Solar Wind-magnetosphere Interaction Research Articles

Prediction of Solar Wind Speed Through Machine Learning From Extrapolated Solar Coronal Magnetic Field

AbstractAn accurate solar wind (SW) speed model is important for space weather predictions, catastrophic event warnings, and other issues concerning SW—magnetosphere interaction. In this work, we construct a model based on convolutional neural network (CNN) and Potential Field Source Surface (PFSS) magnetic field maps, considering a SW source surface of RSS = 2.5R⊙, aiming to predict the SW speed at the Lagrange‐1 (L1) point of the Sun‐Earth system. The input of our model consists of four PFSS magnetic field maps at RSS, which are three, four, five, and six days before the target epoch. Reduced maps are used to promote the model's efficiency. We use the Global Oscillation Network Group (GONG) photospheric magnetograms and the potential field extrapolation model to generate PFSS magnetic field maps at the source surface. The model provides predictions of the quasi‐continuous test data set, which is generated by randomly assigning 120 data segments that are individually continuous in time, with an averaged correlation coefficient (CC) of 0.53 ± 0.07 and a root mean square error (RMSE) of 80.8 ± 4.8 km/s in an eight‐fold validation training scheme with the time resolution of the data as small as one hour. The model also has the potential to forecast high speed streams of the SW, which can be quantified with a general threat score of 0.39.

Structure and dynamics of the Hermean magnetosphere revealed by electron observations from the Mercury electron analyzer after the first three Mercury flybys of BepiColombo

The Mercury electron analyzer (MEA) obtained new electron observations during the first three Mercury flybys by BepiColombo on October 1, 2021 (MFB1), June 23, 2022 (MFB2), and June 19, 2023 (MFB3). BepiColombo entered the dusk side magnetotail from the flank magnetosheath in the northern hemisphere, crossed the Mercury solar orbital equator around midnight in the magnetotail, traveled from midnight to dawn in the southern hemisphere near the closest approach, and exited from the post-dawn magnetosphere into the dayside magnetosheath. We aim to identify the magnetospheric boundaries and describe the structure and dynamics of the electron populations observed in the various regions explored along the flyby trajectories. We derive 4s time resolution electron densities and temperatures from MEA observations. We compare and contrast our new BepiColombo electron observations with those obtained from the Mariner 10 scanning electron spectrometer (SES) 49 years ago. A comparison to the averaged magnetospheric boundary crossings of MESSENGER indicates that the magnetosphere of Mercury was compressed during MFB1, close to its average state during MFB2, and highly compressed during MFB3. Our new MEA observations reveal the presence of a wake effect very close behind Mercury when BepiColombo entered the shadow region, a significant dusk-dawn asymmetry in electron fluxes in the nightside magnetosphere, and strongly fluctuating electrons with energies above 100s eV in the dawnside magnetosphere. Magnetospheric electron densities and temperatures are in the range of 10-30 cm$^ $ and above a few 100s eV in the pre-midnight-sector, and in the range of 1-100 cm$^ $ and well below 100 eV in the post-midnight sector, respectively. The MEA electron observations of different solar wind properties encountered during the first three Mercury flybys reveal the highly dynamic response and variability of the solar wind-magnetosphere interactions at Mercury. A good match is found between the electron plasma parameters derived by MEA in the various regions of the Hermean environment and similar ones derived in a few cases from other instruments on board BepiColombo.

A simplified geospace model for satellite design

This study introduced a simplified, integrated computational model to estimate the drag coefficient and surface charging within the plasma wake of Low Earth Orbit (LEO) spacecraft influenced by various solar activities. The model constituted four core modules: a solver for the solar wind-magnetosphere interaction, a magnetosphere-ionosphere coupling for electric field mapping, an ionization model for the F-layer of the ionosphere, and an estimation model for excess satellite drag and plasma wake size. The initial module adopted a simplified 1D ideal Magnetohydrodynamic (MHD) model while incorporating magnetosphere-ionosphere interactions to derive electric field data near Earth’s boundary. A simplified ionospheric model for the F-layer was implemented to compute the O+ and electron densities. Subsequently, the spacecraft drag coefficient and the plasma wake size were determined for varying solar wind speed inputs corresponding to quiet, intense, and extreme space weather conditions. In the case of extreme conditions with a solar wind speed of 1000 km/s, the results indicated that the excess satellite drag coefficient and plasma wake size increased to around ten percent.

