High time resolution analysis of solar hard X-ray flares observed on board the ESRO TD-1A satellite
High time resolution analysis of solar hard X-ray flares observed on board the ESRO TD-1A satellite
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DOI：
10.1007/bf00151992
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发表时间：
1976-06
期刊：
影响因子：
2.8
通讯作者：
Peter Hoyng;John C. Brown;H. F. van Beek
中科院分区：
文献类型：
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作者：
Peter Hoyng;John C. Brown;H. F. van Beek
欧洲空间研究组织TD-1A号卫星上的乌得勒支太阳硬X射线光谱仪S-100用12个波长间隔的通道覆盖25千电子伏以上的能量范围。连续太阳指向与高时间分辨率相结合：四个低能通道（25-90 keV）为1.2 s，其他通道为4.8 s。着重指出，仪器的设计和校准产生的数据几乎没有堆积和其它仪器缺陷。本文给出了1972年3月12日至1973年10月1日期间所有观测良好的耀斑的完整观测资料，其中包括1972年8月1日至8日高度活跃期的4个耀斑。通过仪器响应的去卷积而不是通过拟合技术，每1.2秒计算一次每个事件的光子光谱。利用这些实际光子谱，计算了最佳拟合单次幂律指数γ和25 keV以上的最小（厚靶）电子注入率F25，给出了每一事例1.2s间隔γ和F25的结果。对所有这些结果的检验初步表明，纯粹的脉冲性质的事件和延长事件之间存在真实的区别。具体而言：（1）该系列中存在的波动被证明是兼容的泊松噪声的计数率。(2)It强调指出，在没有空间分辨率的情况下，X射线源必须用总计数率的e-折叠时标τ来表征;通过对整个事件中的单个τ的检查，在统计上很少有短至1.2 s的真实的τ，证实了（1）。（3）对所有事件进行了傅立叶分析，没有小事件显示出统计上显著的周期性，但1972年8月4日的大事件在流量和光谱指数上都显示出30、60和120 s的真实的周期。（4）在统计上，不同光子能量下的尖峰峰值之间存在真实的很小的时间差（<0. 2 s），并对F25、γ等参数的瞬时值与时间尺度之间的相关性进行了研究。大多数结果都是否定的，但在1972年8月4日和7日的事件中，沿着（F25，γ）平面的一条非常明确的路径，给出了电子加速过程的洞察力。最后，关于我们的分析对粒子加速物理学的意义，得出了一些一般性的结论，包括两类事件的可能性。具体而言，所提出的严重问题的大电子通量（等效电流1017 A）的数据要求进行了讨论有关耀斑理论。绕过这些问题的一些可能性，如在约束区域的再加速，被简要地考虑。
The Utrecht solar hard X-ray spectrometer S-100 on board the ESRO TD-1A satellite covers the energy range above 25 keV with 12 logarithmically spaced channels. Continuous sun-pointing is combined with high time resolution: 1.2 s for the four low energy channels (25–90 keV) and 4.8 s for the others. It is emphasized that the instrument design and calibration yield data virtually free of pile-up and other instrumental defects.A complete set of observations is presented for all well-observed flares during the period March 12, 1972 to October 1, 1973, including four from the highly active period August 1–8, 1972. Photon spectra are computed every 1.2 s for each event by deconvolution through the instrument response, rather than by fitting techniques. Using these actual photon spectra, the index γ for the best fitting single power law and the minimum (thick target) injection rate of electrons above 25 keV,F25, are calculated.Results for γ andF25at 1.2 s intervals are presented for each event. Examination of all these results tentatively suggests a real distinction between events of a purely impulsive nature and prolonged events.Techniques of time series analysis are applied to the burst time profiles. Specifically:(1)The fluctuations present in the series are shown to be compatible with Poisson noise in the count rate.(2)It is emphasized that, without spatial resolution, the X-ray source must be characterized by thee-folding time scaleτof thetotalcount rate; examination of individual τ's through the event shows very few statistically real τ's as short as 1.2 s, confirming (1).(3)For all events, the series are Fourier analysed; no small events showed statistically significant periodicities, but the large event of August 4, 1972 exhibited real periods of 30, 60 and 120 s in both the flux and the spectral index.(4)Statistically real, small timing differences (∼0.2 s) are shown to exist between spike peaks at different photon energies.A search is made for correlations between instantaneous values of inferred parameters (e.g.F25, γ and the time scales). Most results are negative, but in the August 4 and 7, 1972 events a very well defined path was followed through the (F25, γ)-plane, giving insight into the electron acceleration process.Finally some general conclusions are drawn concerning the implications of our analysis for the physics of particle acceleration, including the possibility of two classes of event. Specifically, the severe problems posed by the large electron fluxes (equivalent current ∼1017A) demanded by the data are discussed in relation to flare theories. Some possibilities for getting around these problems, such as by reacceleration in a confinement region, are briefly considered.