JGR:Space physics

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Wiley Online Library : Journal of Geophysical Research: Space Physics
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Thu, 03/15/2018 - 16:28
Abstract

No abstract is available for this article.

Observation and Numerical Simulation of Cavity Mode Oscillations Excited by an Interplanetary Shock

Thu, 03/15/2018 - 15:56
Abstract

Cavity mode oscillations (CMOs) are basic magnetohydrodynamic eigenmodes in the magnetosphere predicted by theory and are expected to occur following the arrival of an interplanetary shock. However, observational studies of shock-induced CMOs have been sparse. We present a case study of a dayside ultralow-frequency wave event that exhibited CMO properties. The event occurred immediately following the arrival of an interplanetary shock at 0829 UT on 15 August 2015. The shock was observed in the solar wind by the Time History of Events and Macroscale Interactions during Substorms-B and -C spacecraft, and magnetospheric ultralow-frequency waves were observed by multiple spacecraft including the Van Allen Probe-A and Van Allen Probe-B spacecraft, which were located in the dayside plasmasphere at L ∼1.4 and L ∼ 2.4, respectively. Both Van Allen Probes spacecraft detected compressional poloidal mode oscillations at ∼13 mHz (fundamental) and ∼26 mHz (second harmonic). At both frequencies, the azimuthal component of the electric field (Eϕ) lagged behind the compressional component of the magnetic field (Bμ) by ∼90°. The frequencies and the Eϕ-Bμ relative phase are in good agreement with the CMOs generated in a dipole magnetohydrodynamic simulation that incorporates a realistic plasma mass density distribution and ionospheric boundary condition. The oscillations were also detected on the ground by the European quasi-Meridional Magnetometer Array, which was located near the magnetic field footprints of the Van Allen Probes spacecraft.

Statistical Study of Nightside Quiet Time Midlatitude Ionospheric Convection

Thu, 03/15/2018 - 15:56
Abstract

Previous studies have shown that F region midlatitude ionospheric plasma exhibits drifts of a few tens of meters per second during quiet geomagnetic conditions, predominantly in the westward direction. However, detailed morphology of this plasma motion and its drivers are still not well understood. In this study, we have used 2 years of data obtained from six midlatitude SuperDARN radars in the North American sector to derive a statistical model of quiet time midlatitude plasma convection between 52° and 58° magnetic latitude (MLAT). The model is organized in MLAT-MLT (magnetic local time) coordinates and has a spatial resolution of 1° × 7 min with thousands of velocity measurements contributing to most grid cells. Our results show that the flow is predominantly westward (20–55 m/s) and weakly northward (0–20 m/s) deep on the nightside but with a strong seasonal dependence such that the flows tend to be strongest and most structured in winter. These statistical results are in good agreement with previously reported observations from Millstone Hill incoherent scatter radar measurements for a single latitude but also show some interesting new features, one being a significant latitudinal variation of zonal flow velocity near midnight in winter. Our analysis suggests that penetration of the high-latitude convection electric fields can account for the direction of midlatitude convection in the premidnight sector, but postmidnight midlatitude convection is dominated by the neutral wind dynamo.

Analysis and Hindcast Experiments of the 2009 Sudden Stratospheric Warming in WACCMX+DART

Thu, 03/15/2018 - 14:08
Abstract

The ability to perform data assimilation in the Whole Atmosphere Community Climate Model eXtended version (WACCMX) is implemented using the Data Assimilation Research Testbed (DART) ensemble adjustment Kalman filter. Results are presented demonstrating that WACCMX+DART analysis fields reproduce the middle and upper atmosphere variability during the 2009 major sudden stratospheric warming (SSW) event. Compared to specified dynamics WACCMX, which constrains the meteorology by nudging towards an external reanalysis, the large-scale dynamical variability of the stratosphere, mesosphere, and lower thermosphere are improved in WACCMX+DART. This leads to WACCMX+DART better representing the downward transport of chemical species from the mesosphere into the stratosphere following the SSW. WACCMX+DART also reproduces most aspects of the observed variability in ionosphere total electron content (TEC) and equatorial vertical plasma drift during the SSW. Hindcast experiments initialized on January 5, 10, 15, 20, and 25 are used to assess the middle and upper atmosphere predictability in WACCMX+DART. A SSW, along with the associated middle and upper atmosphere variability, is initially predicted in the hindcast initialized on January 15, which is ∼10 days prior to the warming. However, it is not until the hindcast initialized on January 20 that a major SSW is forecast to occur. The hindcast experiments reveal that dominant features of the TEC can be forecast ∼10-20 days in advance. This demonstrates that whole atmosphere models that properly account for variability in lower atmosphere forcing can potentially extend the ionosphere-thermosphere forecast range.

