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We have shown that diamagnetic structures (DSs), which form the basis of the slow quasi-stationary solar wind (SW), are observed in Earth’s orbit as a sequence of DSs of various scales. The analysis of this phenomenon indicates that diamagnetic plasmoids in SW, whose concept was introduced by Karlsson in 2015, are identical to small-scale DSs. We have found that the impact of a sequence of DSs in the slow SW on Earth’s magnetosphere causes an increase in geomagnetic activity. Isolated DSs generate short-term magnetic disturbances whose duration is approximately equal to the DS duration. Hence, a sequence of DSs can cause sawtooth substorms. We emphasize that the interaction of DS in the slow SW under northward interplanetary magnetic field can be associated with penetration of DS high-density plasma into the magnetosphere.

Jupiter has a strong magnetic field, and a huge magnetosphere is formed through the solar wind-Jupiter interaction. The generated magnetosphere–ionosphere system is reproduced based on the 9-component Magnetohydrodynamics (MHD) and the current conservation in the ionosphere. Assuming Io plasma emission rate 1.4 t/sec, this paper reproduces self-consistently global magnetic configuration, generations of the field-aligned current (FAC) and aurora, formation of the Io plasma disk at 8–20 RJ, plasma corotation, instability in the plasma disk, transition from the Io plasma disk to the plasma sheet at 20–150 RJ, and the plasmoid ejection. The rotating Io plasma in the disk forms instabilities that promotes radial diffusion. H+ is supplied from the ionosphere along high-latitude magnetic field lines and mixed with heavy ions around 15–20 RJ. Beyond 20 RJ, mixed plasma diffuses further outward by the centrifugal force that can exceed magnetic tension. In the ionosphere, the main oval occurs at 13.7°–15.5° colatitude. The Io disk is inner side of magnetic field lines traced from the low-latitude edge of the main oval. Along magnetic field lines, the main oval is mapped from the outer edge of the Io disk to the entire plasma sheet accompanying rotation delay. Due to the corotation limit, convection is accompanied by plasmoid ejection. Back reaction of plasmoid ejection affects even transport process in the Io disk. The downward FAC occurs in the polar cap showing variability. The region of externally driven Dungey convection seems quite narrow.

A magnetosphere controls a planet's evolution by suppressing or enhancing atmospheric loss to space. In situ measurements of Uranus' magnetosphere from the Voyager 2 flyby in 1986 provide the only direct evidence of magnetospheric transport processes responsible for this atmospheric escape at Uranus. Analysis of high‐resolution Voyager 2 magnetic field data in Uranus' magnetotail reveals the presence of a loop‐like plasmoid filled with planetary plasma traveling away from the planet. This first plasmoid observation in an Ice Giant magnetosphere elucidates that (1) both internal and external forces play a role in Uranus' magnetospheric dynamics, (2) magnetic reconnection contributes to the circulation of plasma and magnetic flux at Uranus, and (3) plasmoids may be a dominant transport mechanism for mass loss through Uranus' magnetotail.

An electrodynamic model of ball lightning is proposed, according to which it is considered as a collection of plasmoids, consisting of electrons and protons, which rotate in closed orbits. Protons are retained in the orbit due to Coulomb attraction to the electron ring, while electrons are drifting in the crossed electric and the magnetic field, generated by the protons’ motion. This system has a non-compensated positive electric charge. These plasmoids placed inside a water shell serve to isolate a vacuum cavity from the atmosphere and to create a force, preventing expansion of proton rings. A mechanism of ball lightning creating near a loop of linear lightning channel is discussed. Ultraviolet radiation of the lightning discharge ionizes air, and due to the action of radio-frequency radiation with a non-uniform spatial distribution of intensity, a vacuum cavity is formed. The action on the plasma exerted by the crossed magnetic and eddy electric fields leads to separation and acceleration of charges. Losing a part of electrons, the system acquires a positive charge. Due to motion of water drops in the non-uniform field of this charge a dielectric shell around the ensemble of plasmoids is formed. A scheme of setup for ball lightning creation in laboratory is proposed.

The dissipation processes which transform electromagnetic energy into kinetic particle energy in space plasmas are still not fully understood. Of particular interest is the distribution of the dissipated energy among different species of charged particles. The Jovian magnetosphere is a unique laboratory to study this question because outflowing ions from the moon Io create a high diversity in ion species. In this work, we use multispecies ion observations and magnetic field measurements by the Galileo spacecraft. We limit our study to observations of plasmoids in the Jovian magnetotail, because there is strong ion acceleration in these structures. Our model predicts that electromagnetic turbulence in plasmoids plays an essential role in the acceleration of oxygen, sulfur, and hydrogen ions. The observations show a decrease of the oxygen and sulfur energy spectral index γ at ∼30 to ∼400 keV/nuc with the wave power indicating an energy transfer from electromagnetic waves to particles, in agreement with the model. The wave power threshold for effective acceleration is of the order of 10 nT2Hz−1, as in terrestrial plasmoids. However, this is not observed for hydrogen ions, implying that processes other than wave-particle interaction are more important for the acceleration of these ions or that the time and energy resolution of the observations is too coarse. The results are expected to be confirmed by improved plasma measurements by the Juno spacecraft.

The products of magnetic reconnection in Saturn's magnetotail are identified in magnetometer observations primarily through characteristic deviations in the north-south component of the magnetic field. These magnetic deflections are caused by travelling plasma structures created during reconnection rapidly passing over the observing spacecraft. Identification of these signatures have long been performed by eye, and more recently through semi-automated methods, however these methods are often limited through a required human verification step. Here, we present a fully automated, supervised learning, feed forward neural network model to identify evidence of reconnection in the Kronian magnetosphere with the three magnetic field components observed by the Cassini spacecraft in Kronocentric radial-theta-phi (KRTP) coordinates as input. This model is constructed from a catalogue of reconnection events which covers three years of observations with a total of 2093 classified events, categorized into plasmoids, travelling compression regions and dipolarizations. This neural network model is capable of rapidly identifying reconnection events in large time-span Cassini datasets, tested against the full year 2010 with a high level of accuracy (87%), true skill score (0.76), and Heidke skill score (0.73). From this model, a full cataloguing and examination of magnetic reconnection events in the Kronian magnetosphere across Cassini's near Saturn lifetime is now possible., 21 pages, 9 figures