SPASE metadata as a building block of a heliophysics science-enabling framework

Heliophysics and space weather research encompass the effects of solar output on practically the entire Solar System and are fundamentally cross-disciplinary. Cross-domain science investigations, such as in Sun-heliosphere interactions, solar wind-magnetosphere interactions, or magnetosphere-ionosphere coupling, often require the use of data, models, and other digital resources pertaining to different heliophysical domains: the Sun, the solar wind, the magnetosphere, the ionosphere, the thermosphere and the mesosphere. Due to differences in measurement platforms, techniques and instruments, heliophysics data obtained from different domains are diverse and complex, making the resource landscape difficult for untrained users to navigate. Without proper and adequate guidance from domain experts, it is often difficult for early-career scientists and non-domain experts to discover useful datasets and to know from where and how to obtain and understand the data they need to support their research. This paper describes the roles of metadata in providing the identification, location, access protocol, and detailed content description of a digital resource. More specifically, we point out that metadata written according to the Space Physics Archive Search and Extract (SPASE) metadata model are fully compatible with the FAIR principles so that digital resources described using the SPASE model can be uniformly Findable, Accessible, Interoperable, and Reusable. SPASE metadata can thus be the key element, the lingua franca so to speak, that enables unfettered information flow between data systems and services throughout the heliophysics data environment and lowers the understandability barrier of the resources to ensure their independent usability. After describing various components of the heliophysics data environment, their metadata requirements for effective operations, and some essential features of the SPASE metadata model, we then illustrate how metadata in SPASE can enable or facilitate the performance of different science tasks. The current status and future outlook of SPASE are also presented.

Imaging the End-to-End Dynamics of the Global Solar Wind-Magnetosphere Interaction

Imaging the End-to-End Dynamics of the Global Solar Wind-Magnetosphere Interaction

How to improve our understanding of solar wind-magnetosphere interactions on the basis of the statistical evaluation of the energy budget in the magnetosheath?

Solar wind (SW) quantities, referred to as coupling parameters (CPs), are often used in statistical studies devoted to the analysis of SW–magnetosphere–ionosphere couplings. Here, the CPs and their limitations in describing the magnetospheric response are reviewed. We argue that a better understanding of SW magnetospheric interactions could be achieved through estimations of the energy budget in the magnetosheath (MS), which is the interface region between the SW and magnetosphere. The energy budget involves the energy transfer between scales, energy transport between locations, and energy conversions between electromagnetic, kinetic, and thermal energy channels. To achieve consistency with the known multi-scale complexity in the MS, the energy terms have to be complemented with kinetic measures describing some aspects of ion–electron scale physics.

Seasonal and diurnal variations of Kelvin-Helmholtz Instability at terrestrial magnetopause

Kelvin-Helmholtz Instability is ubiquitous at Earth’s magnetopause and plays an important role in plasma entry into the magnetosphere during northward interplanetary magnetic fields. Here, using one solar cycle of data from NASA THEMIS (Time History of Events and Macro scale Interactions during Substorms) and MMS (Magnetospheric Multiscale) missions, we found that KHI occurrence rates show seasonal and diurnal variations with the rate being high near the equinoxes and low near the solstices. The instability depends directly on the Earth’s dipole tilt angle. The tilt toward or away from the Sun explains most of the seasonal and diurnal variations, while the tilt in the plane perpendicular to the Earth‐Sun line explains the difference between the equinoxes. The results reveal the critical role of dipole tilt in modulating KHI across the magnetopause as a function of time, highlighting the importance of Sun-Earth geometry for solar wind-magnetosphere interaction and for space weather.