Source Energy Spectrum of the 17-05-2012 GLE

Wed, 03/14/2018 - 17:15
Abstract

Among the several GLE (Ground Level Enhancements) that have presumptuously occurred in the period 2012-2015 the 17th May 2012 is that which is more widely accepted to be a GLE, in view of the high number of high latitude Neutron Monitor (NM) stations that have registered it. In spite of the small amplitude, it was the more prominent of the predicted GLE´s of the present decade (Pérez-Peraza & Juarez-Zuñiga, 2015). However, the lack of latitude effect makes it difficult to study the characteristics of this event in the high energy extreme of the spectrum. Nevertheless, several outstanding works have been able to derive observational spectra at the top of the earth atmosphere for this peculiar GLE. Some of these works find that the flow of protons is characterized by two components. Quite a great number of works have been published in relation with observational features obtained with different instrumentation, but the source phenomena, regarding the generation processes and source physical parameters have not been scrutinized. The main goal of this work is to look at such aspects by means of the confrontation of the different approaches of the observational spectra with our analytical theoretical spectra based on stochastic acceleration and Electric field acceleration from reconnection processes. In this way, we derive a set of parameters which characterize the sources of these two GLE components, leading us to propose possible scenarios for the generation of particles in this particular GLE event.

Autocorrelation study of solar wind plasma and IMF properties as measured by the MAVEN spacecraft

Wed, 03/14/2018 - 17:00
Abstract

It has long been a goal of the heliophysics community to understand solar wind variability at heliocentric distances other than 1 AU, especially at ∼1.5 AU not only due to the steepening of solar wind stream interactions outside 1 AU but also the number of missions available there to measure it. In this study, we use 35 months of solar wind and IMF data taken at Mars by the MAVEN spacecraft to conduct an autocorrelation analysis of the solar wind speed, density, and dynamic pressure, which is derived from the speed and density, as well as the IMF strength and orientation. We found that the solar wind speed is coherent, i.e. has an autocorrelation coefficient above 1/e, over roughly 56 hours, while the density and pressure are coherent over smaller intervals of roughly 25 and 20 hours, respectively, and that the IMF strength is coherent over time intervals of approximately 20 hours, while the cone and clock angles are considerably less steady but still somewhat coherent up to time lags of roughly 16 hours. We also found that when the speed, density, pressure, or IMF strength is higher than average, the solar wind or IMF becomes uncorrelated more quickly, while when they are below average, it tends to be steadier. This analysis allows us to make estimates of the values of solar wind plasma and IMF parameters when they are not directly measured, as well as provide an approximation of the error associated with that estimate.

The Identification of Waves at Discrete Frequencies at the Geostationary Orbit: The Role of the Data Analysis Techniques and the Comparison With Solar Wind Observations

Wed, 03/14/2018 - 16:10
Abstract

Following a recent investigation in which we examined the performance of two methods (the Welch method and the multitaper windowing and F test) on the identification of fluctuations of the solar wind dynamic pressure in streams following interplanetary shocks, we extend our analysis to the magnetospheric field fluctuations detected at the geostationary orbit after the occurrence of the related sudden impulses. First, we show that a contamination of the experimental results, dramatic in statistical investigations, might come from the rotation of measurements in the field-aligned coordinates when the field direction is determined, point by point, by the running averages: this procedure creates spurious events at frequencies related to the length of the running average window. These aspects do not appear in a fixed coordinate system, as determined by evaluating the average field vector for the entire interval. In this system, we examined 124 magnetospheric structures following sudden impulses: the Welch method/multitaper windowing and F test agreement in the wave identification and frequency estimate was achieved for ≈50% of events, and some evidence for higher percentages of events occurs at f ≈ 1.5–1.7, f ≈ 2.2–2.4, ≈3.9–4.2, and, more explicitly, at f ≈ 4.2–4.7 mHz. Oscillation modes with the same characteristics at different local times were rarely observed. An analysis of case events reveals that fluctuations of the solar wind pressure may drive magnetospheric fluctuations at the same frequencies; in addition, the manifestation of modes, not appearing in the solar wind, might be related to the magnetospheric compression or to other processes triggered by the shock arrival.

