SuperDARN studies of magnetospheric ULF waves and boundaries

在行星际和近地空间的磁场和热电离气体（等离子体）内传播的超低频（ULF）波构成了太阳等离子体流出流（太阳风）和地球磁场环境（磁层）内部和之间交换能量的最重要手段之一。众所周知，磁层极低频波与极光弧、亚暴、辐射带通电和磁重联等重要现象有关。然而，驱动磁层中许多离散极低频波活动的源机制仍未得到证实，目前是一个相当有争议的话题。特别地，在磁层中有一类极低频波叫做场线共振（FLR），地球的磁力线在它们的特征频率上共振，就像弦上的驻波一样。值得注意的是，这些flr经常在非常离散和可重复的频率上被观察到，其原因尚不清楚。一个新出现的想法是，太阳风中的离散振荡直接驱动磁层中的超高频波，包括离散的flr。该提案的第一个目标是确定由太阳风波源直接驱动的磁层极低频波的比例。第二个目标是研究磁层极低频波从磁层顶边界到内磁层再到电离层在时间和空间上的演化。为了实现这些目标，将利用超级双极光雷达网络（SuperDARN）编制和分析磁层极低频波事件数据库。超级双极光雷达网络是一个国际高频雷达网络，以高时间和空间分辨率测量高纬度电离层等离子体流。superdamn对流图还将用于开发一种新的电离层对流梯度技术，以研究磁层边界和动力学。

Ultra-low-frequency (ULF) waves propagating within the magnetic field and hot ionized gas (plasma) of interplanetary and near-Earth space constitute one of the most important means by which energy is exchanged within and between the outflowing stream of solar plasma, the solar wind, and the Earth's magnetic field environment, the magnetosphere. Magnetospheric ULF waves are known to be associated with important phenomena such as auroral arcs, substorms, radiation belt energization, and magnetic reconnection. Yet the source mechanism driving much of the discrete ULF wave activity in the magnetosphere remains unconfirmed and is currently a topic of considerable debate. In particular there is a class of ULF wave in the magnetosphere called the field line resonance (FLR) where the Earth's magnetic field lines resonate at their characteristic frequency like a standing wave on a string. Remarkably these FLRs are often observed at very discrete and reproducible frequencies and the reason for this is not understood. An emerging idea is that discrete oscillations in the solar wind directly drive ULF waves in the magnetosphere including the discrete FLRs. The first objective of this proposal is to determine what proportion of magnetospheric ULF waves are driven directly by a solar wind wave source. The second objective is to investigate how magnetospheric ULF waves evolve in time and space from the magnetopause boundary to the inner magnetosphere and down to the ionosphere. To achieve these objectives a database of magnetospheric ULF wave events will be compiled and analyzed using the Super Dual Auroral Radar Network (SuperDARN), an international network of high frequency radars which measures high latitude ionospheric plasma flows with high time and spatial resolution. SuperDARN convection maps will also be used to develop a new ionospheric convection gradient technique to study magnetospheric boundaries and dynamics.