The small-scale linear magnetic hole (LMH) is a magnetic dip with a size less than or on the order of ρ i (proton gyroradius), which may contribute to turbulence properties in the solar wind and other astrophysical plasmas. Based on one-month measurements of the Mars Atmosphere and Volatile EvolutioN mission, 174 small-scale LMH events in the Martian magnetosheath are used to investigate their statistical properties in this study. Our results show that small-scale linear LMHs are ubiquitous in the Martian magnetosheath, and their occurrence rate is estimated to be approximately 1.5 events per hour based on one-month observations. Compared with the ambient plasma, the averaged magnitude of the magnetic field in these holes can decrease from 6.8–3.5 nT. Nearly 66% of events have a B min/B value in the range of (0.45, 0.75). The duration of small-scale MHs is mainly less than 0.4 s. For 90% of the events, the size along the solar wind flow is less than ρ i . As the rotation angle increases, the occurrence rate of small-scale LMHs decrease. However, the B min/B, size, and duration of small-scale LMHs have no obvious dependence on their rotation angle.

A magnet system is used in the SPERF to create the magnetic field configuration for simulating the space plasma environment. In this paper, the parameters of the system are designed to achieve the target fields needed by the scaling laws, and the electromagnetic analysis has been performed to validate the results. A procedure to obtain the parameters is proposed based on the investigation into the physical and technological constraints. The vacuum magnetic fields for studying the 3D magnetic reconnection at the magnetopause, Earth’s magnetosphere, and 3D magnetic reconnection driven by a plasma gun are computed. In addition, the engineering complexity is reviewed in brief. This research is crucial to the construction of the SPERF, and it is valuable to designing the magnets applied in other fields.

The Space Plasma Environment Research Facility (SPERF) is a new ground-based experimental device for fundamental research studies on space plasma currently under construction at Harbin Institute of Technology in China. Scientific objectives of the SPERF include studying the asymmetric reconnection dynamics relevant to the interaction between the interplanetary and magnetospheric plasmas, reproducing the inner magnetosphere to simulate the processes of trapping, acceleration, and transport of energetic charged particles restrained in a dipole magnetic field configuration, and revealing the physical mechanism of the dipolarization front in the magnetotail. The device comprises a vacuum chamber, 11 coils consisting of 18 groups of sub-coils that are independently programmablely energized, and the plasma source system to provide the magnetic field and the plasma required by the physical experiments. Thus, each of these 18 groups of sub-coils requires a separate pulsed power supply; furthermore, the 18 pulsed power supplies constitute the pulsed power supply system of the SPERF of which the total storage energy is up to 18.3 MJ, and the technical challenges have to be overcome. The power supply energizing a dipole field coil (labeled OJC coil) wired by the copper wire to provide a dipole magnetic field is the most energetic power supply (labeled OJC power supply) with a 2.42 MJ, 16.8 mF capacitor bank charged to 20 kV. The OJC power supply delivers a current with a peak of 18 kA for a rise time of ∼26.69 ms, and the duration of the current is not less than 95% of the peak over 10 ms to the OJC coil. Meanwhile, the most challenging power supply is the power supply labeled poloidal field power supply with a 5.04 mF capacitor bank charged to 20 kV, which provides the excitation current for the load coil set with the current not less than 360 kA at the typical time of 0.11 ms to produce the sufficient growth of the magnetic field that the experiments need. In this paper, the overall design of the pulsed power supply system, the design concept of the modularization, and the principle selection basis of the key components are presented. The technical details of each power supply will be demonstrated in the future.

The Space Plasma Environment Research Facility (SPERF) is a ground simulation user facility for studying the space plasma physical processes. This study presents the design and construction of a vacuum control system for the SPERF to set up an appropriate vacuum environment for plasma experiments, including the terrestrial space and near space vacuum control systems. Based on the requirements of remote automation, distributed control, centralized management, high reliability, expansibility, and safety, the architecture of the vacuum control system has been divided into three levels. Among these, the local level is the most essential part of the control system, which adopts the programmable logical controller (PLC) with Siemens S7-1500 CPU as the core. The PLC supports multiple communication protocols and can accurately control and monitor the actuators in the process of establishing a vacuum environment. Furthermore, it has the ability to communicate and interact with remote upper computers and the central control system through the supervisory control and data acquisition (scada) software developed based on iFix. Based on the architecture of the vacuum control system, the control process for establishing the vacuum environment, including the ultimate vacuum and experimental vacuum, was designed. It is noteworthy that in experimental vacuum acquisition, the injection of working fluid gas is controlled directly by the central control system, considering the different requirements of the terrestrial space and near space systems for the experimental working pressure and flexibility of the experimental vacuum control. The vacuum control system designed in this study provides technical support for the SPERF to perform the plasma experiments successfully. In addition, it offers reference and insights for the design of vacuum control systems in similar large-scale plasma simulation facilities.

In order to investigate the effects of secondary electrons, which are emitted from the wall, on the performance of a thruster, a one-dimensional fluid model of the plasma sheath in double walls is applied to study the characteristics of a magnetized sheath. The effects of secondary electron emission (SEE) coefficients and trapping coefficients, as well as magnetic field, on the structure of the plasma sheath are investigated. The results show that sheath potential and wall potential rise with the increment of SEE coefficient and trapping coefficient which results in a reduced sheath thickness. In addition, magnetic field strength will influence the sheath potential distributions.