Three‐dimensional structure of magnetic reconnection in the near‐Earth magnetotail is explored using Geotail observations from 1996 to 2012. Magnetic reconnection is identified as a simultaneous ...plasma flow and magnetic field reversal near the neutral sheet with intense out‐of‐plane electron currents. There are 30 events in the region of −32 < X < −18 RE (in the aberrated GSM coordinates) in the magnetotail. The dawn‐dusk width (in the y direction) of the magnetic reconnection site is probably less than 8 RE with its center in the premidnight region. The magnetic field structure in the x‐z plane does not change significantly in the full width of the magnetic reconnection site. The ion inflow‐outflow structure shows a marked edge effect in the duskside. As inflow, ions move toward the equatorial plane with an additional dawnward motion. This dawnward motion is more evident in the duskside. As outflows, ions escape tailward and earthward with a duskward motion, as expected from the Speiser motion, except at the duskside edge. At the duskside edge, almost all ions move dawnward, and only part of high‐energy ions can escape earthward and tailward. There is a possibility that the dawnward flow consists of adjacent plasma sheet plasmas transported by the pressure gradient force at the duskside edge. The present results would be the first step to construct a three‐dimensional structure of magnetic reconnection in various cosmic plasmas.
Key Points
3D structure of magnetic reconnection in the magnetotail is derivedIon flow sturcure has a clear 3D structure in magnetic reconnectionGeotail ion and electron observations in the magnetotail are used
A search for the heaviest isotopes of fluorine, neon, and sodium was conducted by fragmentation of an intense ^{48}Ca beam at 345 MeV/nucleon with a 20-mm-thick beryllium target and identification ...of isotopes in the large-acceptance separator BigRIPS at the RIKEN Radioactive Isotope Beam Factory. No events were observed for ^{32,33}F, ^{35,36}Ne, and ^{38}Na and only one event for ^{39}Na after extensive running. Comparison with predicted yields excludes the existence of bound states of these unobserved isotopes with high confidence levels. The present work indicates that ^{31}F and ^{34}Ne are the heaviest bound isotopes of fluorine and neon, respectively. The neutron dripline has thus been experimentally confirmed up to neon for the first time since ^{24}O was confirmed to be the dripline nucleus nearly 20 years ago. These data provide new keys to understanding the nuclear stability at extremely neutron-rich conditions.
A method based on electron magnetohydrodynamics (EMHD) for the reconstruction of steady, two‐dimensional plasma and magnetic field structures from data taken by a single spacecraft, first developed ...by Sonnerup et al. (2016), https://doi.org/10.1002/2016ja022430, is extended to accommodate inhomogeneity of the electron density and temperature, electron inertia effects, and guide magnetic field in and around the electron diffusion region (EDR), the central part of the magnetic reconnection region. The new method assumes that the electron density and temperature are constant along, but may vary across, the magnetic field lines. We present two models for the reconstruction of electron streamlines, one of which is not constrained by any specific formula for the electron pressure tensor term in the generalized Ohm's law that is responsible for electron unmagnetization in the EDR, and the other is a modification of the original model to include the inertia and compressibility effects. Benchmark tests using data from fully kinetic simulations show that our new method is applicable to both antiparallel and guide‐field (component) reconnection, and the electron velocity field can be better reconstructed by including the inertia effects. The new EMHD reconstruction technique has been applied to an EDR of magnetotail reconnection encountered by the Magnetospheric Multiscale spacecraft on 11 July 2017, reported by Torbert et al. (2018), https://doi.org/10.1126/science.aat2998 and reconstructed with the original inertia‐less version by Hasegawa et al. (2019), https://doi.org/10.1029/2018ja026051, which demonstrates that the new method better performs in recovering the electric field and electron streamlines than the original version.
Plain Language Summary
Magnetic reconnection is a physical process that converts magnetic energy to plasma energy by changing the topology of magnetic field lines. Reconnection occurring at the outer boundary of planetary magnetospheres, called the magnetopause, is key to the entry of solar wind mass and energy into planetary magnetospheres. Reconnection occurring in the nightside portion of the magnetospheres is also key to fast release of magnetic energy during substorms or sudden auroral brightening. However, space plasma and magnetic field in those reconnection regions are invisible to any remote sensing instruments currently available, and should be measured in situ by spacecraft to understand details of the reconnection process. In the present study, we have improved a method for analyzing data from such in‐situ measurements, which can visualize two‐dimensional magnetic field and electron streamline structures in the central part of the reconnection region. The newly developed method allows spatial variations of the electron density and temperature, effects of finite electron mass, and not strictly antiparallel magnetic field configurations in the reconnection region, as commonly observed at the magnetopause, and thus has more applicability. Tests of the method using numerical simulation results and application to actual spacecraft observations demonstrate a better performance than earlier ones.
