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There has been considerable confusion in the literature about what mirror mode (MM), magnetic decrease (MD), and linear magnetic decrease (LMD) structures are and are not. We will reexamine past spacecraft observations to demonstrate the observational similarities and differences between these magnetic and plasma structures. MM structures in planetary magnetosheaths, cometary sheaths, and the heliosheath have the following characteristics: (1) the structures have little or no changes in the magnetic field direction across the magnetic dips; (2) the structures have quasiperiodic spacings, varying from ∼20 proton gyroradii (rp) in the Earth's magnetosheath to ∼57 rp in the heliosheath; and (3) the magnetic dips have smooth edges. Magnetosheath MM structures are generated by the mirror instability where β⊥/β∥ > 1 + 1/β⊥ (β is the plasma thermal pressure divided by the magnetic pressure). In general, the sources of free energy for the mirror instability are reasonably well understood: shock compression, field line draping, and, in the cases of comets and the heliosheath, also ion pickup. The observational properties of interplanetary MDs are as follows: (1) there is a broad range of magnetic field angular changes across them; (2) their thicknesses can range from as little as 2–3 rp to thousands of rp, with no “characteristic” size; and (3) they typically are bounded by discontinuities. The mechanism(s) for interplanetary MD generation is (are) currently unresolved, although at least five different mechanisms have been proposed in the literature. Tsurutani et al. (2009a) have argued against mirror instability for those MDs generated within interplanetary corotating interaction regions. Interplanetary LMDs are by definition a subset of MDs with small angular changes across them (θ < 10°). Are LMDs generated by the mirror instability or by another mechanism? Is it possible that there are several different types of LMDs involving different generation mechanisms? At the present time, no one knows the answers to these latter questions.

Magnetic holes in the solar wind with little or no directional change across the magnetic depression are related to mirror mode structures. Recently, Zhang et al. (2008) determined the characteristic size and shape of such mirror mode structures in the solar wind at 0.72 AU. They found that the mirror mode structure in the solar wind is quite elongated along the field direction. In this report, we examine the size and shape of isolated magnetic holes and train of holes, separately. We find that the isolated holes are slightly smaller in width and more elongated than the multiple holes. This observation suggests a particular evolutionary history of mirror mode structures in the solar wind in which multiple holes coalesce with time into isolated structures more elongated parallel to the magnetic field.

Magnetic field measurements play a crucial role in deep space exploration, contributing significantly to our understanding of planetary habitability and the space plasma environment. Among the various instruments employed in space exploration missions, the fluxgate magnetometer stands out as a widely used tool. However, its zero offset undergoes gradual changes, necessitating regular in-flight calibration. This article comprehensively reviews in-flight calibration methods for spaceborne magnetometers in deep space exploration, leveraging physical phenomena inherent to the space environment. The methods for calculating the zero offset can be divided into two categories. The first group employs formulas, including the Belcher method, Hedgecock method, Davis-Smith method, and both one-dimensional and three-dimensional mirror mode methods. Notably, the Davis-Smith method emerges as the optimal choice among these approaches. The second group employs probability-based solutions, constituting the in-flight calibrati

We report the observation of mirror mode structures by Cluster spacecraft at around X∼-16 RE in the Earth’s magnetotail. The wavelength of the mirror structure is larger than 7000 km, corresponding to tens of ion gyroradii. Features of the mirror structures are similar to those detected in the magnetosheath: the anti-correlation between the magnetic field strength and plasma density, zero phase velocity in the plasma rest frame and linear polarization. The structures were observed in a region bounded by two dipolarizations during a substorm intensification. Thus, the dipolarization process may provide a plasma condition facilitating the growth of the mirror mode structures. Another interesting feature is the electron dynamics within the mirror structures. Thermal electron energy flux has an enhancement at 0° and 180° pitch angles inside the magnetic dips of the first three mirror structures and an enhancement at 90° pitch angle inside the magnetic dip of the last structure. The different electron distribution inside the mirror structures might be a result of different evolution stages of the mirror wave. The last structure may be in the nonlinear stage of the mirror instability, whereas the three others with quasi-sinusoidal waveforms may be in the linear stage. In addition, we found that intense whistler waves were confined within the magnetic dips. We conjecture that whistler waves observed in the first three dips were generated in a remote region, then they were trapped in the mirror mode troughs and transported toward the spacecraft; while the whistler wave detected in the last dip was excited locally by the electron anisotropy instability.

