applied to spacecraft observations of LWs to yield results consistent with ES decay and coalescence. However, recent work has shown that the harmonic fields produced by LWs are more consistent with sheath rectification and nonlinear currents. It is shown here that sheath rectification and nonlinear currents yield bicoherences similar to those expected for ES decay and coalescence, explaining the bicoherences associated with spacecraft observations of LWs. These results show that bicoherence alone cannot be used to identify ES decay and coalescence and emphasize the importance of sheath rectification. Sheath rectification and nonlinear currents produce phase‐coherent fieldsBicoherences are consistent with nonlinear currents and sheath rectificationBicoherence cannot identify electrostatic decay and coalescence

The dual‐spacecraft Van Allen Probes mission has provided a new window into mega electron volt (MeV) particle dynamics in the Earth's radiation belts. Observations (up to E~10 MeV) show clearly the behavior of the outer electron radiation belt at different timescales: months‐long periods of gradual inward radial diffusive transport and weak loss being punctuated by dramatic flux changes driven by strong solar wind transient events. We present analysis of multi‐MeV electron flux and phase space density (PSD) changes during March 2013 in the context of the first year of Van Allen Probes operation. This March period demonstrates the classic signatures both of inward radial diffusive energization and abrupt localized acceleration deep within the outer Van Allen zone (L~4.0 ± 0.5). This reveals graphically that both “competing” mechanisms of multi‐MeV electron energization are at play in the radiation belts, often acting almost concurrently or at least in rapid succession. Clear observations to higher energy than ever beforePrecise detection of where and how acceleration takes placeProvides “new eyes” on megaelectron Volt

Parker Solar Probe is the first mission to probe in situ the innermost heliosphere, revealing an exceptionally dynamic and structured outer solar corona. Its payload includes a search‐coil magnetometer (SCM) that measures up to three components of the fluctuating magnetic field between 3 Hz and 1 MHz. After more than 3 years of operation, the SCM has revealed a multitude of different wave phenomena in the solar wind. Here we present an overview of some of the discoveries made so far. These include oblique and sunward propagating whistler waves that are important for their interaction with energetic electrons, the first observation of the magnetic signature associated with escaping electrons during dust impacts, the first observation of the magnetic field component for slow extraordinary wave modes during type III radio burst events, and more. This study focuses on the major observations to date, including a description of the instrument and lessons learned. The search‐coil magnetometer (SCM) search‐coil magnetometer on Parker Solar Probe is an instrument that measures fluctuations of the magnetic field in the solar wind. The instrument covers frequencies ranging from 3 Hz to 1 MHz. After 3 years of operation the SCM has revealed a wealth of different wave phenomena. Here, we describe some of the highlights. These include whistler waves that propagate oblique to the magnetic field, the first observation of the magnetic signature associated with the impact of dust particles, and the first observation of the magnetic signature of high‐frequency coherent waves that are associated with solar radio bursts. We present an overview of 3 years of results from the search‐coil magnetometer (SCM) on Parker Solar ProbeThe SCM reveals the magnetic signature of dust impacts and of slow extraordinary waves associated with type III radio burstsThe SCM reveals in detail oblique whistlers and the radial evolution of turbulence at kinetic scales We present an overview of 3 years of results from the search‐coil magnetometer (SCM) on Parker Solar Probe The SCM reveals the magnetic signature of dust impacts and of slow extraordinary waves associated with type III radio bursts The SCM reveals in detail oblique whistlers and the radial evolution of turbulence at kinetic scales

Electrostatic solitary waves (ESWs) are a type of nonlinear time‐domain plasma structure (TDS) generally defined by bipolar electric fields and propagation parallel to the local magnetic field. Formation mechanisms for TDSs in the magnetosphere have been studied extensively and are associated with plasma boundary layers and the braking of bursty bulk flows (BBFs). However, the rapid timescales over which these TDSs occur (<2 ms) make them infeasible to count by eye over large time periods. Furthermore, high‐cadence data are not always available. The Solitary Wave Detector (SWD) on NASA's Magnetospheric Multiscale (MMS) mission quantifies the occurrence and amplitude of TDS throughout the constellation's orbit; analysis of burst (65 kS/s) parallel electric field data indicates that the SWD captures approximately 60% of all bipolar TDS encountered in the tail region, enabling large‐scale examination of their occurrence. Maps of TDS occurrence rates during several years of the MMS mission were generated from SWD data, showing enhanced TDS density in the tail region between 6 and 9 Re; enhance occurrence in or near shocks; and an unexpected enhancement in the dawn side of the tail and in the radiation belt. The MMS Solitary Wave Detector records time‐domain structures in Earth's magnetosphereSWD maps highlight regions like the Van Allen belts and the bursty bulk flow braking regionThe SWD shows intriguing nonlinear activity in the shocks, magnetotail, flank, and dawn‐side outer radiation belt The MMS Solitary Wave Detector records time‐domain structures in Earth's magnetosphere SWD maps highlight regions like the Van Allen belts and the bursty bulk flow braking region The SWD shows intriguing nonlinear activity in the shocks, magnetotail, flank, and dawn‐side outer radiation belt

