Ionospheric Convection Pattern Research Articles

Development of the Chinese Dual Auroral Radar Network and Preliminary Results

AbstractLed by the National Space Science Center of the Chinese Academy of Sciences, we have built a Chinese dual auroral radar network in northern China, which is called the CN‐DARN. The CN‐DARN consists of three pairs of high‐frequency coherent scattering radar facilities and is one of the key parts of the Chinese Meridian Project Phase II. It has been fully constructed and started trial operations at the end of 2023. The detection range of the radar network extends longitudinally over approximately 9 hr of local times and covers the middle to high latitudes of the entire Asia region above 40. In this paper, we present the basic design of the CN‐DARN and its preliminary observations of ionospheric irregularities, subauroral polarization streams (SAPSs) and traveling ionospheric disturbances (TIDs). We also investigate its contribution to the ionospheric convection pattern of the Northern Hemisphere derived from Super Dual Auroral Radar Network (SuperDARN) observations. The results indicate that the CN‐DARN provides excellent measurements and better specifications of flows in the Asian sector, improving our understanding of the global‐scale ionospheric convection pattern in the Northern Hemisphere. These encouraging results lead us to believe that the CN‐DARN will play an important role in studies on the evolution of ionospheric irregularities, the characteristics and evolution of SAPSs, the propagation of TIDs, and global‐scale ionospheric convection dynamics.

TRICE‐2/SuperDARN Observations and Comparison With the Associated MMS Magnetopause Crossing

AbstractTwo sounding rockets, designated TRICE‐2, were launched on 8 December 2018 into the northern cusp region. The two rockets were designated the high‐ and low‐flyers, respectively, and launched 2 min apart to investigate cusp structures, specifically their spatial or temporal nature. 2 hr prior to the cusp encounter by the TRICE‐2 rockets, the MMS satellites, located in the magnetopause boundary layer, observed switching ion beams under very similar IMF conditions as later observed by TRICE‐2. The observed ion beam switch in the boundary layer defined the location of the primary dayside X‐line. Both, TRICE‐2 and MMS, also observed the signatures of multiple X‐lines at the magnetopause, overlapping ion‐energy dispersions in the cusp and counterstreaming ion beams in the magnetopause boundary layer, respectively. In addition to the TRICE‐2 cusp observations, ionospheric convection patterns from the SuperDARN radar are used to explain the vastly different cusp ion signatures observed by the TRICE‐2 rockets. While the high‐flyer rocket progressed north through the center of the cusp, the low‐flyer rocket drifted off to the east and crossed into the dusk convection cell, traveling perpendicular to the ionospheric convection direction before reaching the poleward oriented section of the convection cell also observed by the high‐flyer counterpart.

Multi‐Instrument Observations of the Evolution of Polar Cap Patches Associated With Flow Shears and Particle Precipitation

AbstractSimultaneous observations from Defense Meteorological Satellite Program, Swarm, Resolute Bay all‐sky imagers, GPS Total Electron Content and Super Dual Auroral Radar Network, are used to investigate the evolution and key characteristics of the Tongue of Ionization (TOI) being restructured into a polar cap patch. Six satellites crossed the TOI of patch as it moved from the dayside to the nightside. It was initially hot, then a mix of both cold and hot, and finally it became a cold patch. This suggests that cold patch is not only a result of solar extreme ultraviolet radiation, but may also develop when a hot patch cools down. Soft‐electron precipitation and flow shears both contribute to the TOI restructuring and the appearance of polar cap patch. The plasma density of patch at ∼500 km was at least 4 times higher than at ∼800 km. The plasma density enhancement gradually decreased as the patch evolved due to decreased production and transport of cold nightside low‐density plasma. Moreover, the duskward motion of the patch was influenced by changes in the ionospheric convection pattern.

GPS Loss of Lock Events and Their Dependence on the Interplanetary Magnetic Field Orientation

AbstractThe study investigates the influence of interplanetary magnetic field (IMF) orientation on loss of lock (LoL) events in Global Positioning System signals. We analyzed LoLs recorded on two Swarm satellites between July 2014 and December 2021, examining how the signs of the IMF Bx, By, and Bz components affect the distribution of events at high latitudes. Our results reveal an asymmetric distribution of LoL events over 75° magnetic latitude. In the Northern hemisphere, more events occur in the post‐noon sector with negative IMF By, and in the pre‐noon sector with positive IMF By. Conversely, in the Southern hemisphere, pre‐noon events increase with negative IMF By, while post‐noon events increase with positive IMF By. At lower latitudes (50°–75°), IMF By does not significantly affect the event distribution, which mainly concentrates in the night sector for both hemispheres. Additionally, we found a connection between IMF By and Bx, primarily due to the IMF spiral structure. Finally, we discuss our findings in the context of the SuperDARN data‐driven model of ionospheric convection patterns, which shows that LoL events frequently cluster in the cusp region, as well as the area where the two convection cells separate.