Medium-Scale Traveling Ionospheric Disturbances Observed by Detrended Total Electron Content Maps Over Brazil

Wed, 03/14/2018 - 16:06
Abstract

A ground-based network of Global Navigation Satellite Systems receivers has been used to monitor medium-scale traveling ionospheric disturbances (MSTIDs). MSTIDs were studied using total electron content perturbation maps and keograms over south-southeast of Brazil during the period from December 2012 to February 2016. In total, 826 MSTIDs were observed mainly in daytime, thus presenting median values of horizontal wavelength, period, and horizontal phase velocity of 452 ± 107 km, 24 ± 4 min. and 323 ± 81 m/s, respectively. The direction of propagation varies on the season: during the winter (June–August), the waves preferentially propagated to north-northeast, while in the other seasons the waves propagated to other directions. The anisotropy observed in the MSTID propagation direction could be associated with the region of the gravity wave generation that takes place in the troposphere. We also found that the MSTIDs were observed most frequently during the daytime, between 11 and 15 local time in winter and near to dusk solar terminator (17–19 local time) in the other seasons. Furthermore, the occurrence of MSTIDs was higher in winter. We suggest that atmospheric gravity waves in the thermosphere, mesosphere, and troposphere could play an important role in generating the MSTIDs and the propagation direction may depend on location of the wave sources.

Quantitative Evaluation of Radial Diffusion and Local Acceleration Processes During GEM Challenge Events

Wed, 03/14/2018 - 16:06
Abstract

We simulate the radiation belt electron flux enhancements during selected Geospace Environment Modeling (GEM) challenge events to quantitatively compare the major processes involved in relativistic electron acceleration under different conditions. Van Allen Probes observed significant electron flux enhancement during both the storm time of 17–18 March 2013 and non–storm time of 19–20 September 2013, but the distributions of plasma waves and energetic electrons for the two events were dramatically different. During 17–18 March 2013, the SYM-H minimum reached −130 nT, intense chorus waves (peak Bw ~140 pT) occurred at 3.5 < L < 5.5, and several hundred keV to several MeV electron fluxes increased by ~2 orders of magnitude mostly at 3.5 < L < 5.5. During 19–20 September 2013, the SYM-H remained higher than −30 nT, modestly intense chorus waves (peak Bw ~80 pT) occurred at L > 5.5, and electron fluxes at energies up to 3 MeV increased by a factor of ~5 at L > 5.5. The two electron flux enhancement events were simulated using the available wave distribution and diffusion coefficients from the GEM focus group Quantitative Assessment of Radiation Belt Modeling. By comparing the individual roles of local electron heating and radial transport, our simulation indicates that resonant interaction with chorus waves is the dominant process that accounts for the electron flux enhancement during the storm time event particularly near the flux peak locations, while radial diffusion by ultralow-frequency waves plays a dominant role in the enhancement during the non–storm time event. Incorporation of both processes reasonably reproduces the observed location and magnitude of electron flux enhancement.

The Role of Localized Compressional Ultra-low Frequency Waves in Energetic Electron Precipitation

Wed, 03/14/2018 - 16:02
Abstract

Typically, ultra-low frequency (ULF) waves have historically been invoked for radial diffusive transport leading to acceleration and loss of outer radiation belt electrons. At higher frequencies, very low frequency waves are generally thought to provide a mechanism for localized acceleration and loss through precipitation into the ionosphere of radiation belt electrons. In this study we present a new mechanism for electron loss through precipitation into the ionosphere due to a direct modulation of the loss cone via localized compressional ULF waves. We present a case study of compressional wave activity in tandem with riometer and balloon-borne electron precipitation across keV-MeV energies to demonstrate that the experimental measurements can be explained by our new enhanced loss cone mechanism. Observational evidence is presented demonstrating that modulation of the equatorial loss cone can occur via localized compressional wave activity, which greatly exceeds the change in pitch angle through conservation of the first and second adiabatic invariants. The precipitation response can be a complex interplay between electron energy, the localization of the waves, the shape of the phase space density profile at low pitch angles, ionospheric decay time scales, and the time dependence of the electron source; we show that two pivotal components not usually considered are localized ULF wave fields and ionospheric decay time scales. We conclude that enhanced precipitation driven by compressional ULF wave modulation of the loss cone is a viable candidate for direct precipitation of radiation belt electrons without any additional requirement for gyroresonant wave-particle interaction. Additional mechanisms would be complementary and additive in providing means to precipitate electrons from the radiation belts during storm times.