We present the first statistical study of magnetic structures and associated energy dissipation observed during a single period of turbulent magnetic reconnection, by using the \textit{in-situ} measurements of the Magnetospheric Multiscale mission in the Earth's magnetotail on July 26, 2017. The structures are selected by identifying a bipolar signature in the magnetic field and categorized as plasmoids or current sheets via an automated algorithm which examines current density and plasma flow. The size of the plasmoids forms a decaying exponential distribution ranging from sub-electron up to ion scales. The presence of substantial number of current sheets is consistent with a physical picture of dynamic production and merging of plasmoids during turbulent reconnection. The magnetic structures are locations of significant energy dissipation via electric field parallel to the local magnetic field, while dissipation via perpendicular electric field dominates outside of the structures. Significant energy also returns from particles to fields., 17 pages, 3 figures, proofing version, accepted for publication in Geophysical Research Letters

著者人数: 13名, Accepted: 2019-12-11, 資料番号: SA1190210000

The expediency of using the radar method for detecting radiation contamination at long distances is substantiated in this article. The design of a radar for the detecting of small radioactive formations in the air at the long distances is developed. The dependence of the reflection coefficient of microwave radiation on the wavelength for determining the level of radioactive radiation is established. The investigation results of radioactive contamination in the atmosphere are presented.

We conduct a statistical analysis of 2,094 reconnection events in Saturn's near-equatorial magnetotail previously identified in Cassini magnetometer data from intervals during 2006 and 2009/2010. These consist of tailward propagating plasmoids and planetward propagating dipolarizations, with approximately twice as many plasmoids as dipolarizations. We organize these by three related planetary period oscillation (PPO) phase systems, the northern and southern PPO phases relative to noon, the same phases retarded by a radial propagation delay, and the local retarded phases that take account of the azimuth (local time) of the observation. Clear PPO modulation is found for both plasmoid and dipolarization events, with local retarded phases best organizing the event data with the modulation in event frequency propagating across the tail as the PPO systems rotate. This indicates that the events are localized in azimuth, rather than simultaneously affecting much of the tail width. Overall, events occur preferentially by factors of ~3 at northern and southern phases where the tail current sheet is expected locally to be thinnest in the PPO cycle, with field lines contracting back from their maximum radial displacement, compared with the antiphase conditions. Separating the events into those representing the start of independent reconnection episodes, occurring at least 3 hr after the last, and events in subsequent clusters, shows that the above phases are predominantly characteristic of the majority cluster events. The phases at the start of independent reconnection episodes are typically ~60° earlier.

Reconnection is a fundamentally important process in planetary magnetospheres, with both local and global effects. At Saturn, observations of the magnetotail reconnection site (or x‐line) are rare, with only one in‐situ encounter reported to date. In this work, an extensive database of plasmoids and dipolarizations [Smith et al., 2016] was investigated from a multi instrument perspective in order to probe the location and variability of the magnetotail x‐line. Several clear intervals were identified in which the x‐line location could be indirectly inferred to move on relatively short timescales. Two case studies are presented, the first of which concerns short lived flows, suggesting the reconnection sites can be either short lived (∼10 minutes) or extremely azimuthally limited (∼3RS/0.4 hours of local time). The second interval concerns the tailward motion of the reconnection site (or sites), inferred from the increasing electron temperature (and diminishing electron density) associated with the flows. This tailward motion occurs over ∼2.5 hours (approximately a quarter of a planetary rotation). The composition of the suprathermal plasma suggests that this could be an example of the gradual depletion of mass loaded flux tubes (that must occur prior to lobe reconnection). These case studies are consistent with previous statistical work that suggested that the site of reconnection in the Kronian magnetotail can be highly dynamic.

Determining the magnetic field structure, electric currents, and plasma distributions within flux transfer event (FTE)-type flux ropes is critical to the understanding of their origin, evolution, and dynamics. Here the Magnetospheric Multiscale mission's high-resolution magnetic field and plasma measurements are used to identify FTEs in the vicinity of the subsolar magnetopause. The constant-alpha flux rope model is used to identify quasi-force free flux ropes and to infer the size, the core magnetic field strength, the magnetic flux content, and the spacecraft trajectories through these structures. Our statistical analysis determines a mean diameter of 1,700 ± 400 km (~30 ± 9 d(sub i)) and an average magnetic flux content of 100 ± 30 kWb for the quasi-force free FTEs at the Earth's subsolar magnetopause which are smaller than values reported by Cluster at high latitudes. These observed nonlinear size and magnetic flux content distributions of FTEs appear consistent with the plasmoid instability theory, which relies on the merging of neighboring, small-scale FTEs to generate larger structures. The ratio of the perpendicular to parallel components of current density, R(sub J), indicates that our FTEs are magnetically force-free, defined as R(sub J) < 1, in their core regions (

Plasma structures with enhanced dynamic pressure, density, or speed are often observed in Earth's magnetosheath. We present a statistical study of these structures, known as jets and fast plasmoids, in the magnetosheath, downstream of both the quasi-perpendicular and quasi-parallel bow shocks. Using measurements from the four Magnetospheric Multiscale (MMS) spacecraft and OMNI solar wind data from 2015-2017, we present observations of jets during different upstream conditions and in the wide range of distances from the bow shock. Jets observed downstream of the quasi-parallel bow shock are seen to propagate deeper and faster into the magnetosheath and on toward the magnetopause. We estimate the shape of the structures by treating the leading edge as a shock surface, and the result is that the jets are elongated in the direction of propagation but also that they expand more quickly in the perpendicular direction as they propagate through the magnetosheath.

Saturn's aurora represents the ionospheric response to plasma processes occurring in the planet's entire magnetosphere. Short-lived ∼1-hr quasiperiodic high-energy electron injections, frequently observed in in situ particle and radio measurements, should therefore entail an associated flashing auroral signature. This study uses high time-resolution ultraviolet (UV) auroral imagery from the Cassini spacecraft to demonstrate the continuous occurrence of such flashes in Saturn's northern hemisphere and investigate their properties. We find that their recurrence periods of order 1 hr and preferential occurrence near dusk match well with previous observations of electron injections and related auroral hiss features. A large spread in UV auroral emission power, reaching more than 50% of the total auroral power, is observed independent of the flash locations. Based on an event observed both by the Hubble Space Telescope and the Cassini spacecraft, we propose that these auroral flashes are not associated with low-frequency waves and instead directly caused by recurrent small-scale magnetodisc reconnection on closed field lines. We suggest that such reconnection processes accelerate plasma planetward of the reconnection site toward the ionosphere inducing transient auroral spots while the magnetic field rapidly changes from a bent-back to a more dipolar configuration. This manifests as a sawtooth-shaped discontinuity observed in magnetic field data and indicates a release of magnetospheric energy through plasmoid release.

