Ionospheric disturbances caused by SGR 1900+14 giant gamma ray flare in 1998: Constraints on the energy spectrum of the flare
Ionospheric disturbances caused by SGR 1900+14 giant gamma ray flare in 1998: Constraints on the energy spectrum of the flare
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DOI：
10.1029/2008ja013119
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发表时间：
2008-07
影响因子：
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通讯作者：
Y. Tanaka;T. Terasawa;M. Yoshida;T. Horie;M. Hayakawa
中科院分区：
文献类型：
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作者：
Y. Tanaka;T. Terasawa;M. Yoshida;T. Horie;M. Hayakawa
[1] 1998年8月27日，位于银河中心附近的一颗奇异中子星软伽马射线中继器（SGR）1900+14产生了巨大的耀斑。来自巨型耀斑的伽马射线异常电离了较低的电离层，电离层扰动被检测为传播距离相对较短（870公里）的VLF信号的大幅变化。耀斑的峰值通量如此之大，以至于航天器上所有的伽马射线探测器都饱和了；因此，最强烈时期的通量和光谱很难确定。田中等人。 (2007) 最近从 Geotail 数据中得出了耀斑的准确峰值通量。通过基于这种精确估计的模型计算以及与短距离VLF数据的比较，我们发现最强时期的光谱是一个温度（kT = 240 keV）光学薄热轫致辐射（OTTB）。这一结果为我们揭示巨型耀斑的发射和触发机制提供了线索。
[1] On 27 August 1998, the Soft Gamma Ray Repeater (SGR) 1900+14, which is an exotic neutron star located near the Galactic Center, produced a giant flare. Gamma rays from the giant flare unusually ionized the lower ionosphere, and the ionospheric disturbance was detected as a large-amplitude change of the VLF signal whose propagation distance is relatively short (870 km). The peak flux of the flare was so huge that it saturated all the gamma ray detectors on the spacecraft; consequently, the flux and the spectrum during the most intense period was poorly determined. Tanaka et al. (2007) have recently derived the accurate peak flux of the flare from the Geotail data. By means of model calculations based on this accurate estimation and their comparisons with the short-distance VLF data, we have found that the spectrum during the most intense period was one temperature (kT = 240 keV) optically thin thermal Bremsstrahlung (OTTB). This result provides us with a clue to reveal the emission and triggering mechanisms of the giant flare.