A study of the oscillation mode of Pi2 geomagnetic pulsations

Pi2地磁脉动振荡模式的研究

• 批准号: 06640568
• 负责人: TAKAHASHI Kazue
• 金额: $ 1.34万
• 依托单位: Nagoya University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for General Scientific Research (C)
• 财政年份: 1994
• 资助国家: 日本
• 起止时间: 1994 至 1995
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-06640568/
• 关键词: Geomagnetic pulsations; Magnetospheric substorms; MHD waves

The spatial variation of the properties of magnetospheric Pi 2 pulsations is studied using magnetic field records acquired simultaneously by the Active Magnetospheric Particle Tracer Explorers Charge Composition Explorer (AMPTE CCE) satellite at radial distances less than 6.6 Earth radii (RE) and at geomagnetic latitudes from -16ﾟ to 16ﾟ and at the Kakioka ground station located at magnetic shell of L=1.23. Pi 2 magnetic pulsations are identified from the Kakioka data acquired within 3 hours of midnight, but no restriction is imposed on the local time of CCE.An automated Pi 2 selection procedure resulted in 249 events from the Kakioka data. We have characterized magnetic field variations in the radial (b_x), azimuthal (b_y), and compressional (b_z) components at CCE in terms of their spectral density, coherence, and phase relative to those of the Pi 2 pulsation in the horizontal (H) component of the Kakioka data and then examined how these parameters depend on the location of CCE.It is … More found that high-coherence events (coherence between CCE and Kakioka>0.6) are observed primarily when CCE is on the nightside and at L<4. For these events the magnetic field perturbations at CCE are dominated by the ploidal components b_x and b_z and these components exhibit a ground to satellite cross phase of either -0 or -180ﾟ, depending on the location of the satellite. The spatial phase structure is consistent with the eigenmode structure of a compressional cavity-mode type resonance excited between two reflecting boundaries. We find no evidence supporting the view that ground Pi 2 are mid-latitude toroidal field line resonances excited in response to source waves on auroral zone field lines. Rather, the results imply that mid-latitude (2<L<5) Pi 2 pulsations observed on the ground originate from a cavity-mode type resonance excited in the inner magnetosphere bounded below by the ionosphere and at high altitudes by an Alfven velocity gradient. The cavity resonance is probably excited by earthward propagating fast mode waves launched at substorm onset by the large scale magnetic reconfiguration associated with cross-tail current disruption. Less

利用主动磁层粒子示踪探测器电荷组成探测器(AMPTE CCE)卫星在径向距离小于6.6地球半径(RE)、地磁纬度为-16ﾟ~16ﾟ和位于L=1.2 3磁壳的鹿冈地面站同时获得的磁场记录，研究了磁层PI 2脉动特性的空间变化.PI 2磁脉动是从午夜3小时内采集的Kakioka数据中识别出来的，但对CCE的当地时间没有限制。自动的PI 2选择程序从Kakioka数据中产生了249个事件。我们用Kakioka资料水平(H)分量PI 2脉动的频谱密度、相干性和相位来描述CCE的径向(B_X)、方位(B_Y)和压缩(B_Z)分量的磁场变化，然后研究了这些参数如何依赖于CCE的位置。这是…进一步发现，高相干事件(CCE与Kakioka&gt0.6之间的相干性)主要在CCE在夜间和L附近观测到。对于这些事件，CCE的磁场扰动主要是由倍面分量b_x和b_z主导的，这些分量表现出地面到卫星的交叉相位-0或-180ﾟ，这取决于卫星的位置。空间位相结构与在两个反射边界之间激发的压缩腔模型共振的本征模结构一致。我们没有找到证据支持地面pI2是响应极光带场线上的源波而激发的中纬度环向场线共振的观点。相反，结果表明，地面上观测到的中纬度(2&lt；L；5)pI2脉动起源于由电离层约束的内磁层中的腔模共振，以及由阿尔芬速度梯度在高海拔激发的腔模共振。空腔共振可能是由亚暴开始时的向地球传播的快模波激发的，这种快模波是由与交叉尾电流破裂相关的大尺度磁场重新配置引起的。较少

项目成果

S.Ohtani,T.Higuchi,A.T.Y.Lui,and K.Takahashi: "Magnetic fluctuations associates with tail current disruption:Fractal analysis" Journal of Geophysical Research. 100. 19,135-19,145 (1995)

S.Ohtani、T.Higuchi、A.T.Y.Lui 和 K.Takahashi：“磁波动与尾电流干扰相关：分形分析”地球物理研究杂志。

Takahashi,K.: "Studies of magnetospheric ULF waves using Active Magnetospheric Particle Tracer Explorers Charge Composition Explorer" Journal of Geomagnetism and Geoelectricity. 46(11). 953-970 (1994)

Takahashi,K.：“使用主动磁层粒子示踪探测器电荷成分探测器对磁层 ULF 波进行研究”地磁学和地电杂志。

K.Takahashi: "Studies of magnetospheric ULF waves using Active Magnetospheric Particle Tracer Explorers Charge Composition Explorer" Journal of Geomagnetism and Geoelectricity. 46. 953-970 (1994)

K.Takahashi：“使用主动磁层粒子示踪探测器电荷成分探测器对磁层 ULF 波进行研究”地磁学和地电杂志。

Ohtani,S.,T.Higuchi,A.T.Y.Lui,and K.Takahashi: "Magnetic fluctuations associates with tail current disruption:Fractal analysis" Journal of Geophysical Research. 100(A10). 19,135-19,145 (1995)

Ohtani,S.,T.Higuchi,A.T.Y.Lui,and K.Takahashi：“磁波动与尾电流破坏相关：分形分析”地球物理研究杂志。

Takahashi, K.: "Studies of magnetospheric ULF waves using Active Magnetospheric Particle Tracer Explorers Charge Composition Explorer" Journal of Geomagnetism and Geoelectricity. Vol 46, No.11. 953-970 (1994)

Takahashi, K.：“使用主动磁层粒子示踪探测器电荷成分探测器对磁层 ULF 波进行研究”地磁学和地电杂志。