Key Points
Method to reconstruct two‐dimensional plasma and field structures from spacecraft data based on compressible electron magnetohydrodynamics
The new method accommodates nonuniform density/temperature, finite electron inertia, and guide magnetic field in the reconnection region
The new method successfully benchmarked by use of fully kinetic simulation results and applied to a magnetotail reconnection event
Mammalian target of rapamycin (mTOR) inhibitors are the main immunosuppressive drugs for organ transplant recipients. Nevertheless, the mechanisms by which mTOR inhibitors induce immunosuppression is ...not fully understood. Myeloid‐derived suppressor cells (MDSCs) maintain host immunity; however, the relationship between mTOR inhibitors and MDSCs is unclear. Here, the results from a murine cardiac transplantation model revealed that rapamycin treatment (3 mg/kg, intraperitoneally on postoperative days 0, 2, 4, and 6) led to the recruitment of MDSCs and increased their expression of inducible nitric oxide synthase (iNOS). Immunohistochemical analysis revealed that rapamycin induced the migration of iNOS‐expressing MDSCs into the subintimal space within the allograft vessels, resulting in a significant prolongation of graft survival compared with that in the untreated group (67 days vs. 7 days, respectively). These effects were counterbalanced by the administration of an anti‐Gr‐1, which reduced allograft survival to 21 days. Moreover, adoptive transcoronary arterial transfer of MDSCs from rapamycin‐treated recipients prolonged allograft survival; this increase was reversed by the anti‐Gr‐1 antibody. Finally, co‐administration of rapamycin and a mitogen‐activated protein kinase kinase (MEK) inhibitor trametinib reversed rapamycin‐mediated MDSC recruitment. Thus, the mTOR and Raf/MEK/extracellular signal regulated kinase (ERK) signaling pathways appear to play an important role in MDSC expansion.
Rapamycin blunts immune reactions through induction of functional myeloid‐derived suppressor cells in murine cardiac transplant recipients.
We present Magnetospheric Multiscale observations of an electron‐scale reconnecting current sheet in the mixing region along the trailing edge of a Kelvin‐Helmholtz vortex during southward ...interplanetary magnetic field conditions. Within this region, we observe intense electrostatic wave activity, consistent with lower‐hybrid waves. These waves lead to the transport of high‐density magnetosheath plasma across the boundary layer into the magnetosphere and generate a mixing region with highly compressed magnetic field lines, leading to the formation of a thin current sheet associated with electron‐scale reconnection signatures. Consistencies between these reconnection signatures and a realistic, local, fully‐kinetic simulation modeling this current sheet indicate a temporal evolution of the observed electron‐scale reconnection current sheet. The multi‐scale and inter‐process character of this event can help us understand plasma mixing connected to the Kelvin‐Helmholtz instability and the temporal evolution of electron‐scale reconnection.
Plain Language Summary
Like wind blowing over water, the stream of ionized gas released from the Sun, called the solar wind, can lead to waves and rolled‐up vortex structures at the boundary of Earth's magnetosphere, called the magnetopause. These so‐called Kelvin‐Helmholtz waves have been shown to be connected to various different plasma processes on different scales. This multi‐scale and multi‐process character makes them an ideal candidate to study the relation between these processes from both spacecraft observations and simulations. By using spacecraft data from the Magnetospheric Multiscale mission, which was designed for the study of small‐scale plasma processes in Earth's magnetosphere, we show observations of electron‐scale magnetic reconnection, an explosive energy conversion process in plasmas, in a region along the trailing edge of these waves. These observations shed new light on the multi‐scale and multi‐process character of the Kelvin‐Helmholtz instability and the energy conversion processes along its boundary.
Key Points
A reconnecting electron‐scale current sheet is observed by Magnetospheric Multiscale (MMS) in mixing plasma along the trailing edge of a Kelvin‐Helmholtz vortex
Realistic 2.5D fully‐kinetic simulation shows reasonable agreement with MMS data
Consistencies between the simulation and MMS indicate a temporal evolution of the reconnecting current sheet
The Kelvin‐Helmholtz instability is a key process for the transport of solar wind plasma into the Earth's magnetosphere when the interplanetary magnetic field (IMF) is northward. Previous kinetic ...simulations for symmetric layers have demonstrated that the flow vortices compress the magnetopause current layer and induce magnetic reconnection, leading to the rapid streaming of solar wind plasma into the vortices along newly reconnected field lines. Using fully kinetic 3‐D simulations, we demonstrate that the inherent density asymmetry across the boundary layer leads to a spectrum of oblique interchange instabilities along the magnetospheric side of the vortices. These secondary instabilities give rise to turbulence, which transports the solar wind plasma originally stored within the flow vortices deep into the magnetosphere. Simple estimates suggest that this turbulent transport may contribute significantly to the formation of the Earth's low‐latitude boundary layer and the cold‐dense plasma sheet during prolonged periods of northward IMF.
