Journals
2026 EN
Shim J. S. · Robinson R. M. · GarciaSage K.
+4 more
Abstract The Geospace Dynamics Constellation (GDC) mission aims to investigate the dynamic coupling between the magnetosphere, ionosphere, and thermosphere by resolving key spatiotemporal processes at scales ranging from local to global. A key aspect is GDC's ability to reconstruct hemispheric‐scale high‐latitude electrodynamics with comprehensive measurements at multiple local times. This study evaluates the accuracy of GDC reconstructions of electric potential (PHI) and Joule Heating (JH) derived from the AMPERE‐derived electrodynamic properties of the high‐latitude ionosphere (ADELPHI) and Weimer 2005 models by comparing them to the original model outputs used as ground truth. Accuracy is assessed across four selected geomagnetic storm events with GDC reconstructions spanning from Day 91 after GDC launch to the end of the mission using a 20‐day cadence. As the mission progresses, the constellation evolves into three well‐separated orbital pairs with increasing local time separation, significantly improving the PHI and JH reconstruction accuracy. To assess accuracy, we compute several performance metrics. Results from both models show that for the specific application of reconstructing large‐scale high‐latitude electrodynamics, performance metrics improve over mission time as the constellation evolves, reflecting better sampling and constraint for the reconstructions. Notably, however, even during the early mission stage, reconstructions can sometimes be as accurate as in the later stage, depending on the fortuitous sampling of appropriate local time sectors. This quantitative assessment underscores the critical role of orbital geometry and sampling diversity in fulfilling GDC's science objectives and advancing the understanding of space weather dynamics. It also provides a tool for optimizing the GDC orbital characteristics.
Journals
2026 EN
Barik Krushna C. · Omura Yoshiharu · Singh Satyavir
Abstract We present an event of chorus waves embedded within a magnetic hole (MH) in the Earth's magnetosheath, observed by the Magnetospheric Multi‐Scale (MMS) mission on 1 March 2016. Unlike conventional cases where chorus waves are typically detected near the center of a magnetic depression, in this event lower‐band chorus waves appear predominantly at the two edges of the ion‐scale MH. We examine the coupled dynamics of electrons under the simultaneous influence of the MH and the chorus waves. Our analysis shows that electrons are trapped within the MH cavity at critical pitch angles, while additional nonlinear trapping occurs along the field‐aligned direction due to interactions with the parallel wave electric field. The presence of enhanced parallel electron temperature anisotropy inside the MH further indicates electron heating associated with these processes. A detailed examination across multiple electron energy channels highlights the key role of wave‐particle interactions in shaping electron distributions within MHs. These results provide new insight into how chorus waves can operate in unconventional locations within magnetic structures, broadening our understanding of electron dynamics and heating in the turbulent magnetosheath.
Journals
2026 EN
Budhathoki Dipesh · Qiu Shican
Abstract Hall magnetic fields at Earth's dayside magnetopause provide key diagnostics for collisionless reconnection and the associated Hall‐current closure. Using observations from Magnetospheric Multiscale (MMS) mission, we present a unified framework to classify out‐of‐plane Hall fields by peak composition—central unipolar ( C ), sunward bipolar ( S + C ), earthward bipolar ( C + E ), and tripolar ( S + C + E ) ‐ and by their displacement relative to the magnetopause midplane. We apply this framework to seven bipolar events (H1–H7) and relate Hall‐field displacement to the Hall‐region density asymmetry parameter. For the first five earthward‐type events (H1–H5), Hall‐density asymmetry covaries with the observed displacement of the bipolar Hall field structure, indicating that asymmetric Hall‐density produces a larger offset of the peak amplitude toward the magnetosphere. Previously, the sunward‐type event H6 was displaced toward the magnetosheath with moderate Hall‐field asymmetry. On 16 October 2015 (H7), we find a sunward bipolar ( S + C ) signature but displaced deep into the magnetosphere, reaching a nearly symmetric Hall‐field ratio despite high Hall‐density asymmetry. In H7, the absence of a magnetospheric E peak, together with the complete traversal of the Hall‐region into the magnetosphere, rules out a tripolar configuration previously proposed for H6. In addition, sequential electron jets and a new pattern in the bipolar normal electric field coincide with the magnetospheric Hall interval in H7. This suggests that displaced Hall electron dynamics, together with extreme asymptotic density and high temperature asymmetry, reshaped the bipolar Hall magnetic field. The findings of this study provide observational constraints for kinetic Hall models of asymmetric guide‐field reconnection.
Journals
2026 EN
Laakso H. · Le G. · Pfaff R.
