High Frequency Analyzer (HFA) of Plasma Wave Experiment (PWE) onboard the Arase spacecraft
High Frequency Analyzer (HFA) of Plasma Wave Experiment (PWE) onboard the Arase spacecraft
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DOI：
10.1186/s40623-018-0854-0
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发表时间：
2018-05-16
影响因子：
3
通讯作者：
Obara, Takahiro
中科院分区：
文献类型：
--
作者：
Kumamoto, Atsushi;Tsuchiya, Fuminori;Obara, Takahiro
高频分析仪是Arase（ERG）航天器上等离子体波实验的一个子系统。HFA的主要目的包括：（1）通过观测上混合共振波确定航天器周围的电子数密度;（2）测量20 kHz以上频率范围内哨声模式合唱的电磁场分量;（3）观测暴时磁层中激发的无线电波和等离子体波。由线探头天线检测到的两个交流电场分量和由磁探测线圈检测到的一个交流磁场分量被馈送到HFA。通过在HFA中应用模拟和数字信号处理，在10 kHz至10 MHz的频率范围内，以8 s的间隔获得两个电场（EE模式）或一个电场和一个磁场（EB模式）的频谱图。对于等离子体层顶的观测，HFA也可以工作在PP（等离子体层顶）模式下，在该模式下，以1 s的间隔获得低于1 MHz的一个电场分量的谱图。在2017年1月至7月的初步运行中，获得了以下结果：（1）在地磁平静和扰动条件下，HFA观测到了UHR波、极光千米辐射（AKR）、哨声模式合唱、静电电子回旋谐波和非热陆地连续辐射。(2)在2017年6月10日偏振观测的测试业务中，观测到了北方极地地区不同来源的基R-X和L-O模AKR以及二次谐波R-X模AKR。(3)对HFA谱图进行了半自动超高频频率识别。在计算机识别中，我们使用了一种通过检查强度和带宽来缩小UHR频率候选的算法。然后，由计算机识别的UHR频率进行检查，并在需要时由操作人员进行校正。从确定的UHR频率导出的电子数密度将是有用的等离子体层和顶侧电离层的风暴时间演化的调查。
The High Frequency Analyzer (HFA) is a subsystem of the Plasma Wave Experiment onboard the Arase (ERG) space-craft. The main purposes of the HFA include (1) determining the electron number density around the spacecraft from observations of upper hybrid resonance (UHR) waves, (2) measuring the electromagnetic field component of whistler-mode chorus in a frequency range above 20 kHz, and (3) observing radio and plasma waves excited in the storm-time magnetosphere. Two components of AC electric fields detected by Wire Probe Antenna and one component of AC magnetic fields detected by Magnetic Search Coils are fed to the HFA. By applying analog and digital signal processing in the HFA, the spectrograms of two electric fields (EE mode) or one electric field and one magnetic field (EB mode) in a frequency range from 10 kHz to 10 MHz are obtained at an interval of 8 s. For the observation of plasmapause, the HFA can also be operated in PP (plasmapause) mode, in which spectrograms of one electric field component below 1 MHz are obtained at an interval of 1 s. In the initial HFA operations from January to July, 2017, the following results are obtained: (1) UHR waves, auroral kilometric radiation (AKR), whistler-mode chorus, electrostatic electron cyclotron harmonic waves, and nonthermal terrestrial continuum radiation were observed by the HFA in geomagnetically quiet and disturbed conditions. (2) In the test operations of the polarization observations on June 10, 2017, the fundamental R-X and L-O mode AKR and the second-harmonic R-X mode AKR from different sources in the northern polar region were observed. (3) The semiautomatic UHR frequency identification by the computer and a human operator was applied to the HFA spectrograms. In the identification by the computer, we used an algorithm for narrowing down the candidates of UHR frequency by checking intensity and bandwidth. Then, the identified UHR frequency by the computer was checked and corrected if needed by the human operator. Electron number density derived from the determined UHR frequency will be useful for the investigation of the storm-time evolution of the plasmasphere and topside ionosphere.