Dayside Magnetosheath Research Articles

Movies for "Hybrid simulations of the cusp and dayside magnetosheath dynamics under quasi-radial interplanetary magnetic fields"

Movies for "Hybrid simulations of the cusp and dayside magnetosheath dynamics under quasi-radial interplanetary magnetic fields"

Dataset for "Hybrid simulations of the cusp and dayside magnetosheath dynamics under quasi-radial interplanetary magnetic fields"

Dataset for "Hybrid simulations of the cusp and dayside magnetosheath dynamics under quasi-radial interplanetary magnetic fields"

Anomalous Reconnection Layer at Earth's Dayside Magnetopause

AbstractObservations by the Magnetospheric Multiscale spacecraft (MMS) of an unusual layer, located between the dayside magnetosheath and the magnetosphere, alternating with encounters with the magnetosheath during an extended time period between December 31, 2015 and January 01, 2016, when the interplanetary magnetic field was strongly southward and the Earth's dipole tilt large and negative, are presented. It appears to have been magnetically connected to both magnetosphere and magnetosheath. The layer appears to be located mostly on closed field lines and was bounded by a rotational discontinuity (RD) at its magnetosheath edge and by the magnetosphere on its earthward side. A separatrix layer, with heated magnetosheath electrons streaming unidirectionally along the field lines, was present sunward of the RD. We infer that the layer was started by a dominant reconnection site well north of the spacecraft and that it may have gained additional width, from a large drop in solar wind density and ram pressure, which preceded the beginning of the event by more than an hour. Relative to the magnetosheath, in which the magnetic field was strongly southward, this unusual layer was characterized by a less southward, more dawnward magnetic field of lower magnitude. The plasma density and flow speed in the region were lower than in the magnetosheath, albeit with Alfvénic jetting occurring at the magnetosheath edge as well as at the magnetospheric edge of the layer. The closing of the magnetic field lines requires the existence of another reconnection site, located southward/tailward of MMS.

Soft X-ray and ENA Imaging of the Earth's Dayside Magnetosphere.

The LEXI and SMILE missions will provide soft X‐ray images of the Earth's magnetosheath and cusps after their anticipated launch in 2023 and 2024, respectively. The IBEX mission showed the potential of an Energetic Neutral Atom (ENA) instrument to image dayside magnetosheath and cusps, albeit over the long hours required to raster an image with a single pixel imager. Thus, it is timely to discuss the two imaging techniques and relevant science topics. We simulate soft X‐ray and low‐ENA images that might be observed by a virtual spacecraft during two interesting solar wind scenarios: a southward turning of the interplanetary magnetic field and a sudden enhancement of the solar wind dynamic pressure. We employ the OpenGGCM global magnetohydrodynamics model and a simple exospheric neutral density model for these calculations. Both the magnetosheath and the cusps generate strong soft X‐rays and ENA signals that can be used to extract the locations and motions of the bow shock and magnetopause. Magnetopause erosion corresponds closely to the enhancement of dayside reconnection rate obtained from the OpenGGCM model, indicating that images can be used to understand global‐scale magnetopause reconnection. When dayside imagers are installed with high‐ENA inner‐magnetosphere and FUV/UV aurora imagers, we can trace the solar wind energy flow from the bow shock to the magnetosphere and then to the ionosphere in a self‐standing manner without relying upon other observatories. Soft X‐ray and/or ENA imagers can also unveil the dayside exosphere density structure and its response to space weather.

Asymmetries in the Earth's dayside magnetosheath: results from global hybrid-Vlasov simulations

