A systematic study of ULF Waves Above FH+ from GEOS 1 and 2 Measurements and Their Relationships with proton ring distributions
A systematic study of ULF Waves Above FH+ from GEOS 1 and 2 Measurements and Their Relationships with proton ring distributions
复制标题
DOI：
10.1029/ja087ia08p06219
复制
发表时间：
1982-08
影响因子：
--
通讯作者：
S. Perraut;A. Roux;P. Robert;R. Gendrin;J. Sauvaud;J. Bosqued;G. Kremser;A. Korth
中科院分区：
文献类型：
--
作者：
S. Perraut;A. Roux;P. Robert;R. Gendrin;J. Sauvaud;J. Bosqued;G. Kremser;A. Korth
对在地球同步轨道磁天线上观测到的频率范围为0.2 '12赫兹的超低频噪声进行了详细分析，结果表明，在质子回旋频率之上出现的结构发射的性质，Russell等人（1970年）和Gurnett（1976年）曾报告过质子回旋频率的存在。这些波在地磁赤道附近，在所有的L值之间的0.04和0.08被观察到。它们在垂直于直流磁场的方向上传播。波由谐波相关的单色辐射组成。基本频率一般是当地质子回旋频率的顺序。有时，基波和第一谐波会丢失。如果存在多于一个基频，则在不同发射之间经常发生非线性耦合。单个事件的振幅从几十毫伽马到几百毫伽马不等。持续时间从几十分钟到几个小时不等。在探测器的灵敏度范围内（1 Hz时为10−2 γ Hz− 12，8 Hz时为10−3 γ Hz− 12），在给定的一小时内发生发射的平均概率为12%，这个数字在下午和午夜前的扇区增加到30%。从两个地球同步轨道粒子实验中同时观测到的质子通量表明，对于90°俯仰角的粒子，这些波通常与在某一能量（5千电子伏特至30千电子伏）处达到峰值的分布函数有关。这种环状分布为nFH+（n =运行数）附近的非共振（k = 0）不稳定性的激发提供了能量来源。提出了一个理论模型，定性地解释了所观察到的波的主要特征。
A detailed analysis of the ULF noise observed on the GEOS magnetic antennas in the frequency range ∼0.2'12 Hz has revealed the properties of structured emissions occurring just above the proton gyrofrequency whose existence was reported by Russell et al. (1970) and Gurnett (1976). These waves are observed in the vicinity of the geomagnetic equator at all L values between ∼4 and ∼8. They propagate in a direction perpendicular to the dc magnetic field. The waves consist of harmonically related monochromatic emissions. The fundamental frequency is generally of the order of the local proton gyrofrequency. Sometimes the fundamental and first harmonics are missing. If there is more than one fundamental frequency present, nonlinear coupling often occurs between the different emissions. The amplitudes of individual events vary from some tens of milligammas to some hundreds. Their duration ranges from some tens of minutes to some hours. Within the range of sensitivity of the detectors (10−2 γ Hz−1/2 at 1 Hz, 10−3 γ Hz−1/2) at 8 Hz the average probability of emission occurrence during a given hour is 12%, this number increases to ∼30% during the afternoon and in the pre-midnight sectors. Simultaneous observations of proton fluxes, as obtained from the two GEOS particle experiments show that these waves are often associated with distribution functions peaking at some energy (5 ≲ E ≲ 30 keV) for 90° pitch angle particles. This ring-like distribution provides the energy source for the excitation of non-resonant (k∥ = 0) instabilities near nFH+ (n = running number). A theoretical model is presented that qualitatively explains the main characteristics of the observed waves.