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Two‐dimensional Hall reconnection model can explain the fast release of magnetic energy and most of its predictions have been demonstrated by in situ satellite observations. However, the three‐dimensional effect to reconnection remains poorly known. Recent numerical simulations have shown that three‐dimensional evolution is more complex than two‐dimensional in that reconnection occurs in multiple sites that are not necessarily in the primary neutral current sheet. Here, we present the first observational evidence for localized secondary reconnection at the separatrix surface of a magnetic flux rope (MFR). This secondary reconnection occurs between the axial magnetic field of the MFR, which points out‐of‐plane of the Earth's magnetopause reconnection, and the magnetospheric field. This three‐dimensional electron‐scale reconnection in the exhaust facilitates the cross‐scale energy conversion from the macro‐scale down to electron‐scale. Plain Language Summary: Magnetic reconnection releases large amounts of magnetic energy in astrophysical, space and laboratory plasmas. For the decades, the reconnection has been investigated largely based on two‐dimensional models while the three‐dimensional effect to reconnection remains poorly known. It has been shown by numerical simulation that three‐dimensional evolution, because of the freedom in the out‐of‐plane direction, is turbulent and distinct from the two‐dimension laminar reconnection in that reconnection occurs in multiple sites that are not necessarily in the primary neutral current sheet. The turbulent reconnection is characterized by the formation and interaction of multiple flux ropes, or chaotic magnetic field lines in the outflow region. Although small‐scale magnetic flux ropes and their interactions have been observed, one important missing piece is whether reconnection occurs at the region away from the neutral current sheet. Here we present the first evidence for localized secondary reconnection at the separatrix surface of the primary reconnection. This secondary reconnection occurs between the axial magnetic field of the flux rope, which points out‐of‐plane of the magnetopause reconnection, and the magnetospheric field. This three‐dimensional patchy reconnection in the exhaust facilitates the cross‐scale energy conversion from the macro‐scale down to electron‐scale and leads to a turbulent evolution of reconnection. Key Points: Three‐dimensional secondary electron‐scale reconnection was observed at the separatrix of a flux rope in the magnetosphereNew light on the destiny of flux rope from a three‐dimensional perspective: dissipation through the reconnection of the core fieldThe cross‐scale energy conversion is through the formation and dissipation of flux ropes [ABSTRACT FROM AUTHOR]

Since many applications of YBCO tapes operate in external magnetic fields, it is necessary to investigate the magneto-angular dependence of critical current and n-values in coated conductors. In this paper, five commercial YBCO tapes with different microstructures produced by three different manufacturers are chosen. The selected samples have a width of 2.0, 4.0, 4.8, 6.0 or 12 mm, with copper, brass or stainless steel laminations. The critical current density dependence Jc(B, θ) and n-values characteristics n(B, θ) of the tapes are comprehensively measured under various magnetic fields and orientations. Afterwards, the obtained experimental data sets are successfully fitted using a novel multi-objective model which considers the material anisotropy. By using this approach, a fitting function Ic(B, θ) can always be obtained to accurately describe the experimental data, regardless of the fabrication and width differences of the superconducting tapes. Moreover, our experiment shows that when subject to different external magnetic fields, the angular dependence of n-values characteristics is directly correlated with the corresponding critical current profiles. Our results are helpful to predict the critical current of electromagnetically interacting 2G HTS wires, thereby improving the design and performance of the devices made from YBCO tapes. [ABSTRACT FROM AUTHOR]

Some high-speed rotating micro-machines and micro-vibration devices rely on the use of whirling micro-shafts subject to the effect of gravity and magnetic fields. At present, the consequences of the interaction between the elastic deformation of such shafts and the magnetic/gravitational field effects remain unresolved. Focusing on micro-scale whirling shafts with very high torsional rigidity, this study presents a theoretical treatment grounded in the theory of micro-continuum elasticity to examine the ramification of this interaction. The differential transformation method (DTM) is used to obtain extensive numerical results for qualitative assessments of the magnetic-gravitational effects interaction on standing, hanging and horizontally positioned spinning micro-scale shafts. The influence of bearing-support flexibility on the response of the whirling micro-shaft is also considered with rotational and translational springs. The gravitational sag reduces the stability of whirling standing micro-shafts and increases that of the hanging micro-shafts. Further, for all the micro-shafts configurations investigated, the magnetic field is observed to stiffen the response of the shaft and favorably shifts the critical points of vibration of the whirling shafts forward. [ABSTRACT FROM AUTHOR]

Nowadays, superconducting high field magnets are used in numerous applications due to their superior properties. High temperature superconductors (HTS) are usually used for production of circular pancake or racetrack coils. However different geometries of HTS coils might be required for some specific applications. In this study, the HTS coil wound on a rectangular frame was fully characterized in homogeneous DC background field. The study contains measurements of critical current angular dependencies. The critical current of the entire coil and two selected strands under different magnitudes and orientations of external magnetic fields are measured. The critical regions of the coil in different angular regimes are determined. This study brings better understanding of the in- field performance of HTS coils wound on frames with right-angles. [ABSTRACT FROM AUTHOR]