Abstract. Bounded by the bow shock and the magnetopause, the magnetosheath forms the interface between solar wind and magnetospheric plasmas and regulates solar wind–magnetosphere coupling. Previous works have revealed pronounced dawn–dusk asymmetries in the magnetosheath properties. The dependence of these asymmetries on the upstream parameters remains however largely unknown. One of the main sources of these asymmetries is the bow shock configuration, which is typically quasi-parallel on the dawn side and quasi-perpendicular on the dusk side of the terrestrial magnetosheath because of the Parker spiral orientation of the interplanetary magnetic field (IMF) at Earth. Most of these previous studies rely on collections of spacecraft measurements associated with a wide range of upstream conditions which are processed in order to obtain average values of the magnetosheath parameters. In this work, we use a different approach and quantify the magnetosheath asymmetries in global hybrid-Vlasov simulations performed with the Vlasiator model. We concentrate on three parameters: the magnetic field strength, the plasma density, and the flow velocity. We find that the Vlasiator model reproduces the polarity of the asymmetries accurately but that their level tends to be higher than in spacecraft measurements, probably because the magnetosheath parameters are obtained from a single set of upstream conditions in the simulation, making the asymmetries more prominent. A set of three runs with different upstream conditions allows us to investigate for the first time how the asymmetries change when the angle between the IMF and the Sun–Earth line is reduced and when the Alfvén Mach number decreases. We find that a more radial IMF results in a stronger magnetic field asymmetry and a larger variability of the magnetosheath density. In contrast, a lower Alfvén Mach number leads to a reduced magnetic field asymmetry and a decrease in the variability of the magnetosheath density, the latter likely due to weaker foreshock processes. Our results highlight the strong impact of the quasi-parallel shock and its associated foreshock on global magnetosheath properties, in particular on the magnetosheath density, which is extremely sensitive to transient quasi-parallel shock processes, even with the perfectly steady upstream conditions in our simulations. This could explain the large variability of the density asymmetry levels obtained from spacecraft measurements in previous studies.

Dynamics of Plasma Turbulence at Earth’s Bow Shock and through the Magnetosheath

Abstract Earth’s magnetosheath can be treated as a natural laboratory to study turbulence development in confined space. The present study focuses on the characteristics of turbulent cascade downstream of the bow shock, where properties of turbulence are known to differ from those in the upstream solar wind. Characteristics of the turbulent spectrum are considered in two distinct points of the magnetosheath for two case studies. The analysis is based on high-resolution measurements of plasma parameters by the Spektr-R spacecraft and magnetic field data by the Themis/Arthemis mission. The measurements are performed for two distinct cases: in the dayside magnetosheath behind the quasi-perpendicular bow shock and in the nightside flank of the magnetosheath behind the quasi-parallel bow shock. The study focuses on the scales at which kinetic effects in plasma become significant and the turbulent spectrum is known to break. The analysis reveals that modification of the fluctuation spectrum at the bow shock is controlled by the distance of the measurement point from the bow shock’s nose. Also, performed statistical results suggest the influence of the large-scale parameters of the upstream solar wind and the type of the bow shock on the turbulent spectrum’s modification in the downstream region.

Magnetosheath Microstructure: Mirror Mode Waves and Jets during Southward IP Magnetic Field

AbstractIn the Earth's magnetosheath plasma waves, nonlinear structures associated with characteristic ion populations can occur. Understanding the interaction of the solar wind with the magnetosphere requires a deeper knowledge of the underlying magnetosheath kinetic microstructure. We study a 45 min interval when the MMS spacecraft observed a southward magnetic field (Bz < 0 nT) in the dayside magnetosheath. Using magnetic field and plasma data, we analyze three transient dynamic pressure enhancements identified as magnetosheath jets. The characteristics of these jets are different, suggesting different origins. While two of them, called J1 and J2, exhibit large increment in velocity and almost no density increment, the third jet (J3) shows large density enhancements with almost no velocity increment. The duration of J3 is ∼7 times longer than those of J1 and J2. J3 occurs at the region where the negative Bz becomes positive. Ion distributions inside the jets are different. J1 and J2 show a secondary field‐aligned beam, which is not present in J3, suggesting that magnetic reconnection at the magnetopause is responsible for their formation. Distributions inside J3 are more isotropic. B field and plasma signatures inside J3 correspond to the crossing of a sector boundary, similar to the heliospheric plasma sheet, suggesting that J3 forms by the evolution and interaction of a solar wind structure with the bow shock and magnetosheath. Fluctuations inside J3 have larger transverse components, although they propagate at large angles to B. In contrast, waves in regions between the jets are compressive and are identified as mirror mode waves.

