Northward Interplanetary Magnetic Field Research Articles

Transport Path of Cold‐Dense Plasmas in the Dusk Magnetotail Plasma Sheet: MMS Observations

AbstractThe near‐Earth plasma sheet becomes cold and dense under northward interplanetary magnetic field (IMF) condition, which suggests efficient solar wind plasma entry into the magnetosphere across the magnetopause for northward IMF and a possible contribution of ionospheric oxygen ion outflow. The cold and dense characteristics of the plasma sheet are more evident in the magnetotail flank regions that are the interface between cold solar wind plasma and hot magnetospheric plasma. Several physical mechanisms have been proposed to explain the solar wind plasma entry across the magnetopause and resultant formation of the cold‐dense plasma sheet (CDPS) in the tail flank regions. However, the transport path of the cold‐dense plasma inside the magnetotail has not been understood yet. Here, we present a case study of the CDPS in the dusk magnetotail by magnetospheric multiscale (MMS) spacecraft under strongly northward IMF and high‐density solar wind conditions. The ion distribution function consists of high‐ and low‐energy components, and the low‐energy one intermittently shows energy dispersion in the directions parallel and antiparallel to the local magnetic field. The time‐of‐flight analysis of the energy‐dispersed low‐energy ions suggests that these ions originate in the region farther down the tail, move along the magnetic field toward the ionosphere and then come back to the magnetotail by the mirror reflection. The pitch‐angle dispersion analysis gives consistent results on the traveling time and path length of the energy‐dispersed ions. Based on these observations, we discuss possible generation mechanisms of the energy‐dispersed structure of the low‐energy ions during the northward IMF.

Multi-scale evolution of Kelvin–Helmholtz waves at the Earth's magnetopause during southward IMF periods

At the Earth's low-latitude magnetopause, the Kelvin–Helmholtz instability (KHI), driven by the velocity shear between the magnetosheath and magnetosphere, has been frequently observed during northward interplanetary magnetic field (IMF) periods. However, the signatures of the KHI have been much less frequently observed during southward IMF periods, and how the KHI develops under southward IMF has been less explored. Here, we performed a series of realistic 2D and 3D fully kinetic simulations of a KH wave event observed by the Magnetospheric Multiscale (MMS) mission at the dusk-flank magnetopause during southward IMF on September 23, 2017. The simulations demonstrate that the primary KHI bends the magnetopause current layer and excites the Rayleigh–Taylor instability (RTI), leading to penetration of high-density arms into the magnetospheric side. This arm penetration disturbs the structures of the vortex layer and produces intermittent and irregular variations of the surface waves which significantly reduces the observational probability of the periodic KH waves. The simulations further demonstrate that in the non-linear growth phase of the primary KHI, the lower-hybrid drift instability (LHDI) is induced near the edge of the primary vortices and contributes to an efficient plasma mixing across the magnetopause. The signatures of the large-scale surface waves by the KHI/RTI and the small-scale fluctuations by the LHDI are reasonably consistent with the MMS observations. These results indicate that the multi-scale evolution of the magnetopause KH waves and the resulting plasma transport and mixing as seen in the simulations may occur during southward IMF.

Test Particle Simulation of Solar Wind Transport into the Magnetosphere during Northward IMF

以ACE卫星实时观测数据驱动的全球磁流体模拟为背景场，选取2003年10月22－24日行星际磁场（IMF）持续北向的事件，使用试验粒子方法，对太阳风粒子向磁层输运的过程进行模拟研究，分析北向IMF下太阳风粒子注入磁层过程中粒子在磁层内的空间分布和时间演化特征。IMF北向期间，进入环电流区域的粒子在晨侧区域的密度大于昏侧，且晨侧的粒子分布范围更广。背阳面磁鞘中的太阳风粒子可以通过低纬边界层进入磁层，但很难通过南北侧磁层顶进入磁层。进入磁尾的太阳风粒子聚集形成冷而密的等离子体片（CDPS），模拟中CDPS的空间分布和密度大小与观测数据符合。在IMF长时间北向期间，磁尾的粒子数量呈现随时间增长的趋势，并存在约20 min的小幅度准周期变化和约5~6 h的较大幅度的准周期变化。

Transpolar Arcs: Seasonal Dependence Identified by an Automated Detection Algorithm