The magnetoelectric (ME) effect in a ME composite structure in which a magnetostrictive component is bonded with a piezoelectric component was studied theoretically, based on the hyperbolic nonlinear constitutive relation of magnetostriction and the piezoelectric equations. A quantitative relation was established analytically for the ME effect and the influencing factors, such as the magnetic bias field and the structure dimensions. It was verified that the theoretical model agrees qualitatively with the experimental results published in Ref. 7. It can also be predicted by the model that the ME effect can be improved by optimizing the structure dimensions. [ABSTRACT FROM AUTHOR]

Magnetic reconnection and turbulence are the two most important energy dissipation processes in plasma. These two processes intertwine with each other and play important roles in their respective dynamic evolution. Here, we present the first evidence that secondary reconnections occur in the turbulent outflow driven by a primary reconnection in the Earth's magnetotail. We have identified 14 secondary reconnections in a large number of current filaments in the turbulent outflow, which persisted for about one and half an hour. Most of these secondary reconnections were electron‐only reconnection that has recently been discovered in the magnetosheath. These secondary reconnections entangled the magnetic field lines and dissipated the magnetic energy in the outflow region far away from the primary X line. Plain Language Summary: Magnetic reconnection usually evolves into turbulent state. The role of turbulence in reconnection is one of the most outstanding questions in reconnection. By using the unprecedented high‐cadence data from the magnetospheric multiscale mission, we present the first evidence that secondary reconnections occur in the turbulent outflow driven by a primary reconnection in the Earth's magnetotail. Most of these secondary reconnections occurred in electron‐scale current sheets and were without ion couplings. These secondary reconnections future released energy in the outflow region besides the primary X line. These results are important for understanding the turbulent reconnection, which is ubiquitous in the astrophysical system but barely investigated by in situ measurements. Key Points: First observation of secondary reconnections in the turbulent outflow driven by primary reconnectionThese secondary reconnections occurred in current sheets with broad shear angles and different orientationsMost of these secondary reconnections were without clear ion couplings [ABSTRACT FROM AUTHOR]

We report a Magnetospheric Multiscale (MMS) mission observation of magnetic reconnection occurring at the edge of a large‐scale magnetic flux rope (MFR), the cross‐section of which was about 2 RE. The MFR was observed at the duskside in the Earth's magnetotail and was highly oblique with its axis approximately along the XGSM direction. We find an electron‐scale current sheet near the edge of this MFR. The Hall magnetic and electric field, super‐Alfvénic electron outflow, parallel electric field, and positive energy dissipation were observed associated with the current sheet, which indicates that MMS detected a reconnecting current sheet with a large guide field. Interestingly, ions were not coupled in this reconnection, akin to the electron‐only reconnection observed in the turbulent magnetosheath. We further find that the electron‐only reconnection is commonly associated with a macroscopic MFR. This result will shed new light on understanding the multiscale coupling associated with an MFR in space plasmas. Key Points: MMS observed an electron‐only reconnection at the edge of a macroscopic magnetic flux rope in the magnetotailElectron‐only reconnection is ubiquitous in space plasma [ABSTRACT FROM AUTHOR]

Abstract: It has been proposed that, in the near‐Earth magnetotail, earthward propagating flux ropes can merge with the Earth's dipole magnetic field and dissipate its magnetic energy. However, the reconnection diffusion region related to this process has not been identified. Here we report the first in situ observation of magnetic reconnection between an earthward propagating flux rope and the closed magnetic field lines connecting to Earth. Magnetospheric Multiscale (MMS) spacecraft crossed a vertical current sheet between the leading edge of the flux rope (negative Bz) and the geomagnetic field (positive Bz). The subion‐scale current sheet, super‐Alfvénic electron outflow, Hall magnetic and electric field, conversion of magnetic energy to plasma energy (J·E > 0), and magnetic null were observed during the crossing. All the above signatures indicate that MMS detected the reconnection diffusion region. This result is also relevant to other planets with intrinsic magnetosphere. [ABSTRACT FROM AUTHOR]

Magnetic and transitional behaviors are investigated in Mn1.9Co0.1Sb intermetallic compound. Mn2Sb is a simple ferrimagnet with Neel temperature around 550 K. The Co-introduction results in the appearance of antiferromagnetic state, and therefore, the first-order magnetic transition occurs between antiferromagnetic and ferrimagnetic state, which can be induced by temperature/magnetic field, in Mn1.9Co0.1Sb alloy. Accordingly, a magnetic entropy change as high as 5 J kg-1K-1 and a large magnetoresistance of 46% under the field change of 10 and 50 kOe are achieved, respectively. [ABSTRACT FROM AUTHOR]

Abstract: A conventional Ta/NiFe/Cu/NiFe/FeMn spin valve was prepared to investigate the exchange bias properties with the variations of deposition field. By enhancing the deposition magnetic fields from 50 to 650Oe, increase of exchange bias fields at a given thickness of the pinned NiFe layer has been found in the spin valves. In this paper, we show that this increase is due to the change of magnetic moment distribution at the ferromagnetic and antiferromagnetic interface by comparison of measured results with the interfacial uncompensated model. Therefore, by enhancing deposition magnetic fields, a large exchange-coupling field can be achieved in relatively thicker magnetic films for application. [Copyright &y& Elsevier]