Thermospheric NO Cooling during an Unusual Geomagnetic Storm of 21–22 January 2005: A Comparative Study between TIMED/SABER Measurements and TIEGCM Simulations

The geomagnetic storm is the manifestation of the solar wind–magnetosphere interaction. It deposits huge amount of the solar energy into the magnetosphere–ionosphere–thermosphere (MIT) system. This energy creates global perturbations in the chemistry, dynamics, and energetics of the MIT system. The high latitude energy deposition results in the Joule and particle heating that subsequently increases the thermospheric temperature. The thermospheric temperature is effectively regulated by the process of thermospheric cooling emission by nitric oxide via 5.3 µm. A peculiar, intense geomagnetic storm (Dst = −105 nT) occurred during 21–22 January 2005, where the main phase developed during the northward orientation of the z-component of interplanetary magnetic field. We utilized the nitric oxide 5.3 µm infrared emission from the NCAR’s Thermosphere–Ionosphere–Electrodynamics General Circulation Model (TIEGCM) simulation and the Sounding of Atmosphere using Broadband Emission Radiometry (SABER) onboard the thermosphere–ionosphere–mesosphere energetic and dynamics satellite to investigate its response to this anomalous geomagnetic storm. We compared the model results with the observations on both the local and global scales. It is observed that the model results agree very well with the observations during quiet times. However, the model severely underestimates the cooling emission by one-fourth of the observations, although it predicts an enhancement in the thermospheric temperature and densities of atomic oxygen and nitric oxide during the geomagnetic storm.

Editorial: Solar wind–Magnetosphere interactions

Editorial: Solar wind–Magnetosphere interactions

Quantifying the global solar wind-magnetosphere interaction with the Solar-Terrestrial Observer for the Response of the Magnetosphere (STORM) mission concept

Much of what we know about the solar wind’s interaction with the Earth’s magnetosphere has been gained from isolated in-situ measurements by single or multiple spacecraft. Based on their observations, we know that reconnection, whether on the dayside magnetopause or deep within the Earth’s magnetotail, controls the bulk flow of solar wind energy into and through the global system and that nightside activity provides the energized particles that power geomagnetic storms. But by their very nature these isolated in-situ measurements cannot provide an instantaneous global view of the entire system or its cross-scale dynamics. To fully quantify the dynamics of the coupled solar wind-magnetosphere requires comprehensive end-to-end global imaging of the key plasma structures that comprise the magnetosphere which have spatial resolutions that exceeds anything possible with multi-point or constellation situ measurements. Global, end-to-end, imaging provides the pathway to understanding the system as a whole, its constituent parts, and its cross-scale processes on a continuous basis, as needed to quantify the flow of solar wind energy through the global magnetospheric system. This paper describes how a comprehensively-instrumented single spacecraft in a high-altitude, high-inclination orbit coupled with ground-based instruments provides the essential observations needed to track and quantify the flow of solar wind energy through the magnetosphere. This includes observations of the solar wind plasma and magnetic field input, the magnetopause location in soft X-rays, the auroral oval in far ultraviolet, the ring current in energetic neutrals, the plasmasphere in extreme ultraviolet, the exosphere in Lyman-α, and the microstructure of the nightside auroral oval from ground-based all sky cameras.

On the phenomenology of magnetosheath jets with insight from theory, modelling, numerical simulations and observations by Cluster spacecraft