Properties and sources of the dayside martian magnetosphere

This study is based on measurements of the energy-mass analyzer Suprathermal and Thermal Ion Composition instrument (STATIC, McFadden et al., 2015) and magnetometer (MAG, Connerney et al., 2015) on the NASA Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft (Jakosky et al., 2015). 48 passes of MAVEN at SZA < 70° in the northern hemisphere on the day side of Mars (in order to avoid the influence of remnant magnetic field) were selected with condition to have continuous observations of STATIC from ionosphere to magnetosheath (“complete” observation crossings). It was found that in the vast majority of such “complete” crossings there is a layer between the ionosphere and magnetosheath, where two oxygen ion populations are observed: (1) heated ionospheric ions and (2) higher energy oxygen ions. The heated ionospheric ions are located just above the cold ionospheric ions and is identified by the increase of energy and temperature and decrease of number density. The second ion population has a wide energy spread from a few eV to hundreds of eV and has a velocity distribution typical to pick-up ions. The quite similar characteristics of the pick-ions just upstream of the magnetopause and characteristics of the second ions component in the layer between magnetosheath and ionosphere suggests their common origin. Pick-up ions in this layer have energies from a few to hundred electron volts have gyroradii comparable or significantly larger (from ~80 to ~570 km) than the thickness of this layer (~90 km).Pick-up ions from magnetosheath penetrate into upper ionosphere and interact with ionospheric ions and upper atmosphere. The population of pick-up ions provides additional energy source to the ionosphere and the upper atmosphere of Mars.The layer between dayside magnetosheath and ionosphere is not sufficiently studied and has many different names (see Espley, 2018). The physical state and properties of this layer (formed by combination of hydrodynamic and kinetic processes) are very much different from magnetosheath and ionosphere. This is defined as the dayside magnetosphere of Mars (Vaisberg et al., 2018).

Kinetic-scale Flux Rope in the Magnetosheath Boundary Layer

Abstract We here present a new type of kinetic-scale (∼1 ion gyroradius) flux rope (KFR) in the Earth’s dayside magnetosheath boundary layer with Magnetospheric Multiscale high temporal cadence data. This structure exhibits a slight twist of magnetic field that is possibly generated by a field-aligned current, which differs from typical dayside flux ropes usually observed within the current sheet where magnetic reconnection can occur. The perpendicular electron fluxes within 19–52 eV are increased ∼10% inside the KFR. Detailed analysis shows that these perpendicular electrons may encounter their mirror point (at the position of the KFR, strong field region) when traveling from the magnetosheath toward the ionosphere and will be reflected to the magnetosheath. A possible scenario is that this KFR is different from previous flux ropes that transfer electron flux to the magnetosphere but could intercept magnetosheath large pitch angle electron flux to the magnetosphere.

Propagating and Dynamic Properties of Magnetic Dips in the Dayside Magnetosheath: MMS Observations

AbstractThe magnetosheath is inherently complex and rich, exhibiting various kinds of structures and perturbations. It is important to understand how these structures propagate and evolve and how they relate to the perturbations. Here we investigate a kind of magnetosheath structure known as a magnetic dip (MD). As far as we are aware, there have been no previous studies concerning the evolution (contracting or expanding) of these types of structures, and their propagation properties cannot be unambiguously determined. In this study, using Magnetospheric MultiScale (MMS) high‐temporal resolution data and multispacecraft analysis methods, we obtain the propagation and dynamic features of a set of MDs. Four different types of MDs are identified: “frozen‐in,” “expanding,” “contracting,” and “stable‐propagating.” Significantly, a stable‐propagation event is observed with a sunward propagation component. This indicates that the source of the structure in this case is closely associated with the magnetopause, which provides strong support to the contention in earlier research. We further reveal the mechanism leading to the MD contraction or expansion. The motion of the MDs boundary is found closely related with the dynamic pressure. The scale of the contracting and expanding events are typically ~5–20 ρi (ion gyroradius), significantly smaller than that of frozen‐in events (~40 ρi). The observations could relate large‐scale (more than several tens of ρi) and kinetic‐scale (less than ρi) MDs, by revealing an evolution that spans these different scales, and help us better understand the variation and dynamics of magnetosheath structures and plasmas.