AbstractTranspolar arcs (TPAs) are auroral features that occur polewards of the main auroral oval suggesting that the magnetosphere has acquired a complicated magnetic topology. They are primarily a northward interplanetary magnetic field (IMF) auroral phenomenon, and their formation and evolution have no single explanation that is unanimously agreed upon. An automated detection algorithm has been developed to detect the occurrence of TPAs in UV images captured from the Special Sensor Ultraviolet Spectrographic Imager (SSUSI) instrument onboard the Defense Meteorological Satellite Program (DMSP) spacecraft, in order to further study their occurrence. Via this detection algorithm TPAs are identified as a peak in the average radiance intensity poleward of 12.5° colatitude, in two or more of the wavelengths/bands sensed by SSUSI. Using the detection algorithm for the years 2010 to 2016, over 5000 images containing TPAs are identified. The occurrence of these TPAs shows a seasonal dependence, with more arcs being visible in the winter hemisphere. The orbital plane of DMSP has been investigated as a possible explanation of the dependences in the results of the detection algorithm. For the spacecraft of interest this leads to a preferential observation of the northern hemisphere with the detection algorithm missing TPAs in the southern hemisphere around 01–06 UT. No seasonal bias has been found for these spacecraft. We discuss the ramifications of these findings in terms of proposed TPA generation mechanisms and suggest reasons for the seasonal dependence including it being a reflection of probability of seeing TPAs due to visibility.

The Structure of the Cusp Diamagnetic Cavity and Test Particle Energization in the GAMERA Global MHD Simulation

AbstractElectrons with energies ≥40 keV can be found at low density in many different regions of Earth's magnetosphere. A litany of fundamental questions in space physics have focused on the acceleration mechanism of these particles, given that the sources of plasma are the relatively cool ionosphere and solar wind (∼1–100s eV). Upgraded global solar wind‐magnetosphere simulations which can resolve mesoscale dynamics have the ability to enhance our understanding of these high energy particles. This is because the energization of particles often takes the form of a sequence of discrete steps, potentially occurring in different regions of the magnetosphere and due to both meso‐ and global‐scale processes. First, brief results are presented from the Grid Agnostic MHD for Extended Research Applications (GAMERA) global simulation on the structure of the cusp diamagnetic cavity for northward and southward IMF. Then, the Conservative Hamiltonian Integrator for Magnetospheric Particles (CHIMP) framework, with both guiding center and full Lorentz integrators, evolves necessary parameters such as the energy and pitch angle of electron test particles to investigate particle acceleration inside the cavity, as well as the ultimate fate of electrons accelerated inside the cavity. The simulation shows that particles can gain ≥ 10 keV inside the cavity and subsequently leak into the magnetosheath or onto dipolar field lines where they execute different types of bounce motion. The distribution of test particles initialized inside the cavity is compared with Magnetospheric Multi‐Scale (MMS) observations.

Three‐Dimensional Global Hybrid Simulations of High Latitude Magnetopause Reconnection and Flux Ropes During the Northward IMF

AbstractWhen the interplanetary magnetic field (IMF) is northward, magnetic reconnection between the IMF and the geomagnetic field can occur at the high latitude magnetopause, which allows energy transfer from the solar wind into Earth's magnetosphere. In this letter, by using three‐dimensional global hybrid simulations, we find that during the northward IMF, high latitude magnetic reconnection both poleward and equatorward of the cusp can occur almost simultaneously. High latitude magnetopause flux ropes (HLMFRs) with four topologies of magnetic field lines can be formed by multiple X‐line reconnection. At the center of the HLMFRs, there is a decrease in the surrounding magnetic field magnitude (weak core field) and an increase in parallel temperature. When the IMF is purely northward, the HLMFRs are located at the noon‐midnight meridian plane. When the IMF has a positive component, the HLMFRs in the northern hemisphere shift duskward.