Introduction: During recent years magnetosheath plasma structures called “jets” are identified in spacecraft data as localized regions in the magnetosheath where the dynamic pressure is enhanced compared to the background. Although the nomenclature and detection algorithms vary from author to author, magnetosheath jets are part of a larger class of phenomena which can be globally called magnetosheath irregularities. In this review we focus on elements of jets phenomenology less discussed in the literature, though sustained by theoretical models for solar wind magnetosphere interaction, numerical studies based on Vlasov equilibrium models or kinetic numerical simulations.Methods: The self-consistency of magnetosheath jets and the preservation of their physical identity (shape and physical properties), implicitly assumed in many recent experimental studies, is discussed in modelling and simulations studies and results as a consequence of kinetic processes at the edges of the jets. These studies provide evidence for the fundamental role played by a polarization electric field sustaining the forward motion of the jet with respect to the background plasma. Another natural consequence is the backward motion of surrounding magnetosheath plasma at the edges of jets. The conservation of magnetic moment of ions leads to a decrease of jets forward speed when it moves into increasing magnetic field. Our review is complemented by an analysis of magnetosheath data recorded by Cluster in 2007 and 2008. We applied an algorithm to detect jets based on searching localized enhancements of the dynamic pressure.Results: This algorithm identifies a number of 960 magnetosheath jets (354 events in 2007 versus 606 events in 2008). A statistical analysis of jet plasma properties reveals an asymmetric distribution of the number of jets as well as a dawn-dusk asymmetry of jets temperature and density. The perturbative effects of jets on the background magnetosheath density/temperature are stronger in the dusk/dawn flank. We also found evidence for deceleration and perpendicular heating of jets with decreasing distance to the Earth. The braking of jets is correlated with the variation of the magnetic field intensity: the stronger the magnetic field gradient, the more efficient is the jet breaking.

Further investigation of the effect of upstream solar-wind fluctuations on solar-wind/magnetosphere coupling: Is the effect real?

There is a general consensus that fluctuations in the solar wind magnetic field and/or the Alfvenicity of the solar wind drive a solar wind-magnetosphere interaction. 11 years of hourly-averaged solar wind and magnetospheric geomagnetic indices are used to further examine this hypothesis in detail, confirming that geomagnetic activity statistically increases with the amplitude of upstream fluctuations and with the Alfvénicity, even when solar-wind reconnection driver functions are weak and reconnection on the dayside magnetopause should vanish. A comparison finds that the fluctuation-amplitude effect appears to be stronger than the Alfvénicity effect. In contradiction to the generally accepted hypothesis of driving an interaction, it is also demonstrated that many solar wind parameters are correlated with the fluctuation amplitude and the Alfvénicity. As a result, we caution against immediately concluding that the latter two parameters physically drive the overall solar-wind/magnetosphere interaction: the fluctuation amplitude and Alfvénicity could be acting as proxies for other more-relevant variables. More decisive studies are needed, perhaps focusing on the roles of ubiquitous solar-wind strong current sheets and velocity shears, which drive the measured amplitudes and Alfvénicities of the upstream solar-wind fluctuations.

Solar wind magnetic holes can cross the bow shock and enter the magnetosheath

Abstract. Solar wind magnetic holes are localized depressions of the magnetic field strength, on timescales of seconds to minutes. We use Cluster multipoint measurements to identify 26 magnetic holes which are observed just upstream of the bow shock and, a short time later, downstream in the magnetosheath, thus showing that they can penetrate the bow shock and enter the magnetosheath. For two magnetic holes, we show that the relation between upstream and downstream properties of the magnetic holes are well described by the MHD (magnetohydrodynamic) Rankine–Hugoniot (RH) jump conditions. We also present a small statistical investigation of the correlation between upstream and downstream observations of some properties of the magnetic holes. The temporal scale size and magnetic field rotation across the magnetic holes are very similar for the upstream and downstream observations, while the depth of the magnetic holes varies more. The results are consistent with the interpretation that magnetic holes in Earth's and Mercury's magnetosheath are of solar wind origin, as has previously been suggested. Since the solar wind magnetic holes can enter the magnetosheath, they may also interact with the magnetopause, representing a new type of localized solar wind–magnetosphere interaction.

