Multipoint Observations of Compressional Pulsations: Testing Possible Generation Mechanisms

被称为pc5脉冲的超低频率电磁波（周期为3到15分钟）已经被研究了50多年。它们是一种重要的磁层现象，因为它们将能量从一种形式转换为另一种形式，并将能量从一个位置传输到另一个位置。尽管对这些波提出了许多物理解释，但它们的起源仍然未知。这个提议试图确定一类波的起源。压缩pc5脉动。本提案的首席研究员将由一名研究生协助执行本研究方案。这些是pc5频率范围内的波，它们沿着背景磁场的方向振荡。对这些波提出了三种机制：由压力各向异性引起的漂移镜不稳定性、漂移反弹不稳定性和等离子体片等离子体注入内磁层。赤道附近的THEMIS观测和极地轨道上的星团观测相结合，现在可以确定这些机制中哪一个正在运作。以下问题已被确定为研究：在黎明和黄昏磁层中产生压缩脉动的机制是什么？2. 压缩脉动的特征是什么，包括它们的空间范围和纬度结构？3. 是什么机制产生了频率加倍的纵波子类别（波的压缩分量的频率是横向分量的两倍）？超热粒子如何对脉动做出反应？

The ultra-low frequency (3 to 15 minute periods) electromagnetic waves called Pc 5 pulsations have been studied for over 50 years. They are an important magnetospheric phenomenon because they convert energy from one form to another and transmit energy from one location to another. Although there have been a number of physical explanations proposed for these waves their origin remains unknown. This proposal seeks to determine the origin of one class of these waves ? compressional Pc 5 pulsations. The Principal Investigator of this proposal will be assisted by a graduate student in carrying out this research protocol. These are waves in the Pc 5 frequency range for which there are oscillations along the direction of the background magnetic field. Three mechanisms have been proposed for these waves: drift mirror instabilities due to pressure anisotropies, drift bounce instabilities and injection of blobs of plasma sheet plasma into the inner magnetosphere. The combination of THEMIS observations near the equator and Cluster observations in polar orbit now makes it possible to determine which of these mechanisms are operating. The following questions have been identified for study: 1. What mechanism generates compressional pulsations in the dawn and dusk magnetosphere? 2. What are the characteristics of the compressional pulsations, including their spatial extent and latitudinal structure? 3. What mechanism generates the subcategory of compressional waves exhibiting frequency doubling (the frequency of the compression component of the waves is twice that of the transverse components) and how do suprathermal particles respond to the pulsations?