Plasma wave observation and sounder experiments (PWS) using the Akebono (EXOS-D) satellite ― instrumentation and initial results including discovery of the high altitude equatorial plasma turbulence
Plasma wave observation and sounder experiments (PWS) using the Akebono (EXOS-D) satellite ― instrumentation and initial results including discovery of the high altitude equatorial plasma turbulence
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DOI：
10.5636/jgg.42.411
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发表时间：
1990
期刊：
影响因子：
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通讯作者：
H. Oya;A. Morioka;Kaori Kobayashi;M. Iizima;T. Ono;H. Miyaoka;Toshimi Okada;T. Obara
中科院分区：
文献类型：
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作者：
H. Oya;A. Morioka;Kaori Kobayashi;M. Iizima;T. Ono;H. Miyaoka;Toshimi Okada;T. Obara
1989年3月4日，“阿克波诺”（EXOS-D）卫星上的天线部署和仪器开启后，成功进行了等离子体波和探测器实验（PWS）。在自然等离子体波观测中，在20kHz ~ 5MHz的PWS频率范围内观测到等离子体波在整个轨道范围内的动态光谱。结果总结如下：i)在卫星轨道1000公里至远地点高度范围内，总能观测到从电子回旋频率fC到上混合频率fUHR的频率范围，当fC高于局部等离子体频率fP时，或在fP>fC时，覆盖从fP到fUHR的频率范围。从高混合频率发射的全局分布出发，阐明了等离子体层的结构。ii)在与极光粒子加速区相关的区域观测到极光千米辐射。并对AKR的偏振矢量和坡印亭矢量进行了精确测量。这些数据表明，除了研究AKR的产生机制外，还可以研究加速区的结构。在极光粒子加速区获得的AKR数据尤其重要，表明静电等离子体波可能与z模波共存。iii)在等离子层赤道区发现了上层杂化模波的增强；这种增强显示了两种可能的等离子体湍流，第一种是微观不稳定性的增强，这种不稳定性仅被确定为上层混合发射强度的增强，称为“波湍流的赤道增强（EPWAT）”；二是高混合频率不规则变化的增强，提示等离子体密度的湍流变化，称为“密度湍流赤道增强（EPDET）”。EPWAT在海拔1000 ~ 9000千米的范围内环绕磁赤道形成一个圆盘，而EPDET在海拔1000 ~ 9000千米的范围内环绕地理赤道形成另一个圆盘。iv)还进行了PWS的较深实验；结果表明，在fP处存在等离子体共振，在fUHR处存在上层混合共振，在nfC处存在电子回旋频率的谐波（n= 1,2,3，…）。即使在3000km以上的高空范围内，也可以检测到弥漫等离子体共振fDn与静态等离子体波共振fQn的序列。甚至在6000千米的高空也探测到探测仪发射脉冲的超长导管回波。这些实验结果表明，PWS/EXOS-D数据为研究整个全球电离层和等离子层的等离子体和等离子体波，包括极光粒子加速区域，提供了一个非常有希望的关键。
Plasma waves and sounder experiments (PWS) onboard the Akebono (EXOS-D) satellite have been successfully made after deployment of antenna and turn-on of the instruments on March 4, 1989. In natural plasma wave observations, the dynamic spectra of the plasma waves in the whole range of the orbits are observed in the PWS frequency range from 20kHz to 5MHz. The results are summarized as follows.i) The upper hybrid emissions that cover a frequency range from the electron cyclotron frequency fC to the upper hybrid frequency fUHR for the case where fC is higher than the local plasma frequency fP, or cover from fP to fUHR for the case of fP>fC, are always observed in the altitude range from 1000km to apogee of the orbit of the satellite. From the global distribution of the upper hybrid frequency emissions, the structures of the plasmasphere are clarified.ii) Auroral kilometric radiations are observed in the region associated with the auroral particle acceleration regions. Polarization and Poynting vectors of AKR are also precisely measured. The data show the possibility of studies on the structure of the acceleration regions in addition to the generation mechanism of AKR. The AKR data that have been obtained in the acceleration region of the auroral particles are especially important, suggesting the possible co-existence of the electrostatic plasma waves with the Z-mode waves.iii) In the equatorial region of the plasmasphere the enhancement of the upper hybrid mode waves is discovered; the enhancement shows two possible plasma turbulences, the first is the enhancement of the microscopic instabilities that are identified only as the enhancements of the intensity of the upper hybrid emissions and called “equatorial enhancement of the wave turbulence (EPWAT)”; and the second is the enhancement of the irregular change of the upper hybrid frequency suggesting the turbulent variation of the plasma density that is called “equatorial enhancement of the density turbulence (EPDET)”. EPWAT's encircle the magnetic equator forming a disc within the altitude range of 1000km to 9000km, while EPDET's encircle the geographic equator within the altitude range of 1000km to 9000km, forming another disc.iv) Sounder experiments of the PWS have also been carried out; the results show the principal resonances such as plasma resonances at fP, upper hybrid resonances at fUHR, and harmonics of the electron cyclotron frequency at nfC (n=1, 2, 3, ...). The sequence of diffuse plasma resonances fDn with the static plasma wave resonance fQn are also detected even in a high altitude range higher than 3000km. Very long ducted echoes of sounder transmitting pulses have also been detected even at the altitude of 6000km. All these results of the experiments reveal that the PWS/EXOS-D data provide a very promising key for studies of the plasma and plasma waves throughout the entire global ionosphere and plasmasphere, including the regions of auroral particles acceleration.