We have investigated MESSENGER magnetic field data from the Mercury magnetosheath and near solar wind, to identify isolated magnetic field structures (defined as clear, isolated changes in the field magnitude). Their properties are studied in order to determine if they may be considered as analogues to plasmoids and jets known to exist in Earth's magnetosheath. Both isolated decreases of the magnetic field absolute value (‘negative magnetic field structures’) and increases (‘positive structures’) are found in the magnetosheath, whereas only negative structures are found in the solar wind. The similar properties of the solar wind and magnetosheath negative magnetic field structures suggests that they are analogous to diamagnetic plasmoids found in Earth's magnetosheath and near solar wind. The latter have earlier been identified with solar wind magnetic holes. Positive magnetic field structures are only found in the magnetosheath, concentrated to a region relatively close to the magnetopause. Their proximity to the magnetopause, their scale sizes, and the association of a majority of the structures with bipolar magnetic field signatures identify them as flux transfer events (which generally are associated with a decrease of plasma density in the magnetosheath). The positive magnetic field structures are therefore not likely to be analogous to terrestrial paramagnetic plasmoids but possibly to a sub-population of magnetosheath jets. At Earth, a majority of magnetosheath jets are associated with the quasi-parallel bow shock. We discuss some consequences of the findings of the present investigation pertaining to the different nature of the quasi-parallel bow shock at Mercury and Earth.

We comment on the question of when and where reconnection begins in the tail and how it is related to the onset of auroral expansion. This question was addressed in a workshop dedicated to Unsolved Problems in Magnetospheric Physics held in Scarborough, UK, in September 2015. The answer is that it typically occurs first in the midtail a little beyond 20 Re somewhat before midnight about 55 min after a southward turning of the solar wind magnetic field. It appears to be a consequence of plasma sheet thinning down to the scale of an ion gyroradius. The onset of the activation and expansion of auroral activity and accompanying magnetic signatures typically occur within 1 or 2 min of the appearance of signatures of midtail reconnection. The unanswered question is which comes first and whether reconnection is the cause of the auroral expansion. We point out that older observations clearly established that plasmoids (flux ropes) are released from near 20 Re within a few minutes of the usual signatures of expansion onset. This is only possible if reconnection occurs close to the Earth. More detailed observations with modern spacecraft have led to the development of new explanations for the cause of the substorm expansion that appear to neglect older observations. We conclude that it is essential to carefully define the various terms used in the study of substorms and to develop quantitative methods that enable statistical studies of the various processes associated with auroral expansion onset.

Auroral stepwise poleward expansions were clarified by investigating a multiple-onset substorm that occurred on 27 February 2009. Five successive auroral brightenings were identified in all-sky images, occurring at approximately 10 min intervals. The first brightening was a faint precursor. The second brightening had a wide longitude; thus, it represented the Akasofu substorm onset. Other brightenings expanded poleward; thus, they were interpreted to be auroral breakups. These breakups occurred stepwise; that is, later breakups were initiated at higher latitudes. Corresponding reconnection signatures were studied using Time History of Events and Macroscale Interactions during Substorms (THEMIS) satellite observations between 8 and 24 RE down the magnetotail. The Akasofu substorm onset was not accompanied by a clear reconnection signature in the tail. In contrast, the three subsequent auroral breakups occurred simultaneously (within a few minutes) with three successive fast flows at 24 RE; thus, these were interpreted to be associated with impulsive reconnection episodes. These three fast flows consisted of a tailward flow and two subsequent earthward flows. The flow reversal at the second breakup indicated that a tailward retreat of the near-Earth reconnection site occurred during the substorm expansion phase. In addition, the earthward flow at the third breakup was consistent with the classic tailward retreat near the end of the expansion phase; therefore, the tailward retreat is likely to have occurred in a stepwise manner. We interpreted the stepwise characteristics of the tailward retreat and poleward expansion to be potentially associated by a stepwise magnetic flux pileup.

Earthward propagating plasmoids in the Earth's magnetotail have been observed by satellites. Using a multi-fluid global magnetosphere simulation, earthward propagating plamoids are reproduced when ionospheric O+ outflow is included in the global simulation. Controlled simulations show that without ionospheric outflow, the plasmoids generated in the magnetotail during a substorm-SMC cycle only propagate tailward. With ionospheric outflow, earthward plasmoids can be induced through the modification of magnetotail reconnection at multiple X-lines. When multiple X-lines form in the magnetotail, plasmoids may be trapped between multiple reconnection sites. When magnetic reconnection rate is reduced at the near-Earth X-line by the presence of ionospheric O+, the earthward exhaust flow of reconnection occurring at the mid-tail X-line forces the plasmoid to propagate earthward. The propagation speed and spatial size of the simulated earthward plasmoid are consistent with observations from the Cluster satellites.

New Horizons observed consistently and continuously the jovian magnetotail at distances up to ~2500 Jupiter Radii (Rj) during its Jupiter flyby in 2007. The Solar Wind Around Pluto (SWAP) plasma instrument on New Horizons made in situ observations of plasma ions in the energy per charge range of ~21 eV to 7.8 keV. We analyze the SWAP plasma observations and derive the bulk properties of the plasma ions in the deep jovian magnetotail for 64 intervals from ~500 to 1700 Rj, just before the spacecraft start crossing the jovian magnetopause. There is no clear evolution of the plasma parameters over this distance range and we show that the plasma is very diverse over this entire range. There are significant changes in the plasma parameters and the flow direction over times as short as a few hours, showing evidence that boundaries between different plasma structures pass over the spacecraft rapidly. We discuss in detail a few subintervals where two species are observed within the instrument׳s energy per charge range and a set of subintervals where the plasma flow rotates ~20° over just six hours. We finally discuss the mass flux during the subintervals we study and the scenario of expanding plasmoids that propagate tailward and expand and interact to fill the magnetotail. This scenario is supported by the observed plasma diversity and flow characteristics.