Multi‐Scale Ionospheric Poynting Fluxes Using Ground and Space‐Based Observations

AbstractThree events are presented where high‐resolution measurements from the Swarm satellites coincided with excellent F‐region ionospheric coverage from The Super Dual Auroral Radar Network (SuperDARN). Large‐scale ionospheric convection patterns from SuperDARN, together with field‐aligned‐current patterns from he Active Magnetosphere and Planetary Response Experiment (AMPERE), provide information on quasi‐static ionospheric dynamics traversed by Swarm. Because the Swarm observations and orbital path coincided with favorable SuperDARN/AMPERE observing conditions, it was possible to filter the Swarm electric field observations into a quasi‐static component that agreed with the SuperDARN electric field. The residual electric field from Swarm is thus indicative of small‐ and mesoscale dynamics not captured by the convection and field‐aligned current (FAC) patterns. Calculations of the Poynting flux between the different instruments show that dynamics on small‐to mesoscales can be highly variable within structures like FACs. In the events shown, small‐ and medium‐scale Poynting fluxes occasionally dominate over those from large‐scale processes.

High‐Latitude Ionospheric Electrodynamics During STEVE and Non‐STEVE Substorm Events

AbstractPrevious studies have shown that Strong Thermal Emission Velocity Enhancement (STEVE) events occur at the end of a prolonged substorm expansion phase. However, the connection between STEVE occurrence and substorms and the global high‐latitude ionospheric electrodynamics associated with the development of STEVE and non‐STEVE substorms are not yet well understood. The focus of this paper is to identify electrodynamics features that are unique to STEVE events through a comprehensive analysis of ionospheric convection patterns estimated from SuperDARN plasma drift and ground‐based magnetometer data using the Assimilative Mapping of Geospace Observations (AMGeO) procedure. Results from AMGeO are further analyzed using principal component analysis and superposed epoch analysis for 32 STEVE and 32 non‐STEVE substorm events. The analysis shows that the magnitude of cross‐polar cap potential drop is generally greater for STEVE events. In contrast to non‐STEVE substorms, the majority of STEVE events investigated are accompanied by with a pronounced extension of the dawn‐cell into the pre‐midnight subauroral latitudes, reminiscent of the Harang reversal convection feature where the eastward electrojet overlaps with the westward electrojet, which tends to prolong over substorm expansion and recovery phases. This is consistent with the presence of an enhanced subauroral electric field confirmed by previous STEVE studies. The global and localized features of high‐latitude ionospheric convection associated with optical STEVE events characterized in this paper provide important insights into cross‐scale magnetosphere‐ionosphere coupling mechanisms that differentiate STEVE events from non‐STEVE substorm events.

Global Asymmetry in ΔX Variations During the 06 April 2000 Geomagnetic Storm: Relative Roles of IMF Bz and By

AbstractThis investigation is directed to understand the asymmetry in ΔX variations caused due to the relative roles played by Interplanetary Magnetic Field (IMF) Bz and IMF By in a particular interval (22:22–22:55 UT), during the main phase of a strong geomagnetic storm event of 06 April 2000 (Ap = 236). Two pairs of antipodal stations, being part of the SuperMAG network, are considered here. Ionospheric convection maps from SuperDARN network are used to understand spatio‐temporal evolution of the DP2 ionospheric convection patterns over high‐latitudes. The two‐dimensional maps of equivalent currents are used to show signatures of global DP2 currents associated with the interplay effect between the two IMF components. Observations show increases in the difference in ΔX variations between nearly antipodal stations from the Japanese‐European/African sector with respect to the same between the nearly antipodal stations from the Pacific/American‐Indian sector. This asymmetry is observed during the period when the absolute magnitude of IMF By is larger than that of IMF Bz resulting in a significant and conspicuous enhancement in IMF |By/Bz|. It is suggested that the distortions in DP2 cells and associated rotation of electrodynamic day‐night divider, bring one pair of stations under the same DP2 cell and one station of the other pair under a different DP2 cell and throat flow region leading to the asymmetry in ΔX variations between the antipodal stations. Therefore, the work highlights the importance of the interplay between IMF Bz and IMF By in determining the ionospheric impact over low latitudes during strong geomagnetic conditions.