Key PointsWe performed 3‐D fully kinetic simulations modeling the Earth's magnetopauseThe KH instability drives turbulence leading to efficient solar wind transportThe estimated transport rate explains the formation of the LLBL and CDPS
At the Earth's low‐latitude magnetopause, clear signatures of the Kelvin‐Helmholtz (KH) waves have been frequently observed during periods of the northward interplanetary magnetic field (IMF), ...whereas these signatures have been much less frequently observed during the southward IMF. Here, we performed the first 3‐D fully kinetic simulation of the magnetopause KH instability under the southward IMF condition. The simulation demonstrates that fast magnetic reconnection is induced at multiple locations along the vortex edge in an early nonlinear growth phase of the instability. The reconnection outflow jets significantly disrupt the flow of the nonlinear KH vortex, while the disrupted turbulent flow strongly bends and twists the reconnected field lines. The resulting coupling of the complex field and flow patterns within the magnetopause boundary layer leads to a quick decay of the vortex structure, which may explain the difference in the observation probability of KH waves between northward and southward IMF conditions.
Plain Language Summary
Space between planets is filled with ionized gas released from the upper atmosphere of the Sun, called the solar wind. Although the Earth's magnetic field basically acts as a barrier to prevent energetic solar wind from penetrating into the region filled with the Earth's magnetic field, called the magnetosphere, it is known that the solar wind frequently leaks into the magnetosphere. The Kelvin‐Helmholtz (KH) instability, which is a flow‐driven instability and can be unstable by the antisunward flowing solar wind, has been considered as an important candidate process for the solar wind leaks. However, past spacecraft observations have revealed that the observation probability of KH waves is very low when the magnetic field in the solar wind, called the interplanetary magnetic field (IMF), is oriented southward, that is, opposite from the Earth's magnetic field. In this study, based on a plasma kinetic simulation, it is found that when the IMF is southward, magnetic reconnection, which is an explosive plasma process that rearranges the magnetic topology across the boundary, occurs at multiple locations in the KH waves and rapidly destroys the wave structures. This may explain the low observation probability of the KH waves under the southward IMF.
Key Points
Three‐dimensional fully kinetic simulation of Kelvin‐Helmholtz instability at the Earth's magnetopause under the southward IMF condition is performed
Fast reconnection causes a rapid decay of the nonlinear vortex structure in the early nonlinear growth phase of the instability
The vortex decay can lead to a lower probability of observing magnetopause Kelvin‐Helmholtz waves/vortices during southward IMF periods
Summary
Odanacatib is a cathepsin K inhibitor investigated for the treatment of postmenopausal osteoporosis. Phase 2 data indicate that 50 mg once weekly inhibits bone resorption and increases bone ...mineral density, with only a transient decrease in bone formation. We describe the background, design and participant characteristics for the phase 3 registration trial.
Introduction
Odanacatib (ODN) is a selective cathepsin K inhibitor being evaluated for the treatment of osteoporosis. In a phase 2 trial, ODN 50 mg once weekly reduced bone resorption while preserving bone formation and progressively increased BMD over 5 years. We describe the phase III Long-Term ODN Fracture Trial (LOFT), an event-driven, randomized, blinded placebo-controlled trial, with preplanned interim analyses to permit early termination if significant fracture risk reduction was demonstrated. An extension was planned, with participants remaining on their randomized treatment for up to 5 years, then transitioning to open-label ODN.
Methods
The three primary outcomes were radiologically determined vertebral, hip, and clinical non-vertebral fractures. Secondary end points included clinical vertebral fractures, BMD, bone turnover markers, and safety and tolerability, including bone histology. Participants were women, 65 years or older, with a BMD T-score ≤−2.5 at the total hip (TH) or femoral neck (FN) or with a prior radiographic vertebral fracture and a T-score ≤−1.5 at the TH or FN. They were randomized to ODN or placebo tablets. All received weekly vitamin D
3
(5600 international units (IU)) and daily calcium supplements as needed to ensure a daily intake of approximately 1200 mg.
Results
Altogether, 16,713 participants were randomized at 387 centers. After a planned interim analysis, an independent data monitoring committee recommended that the study be stopped early due to robust efficacy and a favorable benefit/risk profile. Following the base study closeout, 8256 participants entered the study extension.
Conclusions
This report details the background and study design of this fracture end point trial and describes the baseline characteristics of its participants.