Ion density and phase space density distribution of planetary ions Na+, O+ and He+ in Mercury’s magnetosphere

Photo-ionization of Mercury’s tenuous exosphere contributes to the heavy ion population in the Hermean environment. Observations with the MESSENGER Fast Imaging Plasma Spectrometer (FIPS) have revealed the ion density and spatial distribution of the three most abundant planetary ions or ion groups around Mercury: The Na+-group (mass-per-charge ratio m/q=21–30amu/e), O+-group (m/q=16–20amu/e) and He+. We developed a test-particle model coupled to a neutral exosphere model and two different models of the magnetosphere to simulate the ion density distribution of Na+, He+ and O+. We compare the modeled ion density distribution at aphelion for northward interplanetary magnetic field (IMF) with FIPS observations from the entire orbital phase (23 March 2011 to 30 April 2015). Our model reproduces several observed features but the average ion density is up to 18x too high. However, we find that the discrepancy is less than 3x for other solar wind and exosphere conditions. Comparison with previous simulation studies of the Na+ ion density and magnetic field line resonance observations give an average Na+ density which is on the same order as our estimate. Finally, we model the phase space density (PSD) distribution in four different regions. We find that in three out of four regions only a fraction of the PSD distribution can typically be observed by FIPS. This is mainly due the obstruction of the field-of-view caused by the spacecraft’s sun shield, which blocks plasma with a high vx/vz ratio from entering the instrument.

Drift Orbit Bifurcations and Cross‐Field Transport in the Outer Radiation Belt: Global MHD and Integrated Test‐Particle Simulations

AbstractEnergetic particle fluxes in the outer magnetosphere present a significant challenge to modeling efforts as they can vary by orders of magnitude in response to solar wind driving conditions. In this study, we demonstrate the ability to propagate test particles through global magnetohydrodynamic (MHD) simulations to a high level of precision and use this to map the cross‐field radial transport associated with relativistic electrons undergoing drift orbit bifurcations (DOBs). The simulations predict DOBs primarily occur within an Earth radius of the magnetopause loss cone and appear significantly different for southward and northward interplanetary magnetic field orientations. The changes to the second invariant are shown to manifest as a dropout in particle fluxes with pitch angles close to and indicate DOBs are a cause of butterfly pitch angle distributions within the night‐time sector. The convective electric field, not included in previous DOB studies, is found to have a significant effect on the resultant long‐term transport, and losses to the magnetopause and atmosphere are identified as a potential method for incorporating DOBs within Fokker‐Planck transport models.

Hot Plasma in the Magnetotail Lobes Shows Characteristics Consistent With Closed Field Lines Trapped in the Lobes

AbstractWe examine the magnetotail using data from the Hot Ion Analyzer on Cluster 1 during 2001–2009. We develop and utilize an algorithm in order to identify times during which Cluster 1 is in the magnetotail lobe but observes plasma, which is hotter than our expectations of the lobe. We analyze the prevailing Interplanetary Magnetic Field (IMF) conditions for our algorithm and a reference algorithm (with no particle energy criteria) and find that the periods we select are, on average, nT more toward northward IMF. Examining the temperature in the magnetotail for our periods shows that the morphology of the average temperature is consistent with the Milan et al. (2005, https://doi.org/10.1029/2004JA010835) model of a magnetotail structure during northward IMF, in which closed field lines are prevented from convecting to the dayside, causing them and the plasma trapped on them to protrude into the magnetotail lobes. We also find evidence that of our identified periods may be driven by direct entry into the magnetosphere from the solar wind.

Observational Evidence of Transient Lobe Reconnection Triggered by Sudden Northern Enhancement of IMF Bz

AbstractIn general, lobe reconnection occurs under northward interplanetary magnetic field (IMF) Bz. However, what process can trigger lobe reconnection has not been fully understood. Using observations from SuperDARN radar and Defense Meteorological Satellite Program (DMSP) spacecraft, we found that (a) short‐term sunward ionospheric flow bursts observed by SuperDARN poleward of the cusp showed one‐to‐one correspondent with the sudden increase of the IMF Bz, (b) the sunward flow bursts observed by SurperDARN were associated with sunward ion drifts identified from the DMSP satellite, and (c) a cusp auroral spot, together with an inverse ion energy dispersion, was observed in association with one of the flow bursts. We suggest that these observations provide evidence that the lobe reconnections can be triggered by a sudden increase of the IMF Bz component. What’s more, we found that the reconnection signatures disappeared quickly after the IMF Bz enhancement being over, which indicates that the lobe reconnection triggered by the sudden increase of the IMF Bz is a transient process.