Observations of the plasma environment outside of the Earth's magnetosphere by the Magnetospheric Multiscale Mission Hot Plasma Composition Analyzers (MMS‐HPCAs) allow density measurements of geocoronal hydrogen pickup ions (PUIs). A study of this environment from December 4, 2019 to December 6, 2019, part of a single orbital period of the MMS spacecraft, revealed an inverse square dependence on PUI density. This dependence corresponds well with an inverse‐cube dependence on the neutral hydrogen density within the geocorona. Measuring pickup ions produced from the Earth's geocorona provide an in‐situ analysis of their geocentric density dependence. These measurements also provide a model‐dependent evaluation of the neutral geocorona's expanse and geocentric dependence, which is part of the Earth's extended atmosphere, also known as the exosphere. Pickup ions (PUIs) produced from the hydrogen exosphere are observable with near‐Earth plasma instrumentsPickup ions are distinguishable from solar wind ions through their respective velocity distributionsGeocoronal PUI density decreases with geocentric radius and corresponds to an inverse radius cube neutral dependence Pickup ions (PUIs) produced from the hydrogen exosphere are observable with near‐Earth plasma instruments Pickup ions are distinguishable from solar wind ions through their respective velocity distributions Geocoronal PUI density decreases with geocentric radius and corresponds to an inverse radius cube neutral dependence

A sequence of discrete solar wind structures within the sheath region of an interplanetary coronal mass ejection on November 6, 2015, caused a series of compressions and releases of the dayside magnetosphere. Each compression resulted in a brief adiabatic enhancement of ions (electrons) driving bursts of electromagnetic ion cyclotron (EMIC; whistler mode chorus) wave growth across the dayside magnetosphere. Fine‐structured rising tones were observed in the EMIC wave bursts, resulting in nonlinear scattering of relativistic electrons in the outer radiation belt. Multipoint observations allow us to study the spatial structure and evolution of these sheath structures as they propagate Earthward from L1 as well as the spatio‐temporal characteristics of the magnetospheric response. This event highlights the importance of fine‐scale solar wind structure, in particular within complex sheath regions, in driving dayside phenomena within the inner magnetosphere. On November 6, 2015, a sequence of abrupt changes in Earth’s magnetic field and the associated conditions in the solar wind were observed. Multispacecraft observations allow us to study both the spatial structure and evolution of the solar wind structures that impacted the Earth, as well as the response of Earth’s magnetic field and particles trapped within it. The fine‐scale structures observed in the solar wind are demonstrated to produce distinct magnetospheric particle distributions and wave excitation. This event highlights the importance of fine‐scale solar wind structure in driving magnetospheric phenomena. A sequence of discrete structures within an interplanetary coronal mass ejection sheath are tracked via multipoint measurementsEach structure results in magnetospheric compression, adiabatic enhancement of ions and electrons, and cyclotron wave growthThis event highlights the importance of fine‐scale solar wind structure and sheath regions for driving dayside magnetospheric phenomena A sequence of discrete structures within an interplanetary coronal mass ejection sheath are tracked via multipoint measurements Each structure results in magnetospheric compression, adiabatic enhancement of ions and electrons, and cyclotron wave growth This event highlights the importance of fine‐scale solar wind structure and sheath regions for driving dayside magnetospheric phenomena

To test whether a new formulation of a slow release oxprenolol (SLOx) can produce a steady 24-h antihypertensive effect, we recorded 24-h intraarterial blood pressure (Oxford technique) in eight ambulant in-patients (age 44.5 ± 3.0 years, mean ± SE) with a mild or moderate hypertension who were untreated since three weeks. The study was started seven days after hospitalization and was conducted according to a randomized doubleblind cross-over design. Blood pressure recordings were made after (a) a 7-day administration of SLOx in a single evening dose, and (b) a 7-day administration of placebo. This design allowed to determine the effect of SLOx without interference from nonspecific blood pressure lowering factors. Blood pressure effects of handgrip, submaximal cyclette exercise, and cold pressor test 20–24 h after the administration of SLOx and placebo were also evaluated. The blood pressure tracing was analyzed beat-to-beat by a computer which provided also the analysis of the heart rate data. The 24-h mean systolic and diastolic blood pressure measured during placebo were 144.6 ± 6.4 and 81.1 ± 3.9 mm Hg, the corresponding heart rate being 76.9 ± 3.5 beats/min. SLOx reduced these values by 6.2, 10.6. and 4.8, respectively, all effects being similarly evident throughout the blood pressure recording. The pressor responses to handgrip, cyclette exercise, and cold pressor test were not affected by SLOx. By contrast, the small tachycardic response to handgrip and the large tachycardic response to submaximal cyclette exercise were significantly reduced by the drug. Due to the lower baseline values, the absolute blood pressure and heart rate observed during each test were significantly lower with SLOx than with placebo. Thus a single daily dose of SLOx can lower blood pressure and heart rate of hypertensive patients throughout the 24 h even when these variables are subjected to the excitatory effects of exercise and stress.

The addition of Parker Solar Probe (PSP) to the Heliophysics System Observatory has allowed for the unprecedented ability to study Corotating Interaction Regions (CIRs) at multiple radial distances without significant temporal/longitudinal variations. On September 19, 2019, PSP observed a CIR at ∼0.5 au when it was nearly radially aligned with the Solar Terrestrial Relations Observatory‐Ahead (STEREO‐A) spacecraft at ∼1 au, allowing for an unambiguous assessment of the radial evolution of a single CIR. Bulk plasma and magnetic field signatures of the CIR evolve in a fashion characteristic to previous observations; however, the suprathermal ions are enhanced over a larger longitudinal range at PSP than at STEREO‐A, although at much lower intensities. The longitudinal spread appears to be largely a consequence of magnetic field line topology at CIRs between the compressed slow solar wind upstream and high‐speed stream following the CIR, underscoring the importance of the large‐scale topology of these structures. A CIR was observed by PSP and STA when the spacecraft were near radially alignedThe plasma measurements suggest only radial evolution has occurred between observationsDifferences in fast and slow solar wind magnetic topology lead to a wider longitudinal extent of the suprathermal ion enhancement at PSP A CIR was observed by PSP and STA when the spacecraft were near radially aligned The plasma measurements suggest only radial evolution has occurred between observations Differences in fast and slow solar wind magnetic topology lead to a wider longitudinal extent of the suprathermal ion enhancement at PSP