A case is described of multiple current sheets crossed by the MAGION-2 satellite in the near-midnight quieting auroral oval. The data were obtained by the magnetometer experiment onboard. Results show during a quieting period after a preceding substorm, or during an early growth phase of the next substorm, two double-sheet current bands, POLB and EQUB, located at respectively the polar and equatorial borders of the auroral oval separated by about 500 km in latitude. This is consistent with the double-oval structure during recovery introduced by Elphinstone et al. (1995). Within the POLB, the magnetic field data show simultaneous existence of several narrow parallel bipolar current sheets within the upward current branch (at 69.5–70.3° invariant latitude) with an adjacent downward current branch at its polar side at (70.5–71.3°). The EQUB was similarly stratified and located at 61.2–63.5° invariant latitude. The narrow current sheets were separated on average by about 35 km and 15 km, respectively, within the POLB and EQUB. A similar case of double-oval current bands with small-scale structuring of their upward current branches during a quieting period is found in the data from the MAGION-3 satellite. These observations contribute to the double-oval structure of the late recovery phase, and add a small-scale structuring of the upward currents producing the auroral arcs in the double- oval pattern, at least for the cases presented here. Other observations of multiple auroral current sheets and theories of auroral arc multiplicity are briefly discussed. It is suggested that multiple X-lines in the distant tail, and/or leakage of energetic particles and FA currents from a series of plasmoids formed during preceding magnetic activity, could be one cause of highly stratified upward FA currents at the polar edge of the quieting double auroral oval.

Many previous studies have demonstrated that the interplanetary magnetic field (IMF) can control the magnetospheric dynamics. Immediate magnetospheric responses to the external IMF have been assumed for a long time. The specific processes by which IMF penetrates into magnetosphere, however, are actually unclear. Solving this issue will help to accurately interpret the time sequence of magnetospheric activities (e.g., substorm and tail plasmoids) exerted by IMF. With two carefully selected cases, we found that the penetration of IMF into magnetotail is actually delayed by 1-1.5 h, which significantly lags behind the magnetotail response to the solar wind dynamic pressure. The delayed time appears to vary with different auroral convection intensity, which may suggest that IMF penetration in the magnetotail is controlled considerably by the dayside reconnection. Several unfavorable cases demonstrate that the penetration lag time is more clearly identified when storm/substorm activities are not involved.

Cassini observations during a rapid, high-latitude, dawnside pass from Saturn's lobe to inner magnetosphere on 25 June 2009 provide strong evidence for the formation of a “plasmapause” at Saturn by Vasyliunas-type nightside reconnection of previously mass-loaded flux tubes. A population of hot, tenuous plasma that lies between the lobe and the dense inner magnetospheric plasma is consistent with a region formed by very recent injection from a reconnection region in the tail, including low density, high temperature, supercorotational flow, a significant O+ content, and the near-simultaneous observation of enhanced Saturn kilometric radiation emissions. The sharp boundary between that region and the cool dense inner magnetospheric plasma thus separates flux tubes that were involved in the reconnection from those that successfully traversed the nightside without mass loss. This event demonstrates that tail reconnection can strip off inner magnetospheric plasma in to at least dipole L = 8.6. Clear evidence of flux tube interchange driven by the sharp boundary is found, both inward moving flux tubes of hotter plasma and, for the first time, the outward moving cool population. The outward moving cool regions have azimuthal sizes less than 1 RS, were probably created within the past 1.2 h, and have outflow speeds greater than about 5 km/s. At the outer edge of the reconnected region, there is also a possible signature of Dungey-type lobe reconnection following the initial Vasyliunas-type reconnection. Observations from this event are entirely consistent with previously described global MHD simulations of tail reconnection, plasmoid departure, and Saturnward injection of reconnected flux.

The coronal mass ejection (CME) event on 3 April 2010 is the first fast CME observed by STEREO Sun Earth Connection Coronal and Heliospheric Investigation/Heliospheric Imager for the full Sun-Earth line. Such an event provides us a good opportunity to study the propagation and evolution of CME from the Sun up to 1 AU. In this paper, we study the time-dependent evolution and propagation of this event from the Sun to Earth using the 3-D SIP-CESE (Solar-InterPlanetary Conservation Element and Solution Element) MHD model. The CME is initiated by a simple spherical plasmoid model: a spheromak magnetic structure with high-speed, high-pressure, and high-plasma density plasmoid. The simulation performs a comprehensive study on the CME by comparing the simulation results with STEREO and Wind observations. It is confirmed from the comparison with observations that the MHD model successfully reproduces many features of both the fine solar coronal structure and the typical large-scale structure of the shock propagation and gives the shock arrival time at Earth with an error of similar to 2 h. Then we analyze in detail the several factors affecting the CME's geo-effectiveness: the CME's propagation trajectory, span angle, and velocity.

We revisit the evidence for a "dust cloud" observed by the Cassini spacecraft at Saturn in 2006. The data of four instruments are simultaneously compared to interpret the signatures of a coherent swarm of dust that would have remained near the equatorial plane for as long as six weeks. The conspicuous pattern, as seen in the dust counters of the Cosmic Dust Analyser (CDA), clearly repeats on three consecutive revolutions of the spacecraft. That particular cloud is estimated to about 1.36 Saturnian radii in size, and probably broadening. We also present a reconnection event from the magnetic field data (MAG) that leave behind several plasmoids like those reported from the Voyager flybys in the early 1980s. That magnetic bubbles happened at the dawn side of Saturn's magnetosphere. At their nascency, the magnetic field showed a switchover of its alignment, disruption of flux tubes and a recovery on a time scale of about 30 days. However, we cannot rule out that different events might have taken place. Empirical evidence is shown at another occasion when a plasmoid was carrying a cloud of tiny dust particles such that a connection between plasmoids and coherent dust clouds is probable., Comment: accepted by Advances in Space Research; preprint: 28 pages, 10 figures, 2 tables

Near-Earth reconnection on closed plasma sheet field lines is thought to generate plasmoids. A plasmoid is usually described as a plasma sheet expansion into the lobe, encompassed by closed magnetic loops or the helical fields of a flux rope (in this paper we do not distinguish plasmoids from flux ropes; rather we use the term plasmoid generically). Recently, sharp, highly asymmetric north-then-south bipolar variations (with a larger southward portion) in the magnetic field BZ component have been noted in midtail (XGSM ~ −60 RE) plasmoids. These variations do not fit the classical plasmoid model but are mirror images of earthward moving dipolarization fronts (DFs), which show asymmetric south-then-north BZ bipolar variations with a larger northward portion. Using case and statistical studies from 3 years of Acceleration, Reconnection, Turbulence, and Electrodynamics of the Moon's Interaction with the Sun (ARTEMIS) data (at XGSM ~ −60 RE), we show that magnetic and particle properties of these typically tailward moving fronts, which we refer to as “antidipolarization fronts” (ADFs), are very similar to those of classical, typically earthward moving DFs, except for their BZ polarity and flow direction. First, like DFs and plasmoids, ADFs are associated with auroral electrojet enhancements. Second, like DFs, ADFs exhibit a sharp density decrease, plasma pressure increase, magnetic pressure increase, and particle heating immediately following the sharp BZ change. Third, particle spectra indicate that, as with DFs, there are two distinctly different magnetically separated populations ahead of and behind ADFs. The energy spectrograms of plasmoids, however, indicate a single hot population at the plasmoid center. We conclude that midtail ADFs are likely products of fast reconnection, observed on the tailward side of the reconnection site, just as DFs are products of fast reconnection seen on the earthward side. ADFs are observed at ARTEMIS much less frequently (~10%) than typical plasmoids but twice as frequently as DFs at the same distance. We suggest that ADFs are protoplasmoids that emerge from near-Earth reconnection and evolve quickly into plasmoids as they propagate down the tail.