The Influence of IMF By on the Bow Shock: Observation Result

Wed, 03/14/2018 - 16:02
Abstract

In this study we use the bow shock crossings contained in the Space Physics Data Facility database, collected by four spacecraft (IMP 8, Geotail, Magion-4, and Cluster1) to analyze the effect of the interplanetary magnetic field (IMF) By component on the bow shock position and shape. Although the IMF Bz component is usually considered much more geoeffective than By, we find that the dayside bow shock is more responsive to the eastward component of the IMF than the north-south one. We believe that the explanation lies in the changes that the Bz component induces on the magnetopause location and shape, which largely compensate the corresponding changes in the dayside bow shock location. In the tail, we find that the bow shock cross section is elongated roughly in the direction perpendicular to the IMF direction, which agrees with earlier modeling studies.

The Radial Propagation Characteristics of the Injection Front: A Statistical Study Based On BD-IES and Van Allen Probes Observations

Wed, 03/14/2018 - 16:01
Abstract

Electron flux measurements outside geosynchronous orbit (GSO) obtained by the BeiDa Imaging Electron Spectrometer instrument on board a 55° inclined GSO satellite and inside GSO obtained by the Van Allen Probes are analyzed to investigate the temporal and spatial evolutions of the substorm injection region. In 1 year data started from October 2015, 63 injection events are identified. First, our study shows that the injection signatures can be detected in a large radial extent in one single event, for example, from L ∼ 4.1 to L ∼ 9.3. Second, injection onset times are derived from the energy dispersion of particle injection signatures of each satellite. The difference of the onset times among satellites reveals that the injection boundary, termed as “injection front” in this paper, can propagate both earthward and tailward with a speed varying from a few km/s to ∼100 km/s. Third, evolutions of the upper-cutoff magnetic moments (μuc) of injected electrons are analyzed, upon which the injection events are classified into two categories. In one category, the μuc observed by two radially separated satellites are equal taking into account the error caused by the finite width of energy channels, whereas in the other category, μuc at lower L shells are smaller than those at higher L shells.

Violation of Field Line Conservation and Associated Spatial Scales in Particle-in-Cell Simulations and MMS Data

Tue, 03/13/2018 - 14:55
Abstract

For the first time, space flight technology exists to detect, in situ, violation of magnetic field line conservation. The violation of magnetic line conservation on scales smaller than the system size is a necessary and sufficient condition for finite magnetic field reconnection. We demonstrate that violation of line conservation produces a detectable, structured signature both in particle-in-cell simulations of reconnection and in data from the Magnetospheric Multi-Scale mission. In particle-in-cell simulations of asymmetric reconnection, the quantity—which we call M—that identifies this violation achieves significant values in electron skin depth-scale layers that extend away from the separator, with higher values emerging on the low-density, high-magnetic-field side of the current sheet. At the separator, M owes largely to perpendicular gradients in the parallel electric field, while it attains its highest values away from the separator in dispersed, layered structures associated with gradients in the perpendicular nonideal electric field and electron transport. Sub-ion scale bipolar forms of the quantity also appear further from the separator. In two MMS burst data intervals detecting the electron diffusion region, we find that M exceeds measurement uncertainties both at the separator and near the separatrices. One interval has highly sheared reconnecting fields and the other a stronger guide field. For one event, we determine the location and scale of M and the inner electron diffusion region relative to electron outflows and the magnetic separatrices. The measure can therefore serve as a potent diagnostic for magnetic reconnection in space measurements.

Response of Jupiter's Aurora to Plasma Mass Loading Rate Monitored by the Hisaki Satellite During Volcanic Eruptions at Io