Estimating the fate of oxygen ion outflow from the high-altitude cusp

Abstract. We have investigated the oxygen escape-to-capture ratio from the high-altitude cusp regions for various geomagnetic activity levels by combining EDI and CODIF measurements from the Cluster spacecraft. Using a magnetic field model, we traced the observed oxygen ions to one of three regions: plasma sheet, solar wind beyond a distant X-line or dayside magnetosheath. Our results indicate that 69 % of high-altitude oxygen escapes the magnetosphere, from which most escapes beyond the distant X-line (50 % of total oxygen flux). Convection of oxygen to the plasma sheet shows a strong dependence on geomagnetic activity. We used the Dst index as a proxy for geomagnetic storms and separated data into quiet conditions (Dst&gt;0 nT), moderate conditions (0&gt;Dst&gt;-20 nT), and active conditions (Dst&lt;-20 nT). For quiet magnetospheric conditions we found increased escape due to low convection. For active magnetospheric conditions we found an increase in both parallel velocities and convection velocities, but the increase in convection velocities is higher, and thus most of the oxygen gets convected into the plasma sheet (73 %). The convected oxygen ions reach the plasma sheet in the distant tail, mostly beyond 50 RE.

Energy Spectral Properties of Hydrogen Energetic Neutral Atoms Emitted From the Dayside Atmosphere of Mars

AbstractThe energy spectrum of hydrogen energetic neutral atoms (HENAs) emitted from the dayside atmosphere of Mars reveals the physical processes of their origin and provides means for remote sensing on the Mars plasma environment. We first compile all available energy spectra of sunward flowing HENA using high‐energy resolution data from the neutral particle detectors on Mars Express from February to June 2004. The median value of the HENA directional flux is 1.12 × 105 cm−2·s−1·sr−1 from 0.3 to 5 keV, making Mars a bright source of HENAs. The energy spectra of the measured HENAs can be approximated by a two‐segment power law spectra. Then we compared the measured statistical energy spectra with those from a kinetic particle transport code. The comparison indicates that the measured HENA energy spectrum is harder (more high‐energy components) than the modeled backscattered HENAs. We propose that a population of sunward‐flowing, charge exchange HENAs produced in the dayside magnetosheath is the most probable reason for this difference. This HENA population with unexpected energy spectrum highlights the kinetic nature of the dayside magnetosheath of Mars.

Can Enhanced Flux Loading by High‐Speed Jets Lead to a Substorm? Multipoint Detection of the Christmas Day Substorm Onset at 08:17 UT, 2015

AbstractThis paper describes highly interesting observations of the 25 December 2015 substorm onset at 08:17 UT during northward interplanetary magnetic field (IMF) while magnetosheath contained several intervals of negative Bz. A unique alignment of several spacecraft near the Earth‐Sun line together with magnetohydrodynamic simulations, ground‐based magnetometer, and auroral observations allow a comprehensive timing analysis of the events leading to substorm onset. Perplexingly, prior to substorm onset Geotail measured for 26 min positive IMF Bz just upstream of the bow shock, while simultaneously MMS spacecraft measured several intervals of strong negative Bz in the dayside magnetosheath. These strong pulses of negative Bz in the magnetosheath were associated with high dynamic pressure magnetosheath jets, likely created by foreshock transients during strongly radial IMF interval. Multipoint plasma and magnetic field measurements from ARTEMIS and THEMIS spacecraft were used to determine tail reconnection time at 8:14 and location at x=−33RE. Ground‐based observations of Pi2 pulsations and auroral brightening, with observations of a dipolarization front by THEMIS spacecraft, allowed determination of substorm onset to be at ≈08:17. All MMS spacecraft detected the same magnetosheath jet structure with Bz=−25 nT at ∼08:00 while IMF was northward. Based on DMSP observations and timing analysis we propose that these jets produced magnetopause reconnection leading to final, critical flux enhancement in the midtail region, which may have triggered reconnection 12–14 min later after jet observations.