+2 more
Abstract We investigate the empirical relationship between the spacecraft potential ( V s ) measured by the Electric Field Double Probes, and the electron density ( N e ) measured by the Fast Plasma Instrument on the MMS spacecraft. We derive their relationship during fast‐mode intervals when the Active Spacecraft Potential Control Devices are off. Then we apply this relationship to slow‐mode intervals during the perigee passes where V s can be less than +2 V and N e can exceed 1,000 cm −3 . Because such a parameter range is never observed by MMS during fast‐mode intervals, we define this part of the relationship using simultaneous observations from the Van Allen mission where N e is measured up to 3,000 cm −3 while V s is less than +2 V. We compare the empirical relationship to the predictions by an orbital motion limited theory. This suggests how to model the photoelectron current above +5 V and the collection of ambient electrons for moderate Debye lengths. We apply the empirical relationship (i.e., theoretical curves are not used here) to several consecutive plasmapause crossings by MMS during two magnetic storms. The erosion rates of the plasmasphere were ∼60 cm −3 /day at 7 MLT and ∼30 cm −3 /day at 14 MLT. In the duskside, the erosion rate decreases with L due to increasing flux tube volumes, being about 10–20 cm −3 /day at L ∼ 7. The refilling rates are similar to the erosion rates, but in the dawnside, the refilling is delayed due to a slow expansion of the plasmapause to higher L .
Journals
2026 EN
Gan L. · Cantwell K. · Li W.
+5 more
Abstract Electron microbursts are among the most important loss mechanisms for energetic electrons in the Earth's radiation belts and are often driven by wave‐particle interactions with discrete chorus wave elements. Observations from the Balloon Array for Radiation‐belt Relativistic Electron Losses (BARREL) mission have revealed microburst events with simultaneous burst and smooth precipitation components. We conduct numerical experiments for the reported events and identify the driving mechanisms for these dual‐component structures. A realistic atmospheric backscattering module based on Monte Carlo simulations is incorporated into test particle simulations of wave‐particle interactions to more accurately model electron precipitation. Using parameters constrained by BARREL observations, our simulations reproduce the observed dual‐component microbursts with similar burst‐to‐smooth ratios. Comparative runs show that energy dispersion in precipitation, driven by intense and discrete chorus elements, can naturally produce a smooth component alongside bursty precipitation. This indicates that the smooth component is an intrinsic feature of intense microbursts and contributes significantly to the total electron loss. We show that electron loss rates from microbursts are likely underestimated due to the neglect of these smooth components in observations with insufficient energy resolution. Although the backscattering module does not strongly affect the formation of the smooth component, it does reduce the peak precipitation rate and extends the overall duration of precipitation. These findings highlight the importance of incorporating realistic atmospheric backscattering into wave‐driven precipitation models to improve the accuracy of estimating electron precipitation.
Journals
2026 EN
Schulz L. · Glassmeier K.H. · Turc L.
+5 more
Abstract The wave telescope is an analysis technique for multi‐point spacecraft data that estimates power spectra in reciprocal position space (k$k$ ‐space). It has been used to reveal the spatial properties of waves and fluctuations in space plasmas. Originally designed as an analysis tool for 4 spacecraft constellations, new multi‐scale missions such as HelioSwarm or Plasma Observatory require extension of the technique to larger numbers of spacecraft, which introduces spatial aliasing effects that can largely inhibit physical interpretation and analysis of obtained power spectra. We present a comprehensive algorithm—the extended wave telescope—on how to obtain evaluable power spectra ink$k$ ‐space applying the wave telescope to spacecraft configurations with larger numbers of spacecraft (typicallyn > 4$n > 4$ ). We complement the steps presented in Schulz et al. (2023, https://doi.org/10.5194/angeo‐41‐449‐2023 ), by showing how spacecraft position errors can be included into the calculation of the spatial Nyquist limit (SNL, the upper detection limit ink$k$ ‐space due to aliasing) as well as how to dampen remaining aliasing artifacts within the SNL. We test our implementation of the algorithm on a global hybrid‐Vlasov simulation Vlasiator of Earth's magnetospheric environment, probing the foreshock and magnetosheath with virtual spacecraft. We find good agreement between the virtual spacecraft's and real‐word multi‐spacecraft observations. This highlights the success of our methodology of applying the wave telescope to spacecraft constellations withn > 4$n > 4$ and also demonstrates the capabilities of Vlasiator in simulating the local near Earth space environment. We conclude that the presented algorithm is well‐suited for application on future multi‐scale spacecraft mission data.