Tue, 03/13/2018 - 14:51
Abstract

The production and transport of plasma mass are essential processes in the dynamics of planetary magnetospheres. At Jupiter, it is hypothesized that Io's volcanic plasma carried out of the plasma torus is transported radially outward in the rotating magnetosphere and is recurrently ejected as plasmoid via tail reconnection. The plasmoid ejection is likely associated with particle energization, radial plasma flow, and transient auroral emissions. However, it has not been demonstrated that plasmoid ejection is sensitive to mass loading because of the lack of simultaneous observations of both processes. We report the response of plasmoid ejection to mass loading during large volcanic eruptions at Io in 2015. Response of the transient aurora to the mass loading rate was investigated based on a combination of Hisaki satellite monitoring and a newly developed analytic model. We found that the transient aurora frequently recurred at a 2–6 day period in response to a mass loading increase from 0.3 to 0.5 t/s. In general, the recurrence of the transient aurora was not significantly correlated with the solar wind, although there was an exceptional event with a maximum emission power of ~10 TW after the solar wind shock arrival. The recurrence of plasmoid ejection requires the precondition that an amount comparable to the total mass of magnetosphere, ~1.5 Mt, is accumulated in the magnetosphere. A plasmoid mass of more than 0.1 Mt is necessary in case that the plasmoid ejection is the only process for mass release.

Influence of the IMF cone angle on invariant latitudes of polar region footprints of FACs in the magnetotail: Cluster observation

Tue, 03/13/2018 - 14:41
Abstract

The influence of the interplanetary magnetic field (IMF) cone angle θ (the angle between the IMF direction and the Sun-Earth line) on the invariant latitudes (ILATs) of the footprints of the field-aligned currents (FACs) in the magnetotail has been investigated. We performed a statistical study of 542 FAC cases observed by the four Cluster spacecraft in the northern hemisphere. The results show that there are almost no FACs when the IMF cone angle is less than 10°, and there are indications of the FACs in the PSBLs being weak under the radial IMF conditions. The footprints of the large FAC (>10 nA/m2) cases are within ILATs <71° and mainly within IMF cone angles θ>60°, which implies that the footprints of the large FACs mainly expand equatorward with large IMF cone angle. The equatorward boundary of the FAC footprints in the polar region decreases with increasing IMF cone angle (and has a better correlation for northward IMF), which shows that the IMF cone angle plays an important controlling role in FAC distributions in the magnetosphere-ionosphere coupling system. There is almost no correlation between the poleward boundary and the IMF cone angle for both northward and southward IMF. This is because the poleward boundary movement is limited by an enhanced lobe magnetic flux. This is the first time a correlation between FAC foot prints in the polar region and IMF cone angles has been determined.

Coordinated satellite observations of the Very Low Frequency transmission through the ionospheric D-layer at low latitudes, using broadband radio emissions from lightning

Tue, 03/13/2018 - 14:30
Abstract

Both ray theory and full-wave models of Very Low Frequency transmission through the ionospheric D-layer predict that the transmission is greatly suppressed near the geomagnetic equator. We use data from the low-inclination Communication/Navigation Outage Forecast System satellite to test this semi-quantitatively, for broadband Very Low Frequency emissions from lightning. Approximate ground-truthing of the incident wavefields in the Earth Ionosphere Waveguide is provided by the World Wide Lightning Location Network. Observations of the wavefields at the satellite are provided by the Vector Electric Field Instrument aboard the satellite. The data set comprises whistler observations with the satellite at magnetic latitudes < 26 deg. Thus our conclusions, too, must be limited to the near-equatorial region, and are not necessarily predictive of mid-latitude whistler properties.

We find that in most broadband recordings of radio waves at the satellite, very few of the lightning strokes result in a detectable radio pulse at the satellite. However, in a minority of the recordings, there is enhanced transmission of Very Low Frequency lightning emissions through the D-layer, at a level exceeding model predictions by at least an order-of-magnitude. We show that kilometric-scale D-layer irregularities may be implicated in the enhanced transmission. This observation of sporadic enhancements at low magnetic latitude, made with broadband lightning emissions, is consistent with an earlier review of D-layer transmission for transmission from powerful man-made radio beacons.

4D-var estimation of North Korean rocket exhaust emissions into the ionosphere

Tue, 03/13/2018 - 13:10
Abstract

We have developed a four dimensional variation data assimilation technique (4D-var), and utilized it to reconstruct 3-dimensional images of the ionospheric hole created during Kwangmyongsong-4 rocket launch. Kwangmyongsong-4 was launched southwards from North Korea Sohae space center (124.7o E, 39.6o N) at 00:30 UT on February 7, 2016. The data assimilated were GPS-TEC (Global Positioning System - Total Electron Content) from the South Korean GPS-receiver network. Due to lack of publicized information about Kwangmyongsong-4, the rocket was assumed to inherit its technology from previous launches (Taepodong -2). The created ionospheric hole was assumed to be made by neutral molecules, water (H2O) and hydrogen (H2), deposited in exhaust plumes. The dispersion model was developed based on advection and diffusion equation, and a simple asymmetric diffusion model assumed. From the analysis, using the adjoint technique, we estimated an ionospheric hole with the largest depletion existing around 6-7 mins after launch and gradually recovering within ~30 minutes. These results are in agreement with temporal TEC analyses of the same event from previous studies. Furthermore, Kwangmyongsong-4 second stage exhaust emissions were estimated as 1.9  ×  1026s−1 of which 40 % was H2 and the rest H2O.