The relationship between interhemispheric asymmetries in polar ionospheric convection and the magnetic field line footpoint displacement field

Polar electrodynamics is largely controlled by solar wind and magnetospheric forcing. Different conditions can make plasma convection and magnetic field disturbances asymmetric between hemispheres. So far, these asymmetries have been studied in isolation. We present an explanation of how they are linked via displacements of magnetic field line footpoints between hemispheres, under the assumption of ideal magnetohydrodynamics. This displacement has so far been studied only on a point by point basis; here we generalize the concept to a 2D displacement vector field. We estimate displacement fields from average patterns of ionospheric convection using the Weimer et al. (J. Geophys. Res., 2005a, 110, A05306) model. These estimates confirm that the influence of the interplanetary magnetic field extends deep into the magnetosphere, as predicted by models and in-situ observations. Contrary to predictions, the displacement associated with dipole tilt appears uniform across the nightside, and it exceeds the effect of IMF By. While more research is needed to confirm these specific findings, our results demonstrate how ionospheric observations can be used to infer magnetospheric morphology, and that the displacement field is a critical component for understanding geospace as a coupled two-hemisphere system.

A comparative study of ionospheric TEC diurnal variations at two stations near cusp latitudes in the Southern Hemisphere

Based on ionospheric total electron content (TEC) data for Zhongshan station (ZHS) and Scott Base station (SBA) in Antarctica, acquired during 2010–2020, high-latitude ionospheric TEC diurnal variations of two near cusp latitude stations were studied. The magnetic latitude and longitude differences between the two stations were approximately 5° and 135°, respectively. It was found that during the 11-year solar activity cycle, the maximum diurnal variation of the ionospheric TEC at ZHS occurred mainly between local noon and magnetic noon. Statistically, the TEC peaks occurred closer to local (magnetic) noon under low (high) solar activity conditions. The maximum diurnal variation of ionospheric TEC at SBA occurred mainly around local noon under low solar activity conditions but before magnetic midnight under high solar activity conditions. The effects of solar radiation, particle precipitation, and polar ionospheric convection pattern on the diurnal variation of TEC were investigated. At both stations, photoionization caused by solar radiation was the main reason for the maximum diurnal variation of ionospheric TEC around local noon. During high solar activity with high concentration plasma in the dayside polar ionosphere, the convection pattern was the dominant influence on the maximum diurnal variation of TEC before magnetic midnight (noon) at SBA (ZHS).

Super Dual Auroral Radar Network Expansion and Its Influence on the Derived Ionospheric Convection Pattern

AbstractThe Super Dual Auroral Radar Network (SuperDARN) was built to study ionospheric convection and has in recent years been expanded geographically. Alongside software developments, this has resulted in many different versions of the convection maps data set being available. Using data from 2012 to 2018, we produce five different versions of the widely used convection maps, using limited backscatter ranges, background models and the exclusion/inclusion of data from specific radar groups such as the StormDARN radars. This enables us to simulate how much information was missing from older SuperDARN research. We study changes in the Heppner‐Maynard boundary (HMB), the cross polar cap potential (CPCP), the number of backscatter echoes (n) and the χ2/n statistic which is a measure of the global agreement between the measured and fitted velocities. We find that the CPCP is reduced when the PolarDARN radars are introduced, but then increases again when the StormDARN radars are added. When the background model is changed from the RG96 model, to the most recent TS18 model, the CPCP tends to decrease for lower values, but tends to increase for higher values. When comparing to geomagnetic indices, we find that there is on average a linear relationship between the HMB and the geomagnetic indices, as well as n, which breaks when the HMB is located at latitudes below ∼50° due to the low observational density. Whilst n is important in constraining the maps (maps with n > 400 data points are unlikely to differ), it is insufficient as the sole measure of quality.

HMB Variations Measured by SuperDARN During the Extremely Radial IMFs: Is the Coupling Function Applicable in Radial IMF?

