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磁层中的超低频波动(Ultra Low Frequency Wave,简称ULF波)通常被认为是由外界太阳风/行星际磁场扰动或者磁层内部的等离子体不稳定性激发的.当太阳风动压脉冲作用于磁层顶时,可能在磁层内部激发ULF波,从而将太阳风能量输运到地球磁层中.本文利用磁流体力学(MHD)数值模拟研究不同形式的太阳风动压脉冲作用下,在磁层中激发的ULF波的性质.我们主要关注地球磁层对太阳风动压正/负脉冲以及太阳风动压正-负脉冲对的响应.模拟结果表明,幅度和周期均相同的太阳风动压正脉冲和负脉冲,在磁层中所激发的ULF波幅度,周期均相同,然而相位相差180°.另外,对一个太阳风动压正-负脉冲对作用于偶极磁层的情况,在地球磁层内的某些特定区域仍可观察到磁力线共振(FLRs)现象,磁力线共振的区域分布和动压脉冲的周期以及动压脉冲对之间的时间间隔有关.同时模拟计算结果还表明,与单一脉冲相比较而言,在动压脉冲对的作用下,太阳风能量可以传递到地球磁层中更低纬度的区域.因此本文结果可以帮助我们更好地理解太阳风能量通过ULF波形式输运到地球磁层的机制;同时,还可以为研究有关内磁层中能量粒子对不同的行星际激波的响应方式提供线索.
Ultra Low Frequency Wave (ULF wave) in the magnetosphere is generally considered to be excited by external solar / interplanetary magnetic fields or plasma instability inside the magnetosphere. When the solar wind impulse acts on the magnetic At the top of the layer, it is possible to excite the ULF wave inside the magnetosphere to transport the solar wind energy into the Earth’s magnetosphere.In this paper, we use the MHD numerical simulation to study the effect of different forms of solar wind impulse in the magnetosphere We mainly focus on the response of the Earth’s magnetosphere to positive / negative pulsations of solar wind and positive / negative pulsed pairs of solar winds.The simulation results show that positive and negative pulsations of solar wind with the same amplitude and period Pulse, the amplitude of the ULF wave excited in the magnetosphere is the same but the phases differ by 180 °. In addition, for a positive and negative pulsed pair of solar wind acting on the dipole magnetic layer, Magnetic resonance (FLR) phenomena can still be observed in some specific regions, and the regional distribution of the magnetic resonance and the period of dynamic pressure pulse are related to the time interval between dynamic pressure pulse pairs. Simultaneously, the simulation results Compared with a single pulse, the solar wind energy can be transmitted to the lower latitudes of the Earth’s magnetosphere under the action of a dynamic impulse pulse, so the results of this paper can help us to better understand the solar wind energy through the ULF wave form Transport mechanism to the earth’s magnetosphere and provide clues for studying the response of energy particles in the magnetosphere to different interplanetary shocks.