On the Occurrence of Afternoon Counter Electrojet Over Indian Longitudes During June Solstice in Solar Minimum

Mon, 03/12/2018 - 20:10
Abstract

Studies made earlier using ground-based observations of geomagnetic field over the Indian longitudes revealed that the occurrence of equatorial counter electrojet (CEJ) events in afternoon hours is more frequent during June solstice (May-June-July-August) in solar minimum than in other periods. In general, the June solstice solar minimum CEJ events occur between 1500 local time (LT) and 1800 LT with peak strength of about −10 nT at around 1600 LT. In order to understand the frequent occurrence of these CEJ events, an investigation is carried out using an equatorial electrojet model (Anandarao, 1976, https://doi.org/10.1029/GL003i009p00545) and the empirical vertical drift model by Fejer et al. (2008, https://doi.org/10.1029/2007JA012801). The strength, duration, peak value, and the occurrence time of CEJ obtained using electrojet model match remarkably well with the corresponding observation of average geomagnetic field variations. The occurrence of CEJ is found to be due to solar quiet (Sq) electric field in the westward direction which is manifested as downward drift in Fejer et al. (2008, https://doi.org/10.1029/2007JA012801) model output during 1500–1800 LT. Further, the occurrence of afternoon reversal of Sq electric field in this season is shown to be consistent with earlier studies from Indian sector. Therefore, this investigation provides explicit evidence for the role of westward Sq electric field on the generation of afternoon CEJ during June solstice in solar minimum periods over the Indian sector indicating the global nature of these CEJ events.

Intervals of intense energetic electron beams over Jupiter's poles

Mon, 03/12/2018 - 18:15
Abstract

Juno's Jupiter Energetic particle Detector Instrument (JEDI) often detects energetic electron beams over Jupiter's polar regions. In this paper, we document a subset of intense magnetic field-aligned beams of energetic electrons moving away from Jupiter at high magnetic latitudes both north and south of the planet. The number fluxes of these beams are often dominated by electrons with energies above about 1 MeV. These very narrow beams can create broad angular responses in JEDI with unique signatures in the detector count rates, probably because of >10 MeV electrons. We use these signatures to identify the most intense beams. These beams occur primarily above the swirl region of the polar cap aurora. This polar region is described as being of low brightness and high absorption and the most magnetically "open" at Jupiter.

Formation of Dawn-Dusk Asymmetry in Earth's Magnetotail Thin Current Sheet: A Three-Dimensional Particle-in-Cell Simulation

Mon, 03/12/2018 - 18:10
Abstract

Using a three-dimensional particle-in-cell simulation, we investigate the formation of dawn-dusk asymmetry in Earth's magnetotail. The magnetotail current sheet is compressed by an external driving electric field down to a thickness on the order of ion kinetic scales. In the resultant thin current sheet (TCS) where the magnetic field line curvature radius is much smaller than ion gyroradius, a significant portion of the ions becomes unmagnetized and decoupled from the magnetized electrons, giving rise to a Hall electric field Ez and an additional cross-tail current jy caused by the unmagnetized ions being unable to comove with the electrons in the Hall electric field. The Hall electric field transports via E × B drift magnetic flux and magnetized plasma dawnward, causing a reduction of the current sheet thickness and the normal magnetic field Bz on the duskside. This leads to an even stronger Hall effect (stronger jy and Ez) in the duskside TCS. Thus, due to the internal kinetic effects in the TCS, namely the Hall effect and the associated dawnward E × B drift, the magnetotail dawn-dusk asymmetry forms in a short time without any global, long-term effects. The duskside preference of reconnection and associated dynamic phenomena (such as substorm onsets, dipolarizing flux bundles, fast flows, energetic particle injections, and flux ropes) which has been pervasively observed by spacecraft in the past twenty years can thus be explained as a consequence of this TCS asymmetry.

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