Next generation magnetic field measurements from low-earth orbit satellites enable enhanced space weather operations

Large-scale current systems in the ionosphere and the magnetosphere are intimately controlled by the solar wind-magnetosphere interaction and the magnetosphere-ionosphere coupling. During space weather events, these currents reconfigure and intensify significantly in response to enhanced solar wind-magnetosphere interaction, facilitating explosive energy input from the magnetosphere into the ionosphere-thermosphere system and inducing electric current surges in electric power systems on the ground. Therefore, measurements of magnetic manifestations associated with the dynamic changes of the current systems are crucial for specifying the energy input into the ionosphere-thermosphere system, understanding energy dissipation mechanisms, and predicting the severity of their space weather impacts. We investigate the potential uses of high-quality magnetic field data for space weather operations and propose real-time data products from next generation constellation missions that enable improved space weather forecasting and mitigation.

Evidence of the Alfvén Transition Layer and Particle Precipitation in the Cusp Region: 3D Global PIC Simulation of the Solar Wind–Earth Magnetosphere Interaction

A transition layer, named the Alfvénic transition layer (or ATL), has been clearly evidenced near the outer boundary of the cusp by experimental observations from the Cluster mission. This layer characterized by a local value of Log M A ∼ 1, where M A is the Alfvén Mach number, allows the bulk flow to transit from super-Alfvénic to sub-Alfvénic from the exterior to the interior side of the outer cusp. The ATL has been observed during northward interplanetary magnetic field orientation, and mainly within the meridian plane. Currently, 3D Particle In Cell (PIC) global simulations of the solar wind–magnetosphere interaction are being performed in order to analyze the cusp region and this layer in detail. Present results stress the following points: (i) the ATL has a 3D structure; (ii) within the meridian plane, the ATL appears as a sublayer within a much more extended slow-mode pattern, and it is almost adjacent and located above the upper edge of the stagnant exterior cusp (SEC); and (iii) the plasma deceleration through the ATL is not uniform in the region located above the cusp. In addition, present preliminary results stress that (a) the spiraled streamlines of ion/electron fluxes converge when approaching the cusp, and their intensity strongly increases; and (b) ion and electron energetic fluxes penetrating the cusp region strongly differ in terms of their penetration depths and are issued from different regions of the magnetosphere/magnetosheath. Our results illustrate the importance of 3D effects used with a PIC simulation approach allowing the analysis of each population simultaneously.

Electron Signatures of Reconnection in a Global eVlasiator Simulation.

Geospace plasma simulations have progressed toward more realistic descriptions of the solar wind–magnetosphere interaction from magnetohydrodynamic to hybrid ion‐kinetic, such as the state‐of‐the‐art Vlasiator model. Despite computational advances, electron scales have been out of reach in a global setting. eVlasiator, a novel Vlasiator submodule, shows for the first time how electromagnetic fields driven by global hybrid‐ion kinetics influence electrons, resulting in kinetic signatures. We analyze simulated electron distributions associated with reconnection sites and compare them with Magnetospheric Multiscale (MMS) spacecraft observations. Comparison with MMS shows that key electron features, such as reconnection inflows, heated outflows, flat‐top distributions, and bidirectional streaming, are in remarkable agreement. Thus, we show that many reconnection‐related features can be reproduced despite strongly truncated electron physics and an ion‐scale spatial resolution. Ion‐scale dynamics and ion‐driven magnetic fields are shown to be significantly responsible for the environment that produces electron dynamics observed by spacecraft in near‐Earth plasmas.

Kelvin-Helmholtz Vortices as an Interplay of Magnetosphere-Ionosphere Coupling

The solar wind-magnetosphere interaction drives diverse physical processes on the flanks of Earth’s magnetopause, and in turn these processes couple to the ionosphere. We investigate simultaneous multipoint in-situ spacecraft and ground-based measurements to determine the role of Kelvin-Helmholtz waves at the Earth’s magnetopause and the low-latitude boundary layer in the magnetosphere-ionosphere coupling process. Nonlinear Kelvin-Helmholtz waves develop into flow vortices that twist and/or shear flux tube magnetic fields, thereby generating localized field-aligned currents. Kelvin-Helmholtz vortices on the dusk (dawn) flanks of the magnetosphere generate clockwise (counter-clockwise) rotations and upward (downward) field-aligned currents inside the flux tubes, consistent with the region-1 field-aligned current. We present in-situ MMS and Cluster spacecraft observations of Kelvin-Helmholtz vortices at the magnetopause that map to the poleward edge of the auroral regions. The FAST spacecraft and the ground-based magnetometers from which spherical elementary currents (acting as a proxy for vertical currents) can be calculated observe corresponding field-aligned current signatures. This study demonstrates the role played by the Kelvin-Helmholtz waves in linking magnetopause boundary fluctuations to ionospheric phenomena.