Following a long period of observation and investigation beginning in the early 1970s, it has been firmly established that Earth׳s magnetosphere is defined as much by the geogenic plasma within it as by the geomagnetic field. This plasma is not confined to the ionosphere proper, defined as the region within a few density scale heights of the F-region plasma density peak. Rather, it fills the flux tubes on which it is created, and circulates throughout the magnetosphere in a pattern driven by solar wind plasma that becomes magnetically connected to the ionosphere by reconnection through the dayside magnetopause. Under certain solar wind conditions, plasma and field energy is stored in the magnetotail rather than being smoothly recirculated back to the dayside. Its release into the downstream solar wind is produced by magnetotail disconnection of stored plasma and fields both continuously and in the form of discrete plasmoids, with associated generation of energetic Earthward-moving bursty bulk flows and injection fronts. A new generation of global circulation models is showing us that outflowing ionospheric plasmas, especially O + , load the system in a different way than the resistive F-region load of currents dissipating energy in the plasma and atmospheric neutral gas. The extended ionospheric load is reactive to the primary dissipation, forming a time-delayed feedback loop within the system. That sets up or intensifies bursty transient behaviors that would be weaker or absent if the ionosphere did not “strike back” when stimulated. Understanding this response appears to be a necessary, if not sufficient, condition for us to gain accurate predictive capability for space weather. However, full predictive understanding of outflow and incorporation into global simulations requires a clear observational and theoretical identification of the causal mechanisms of the outflows. This remains elusive and requires a dedicated mission effort.

Although distant-tail plasmoids are perceived to extend across most of the magnetotail (~40 RE), recent studies in the near-Earth region (X > −30 RE) have revealed that near-Earth reconnection (where plasmoids originate) is likely localized and takes place preferentially on the duskside. This discrepancy in plasmoid azimuthal extent suggests that a plasmoid may grow as it moves from near-Earth to the distant tail. Comprehensive multipoint, midtail plasmoid observations can be used to test this hypothesis. Between October 2010 and July 2011 the ARTEMIS spacecraft (P1 and P2) at the Earth-Moon Lagrange points (midtail, X ~ −45 to −65 RE) provided simultaneous two-point observations across the magnetotail for 4 days every lunar month, with a large range of spacecraft separations (0.1 to 25 RE). We find that plasmoids near lunar orbit, like other near-Earth reconnection-related phenomena, occur preferentially on the duskside of the magnetotail. Two-point ARTEMIS observations reveal that the typical plasmoid azimuthal size in our data set is about 5 to 10 RE, much smaller than expected from previous distant-tail observations. Plasmoids with an azimuthal size greater than 9 RE also exist but only at geomagnetic activity levels higher (AEpeak > 400 nT) than typically found in our data set (median AEpeak ~ 230 nT for our plasmoid data set and median AE ~ 100 nT during the entire period of ARTEMIS magnetotail observations). We conclude that plasmoids during small to moderate substorms (AEpeak 400 nT), however, either grow beyond ~10 RE before they reach lunar distance or initially extend across a large portion of the magnetotail.

Plasmoids and other reconnection-related signatures have been observed in Jupiter's magnetotail through analysis of magnetic field and energetic particle data. Previous studies have established the spatial distribution and recurrence period of tail reconnection events, and identified the location of a statistical X-line separating inward and outward flow. Here we present new analysis focusing specifically on 43 plasmoid signatures observed in magnetometer data in order to establish the average properties and internal structure of Jovian plasmoids. We present statistics on the observed plasmoid length scale, duration, radial position, and local time distribution. On average, the observed plasmoids have a ~3 RJ radial extent and ~7 min duration and result in the closure of ~4–8 GWb of open flux from reconnection of open field lines in the postplasmoid plasma sheet. We also determine the amount of mass released and the magnetic flux closed in order to understand the role of tail reconnection in the transport of mass and flux in Jupiter's magnetosphere. The observed plasmoid properties are consistent with a mass loss rate of ~0.7–120 kg/s and a flux closure rate of ~7–70 GWb/d. We conclude that tail reconnection and plasmoid release is an important method of flux transport at Jupiter but likely cannot account for the mass input from Io, suggesting that additional mass loss mechanisms may be significant. Finally, we examine the plasmoid interior structure through minimum variance analysis and find that most plasmoids lack a core field and are better described by magnetic loops rather than flux ropes.

Using two-dimensional particle-in-cell (PIC) together with magnetohydrodynamic (MHD) Q1 simulations of magnetotail dynamics, we investigate the evolution toward onset of reconnection and the subsequent energy transfer and conversion. In either case, reconnection onset is preceded by a driven phase, during which magnetic flux is added to the tail at the high-latitude boundaries, followed by a relaxation phase, during which the configuration continues to respond to the driving. The boundary deformation leads to the formation of thin embedded current sheets, which are bifurcated in the near tail, converging to a single sheet farther out in the MHD simulations. The thin current sheets in the PIC simulation are carried by electrons and are associated with a strong perpendicular electrostatic field, which may provide a connection to parallel potentials and auroral arcs and an ionospheric signal even prior to the onset of reconnection. The PIC simulation very well satisfies integral entropy conservation (intrinsic to ideal MHD) during this phase, supporting ideal ballooning stability. Eventually, the current intensification leads to the onset of reconnection, the formation and ejection of a plasmoid, and a collapse of the inner tail. The earthward flow shows the characteristics of a dipolarization front: enhancement of Bz, associated with a thin vertical electron current sheet in the PIC simulation. Both MHD and PIC simulations show a dominance of energy conversion from incoming Poynting flux to outgoing enthalpy flux, resulting in heating of the inner tail. Localized Joule dissipation plays only a minor role.