A Survey of Dense Low Energy Ions in Earth's Outer Magnetosphere: Relation to Solar Wind Dynamic Pressure, IMF, and Magnetospheric Activity.

The properties of cold, dense, low energy (<150 eV) ions within Earth's magnetosphere between 6 and 14 RE distance are examined using data sampled by Time History of Events and Macroscale Interactions during Substorms spacecraft during a new low‐energy plasma mode that operated from June 2016 to July 2017. These ions are a persistent feature of the magnetosphere during enhanced solar wind dynamic pressure and/or magnetospheric activity. These ions have densities ranging from 0.5 to tens of cm−3, with a mean of ∼1 cm−3 and temperatures of a few to tens of eV, with a mean of ∼13 eV. These yield cold to hot ion density and temperature ratios that are 4.4 and 4×10−3, respectively. Comparisons reveal that the cold ion densities are positively correlated with solar wind dynamic pressure. These ions are organizable, according to their pitch‐angle distribution, as being transverse/convection dominated (interpreted as plume plasma) or magnetic field‐aligned (FAL) (uni‐ or bi‐directional characteristic of ion outflow or cloak plasma). Transverse ions preferentially occur in the prenoon to dusk sectors during sustained active magnetospheric conditions driven by enhanced solar wind dynamic pressure under southward Bz and westward By IMF orientations. Transverse ion velocities (reaching several tens of km/s) have a westward directed tendency with a slight radially outward preference. In contrast FAL ions preferentially occur from morning to noon during northward IMF orientations, enhanced solar wind dynamic pressure, and quiet magnetospheric conditions within several hours after moderate to strong activity. The FAL ions also have bulk velocities ≲30 km/s, with an eastward and radially outward tendency.

Solar Wind Entry Into Midtail Current Sheet via Low‐Latitude Mantle Under Dominant IMF By: ARTEMIS Observation

AbstractIt is expected from global simulations that the low‐latitude mantle may be an important pathway for the solar wind entry into the tail current sheet when interplanetary magnetic field (IMF) By is dominant, which is different from the pathways for northward or southward IMF dominant conditions. To evaluate this pathway and the predicted plasma asymmetries between the southern and northern lobes resulting from the low‐latitude mantle, we analyze 222 current sheet crossing events observed in the midtail. Each of the events is selected to have the spacecraft observe both lobes within 20 min. For the majority of the events, the different north‐south asymmetries of the lobe density observed on the dawnside and duskside corresponding to different IMF By directions are consistent with the appearance of the low‐latitude mantle plasma. No significant north‐south asymmetry in the lobe magnetic field strength is found so that the density asymmetry also results in north‐south asymmetric lobe Alfvén speed. Within the tail current sheet, the cross‐tail profiles show that density can be higher, but temperatures and peak flow speed lower, near the flanks than near midnight. Magnitudes of these current sheet plasma parameters are found to positively correlate with the values of the asymmetric lobe parameters concurrently observed, indicating that the low‐latitude mantle can be a particle source for the current sheet. Also, the asymmetric lobe parameters are positively correlated with some solar wind parameters. These good correlations support the expectation that the pathway through the low‐latitude mantle becomes more important as the IMF By becomes more dominant.

Importance of the Northward IMF for the Quasistatic Mesoscale Field‐Aligned Currents Embedded in the Diminished Region 1/2 Current System in the Dusk Sector

AbstractTo understand the features of the quasistatic field‐aligned currents (FACs) consisting of multiple mesoscale (∼10–100 km) upward and downward FAC regions in the duskside auroral oval, we examined the magnetic field data obtained through the constellation measurements of Swarm satellites for a duration of more than three years. We introduced a method of automated event identification and took the events in 577 satellite orbits that pass through the high‐latitude part of the 14–18 magnetic local time auroral oval. The results of the analysis reveal that the occurrence ratio of the FAC events increases with the IMF BZ, and that the event can be detected at a ratio exceeding 20% for BZ greater than 1 nT. This indicates that the quasistatic mesoscale FACs in the duskside sector are pertinent to a northward IMF condition and that they are not a simple remnant of the diminished Region 1. The results also show that the FAC density tends to increase with the solar wind proton density, implying that the latter is directly associated with FAC generation. The FAC events can occur in a wide range of solar zenith angles, that is, 65–135°, indicating that whether the ionosphere is sunlit or dark is not crucial for the appearance of the event. These results strongly suggest that multiple mesoscale FACs are produced in the low‐latitude boundary layer through a mechanism related to solar wind plasma entry processes that can be more easily attained as the northward component of the IMF increases.