Automatic Identification of Magnetopause Crossing Events

The magnetopause is the key area of mass, momentum and energy coupling between the solar wind and the magnetosphere. The Magnetopause Crossing Events (MCEs) are usually identified by visual inspection of the plots, which is labor intensive and inefficient. Here we develop a novel procedure that is able to rapidly identify MCEs around the subsolar point and accurately define the transition layer between the magnetosphere and the magnetosheath. Here we synthetically consider the characteristics of the variations of the magnetic field and the particle flux for the identification criteria so that false identifications are avoided to the greatest possible. To demonstrate the efficiency of this procedure, it is applied to the THEMIS observations from 2007 to 2018 when THEMISs apogee is near the subsolar point. The procedure successfully determines 16 758 MCEs in about 6 hours on a common PC. The huge number of identified samples of MCEs would benefit the investigations on the magnetopause-related scientific problems, such as indentation of the magnetopause, solar wind-magnetosphere interaction, magnetic reconnection process, and so on. The accuracy and limitation of this algorithm are also analyzed in this paper.

Data Mining Reconstruction of Magnetotail Reconnection and Implications for Its First-Principle Modeling

Magnetic reconnection is a fundamental process providing topological changes of the magnetic field, reconfiguration of space plasmas and release of energy in key space weather phenomena, solar flares, coronal mass ejections and magnetospheric substorms. Its multiscale nature is difficult to study in observations because of their sparsity. Here we show how the lazy learning method, known as K nearest neighbors, helps mine data in historical space magnetometer records to provide empirical reconstructions of reconnection in the Earth’s magnetotail where the energy of solar wind-magnetosphere interaction is stored and released during substorms. Data mining reveals two reconnection regions (X-lines) with different properties. In the mid tail (∼30RE from Earth, where RE is the Earth’s radius) reconnection is steady, whereas closer to Earth (∼20RE) it is transient. It is found that a similar combination of the steady and transient reconnection processes can be reproduced in kinetic particle-in-cell simulations of the magnetotail current sheet.

Solar flare effects in the Earth’s magnetosphere

The Earth’s magnetosphere is the outermost layer of the geospace system deflecting energetic charged particles from the Sun and solar wind. The solar wind has major impacts on the Earth’s magnetosphere, but it is unclear whether the same holds for solar flares—a sudden eruption of electromagnetic radiation on the Sun. Here we use a recently developed whole geospace model combined with observational data from the 6 September 2017 X9.3 solar flare event to reveal solar flare effects on magnetospheric dynamics and on the electrodynamic coupling between the magnetosphere and its adjacent ionosphere, the ionized part of Earth’s upper atmosphere. We observe a rapid and large increase in flare-induced photoionization of the polar ionospheric E-region at altitudes between 90 km and 150 km. This reduces the efficiency of mechanical energy conversion in the dayside solar wind–magnetosphere interaction, resulting in less Joule heating of the Earth’s upper atmosphere, a reconfiguration of magnetosphere convection, as well as changes in dayside and nightside auroral precipitation. This work thus demonstrates that solar flare effects extend throughout the geospace via electrodynamic coupling, and are not limited—as previously believed—to the atmospheric region where radiation energy is absorbed1. The solar wind affects the magnetosphere, but whether this holds true for solar flares was unclear. By combining geospace modelling with observations, solar flares are shown to influence the dynamics of the magnetosphere and its ionosphere coupling.