Magnetic holes at the ion-to-electron kinetic scale (KSMHs) are one of the extremely small intermittent structures generated in turbulent magnetized plasmas. In recent years, the explorations of KSMHs have made substantial strides, driven by the ultra-high-precision observational data gathered from the Magnetospheric Multiscale (MMS) mission. This review paper summarizes the up-to-date characteristics of the KSMHs observed in Earth’s turbulent magnetosheath, as well as their potential impacts on space plasma. This review starts by introducing the fundamental properties of the KSMHs, including observational features, particle behaviors, scales, geometries, and distributions in terrestrial space. Researchers have discovered that KSMHs display a quasi-circular electron vortex-like structure attributed to electron diamagnetic drift. These electrons exhibit noticeable non-gyrotropy and undergo acceleration. The occurrence rate of KSMH in the Earth’s magnetosheath is significantly greater than in the solar wind and magnetotail, suggesting the turbulent magnetosheath is a primary source region. Additionally, KSMHs have also been generated in turbulence simulations and successfully reproduced by the kinetic equilibrium models. Furthermore, KSMHs have demonstrated their ability to accelerate electrons by a novel non-adiabatic electron acceleration mechanism, serve as an additional avenue for energy dissipation during magnetic reconnection, and generate diverse wave phenomena, including whistler waves, electrostatic solitary waves, and electron cyclotron waves in space plasma. These results highlight the magnetic hole’s impact such as wave-particle interaction, energy cascade/dissipation, and particle acceleration/heating in space plasma. We end this paper by summarizing these discoveries, discussing the generation mechanism, similar structures, and observations in the Earth’s magnetotail and solar wind, and presenting a future extension perspective in this active field.

We demonstrate a wavelength switchable high-power passively mode-locked laser based on a large size rectangular core crystalline waveguide and a semiconductor saturable absorption mirror. The wavelength switching is realized by controlling the polarization direction, the 1030 nm or 1050 nm mode-locked pulses are obtained. For 1030 nm single-wavelength configuration, an average power of 16.8-W with 2-ps pulse duration is achieved. For 1050 nm single-wavelength configuration, we obtained 15-W of average output power in pulses with 2.7-ps duration. This work proves that, in the large size rectangular core crystalline waveguide, the gain of 1030 nm laser is different for different polarization states, and the wavelength switching is realized.

According to the principle of system identification, the least squares algorithm and MATLAB system identification toolbox is used to identify the model of the test bench of the vibration mirror swing scan system with the step signal and the vibration mirror swing-sweep angular displacement as the input and output quantities. Taking the identification model as the object, a sliding mode variable structures composite controller of fuzzy switching gain adjustment is designed. In the controller, according to the actual conditions achieved by the sliding mode, the switching gain is effectively estimated, so as to eliminate the interference of uncertain factors and high-frequency vibration. At the same time, the sliding mode function and sliding mode controller of the system needs to be designed. The switching hyperplane of the system is designed using the fuzzy switching method and the desired dynamic characteristics of the system, to ensure the smooth transition of the system state from outside the hyperplane to the convergence of the switching hyperplane. The simulation results show that: the new composite control method eliminates the shortcomings of PD series control, improves the response speed and tracking accuracy of the vibration mirror swing scan system, and improves the overall performance of the system. And it has a strong ability to inhibit the adverse effects caused by changes in the parameters of the controlled object.