The Oxygen Ion Circulation in The Outer Terrestrial Magnetosphere and Its Dependence on Geomagnetic Activity

AbstractWe have quantified the O+ transports in the plasma sheet and lobes (−20 &lt; XGSM&lt;−10RE) and their dependencies on geomagnetic activity, Kp, using Cluster data. We found that they have similar behavior as the polar region O+ outflow as well as the O+ fluxes in the plasma mantle and high‐latitude dayside magnetosheath, in their response to geomagnetic activity. The sum of the total O+ fluxes in the lobes, plasma sheet, plasma mantle, and high‐latitude magnetosheath equals the O+ outflow above the polar regions for any geomagnetic condition. It can be argued that there are no hidden O+ populations for Cluster, in the sense that there are no significant amounts of O+ with energies outside the energy range of the ion spectrometer, Composition Distribution Function, and/or below the spacecraft potential. Therefore, we have obtained a complete picture of the O+ circulation (and escape) in the outer magnetosphere and its dependence on geomagnetic activity.

Precipitation of Hydrogen Energetic Neutral Atoms at the Upper Atmosphere of Mars

AbstractWe study the properties of neutral hydrogen atoms precipitating onto the upper atmosphere of Mars. Energetic neutral atoms (ENAs) are produced by the charge exchange process between protons of solar wind (both upstream and shocked) as well as planetary origins and the Martian exospheric neutrals. Using a global hybrid plasma model for Mars‐solar wind interaction combined with an up‐to‐date exosphere model of Mars, we calculate the fluxes, spatial distributions, energy spectra, and direction distributions of hydrogen ENAs (H‐ENAs) at the Martian exobase for each source proton population. H‐ENAs originating from the upstream solar wind region and the magnetosheath dominate the precipitation. Two percent of the solar wind flux penetrates through the magnetic barrier as H‐ENAs under solar minimum conditions. The precipitating solar wind H‐ENA flux is axially symmetric about Sun‐Mars line, while the magnetosheath and planetary H‐ENAs have higher fluxes and a more‐extended precipitation area in the hemisphere where the convection electric field is pointing away from the planet, causing a significant precipitation beyond the terminator. The observed asymmetry is consistently explained by an asymmetric plasma flow in the dayside magnetosheath. The solar wind dynamic pressure increases the solar wind H‐ENA precipitation normalized by the upstream proton flux, due to a closer bow shock position and thus a higher exospheric column density for charge exchange. The spatial distribution of the magnetosheath solar wind and planetary H‐ENAs becomes more axially symmetric with increased dynamic pressure. The solar wind interaction with Mars exhibits more gas‐dynamic‐like signatures for higher dynamic pressure.

Generation of Electron Whistler Waves at the Mirror Mode Magnetic Holes: MMS Observations and PIC Simulation

AbstractThe 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.

The Morphology of the Solar Wind Magnetic Field Draping on the Dayside of Mars and Its Variability

AbstractThe magnetic field draping pattern in the magnetosheath of Mars is of interest for what it tells us about both the solar wind interaction with the Mars obstacle and the use of the field measured there as a proxy for the upstream interplanetary magnetic field (IMF) clock angle. We apply a time‐dependent, global magnetohydrodynamic model toward quantifying the spatial and temporal variations of the magnetic field draping direction on the Martian dayside above 500‐km altitude. The magnetic field and plasma are self‐consistently solved over one Mars rotation period, with the dynamics of the field morphology considered as the result of the rotation of the crustal field orientation. Our results show how the magnetic field direction on the plane perpendicular to the solar wind flow direction gradually departs from the IMF as the solar wind penetrates toward the obstacle and into the tail region. This clock angle departure occurs mainly inside the magnetic pileup region and tailward of the terminator plane, exhibiting significant dawn‐dusk and north‐south asymmetries. Inside the dayside sheath region, the field direction has the greatest departure from the IMF‐perpendicular component direction downstream of the quasi‐parallel bow shock, which for the nominal Parker spiral is over the dawn quadrant. Thus, the best region to obtain an IMF clock angle proxy is within the dayside magnetosheath at sufficiently high altitudes, particularly over subsolar and dusk sectors. Our results illustrate that the crustal field has only a mild influence on the magnetic field draping direction within the magnetosheath region.