In the Earth’s magnetotail, Japanese Moon orbiter Kaguya repeatedly encountered the plasmoid or plasma sheet. The encounters were characterized by the low energy ion signatures including lobe cold ions, cold ion acceleration in the plasma sheet-lobe boundaries, and hot plasma sheet ions or fast flowing ions associated with plasmoids. Different from the previous observations made in the magnetotail by the GEOTAIL spacecraft, the ions were affected by the existence of the Moon. On the dayside of the Moon, tailward flowing cold ions and their acceleration were observed. However, on the night side, tailward flowing cold ions could not be observed since the Moon blocked them. In stead, ion acceleration by the spacecraft potential and the electron beam accelerated by the potential difference between lunar surface and spacecraft were simultaneously observed. These electron and ion data enabled us to determine the night side lunar surface potential and spacecraft potential only from the observed data for the first time.

[1] Plasma dynamics in the inner magnetosphere are greatly affected by variations in the ion composition. The ratio of hydrogen to oxygen has been shown to be highly dependent on geomagnetic activity. To investigate this dependence, we examine the timing of the injection and subsequent evolution of O+ in the ring current during the storm of 6 August 2011 as observed by Two Wide-angle Imaging Neutral-atom Spectrometers (TWINS) instruments. To help interpret magnetospheric evolution using the global O Energetic Neutral Atom (ENA) emission measured by TWINS, we have employed a multidomain modeling of the global magnetosphere using the Space Weather Modeling Framework. TWINS Energetic Neutral Atom (ENA) imagers have the capability to distinguish between H and O emission and thus the major ion constituents of the ring current. Global composition measurements from TWINS spacecraft show intensifications of the oxygen ENA emission and thus an increase in the transport of ionospheric oxygen into the ring current that occur during the main phase of the storm. Both the observations and the simulation suggests that the peak in O ENA emission is correlated with the substorm injections that occurred during this time. The model also shows a very dynamic magnetosphere that allows for loss of oxygen from the Earth-magnetosphere system through plasmoids capable of transporting oxygen down the tail throughout the magnetic storm. This can possibly be a predominant pathway for loss of oxygen from the magnetosphere.

[1] The dynamics of Saturn's magnetosphere are driven by two major features of the system: First, the dominant source of magnetospheric plasma is the icy moon Enceladus, located deep within the magnetosphere; and second, like Jupiter, Saturn is a very fast rotator, with a rotational period of only 10.7 h. The dynamical imperative is to rid the magnetosphere of the continuously supplied plasma, and the fast rotation provides the mechanisms to do so. Thus, magnetospheric dynamics are intimately related to mass transport processes, including radial diffusion, flux tube interchange, magnetic reconnection, and plasmoid formation. We review recent progress and new questions relating to these processes at Saturn.

The fine magnetic field structure of two successive plasmoids previously reported is investigated by magnetic rotation analysis using four Cluster satellite data. Between these two plasmoids, opposite trends of curvature radius (R-c) variations of the magnetic field lines from the boundary to the inner part are found. The different variations of R-c reflect that the two plasmoids have different magnetic configurations. The electric current density distributions for both plasmoids are found distinct. The B-y increase and abundant field-aligned currents in the narrow core region of the first plasmoid indicate that a possible magnetic flux rope (MFR) core exists inside. The results indicate that the first observed plasmoid is of a magnetic loop (ML) type (with possible MFR core) and the second plasmoid is of a magnetic flux rope (MFR) type. The coexistence of ML and MFR in the near-Earth plasma sheet may imply that multiple X line reconnection can occur by either an antiparallel or a component-parallel way.

[1] This paper seeks to improve understanding of sawtooth events (STEs) that occur during the main phases of geomagnetic storms. We consider the dynamics of diverse space environments encountered during a magnetic storm on 24 March 2002 when four STEs were identified in energetic particle fluxes measured by Synchronous Orbit Particle Analyzers on Los Alamos National Laboratory satellites. Over the reported interval, 28 substorms were identified in magnetometer traces obtained via the SuperMAG international collaboration. Magnetic inclination variations sampled by the Geostationary Operational Environment Satellites 8 and 10 on the nightside indicate that STEs coincided with substorms marked by strong and prolonged dipolarizations. Significantly, the four STEs were accompanied by partial recoveries of the SYM-H index. Two SuperMAG substorms were marked by weak dipolarizations and energetic particle flux increases. The remaining 22 substorms showed no such signatures near 6.6 RE. We regard the latter SuperMAG events as indicating intensifications of the DP 2 current system driven by episodically enhanced reconnection at the distant X line. Presented data are shown to be consistent with the conjecture of Huang et al. (2009) that STEs occur only after open flux in the magnetotail exceeds a critical level near 109 Wb. During STEs, significant quantities of open flux were removed from the magnetotail at near-Earth reconnection lines. It took ~3 h to eject plasmoids and replenish open flux in the magnetotail to a critical level via continued dayside merging, thereby driving quasi-cyclic STE occurrences.

From the 27th to the 28th January 2009, the Cassini spacecraft remotely acquired combined observations of Saturns southern aurorae at radio, ultraviolet and infrared wavelengths, while monitoring ion injections in the middle magnetosphere from energetic neutral atoms. Simultaneous measurements included the sampling of a full planetary rotation, a relevant timescale to investigate auroral emissions driven by processes internal to the magnetosphere. In addition, this interval coincidently matched a powerful substorm-like event in the magnetotail, which induced an overall dawnside intensification of the magnetospheric and auroral activity. We comparatively analyze this unique set of measurements to reach a comprehensive view of kronian auroral processes over the investigated timescale. We identify three source regions in atmospheric aurorae, including a main oval associated with the bulk of Saturn Kilometric Radiation (SKR), together with polar and equatorward emissions. These observations reveal the co-existence of corotational and sub-corototational dynamics of emissions associated with the main auroral oval. Precisely, we show that the atmospheric main oval hosts short-lived sub-corotating isolated features together with a bright, longitudinally extended, corotating region locked at the southern SKR phase. We assign the susbtorm-like event to a regular, internally driven, nightside ion injection possibly triggerred by a plasmoid ejection. We also investigate the total auroral energy budget, from the power input to the atmosphere, characterized by precipitating electrons up to 20 keV, to its dissipation through the various radiating processes. Finally, through simulations, we confirm the search-light nature of the SKR rotational modulation and we show that SKR arcs relate to isolated auroral spots. The resulting findings are discussed in the frame of pending questions.