AbstractThe effect of radial interplanetary magnetic field (IMF ) has been ignored in the solar wind‐magnetosphere‐ionosphere (S‐M‐I) coupling. We present a statistical study of IMF Bx effects on the Heppner‐Maynard Boundary (HMB) midnight latitude calculated from SuperDARN measurements between January 2002 and December 2017. The HMB represents the equatorward extent of the ionospheric convection pattern and can be used as a proxy for the equatorward boundary of the auroral oval. That is, the HMB expands toward lower latitude when the level of S‐M‐I coupling is enhanced. It is found that the averaged HMB midnight latitudes during both sunward and antisunward radial IMFs are around 64–65° magnetic latitude (MLAT). HMB midnight latitude is negatively correlated with the magnitude of IMF Bx as well as solar wind speed, while no significant trend is found between HMB midnight latitude and IMF Bz or By during radial IMF. For antisunward radial IMF, the relationship between upstream parameters and HMB is more dependent than in sunward radial direction. As the first long‐term statistical study focused on HMB during radial IMF conditions, this work provides observational evidence that the IMF Bx plays an important role in the coupling process and the traditional coupling function could not be applicable in the case of radial IMF.

Dayside Cusp Aurorae and Ionospheric Convection Under Radial Interplanetary Magnetic Fields

AbstractDayside cusp aurorae are created from particles precipitating into the cusp, and ionospheric convection is driven by solar wind electric fields. In this study, we coordinated the observations obtained from the all‐sky camera on Svalbard, the Super Dual Auroral Radar Network, SuperMAG magnetometer data, and far ultraviolet imagers on board the Defense Meteorological Satellite Program satellites for the event January 4, 2014 to examine the morphology of aurorae and the patterns of ionospheric convection for radial interplanetary magnetic field (IMF). During the event, a poleward‐moving auroral form and antisunward ionospheric convection were observed when the IMF turned into almost purely radial. Moreover, both types of antisunward and sunward convection were simultaneously observed near the footprint of the cusp at different times during the radial IMF period. The antisunward convection and sunward convection are typically an indicator of the dayside reconnection for the southward IMF and the lobe reconnection for the northward IMF, respectively. All those observations support the concept of low‐latitude dayside and high‐latitude lobe reconnection for the radial IMF. This study further shows that the coexistence of the two types of reconnection for radial IMF, resulting in an interplay of repetitive antisunward and sunward convection.

The Evolution of Long‐Duration Cusp Spot Emission During Lobe Reconnection With Respect to Field‐Aligned Currents

AbstractWe track a remarkably bright and persistent auroral cusp spot emission in the high‐latitude Northern Hemisphere polar cap, well inside the main auroral oval, for approximately 11 hr on 16 and 17 June 2012. The auroral emissions are presented in both the Lyman‐α and Lyman‐Birge‐Hopfield bands, as observed by the Special Sensor Ultraviolet Spectrographic Imager on board two of the Defense Meteorological Satellite Programme spacecraft, and supported by detections of precipitating particles by the same spacecraft. The auroral observations are accompanied by patterns of field aligned currents, obtained from the Active Magnetosphere and Planetary Electrodynamics Response Experiment, along with ionospheric convection patterns from the Super Dual Auroral Radar Network. These data provide unprecedented coverage of a cusp spot, unusually seen in both electron and proton aurora. The location and movement of the auroral emissions, current systems, and ionospheric convection patterns are extremely distorted under the northward to Y‐component‐dominated interplanetary magnetic field. The cusp spot emission region is associated with the sunward flow region of the ionosphere. Ion dispersion signatures are detected on traversal of the region of brightest proton auroral emissions. Proton‐excited Lyman‐α emissions are most evident following impulses of high solar wind density. The auroral emissions, field‐aligned current patterns, and ionospheric convection are consistent with a model of a compressed magnetosphere under strongly northward interplanetary magnetic field, following an impact of an Interplanetary Coronal Mass Ejection and associated magnetic cloud at the magnetopause, inducing high‐latitude lobe reconnection that progresses increasingly tailward during the presented interval.

Separation and Quantification of Ionospheric Convection Sources: 1. A New Technique

AbstractThis paper describes a novel technique that allows separation and quantification of different sources of convection in the high‐latitude ionosphere. To represent the ionospheric convection electric field, we use the Spherical Elementary Convection Systems representation. We demonstrate how this technique can separate and quantify the contributions from different magnetospheric source regions to the overall ionospheric convection pattern. The technique is in particular useful for distinguishing the contributions of high‐latitude reconnection associated with lobe cells from the low‐latitude reconnection associated with Dungey two‐cell circulation. The results from the current paper are utilized in a companion paper (Reistad et al., 2019, https://doi.org/10.1029/2019JA026641) to quantify how the dipole tilt angle influences lobe convection cells. We also describe a relation bridging other representations of the ionospheric convection electric field or potential to the Spherical Elementary Convection Systems description, enabling a similar separation of convection sources from existing models.

