日本地球惑星科学連合2015年大会

講演情報

インターナショナルセッション(ポスター発表)

セッション記号 P (宇宙惑星科学) » P-EM 太陽地球系科学・宇宙電磁気学・宇宙環境

[P-EM09] Dynamics in magnetosphere and ionosphere

2015年5月27日(水) 18:15 〜 19:30 コンベンションホール (2F)

コンビーナ:*中野 慎也(情報・システム研究機構 統計数理研究所)、三好 由純(名古屋大学太陽地球環境研究所)、長谷川 洋(宇宙航空研究開発機構宇宙科学研究所)、田中 良昌(国立極地研究所)、堀 智昭(名古屋大学太陽地球環境研究所 ジオスペース研究センター)

18:15 〜 19:30

[PEM09-P10] Ground-based observation of fine structures of MF/HF auroral radio emissions

*佐藤 由佳1小川 泰信1熊本 篤志2上野 玄太3 (1.国立極地研究所、2.東北大学大学院理学研究科、3.統計数理研究所)

The terrestrial auroral ionosphere is a natural source of electromagnetic waves in the MF/HF ranges (up to 6 MHz) as well as well-known intense VLF/LF emissions (auroral kilometric radiation and auroral hiss). In the MF/HF ranges, three types have been identified at ground level: auroral hiss, medium frequency burst (MFB), and auroral roar. In addition, recent studies have resulted in ground-level detection of auroral kilometric radiation [LaBelle and Anderson, 2011] and discovery of a natural radio emission between fce and 2fce [Broughton et al., 2014]. Previous studies have also shown that observation of fine structures open new frontiers for these auroral radio emissions [e.g., LaBelle et al., 1995; Shepherd et al., 1997; Ye et al., 2006; Bunch and LaBelle, 2009]. In August 2008, we installed new instrumentation referred to as Auroral Radio Spectrograph (ARS) at Kjell Henriksen Observatory (KHO) in Svalbard (latitude 78.15oN, longitude 16.04oE, 75.2o magnetic latitude). ARS consists of magnetic loop antennas whose size is 2.7 m × 6.0 m and two types of receivers: ARS-S and ARS-WF. The former is designed for the continuous measurement of wave spectra with a time resolution of 1 sec, and the latter is designed to obtain waveform data digitalized by an A/D converter with a sampling rate of 10 M samples/s (Nyquist frequency 5 MHz). Using ARS-WF, we succeeded in the first simultaneous measurements of structured 2fce auroral roar and optical aurora during 1710-1750 UT on February 1, 2011. In this event, the structured 2fce auroral roar showed temporal evolutions in frequency band width (300 Hz at minimum) and frequency drift rate (15 kHz/s at maximum). However, because ARS-WF recorded a series of 8 M samples (i.e., only 800-msec data) once every 40 sec, it was difficult to capture the entire temporal evolution of the structured auroral roar. In order to solve this problem, we carry out development and trial manufacture of a new receiver using USRPTM (Universal Software Radio Peripheral). Such software-defined radio (SDR) receiver can implement high-speed, flexible digital signal processing of RF signals. This new receiver is designed to obtain higher-resolution spectra of RF signals pauselessly throughout the night in a wide frequency range up to 6 MHz. It is installed at KHO in Svalbard in March 2015. In this presentation, we also show detailed design of this receiver and some initial results.