The existence of small-scale plasmoids associated with the Hall effect has been often observed in the magnetotail. They are considered as the signature of multiple X-line collisionless reconnection. To study these plasmoids structures, we present some Cluster observations and Hall MHD simulations of their features. In this study, the observation survey is divided into two types. The first one is the isolated plasmoid with two typical plasmoid events the flux-rope-like plasmoid on 3 August 2001 and the closed-loop-like plasmoid on 22 August 2001. The second type contains multiple successive plasmoids, on 12 September 2001 with three neighboring plasmoids structures observed during a substorm. Especially for the second plasmoid, three main features were observed, including a core field in the plasmoid, a quadrupole magnetic field near the X line, and a local plasma convection within the plasmoid. The Grad-Shafranov reconstruction method was used to recover the two-dimensional magnetic field maps for this plasmoid. These results may provide evidence that the small-scale plasmoids frequently observed in the magnetotail may be produced by multiple X-line collisionless reconnection. To study the impact of crosstail magnetic field on the structures of small-scale plasmoids, a 2.5-D Hall MHD simulation was performed. In the case with a guide field By0, the in-plane plasma inflows carrying Byflux enter into the plasmoid due to magnetic reconnection. However, there is no such By flux transport process for the case without guide field. These results demonstrate that a crosstail magnetic field is an important factor in the formation of flux-rope-like plasmoids.

[1] On 12 October 2011, two ARTEMIS probes, in lunar orbit ~9 RE north of the neutral sheet, sequentially observed a tailward-moving, expanding plasmoid. Their observations revealed a multilayered plasma sheet composed of tailward-flowing hot plasma within the plasmoid surrounded by earthward-flowing, less energetic plasma. Prior observations of similar earthward flows ahead of or behind plasmoids have been interpreted as earthward outflow from a continuously active distant-tail neutral line opposite an approaching plasmoid. No evidence of active distant neutral line reconnection was observed by the probes, however, as they traversed the plasmoid's leading and trailing edges, penetrating above its core. We suggest an alternate interpretation: compression of ambient plasma by the tailward-moving plasmoid proper propels the plasma lobeward and earthward, i.e., above and below the plasmoid proper. Using the propagation velocity obtained from timing analysis, we estimate the average plasmoid proper size in its propagation direction to be 9 RE and its expansion rate to be ~7 RE/min at the observation locations. This observation of plasmoid expansion made at the plasmoid boundary is interpreted as plasmoid growth in both the XGSM and the ZGSM directions due to near-Earth-neutral-line reconnection on closed plasma sheet field lines. The velocity inside the plasmoid proper was found to be nonuniform; the core likely moves as fast as 500 km/s, yet the outer layers move more slowly (and in the reverse direction). The absence of lobe reconnection, in particular on the earthward side, suggests that plasmoid formation and expulsion both result from closed plasma sheet field-line reconnection.

[1] Saturn's rapid rotation combined with relatively weak magnetic fields in the outer magnetosphere and sheath lead to conditions that are favorable for the Kelvin-Helmholtz (KH) instability. A Kelvin-Helmholtz unstable magnetopause boundary has important consequences for Saturn's interaction with the solar wind due to mass, momentum, and energy transport that can occur at the magnetopause boundary. Previous attempts to identify vortices have been hampered by limited plasma data to unambiguously reveal vortical flow. The magnetic field data, on the other hand, may be able to identify the KH instability due to intense magnetic fluctuations that are associated with KH vortices. We have conducted two-dimensional hybrid code simulations of Saturn's magnetopause boundary to illustrate the expected magnetic field signatures of KH. Specifically, our simulations show strong field-aligned current sheet filaments or strong bipolar fluctuations of the in-plane magnetic field components, bounding the KH vortices. A global search for these characteristic magnetic field signatures near the magnetopause boundary was made of the Cassini mission data from 2004 to 2009. We find that most of the potential KH activity is found on the dusk flank, contrary to expectations. We suggest that KH growth is supported in the prenoon and subsolar regions and that these vortices are transported through coupling to the rotating planet, past noon and tailward on the dusk flank. In addition, we find many instances in the subsolar magnetosphere of possible plasmoid formation (Bz northward) in conjunction with these intense magnetic field fluctuations.

During its exploration of Saturn's magnetotail the Cassini magnetometer has detected many in situ examples of magnetic reconnection, in the form of plasmoids, traveling compression regions (TCRs), and dipolarizations. Meanwhile, many magnetospheric phenomena have been shown to be organized with particular regularity by planetary period oscillation systems driven separately from the Northern and Southern Hemispheres of the planet. Here we examine the relationship between the occurrence of plasmoids and TCRs and the magnetic phases of the northern and southern systems. We find a striking degree of organization of the events by both northern and southern phases, with events linked preferentially to intervals in which the magnetospheric plasma and field lines are displaced outward from the planet and the current sheet thinned, both effects being likely to favor the occurrence of reconnection and plasmoid-related mass loss. Little evidence is found for significant visibility effects associated with north-south motions of the plasma sheet.

We study nano-sized spherically symmetric plasma structures which are radial nonlinear oscillations of electrons in plasma. The effective interaction of these plasmoids via quantum exchange forces between ions is described. We calculate the energy of this interaction for the case of a dense plasma. The conditions when the exchange interaction is attractive are examined and it is shown that separate plasmoids can form a single object. The application of our results to the theoretical description of stable atmospheric plasma structures is considered., Comment: 11 pages in LaTeX2e, two columns, 2 eps figures; paper was significantly revised, more realistic values for plasma parameters are used, several references were added; matches version to be published in J. Atm. Solar-Terr. Phys

We investigate an extraordinary event showing all the typical magnetic flux rope (MFR) signatures, although it is not really a MFR structure. It occurred on 1 March 2008 in the Earth's magnetotail and was observed by a major tail conjunction of Time History of Events and Macroscale Interactions during Substorms (THEMIS) satellites. THEMIS B and C being located inside the central plasma sheet and almost symmetrically above and below the neutral sheet observed the same tailward retreating MFR-like structure: they indeed detected strong but oppositely directed cross-tail magnetic field excursions: positive “By core” for TH-C and negative for TH-B; an apparent inconsistency. We finally categorize the case under study as a pseudo-MFR event and we doubt that the previously studied MFR-like structures were really rope structures. We suggest that the By excursions are dictated by Ampere's law; they are produced by filamentary field-aligned currents (FACs) created in front of the “akis structure”, as it is introduced by Sarafopoulos, 2008 , Sarafopoulos, 2010 : In a locally thinned plasma sheet, the akis potentially causes charge separation due to non-adiabatic motion and stochastic scattering of ions. In turn, the newly tailward escaped ions drive field-aligned ionospheric currents in order to neutralize this region. We extensively discuss an additional and extremely rare phenomenon of “irregular MFR” cited in the literature and observed by the Cluster satellites; filamentary FACs suffice to reproduce all the observed magnetic field signatures, too.