Empathizing is defined as the drive to identify the mental states of others in order to predict their behavior and respond with an appropriate emotion. Systemizing is defined as the drive to analyze a system in terms of the rules that govern it to predict its behavior. We undertook voxel-by-voxel investigations of regional white matter volume (rWMV) and fractional anisotropy (FA) of diffusion tensor imaging to discover the WM structural correlates of empathizing, systemizing, and their difference (D score: systemizing−empathizing). Whole brain analyses of covariance revealed that across both sexes, the D score was negatively correlated with rWMV in the WM area in the bilateral temporal lobe, near the right inferior frontal gyrus, near the ventral medial prefrontal cortex, and near the posterior cingulate cortex and positively correlated with FA in an area involving the superior longitudinal fasciculus. Post-hoc analyses revealed that these associations were generally formed by both the correlation between WM structures and empathizing as well as the opposite correlation between WM structures and systemizing. A significant effect of interaction between sex and the D score on rWMV, which was mainly observed because of a positive correlation between rWMV and empathizing in females and a negative correlation between rWMV and systemizing in females, was found in an area close to the right inferior parietal lobule and temporoparietal junction. Our results suggest that WM structures involving the default mode network and the mirror neuron system support empathizing, and that a WM structure relating to the external attention system supports systemizing. Further, our results revealed an overlap between positive/negative WM structural correlates of empathizing and negative/positive WM structural correlates of systemizing despite little correlation between empathizing and systemizing, which supports the previously held idea that there is a trade-off between empathizing and systemizing in the brain. •White matter structures associated with empathizing/systemizing and the D score•Empathizing's positive correlates included the key nodes of the default mode network.•They also included the key nodes of the mirror neuron system.•Those of systemizing included the key nodes of the external attention system.

Understanding of single-layer and bilayer thin films of WO 3 and Ta 2 O 5 for electrochromic applications remains elusive. In this study, single layers of WO 3 and Ta 2 O 5 and bilayer thin films of WO 3 /Ta 2 O 5 and Ta 2 O 5 /WO 3 were prepared by the sol–gel method followed by spin coating. X-ray diffraction (XRD) analysis revealed the semicrystalline nature of WO 3 and the absence of significant crystalline planes in Ta 2 O 5 . Raman spectroscopy confirmed the characteristic vibrational modes of WO 3 and Ta 2 O 5 in both single-layer and bilayer thin films. Enhancement in cyclic voltammetry (CV) was observed in Ta 2 O 5 /WO 3 compared to other thin films. Additionally, Ta 2 O 5 /WO 3 exhibited a greater change in transmittance (Δ T ) relative to other configurations. The impact of proton irradiation on the thin films was further investigated, revealing modifications in their structural and phonon vibrational properties. Notably, the CV performance of the irradiated thin films was drastically reduced. X-ray absorption spectroscopy (XAS) provided insights into the modulation of hybridization of O with W/Ta and the charge states of W and Ta in the thin films. This study provides a comprehensive understanding of single-layer and bilayer electrochromic thin films and their response to proton irradiation, paving the way for the development of space-applicable electrochromic bilayer thin films with improved performance and stability.

This paper designs and fabricates an electrostatic-driven dual-axis MEMS micromirror capable of out-of-plane torsional motion about both the X and Y axes. Both torsional axes employ planar comb structures for their drive mechanisms, effectively reducing the fabrication complexity. By leveraging the structural asymmetry introduced during processing in conjunction with resonant operating modes, the inherent disadvantage of planar comb structures for torsional motion is overcome. This study explores the operating principle, structural design, performance simulation, fabrication process, and testing of the micromirror. It proposes an indirect simulation method suitable for planar comb drive structures, providing theoretical support for device fabrication. During fabrication, optimising the removal of isolation material through oxygen–silicon growth enhances the reliability of subsequent processes. Test results demonstrate that the fabricated MEMS micromirror achieves a 26°×22° field of view at a 35 V drive voltage, outputting Lissajous-type scanning patterns. This design aims to propose an indirect simulation method and optimise the process accordingly. Experimental test results show that the simulation method is relatively accurate, with minimal deviation from actual tests. Process optimization improves wafer cleanliness and reduces the time cost of the corresponding process.