Even moderate geomagnetic pulsations can cause fluctuations of &amp;lt;i&amp;gt;fo&amp;lt;/i&amp;gt;F2 frequency of the auroral ionosphere

Abstract. The ionosonde at the Sodankylä Geophysical Observatory (SOD; 67∘ N, 27∘ E; Finland) routinely performs vertical sounding once per minute which enables the study of fast ionospheric variations at a frequency of the long-period geomagnetic pulsations Pc5–6/Pi3 (1–5 mHz). Using the ionosonde data from April 2014–December 2015 and colocated geomagnetic measurements, we have investigated a correspondence between the magnetic field pulsations and variations of the critical frequency of radio waves reflected from the ionospheric F2 layer (foF2). For this study, we have developed a technique for automated retrieval of the critical frequency of the F2 layer from ionograms. As a rule, the Pc5–6/Pi3 frequency band fluctuations in foF2 were observed at daytime during quiet or moderately disturbed space weather conditions. In most cases (about 80 %), the coherence between the foF2 variations and geomagnetic pulsations was low. However in some cases (specified as “coherent”) the coherence was as large as γ2≥0.5. The following conditions are favorable for the occurrence of coherent cases: enhanced auroral activity (6 h maximal auroral electrojet (AE) ≥800 nT), high solar wind speed (V&gt;600 km/s), fluctuating solar wind pressure and northward interplanetary magnetic field. In the cases when the coherence was higher at shorter periods of oscillations, the magnetic pulsations demonstrated features typical for the Alfvén field line resonance.

Transpolar Arcs During a Prolonged Radial Interplanetary Magnetic Field Interval

AbstractTranspolar arcs (TPAs) are believed to predominantly occur under northward interplanetary magnetic field (IMF) conditions with their hemispheric asymmetry controlled by the Sun‐Earth (radial) component of the IMF. In this study, we present observations of TPAs that appear in both the northern and southern hemispheres even during a prolonged interval of radially oriented IMF. The Defense Meteorological Satellite Program (DMSP) F16 and the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) satellites observed TPAs on the dawnside polar cap in both hemispheres (one TPA structure in the southern hemisphere and two in the northern hemisphere) during an interval of nearly earthward‐oriented IMF on October 29, 2005. The southern hemisphere TPA and one of the northern hemisphere TPAs are associated with electron and ion precipitation and mostly sunward plasma flow (with shears) relative to their surroundings. Meanwhile, the other TPA in the northern hemisphere is associated with an electron‐only precipitation and antisunward flow relative to its surroundings. Our observations indicate the following: (a) the TPA formation is not limited to northward IMF conditions; (b) the TPAs can be located on both closed field lines rooted in the polar cap of both hemispheres and open field lines connected to the northward field lines draped over one hemisphere of the magnetopause. We believe that the TPAs presented here are the result of both indirect and direct processes of solar wind energy transfer to the high‐latitude ionosphere.

Observations of Closed Magnetic Flux Embedded in the Lobes During Periods of Northward IMF

AbstractThe high latitude, lobe regions of the magnetosphere are often assumed to contain cool, low energy plasma populations. However, during periods of northward Interplanetary Magnetic Field, energetic plasma populations have occasionally been observed. We present three cases when Cluster observed uncharacteristically “hot” plasma populations in the lobe. For two of the three events, we present simultaneous observations of the plasma sheet observed by Double Star. The similarity between the plasma in the lobe and the plasma sheet suggests that the mechanism that produces plasma at high latitudes is likely to be tail reconnection, resulting in a trapped “wedge” of closed flux about the noon‐midnight meridian. Complementary images from Imager for Magnetopause to Aurora Global Exploration and DMSP/Special Sensor Ultraviolet Spectrographic Imager show that transpolar arcs, which form in each event in at least one hemisphere, directly intersect the footprint of the Cluster spacecraft in all three events. The intersection of the Cluster footprint with the transpolar arcs is synchronous with the observation of the energetic plasma populations in the lobe. This further supports the conclusion that it is likely this energetic plasma observed in the high latitude lobe regions of magnetosphere is on closed field lines.