The present paper studies fundamental features of plasmoid propagation by virtual satellite observations in the simulation box. The plasmoid domain is divided into the plasmoid reconnection region P, where magnetized plasmas with reconnected field lines, heated by dissipation mechanisms of fast reconnection, are accumulated, and the plasmoid core region C, where magnetized plasmas with sheared field lines, initially embedded in the current sheet, is adiabatically compressed. When the virtual satellite is located in a position through which the plasmoid core region passes, it detects distinct changes in quantities at the interface between the regions P and C, where the north-south field component Bz has the bipolar profile and the sheared field component By has the peak value. The observed magnetic field profile is, both quantitatively and qualitatively, in good agreement with the standard one detected by actual satellite observations, although when the satellite location is very close to the X neutral line, where reconnection occurs, the Bz field profile becomes dipolarization-like rather than bipolar. If the satellite detects only the plasmoid region P outside region C, the standard magnetic field profile becomes obscure even if notable plasmoid signatures, such as enhanced plasma temperature and plasma flow, are observed. Unlike the traditional flux rope model based on multiple reconnections, it is demonstrated that the standard magnetic field profile, observed for plasmoids propagating in the geomagnetic tail, is the direct outcome of the single fast reconnection evolution.

As a sequence of Ugai (2010b), the present paper studies in detail the structure and dynamics of large-scale (principal) plasmoid, generated by the fast reconnection evolution in a sheared current sheet with no initial northward field component. The overall plasmoid domain is divided into the plasmoid reconnection region P and the plasmoid core region C. In the region P, the magnetized plasma with reconnected field lines are accumulated, whereas in the region C, the plasma, which was intially embedded in the current sheet and has been ejected away by the reconnection jet, is compressed and accumulated. In the presence of the sheared magnetic field in the east-west direction in the current sheet, the upper and lower parts of the reconnection region P are inversely shifted in the east-west directions. Accordingly, the plasmoid core region C with the accumulated sheared field lines is bent in the north-south direction just ahead of the plasmoid center x=XC, causing the magnetic field component in the north-south direction, whose sign is always opposite to that of the reconnected field lines. Therefore, independently of the sign of the initial sheared field, the magnetic field component Bz in the north-south direction has the definite bipolar profile around XC along the x-axis. At x=XC, the sheared field component has the peak value, and as the sheared fields accumulated in the region C become larger, the bipolar field profile becomes more distinct.

We investigate plasmoid formation in the magnetotail using the global magnetohydrodynamic (MHD) simulation GUMICS-4. Here a plasmoid implies a major reconfiguration of the magnetotail where a part of the tail plasma sheet is ejected downstream, in contrast to small Earthward-propagating plasmoids. We define a plasmoid based solely on the structure of the closed (connected to the Earth at both ends) magnetic field line region. In this definition a plasmoid is partly separated from the ordinary closed field line region by lobe field lines or interplanetary field lines resulting from lobe reconnection. We simulate an event that occurred on 18 February 2004 during which four intensifications of the auroral electroject (AE) index occurred in 8 h. Plasmoids form in the simulation for two of the four AE intensifications. Each plasmoid forms as a result of two consecutive large and fast rotations of the interplanetary magnetic field (IMF). In both cases the IMF rotates 180 degrees at 10 degrees per minute, first from southward to northward and some 15 min later from northward to southward. The other two AE intencifications however are not associated with a plasmoid formation. A plasmoid does not form if either the IMF rotation speed or the angular change of the rotation are small. We also present an operational definition for these fully connected plasmoids that enables their automatic detection in simulations. Finally, we show mappings of the plasmoid footpoints in the ionosphere, where they perturb the polar cap boundary in both hemispheres.

On the basis of the spontaneous fast reconnection model, three-dimensional magnetic field profiles associated with a large-scale plasmoid propagating along the antiparallel magnetic fields are studied in the general sheared current sheet system. The plasmoid is generated ahead of the fast reconnection jet as a result of distinct compression of the magnetized plasma. Inside the plasmoid, the sheared (east-west) field component has the peak value at the plasmoid center located at x=XC, where the north-south field component changes its sign. The plasmoid center corresponds to the so-called contact discontinuity that bounds the reconnected field lines in xXC. Hence, contray to the conventional prediction, the reconnected sheared field lines in xXC. It is demonstrated that the resulting profiles of magnetic field components inside the plasmoid are, in principle, consistent with satellite observations. In the ambient magnetic field region outside the plasmoid too, the magnetic field profiles are in good agreement with the well-known observations of traveling compression regions (TCRs).

The paper presents a summary of results from two different simulations which study the tearing, coalescence and fragmentation of current sheets, the associated production of energetic electrons and of plasma waves from these electrons which could explain drifting pulsation structures observed at radio wavelengths. Using a 2.5-D particle-in-cell (PIC) model of the current sheet it is shown that due to the tearing mode instability the current sheet tears into plasmoids and these plasmoids later on coalesce into larger ones. During these processes electrons are accelerated and they produce observable electromagnetic waves. Furthermore, the 3-D PIC model with two current sheets extended in the electric current direction shows their fast fragmentation associated with the exponential dissipation of the free magnetic field energy. An example of the drifting pulsating structure which is considered to be a radio signature of the above mentioned processes in solar flares is shown.

We analyze the magnetic structures in the near-tail at XGSM = -17.5 RE on September 19, 2003 by Cluster. During the course of a substorm event, the earthward propagating plasmoid and flux ropes in the near-tail are observed. The earthward propagating plasmoid is associated with the bipolar Bz and By signatures. The two flux ropes are embedded within the earthward plasma flows, which might be referred to the population as "BBF-type" flux ropes. The first flux rope diameter is about 0.7 RE and duration based upon the Bz signature is similar to 20 s, while the second one diameter is about 1.4 RE and duration is similar to 30 s. The earthward propagating plasmoid and flux ropes could have influence upon the dipolarization and injection in inner magnetosphere. The Cluster observations of earthward propagating plasmoids on flux ropes are formed repeatedly and ejected tailward in the course of geomagnetically active time.