Journals
2026 EN
Birn Joachim · Runov Andrei
Abstract Using combined MHD/test particle simulations, we further explore characteristics of ion (proton) acceleration tailward of a near‐tail reconnection site related to tailward moving plasmoids. In this paper we focus on local features, addressing specifically energy‐time spectrograms, directional fluxes and phase space distributions, in comparison to some typical ion observations made by the “Acceleration, Reconnection, Turbulence and Electrodynamics of the Moon's Interaction with the Sun” mission near the plasma sheet boundary layer (PSBL) and in the central plasma sheet (CPS). In agreement with the observations, the simulations show boundary populations consisting of a core and an accelerated tailward beam, which decreases in speed but increases in intensity. While the core is found to be of PSBL or lobe origin the beam ions tend to include also origins in the central plasma sheet. Farther inward from the boundary, similar core/beam populations can also be found, both predominantly originating from the outer CPS. The rise in energetic ion fluxes is found to result from acceleration at or near the near‐tail reconnection site. In contrast to the boundary populations, CPS distributions within the tailward moving plasmoid tend to be more isotropic, shifted by their bulk flow speed, again in agreement with observations.
Journals
2026 EN
Zhong Zhihong · Zhou Meng
Abstract Wave‐particle interactions are central to energy conversion and anomalous transport in collisionless plasmas, yet their quantification remains challenging. We present the Seven‐Dimensional Wave‐particle Interaction Spectral Analyzer (WISA‐7D), a framework that directly quantifies secular energy conversion and anomalous effects across frequency space, 3D wavevector space, and 3D velocity phase space. To demonstrate its capability, we apply WISA‐7D to a kinetic Alfvén wave (KAW) packet observed by Magnetospheric Multiscale mission. The results reveal distinct ion and electron energy exchange patterns with this KAW and quantify associated anomalous electric fields and flows. WISA‐7D provides a powerful diagnostic for advancing our understanding of wave‐particle interactions and for validating and refining theoretical models.
Journals
2026 EN
Waheed Abdul · Wu Yifan · Tao Xin
Abstract Electron cyclotron harmonic (ECH) waves, a subset of electron Bernstein modes, are characterized by their distinct harmonic frequency structures. In the outer magnetosphere of the Earth, these waves play a vital role in electron scattering, pitch‐angle diffusion, and the subsequent precipitation of particles into the ionosphere. In contrast, their properties in the vicinity of the Lunar surface remain relatively poorly understood. In this study, we investigate the statistical characteristics of ECH waves using 8 years of observations from the ARTEMIS mission, with the objective of systematically characterizing their behavior across diverse Lunar plasma environments. Our analysis indicates that the overall occurrence rate of ECH waves within the regionr ≤ 12 R L$r\le 12{R}_{L}$ is approximately 0.099%, but this rate rises to more than 1% on the anti‐sun side in close proximity to the Moon. Moreover, the majority of ECH wave events are detected when the Moon resides within the Earth's magnetotail. On the anti‐sun side, enhanced ECH wave amplitudes are most pronounced in the near Lunar surface region. These results demonstrate that the local Lunar plasma environment strongly influences ECH wave activity, with Lunar magnetic field anomalies significantly modulating the occurrence rate of ECH waves while exerting no substantial influence on their amplitude. Collectively, these findings provide new insights into the plasma processes operating near the Lunar surface.
Journals
2026 EN
Hosner M. · Nakamura R. · Schmid D.
+1 more
Abstract In the Earth's magnetotail bursty bulk flows are often associated with dipolarizing magnetic flux bundles. The leading edges of such earthward‐moving flux bundles are called dipolarization fronts (DF). In the present study we investigate the characteristics of ion‐scale oscillations embedded inside DFs, using observations from NASA's Magnetospheric Multiscale mission (MMS) between 2017 and 2022. By applying wavelet and spectral analysis methods to multi‐point measurements, we obtain a statistical picture of the magnetic and electric field fluctuations from parameters such as the polarization, propagation direction and velocity in the central and outer plasma sheet. More than 96% of the observed events show enhanced power around the proton cyclotron frequency. The power maximum occurred either at the beginning or end of the DF. For a large portion of DF events, in particular those in the central plasma sheet, the power enhancement is due to the DF itself as expected from the ion scale‐thin DFs. However, ion‐scale fluctuations embedded in the DF are observed for the majority of the cases in the outer plasma sheet. While some limited cases are associated with electromagnetic ion cyclotron waves, most of these fluctuations can be interpreted as static co‐moving structures, generated by local Hall or field‐aligned currents. There are quite a number of fluctuations suggesting a rippled dipolarization front predominantly for the events in the outer plasma sheet.