Auroral latitude Pc 5 field line resonances: Quantized frequencies, spatial characteristics, and diurnal variation
Auroral latitude Pc 5 field line resonances: Quantized frequencies, spatial characteristics, and diurnal variation
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极光纬度 Pc 5 场线共振：量化频率、空间特征和昼夜变化
DOI：
10.1029/93ja02903
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发表时间：
1994
影响因子：
--
通讯作者：
D. Mcdiarmid
中科院分区：
文献类型：
--
作者：
C. Ziesolleck;D. Mcdiarmid
根据鹅湾雷达、加拿大地球近邻等离子体起源极光网络（OPEN）统一研究（CANOPUS）磁力计阵列的几个站和CANOPUS子午线扫描光度计的观测，最近的工作表明存在具有离散和非常稳定频率的Pc 5超低频波（1.3、1.9、2.7和3.3 mHz，变化<10%）。这些ULF波被解释为MHD波导/腔模式驱动的场线共振的结果，可能是由磁层顶的脉冲刺激或低纬度边界层中的Kelvin-Helmholtz不稳定性激发的。然而，这些频率在长时间内的稳定性仍然是一个谜，因为它似乎与磁层的动态行为不一致。为了确定这些频率是否也观察到在昼侧磁层，其中一个拟议的源机制预测他们应该看到，我们已经研究了最近记录的Pc 5脉动的时间和空间特征的CANOPUS磁强计阵列。纯状态滤波技术被用来确定Pc 5信号特性及其时间和空间变化。结果表明，在整个昼侧和黄昏磁层中似乎都观测到了具有量子化频率的超低频波信号。然而，也看到了高于先前报告值和介于先前报告值之间的频率。在正确地确定基本频率和它们的稳定性在多色，高度调幅信号的存在下的困难被指出。在午后部门观察到的信号特征被发现是显着不同的相比，在中午看到的。而当地上午和中午Pc 5显示出典型的磁力线谐振特性，环形模式信号特征占主导地位，在当地下午和晚上。这种不对称的原因尚不清楚。方位波数一般都很小，并表现出线性依赖于Pc 5信号频率，这意味着独立于波频率的反向阳相速度。
On the basis of observations with the Goose Bay Radar, several stations of the the Canadian Auroral Network for the Origin of Plasmas in the Earth's Neighborhood (OPEN) Unified Study (CANOPUS) magnetometer array, and a CANOPUS meridian scanning photometer, recent work has indicated the existence of Pc 5 ULF waves with discrete and remarkably stable frequencies (1.3, 1.9, 2.7 and 3.3 mHz with <10% variation) in the local midnight and early morning (predawn) sectors. These ULF waves were interpreted as the consequence of field line resonances driven by MHD waveguide/cavity modes, possibly excited by impulsive stimulation of the magnetopause or by Kelvin-Helmholtz instabilities in the low-latitude boundary layer. However, the reported stability of these frequencies over long periods of time remains a puzzle, as it seems to be inconsistent with the dynamic behavior of the magnetosphere. In order to establish if these frequencies are also observed in the dayside magnetosphere, where one of the proposed source mechanisms predicts they should be seen, we have examined the temporal and spatial characteristics of Pc 5 pulsations recorded recently with the CANOPUS magnetometer array. Pure state filtering techniques were used to determine the Pc 5 signal characteristics and their temporal and spatial variation. The results show that ULF wave signals with quantized frequencies seem to be observed throughout the dayside and dusk magnetosphere. However, frequencies both higher than and between previously reported values were also seen. The difficulty in correctly determining fundamental frequencies and their stability in the presence of polychromatic, highly amplitude-modulated signals is noted. The signal characteristics observed in the postnoon sector were found to be significantly different compared with those seen at prenoon. While local morning and noon Pc 5 revealed typical field line resonance characteristics, toroidal mode signal characteristics prevailed in the local afternoon and evening. The reason for this asymmetry is unknown. The azimuthal wave numbers were generally small and showed a linear dependence on the Pc 5 signal frequency, implying antisunward phase velocities independent of the wave frequency.