Ionospheric Plasma Irregularities Characterized by the Swarm Satellites: Statistics at High Latitudes

AbstractThe polar ionosphere is often characterized by irregularities and fluctuations in the plasma density. We present a statistical study of ionospheric plasma irregularities based on the observations from the European Space Agency's Swarm mission. The in situ electron density obtained with the Langmuir probe and the total electron content from the onboard global positioning system receiver are used to detect ionospheric plasma irregularities. We derive the irregularity parameters from the electron density in terms of the rate of change of density index and electron density gradients. We also use the rate of change of total electron content index as the irregularity parameter based on the global positioning system data. The background electron density and plasma irregularities are closely controlled by the Earth's magnetic field, with averaged enhancements close to the magnetic poles. The climatological maps in magnetic latitude/magnetic local time coordinates show predominant plasma irregularities near the dayside cusp, polar cap, and nightside auroral oval. These irregularities may be associated with large‐scale plasma structures such as polar cap patches, auroral blobs, auroral particle precipitation, and the equatorward wall of the ionospheric trough. The spatial distributions of irregularities depend on the interplanetary magnetic field (IMF). By filtering the irregularity parameters according to IMF By, we find a clear asymmetry of the spatial distribution in the cusp and polar cap between the Northern (NH) and Southern Hemispheres (SH). For negative IMF By, irregularities are stronger in the dusk (dawn) sector in the NH (SH) and vice versa. This feature is in agreement with the high‐latitude ionospheric convection pattern that is regulated by the IMF By component. The plasma irregularities are also controlled by the solar activity within the current declining solar cycle. The irregularities in the SH polar cap show a seasonal variation with higher values from September to April, while the seasonal variation in the NH is only obvious around solar maximum during 2014–2015.

Global Three‐Dimensional Simulation of the Earth's Magnetospheric and Ionospheric Responses to Small‐Scale Magnetic Flux Ropes in the Solar Wind

AbstractThe orientation of magnetic flux ropes in the solar wind is an important component that affects interactions with the Earth's magnetosphere and ionosphere. In this study, we performed global magnetohydrodynamic (MHD) simulations on the responses of the magnetosphere and ionosphere to the impact of small‐scale magnetic flux ropes (SMFRs). We considered four types of SMFR structures according to the alignment direction of the flux rope axis in the plane perpendicular to the Sun‐Earth line. The flux rope axis of the two types is oriented in the north‐south direction, while the flux rope axis of the other two types is oriented along the dusk‐dawn direction. Accordingly, the By and Bz profiles of the SMFR types vary as the SMFR passes through the Earth. The main features of the response are as follows: (i) The magnetic reconnection on both the dayside and nightside is well organized by the specific profiles of By and Bz. (ii) One type of SMFRs where Bz turns from south to north and By remains duskward leads to plasmoid formation in the tail, distinguishing it from the other types. (iii) The temporal responses of the tail plasma flow, cross‐tail electric field, tail plasma pressure, and cross‐polar cap potential depend on the specific profiles of By and Bz, causing different response times. (iv) The evolution of ionospheric convection pattern sensitively depends on the magnetic field variation within SMFRs. (v) The peak value of cross‐polar cap potential ranges from 25 kV to >50 kV, providing energy storage suitable for substorm expansion.

Statistical Patterns of Ionospheric Convection Derived From Mid‐latitude, High‐Latitude, and Polar SuperDARN HF Radar Observations

AbstractOver the last decade, the Super Dual Auroral Radar Network (SuperDARN) has undergone a dramatic expansion in the Northern Hemisphere with the addition of more than a dozen radars offering improved coverage at mid‐latitudes (50°–60° magnetic latitude) and in the polar cap (80°–90° magnetic latitude). In this study, we derive a statistical model of ionospheric convection (TS18) using line‐of‐sight velocity measurements from the complete network of mid‐latitude, high‐latitude, and polar radars for the years 2010–2016. These climatological patterns are organized by solar wind, interplanetary magnetic field (IMF), and dipole tilt angle conditions. We find that for weak solar wind driving conditions the TS18 model patterns are largely similar to the average patterns obtained using high‐latitude radar data only. For stronger solar wind driving the inclusion of mid‐latitude radar data at the equatorward extent of the ionospheric convection can increase the measured cross‐polar cap potential (ΦPC) by as much as 40%. We also derive an alternative model organized by the Kp index to better characterize the statistical convection under a range of magnetic activity conditions. These Kp patterns exhibit similar IMF By dependencies as the TS18 model results and demonstrate a linear increase in ΦPC with increasing Kp for a given IMF orientation. Overall, the mid‐latitude radars provide a better specification of the flows within the nightside Harang reversal region for moderate to strong solar wind driving or geomagnetic activity, while the polar radars improve the quality of velocity measurements in the deep polar cap under all conditions.

