Research On The Effect Of The Interaction Of Spacecraft With Plasma On The Measure Of The Electric Field

The in-depth exploration of the Sun-Earth coupling process and the real-time monitoring on the space weather will help to safeguard the increasingly frequent space activities.The space electric field date can be used to reveal the key issues such as the energy source and acceleration mechanism of the space particles,the escape of the material in the polar region and the conversion and transport of the solar wind energy to the earth's magnetosphere-ionosphere.However,due to the interaction between the satellite immersed in the plasma and the background environment,the measurement accuracy on electric field using the double-probe is greatly affected.Therefore,this work used SPIS(Spacecraft Plasma Interaction Software)to numerically simulate the interaction between the satellite and plasma,and then analyzed the influence of their coupling process on double-probe measurement.The analysis results show that: 1)under the same plasma environment,although Debye length is the same,the the object with smaller size has a smaller plasma sheath,i.e.the electric potential near the smaller object decreases significantly with the diatance from the surface;2)in the vicinity of the satellite,photoelectron and secondary electron dominate in shielding the potential.The participation of these particles with lower energy makes the thickness of the sheath much smaller than Debye length,and this difference is greater with the increase of background plasma temperature;3)according to the simulation results,we give the thickness of the sheath near the satellite in different plasma environments and the suggested value for the length of the boom of the electric field instrument;4)by studying on the probe sheath under different plasma environment of Volt-Ampere curve,we verified that the introduction of bias current can significantly improve the detecting precision of the probe.We also give optimal point of the bias current of probe in different plasma environment.This work provides important reference for the design of the following field instrument detecting the magnetosphere.In addition,particle acceleration and energy dissipation in the electromagnetic environment are outstanding problems and key research in the domain of space physics,astrophysics and laboratory.However,one of the biggest challenges in understanding energy conversion processes is the coupling of physical processes on spatial and temporal scales,especially on the small spatial scales and the fast temporal scales.Here,using the data from Magnetospheric Multiscale mission(MMS),we study the electron acceleration process by the electric field in an electron-scale magnetic hole: 1)through the analysis on the observation results,we obtained the three dimensional magnetic hole structure and found the shrinking process for this type of small scale structure for the first time,and provided a reasonable explanation to the shrinking;2)combined with the observation results,we analyzed the electric field distribution within the structure,and proposed a new non-adiabatic acceleration process,which has a strong energy dependence and can change the electron distribution;3)we developed a new 3-D magnetic field numerical model of magnetic hole,and also used the test particle simulation code developed by ourselves to simulate the motion of electrons in magnetic hole.The simulation results show that the shrinking magnetic holes can modify the pitch angle distribution of electrons and the result is in accordance with the observation,which verifies our theoretical analysis.This study can help to understand small-scale structures and energy dissipation in the magnetic turbulence,and have some significance on future detection of such small structures by electric field instruments.