The SMILE Soft X-ray Imager (SXI) CCD design and development

SMILE, the Solar wind Magnetosphere Ionosphere Link Explorer, is a joint science mission between the European Space Agency and the Chinese Academy of Sciences. The spacecraft will be uniquely equipped to study the interaction between the Earth's magnetosphere-ionosphere system and the solar wind on a global scale. SMILE's instruments will explore this science through imaging of the solar wind charge exchange soft X-ray emission from the dayside magnetosheath, simultaneous imaging of the UV northern aurora and in-situ monitoring of the solar wind and magnetosheath plasma and magnetic field conditions. The Soft X-ray Imager (SXI) is the instrument being designed to observe X-ray photons emitted by the solar wind charge exchange process at photon energies between 200 eV and 2000 eV . X-rays will be collected using a focal plane array of two custom-designed CCDs, each consisting of 18 μm square pixels in a 4510 by 4510 array. SMILE will be placed in a highly elliptical polar orbit, passing in and out of the Earth's radiation belts every 48 hours. Radiation damage accumulated in the CCDs during the mission's nominal 3-year lifetime will degrade their performance (such as through decreases in charge transfer efficiency), negatively impacting the instrument's ability to detect low energy X-rays incident on the regions of the CCD image area furthest from the detector outputs. The design of the SMILE-SXI CCDs is presented here, including features and operating methods for mitigating the effects of radiation damage and expected end of life CCD performance. Measurements with a PLATO device that has not been designed for soft X-ray signal levels indicate a temperature-dependent transfer efficiency performance varying between 5×10−5 and 9×10−4 at expected End of Life for 5.9 keV photons, giving an initial set of measurements from which to extrapolate the performance of the SXI CCDs.

Atmospheric loss from the dayside open polar region and its dependence on geomagnetic activity: implications for atmospheric escape on evolutionary timescales

Abstract. We have investigated the total O+ escape rate from the dayside open polar region and its dependence on geomagnetic activity, specifically Kp. Two different escape routes of magnetospheric plasma into the solar wind, the plasma mantle, and the high-latitude dayside magnetosheath have been investigated separately. The flux of O+ in the plasma mantle is sufficiently fast to subsequently escape further down the magnetotail passing the neutral point, and it is nearly 3 times larger than that in the dayside magnetosheath. The contribution from the plasma mantle route is estimated as ∼ 3. 9 × 1024exp(0. 45 Kp) [s−1] with a 1 to 2 order of magnitude range for a given geomagnetic activity condition. The extrapolation of this result, including escape via the dayside magnetosheath, indicates an average O+ escape of 3 × 1026 s−1 for the most extreme geomagnetic storms. Assuming that the range is mainly caused by the solar EUV level, which was also larger in the past, the average O+ escape could have reached 1027–28 s−1 a few billion years ago. Integration over time suggests a total oxygen escape from ancient times until the present roughly equal to the atmospheric oxygen content today.

Temperature variations in the dayside magnetosheath and their dependence on ion‐scale magnetic structures: THEMIS statistics and measurements by MMS

AbstractThe magnetosheath contains an array of waves, instabilities, and nonlinear magnetic structures which modify global plasma properties by means of various wave‐particle interactions. The present work demonstrates that ion‐scale magnetic field structures (∼0.2–0.5 Hz) observed in the dayside magnetosheath are statistically correlated to ion temperature changes on orders 10–20% of the background value. In addition, our statistical analysis implies that larger temperature changes are in equipartition to larger amplitude magnetic structures. This effect was more pronounced behind the quasi‐parallel bow shock and during faster solar wind speeds. The study of two separate intervals suggests that this effect can result from both local and external drivers. This manuscript presents two separate case studies, one from using THEMIS (Time History of Events and Macroscale Interactions during Substorms) data and another from Magnetospheric Multiscale; these measurements are then supported by extensive THEMIS statistical observations. These results could partly explain the 10–20% dawn‐favored asymmetry of the magnetosheath ion temperature seed population and contribute to the dawn‐favored asymmetry of cold component ions in the cold dense plasma sheet.