Simultaneous observations of traveling convection vortices: Ionosphere‐thermosphere coupling

AbstractWe present simultaneous observations of magnetosphere‐ionosphere‐thermosphere coupling over Svalbard during a traveling convection vortex (TCV) event. Various spaceborne and ground‐based instruments made coordinated measurements, including magnetometers, particle detectors, an all‐sky camera, European Incoherent Scatter (EISCAT) Svalbard Radar, Super Dual Auroral Radar Network (SuperDARN), and SCANning Doppler Imager (SCANDI). The instruments recorded TCVs associated with a sudden change in solar wind dynamic pressure. The data display typical features of TCVs including vortical ionospheric convection patterns seen by the ground magnetometers and SuperDARN radars and auroral precipitation near the cusp observed by the all‐sky camera. Simultaneously, electron and ion temperature enhancements with corresponding density increase from soft precipitation are also observed by the EISCAT Svalbard Radar. The ground magnetometers also detected electromagnetic ion cyclotron waves at the approximate time of the TCV arrival. This implies that they were generated by a temperature anisotropy resulting from a compression on the dayside magnetosphere. SCANDI data show a divergence in thermospheric winds during the TCVs, presumably due to thermospheric heating associated with the current closure linked to a field‐aligned current system generated by the TCVs. We conclude that solar wind pressure impulse‐related transient phenomena can affect even the upper atmospheric dynamics via current systems established by a magnetosphere‐ionosphere‐thermosphere coupling process.

Role of IMF By in the prompt electric field disturbances over equatorial ionosphere during a space weather event

AbstractOn 7 January 2005 (Ap=40) prompt penetration electric field perturbations of opposite polarities were observed over Thumba and Jicamarca on a few occasions during 13:45–16:30 UT. However, the electric field was found to be eastward during 14:45–15:30 UT over both Thumba and Jicamarca contrary to the general expectation wherein opposite polarities are expected at nearly antipodal points. On closer scrutiny, three important observational features are noticed during 14:10–15:15 UT. First, during 14:10–14:45 UT, despite increasing southward interplanetary magnetic field (IMF) Bz condition, the already westward electric field over Thumba weakened (less westward) while the eastward electric field over Jicamarca intensified (more eastward). Second, the electric field not only became anomalously eastward over Thumba but also got intensified further during 14:45–15:00 UT similar to Jicamarca. Third, during 15:00–15:15 UT, despite IMF Bz remaining steadily southward, the eastward electric field continued to intensify over Thumba but weakened over Jicamarca. It is suggested that the changes in IMF By component under southward IMF Bz condition are responsible for skewing the ionospheric equipotential patterns over the dip equator in such a way that Thumba came into the same DP2 cell as that of Jicamarca leading to anomalous electric field variations. Magnetic field measurements along the Indian and Jicamarca longitude sectors and changes in high‐latitude ionospheric convection patterns provide credence to this proposition. Thus, the present investigation shows that the variations in IMF By are fundamentally important to understand the prompt penetration effects over low latitudes.

Key Ground-Based and Space-Based Assets to Disentangle Magnetic Field Sources in the Earth’s Environment

The magnetic field measured on the ground or in space is the addition of several sources: from flows within the Earth’s core to electric currents in distant regions of the magnetosphere. Properly separating and characterizing these sources requires appropriate observations, both ground-based and space-based. In the present paper, we review the existing observational infrastructure, from magnetic observatories and magnetometer arrays on the ground to satellites in low-Earth (Swarm) and highly elliptical (Cluster) orbits. We also review the capability of SuperDARN to provide polar ionospheric convection patterns supporting magnetic observations. The past two decades have been marked by exciting new developments in all observation types. We review these developments, focusing on how they complement each other and how they have led or could lead in the near future to improved separation and modeling of the geomagnetic sources.