Longitudinal phase variations of Pc 4‐5 micropulsations
Longitudinal phase variations of Pc 4‐5 micropulsations
复制标题
Pc 4-5 微脉动的纵向相位变化
DOI：
10.1029/ja083ia06p02481
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发表时间：
1978
影响因子：
--
通讯作者：
G. Rostoker
中科院分区：
文献类型：
--
作者：
J. Olson;G. Rostoker
对1974年7月1日至10月10日期间的61个相对未受污染的Pc 4-5微脉动进行了纵向相位变化的研究。这些数据是从阿尔伯塔大学在1974年夏季和初秋期间操作的东西向磁力仪线路上获得的。从我们的分析中发现纵向相移与频率之间的直接相关性，其形式为m =（1.4 ± 0.4）f + 0.26，其中f是以毫赫兹为单位的频率，m是由测量的相移导出的方位波数。这种关系表明相速度与频率无关，其幅度为V = 14 km/s。相移的符号，以及表观相速度的方向，在当地中午前1-2小时突然改变。信号似乎是从这个午前区域向终端传播的;也就是说，它们在早上向西移动，在下午向东移动。这相速度的幅度和符号是一致的，提出的生成机制，调用开尔文-亥姆霍兹不稳定性在磁层顶边界。
A set of 61 relatively uncontaminated Pc 4-5 micropulsations from the interval July 1 through October 10, 1974, were examined for longitudinal phase changes. The data were obtained from the east-west line of magnetometers operated by the University of Alberta over the summer and early fall of 1974. From our analysis a direct correlation between longitudinal phase shift and frequency is found which is of the form m = (1.4 ± 0.4) f + 0.26, where f is the frequency in millihertz and m is the azimuthal wave number derived from the measured phase shift. This relationship indicates a phase velocity which is independent of frequency and whose magnitude is Vϕ ≃ 14 km/s. The sign of the phase shift, and thus the direction of apparent phase velocity, changes abruptly 1–2 hours before local noon. The signals appear to propagate away from this prenoon region toward the terminators; that is, they move westward in the morning hours and eastward during the afternoon hours. Both the magnitude and the sign of this phase velocity are consistent with proposed generation mechanisms which invoke the Kelvin-Helmholtz instability at the magnetopause boundary.