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.

Magnetohydrodynamic Turbulence in the Earth’s Magnetotail From Observations and Global MHD Simulations

Magnetohydrodynamic (MHD) turbulent flows are found in the solar wind, the magnetosheath and the magnetotail plasma sheet. In this paper, we review both observational and theoretical evidence for turbulent flow in the magnetotail. MHD simulations of the global magnetosphere for southward interplanetary magnetic field (IMF) exhibit nested vortices in the earthward outflow from magnetic reconnection that are consistent with turbulence. Similar simulations for northward IMF also exhibit enhanced vorticity consistent with turbulence. These result from Kelvin-Helmholtz (KH) instabilities. However, the turbulent flows association with reconnection fill much of the magnetotail while the turbulent flows associated with the KH instability are limited to a smaller region near the magnetopause. Analyzing turbulent flows in the magnetotail is difficult because of the limited extent of the tail and because the flows there are usually sub-magnetosonic. Observational analysis of turbulent flows in the magnetotail usually assume that the Taylor frozen-in-flow hypothesis is valid and compare power spectral density vs. frequency with spectral indices derived for fluid turbulence by Kolmogorov in 1941. Global simulations carried out for actual magnetospheric substorms in the tail enable the results of the simulations to be compared directly with observed power spectra. The agreement between the two techniques provides confidence that the plasma sheet plasma is actually turbulent. The MHD results also allow us to calculate the power vs. wave number; results that also support the idea that the tail is turbulent.

Effects of the IMF Direction on Atmospheric Escape From a Mars‐like Planet Under Weak Intrinsic Magnetic Field Conditions

AbstractDirection of the upstream interplanetary magnetic field (IMF) significantly changes the magnetospheric configuration, influencing the atmospheric escape mechanism. This paper investigates effects of IMF on the ion escape mechanism from a Mars‐like planet that has a weak dipole magnetic field directing northward on the equatorial surface. The northward (parallel to the dipole at subsolar), southward (antiparallel), and Parker‐spiral IMFs under present solar wind conditions are compared based on multispecies magnetohydrodynamics simulations. In the northward IMF case, molecular ions escape from the high‐latitude lobe reconnection region, where ionospheric ions are transported upward along open field lines. Atomic oxygen ions originating either in the ionosphere or oxygen corona escape through a broader ring‐shaped region. In the southward IMF case, the escape flux of heavy ions increases significantly and has peaks around the equatorial dawn and dusk flanks. The draped IMF can penetrate into the subsolar ionosphere by erosion, and the IMF becomes mass‐loaded as it is transported through the dayside ionosphere. The mass‐loaded draped IMF is carried to the tail, contributing to ion escape. The escape channels in the northward and southward IMF cases are different from those in the Parker‐spiral IMF case. The escape rate is the lowest in the northward IMF case and comparable in the Parker‐spiral and southward IMF cases. In the northward IMF case, a weak intrinsic dipole forms a magnetosphere configuration similar to that of Earth, quenching the escape rate, while the Parker‐spiral and southward IMFs cause reconnection and erosion, promoting ion escape from the upper atmosphere.

A space hurricane over the Earth\u2019s polar ionosphere

In Earth’s low atmosphere, hurricanes are destructive due to their great size, strong spiral winds with shears, and intense rain/precipitation. However, disturbances resembling hurricanes have not been detected in Earth’s upper atmosphere. Here, we report a long-lasting space hurricane in the polar ionosphere and magnetosphere during low solar and otherwise low geomagnetic activity. This hurricane shows strong circular horizontal plasma flow with shears, a nearly zero-flow center, and a coincident cyclone-shaped aurora caused by strong electron precipitation associated with intense upward magnetic field-aligned currents. Near the center, precipitating electrons were substantially accelerated to ~10 keV. The hurricane imparted large energy and momentum deposition into the ionosphere despite otherwise extremely quiet conditions. The observations and simulations reveal that the space hurricane is generated by steady high-latitude lobe magnetic reconnection and current continuity during a several hour period of northward interplanetary magnetic field and very low solar wind density and speed.