We present in‐depth analysis of three southward‐moving meso‐scale (ion‐to magnetohydrodynamic‐scale) flux transfer events (FTEs) and subsequent crossing of a reconnecting magnetopause current sheet ...(MPCS), which were observed on 8 December 2015 by the Magnetospheric Multiscale spacecraft in the subsolar region under southward and duskward magnetosheath magnetic field conditions. We aim to understand the generation mechanism of ion‐scale magnetic flux ropes (ISFRs) and to reveal causal relationship among magnetic field structures, electromagnetic energy conversion, and kinetic processes in magnetic reconnection layers. Results from magnetic field reconstruction methods are consistent with a flux rope with a length of about one ion inertial length growing from an electron‐scale current sheet (ECS) in the MPCS, supporting the idea that ISFRs can be generated through secondary reconnection in an ECS. Grad‐Shafranov reconstruction applied to the three FTEs shows that the FTEs had axial orientations similar to that of the ISFR. This suggests that these FTEs also formed through the same secondary reconnection process, rather than multiple X‐line reconnection at spatially separated locations. Four‐spacecraft observations of electron pitch‐angle distributions and energy conversion rate j·E′=j·E+ve×B $\mathbf{j}\cdot {\mathbf{E}}^{\prime }=\mathbf{j}\cdot \left(\mathbf{E}+{\mathbf{v}}_{\mathrm{e}}\times \mathbf{B}\right)$ suggest that the ISFR had three‐dimensional magnetic topology and secondary reconnection was patchy or bursty. Previously reported positive and negative values of j·E′ $\mathbf{j}\cdot {\mathbf{E}}^{\prime }$, with magnitudes much larger than expected for typical MP reconnection, were seen in both magnetosheath and magnetospheric separatrix regions of the ISFR. Many of them coexisted with bi‐directional electron beams and intense electric field fluctuations around the electron gyrofrequency, consistent with their origin in separatrix activities.
Plain Language Summary
Magnetic reconnection is a physical process that converts magnetic energy into plasma energy by changing the connectivity of magnetic field lines from one region to another. Magnetic reconnection at the outer boundary of planetary magnetospheres, known as the magnetopause (MP), is key to the entry of solar wind plasma and energy into the magnetospheres that forms the basis for space weather phenomena in the magnetospheres. MP reconnection often occurs in a transient or patchy manner, forming magnetic flux ropes (FRs) with helical field lines of various sizes. They may become an important pathway for fast coupling between the solar wind and magnetosphere. However, the generation mechanism of a subclass of FRs, relatively small “ion‐scale” FRs, is poorly understood. Computer simulations show that they are formed in thin and elongated current sheets of single active reconnection site, but this scenario has not been confirmed by observations. Our observations based on NASA's Magnetospheric Multiscale mission show that ion‐scale FR can form in a thin current sheet of single ongoing reconnection site at Earth's MP. The observed FR showed signatures of complex field line connectivity and localized conversion from electromagnetic to electron energy and vice versa, indicating complex MP dynamics.
Key Points
Ion‐scale magnetic flux rope (ISFR) can be generated from reconnecting electron‐scale current sheet at the subsolar magnetopause (MP)
Preceding mesoscale flux ropes had axial directions akin to that of the ISFR in the MP, suggesting the same generation mechanism
The ISFR had complex magnetic topology with three‐dimensional effects and involved patchy, intense energy conversion in separatrix regions
We examine traversals on 20 November 2001 of the equatorial magnetopause boundary layer simultaneously at ∼1500 magnetic local time (MLT) by the Geotail spacecraft and at ∼1900 MLT by the Cluster ...spacecraft, which detected rolled‐up MHD‐scale vortices generated by the Kelvin‐Helmholtz instability (KHI) under prolonged northward interplanetary magnetic field conditions. Our purpose is to address the excitation process of the KHI, MHD‐scale and ion‐scale structures of the vortices, and the formation mechanism of the low‐latitude boundary layer (LLBL). The observed KH wavelength (>4 × 104 km) is considerably longer than predicted by the linear theory from the thickness (∼1000 km) of the dayside velocity shear layer. Our analyses suggest that the KHI excitation is facilitated by combined effects of the formation of the LLBL presumably through high‐latitude magnetopause reconnection and compressional magnetosheath fluctuations on the dayside, and that breakup and/or coalescence of the vortices are beginning around 1900 MLT. Current layers of thickness a few times ion inertia length ∼100 km and of magnetic shear ∼60° existed at the trailing edges of the vortices. Identified in one such current sheet were signatures of local reconnection: Alfvénic outflow jet within a bifurcated current sheet, nonzero magnetic field component normal to the sheet, and field‐aligned beam of accelerated electrons. Because of its incipient nature, however, this reconnection process is unlikely to lead to the observed dusk‐flank LLBL. It is thus inferred that the flank LLBL resulted from other mechanisms, namely, diffusion and/or remote reconnection unidentified by Cluster.
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