High-resolution spectral features observed in the inner radiation belt trapped electron population
High-resolution spectral features observed in the inner radiation belt trapped electron population
复制标题
在内辐射带捕获电子群中观察到的高分辨率光谱特征
DOI：
10.1029/ja086ia04p02341
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发表时间：
1981
影响因子：
--
通讯作者：
J. Reagan
中科院分区：
文献类型：
--
作者：
W. L. Imhof;E. Gaines;J. Reagan
P78-1卫星对内辐射带L壳层下边缘捕获的68至1120 keV电子进行了精细分辨率测量，为先前发现（Imhof和Smith，1965年）能谱峰值的出现提供了更多信息。在某些情况下，数据已经产生了上限的峰的宽度小至26千电子伏。峰值的能量随着L值的增加而缓慢降低，其速率使得计算出的经度漂移周期在它们出现的整个L壳层范围内几乎保持不变：通常从1.2到1.4，但偶尔会高达1.2。这些峰值经常在600-km高度处观察到，在具有100 km或更大的最小漂移高度的更持久的被捕获电子群体中，并且与在L值（1.5-1.85）处从内带沉淀的准被捕获电子中的峰值形成对比，准被捕获电子中的峰值随着L值的增加能量降低得更快（Imhof等人，1974，1978; Vampola和Kuck，1978）。内带下边缘的光谱通常包含不断变化的尖锐特征，这可能是由于新的注入和/或重新分布以及由于大气散射导致的捕获电子的快速损失。对于窄峰，观察到的中心能量随L值的微小但显着的变化（维持恒定的经度漂移期）与之前对捕获在给定L壳层上的几乎单能电子的解释一致，该解释是由于捕获在较高L壳层上的电子的重新分布而导致的（Imhof等人，1966; Cladis，1966）。在该假设中，能量选择性被假定为来自准共振过程，由此电子由于地磁波动而被加速，地磁波动的周期与电子的方位角漂移周期相当。在这里介绍的一种情况下，狭窄的峰值被观察到在一个广泛的L壳间隔上只有一个卫星通过，但不存在24小时之前或之后，这表明峰值可能已被观察到的结果，从脉冲事件的漂移分散。
Fine resolution measurements from the P78-1 satellite of 68- to 1120-keV electrons trapped at the lower L shell edge of the inner radiation belt have provided additional information on the previous discovery (Imhof and Smith, 1965) of the occurrences of peaks in the energy spectra. In some cases the data have yielded upper limits on the widths of the peaks as small as 26 keV. The energies of the peaks decrease slowly with increasing L value at a rate such that the calculated longitude drift periods remain nearly the same over the full L shell range for which they appear: often from ∼1.2 to ∼1.4 but occasionally up to L shells as high as ∼2.2. These peaks are frequently observed at ∼600-km altitude in the more durably trapped electron population having minimum drift altitudes of 100 km or greater and are to be contrasted with peaks in the quasi-trapped electrons precipitating from the inner belt at L ≃(1.5–1.85) that decrease in energy much more rapidly with increasing L value (Imhof et al., 1974, 1978; Vampola and Kuck, 1978). The spectra at the lower edge of the inner belt often contain sharp features which are continually changing, perhaps as a result of new injections and/or redistributions and the rapid loss of trapped electrons due to atmospheric scattering. For the narrow peaks the observed small but significant changes in central energy with L value that maintain a constant longitude drift period are consistent with the previous interpretation of the nearly monoenergetic electrons trapped on a given L shell resulting from a redistribution of electrons trapped on somewhat higher L shells (Imhof et al., 1966; Cladis, 1966). In that hypothesis the energy selectivity was postulated to result from a quasi-resonance process whereby the electrons were accelerated as a result of the geomagnetic fluctuations that had periods comparable to the azimuthal drift periods of the electrons. In one case presented here, narrow peaks were observed over a broad L shell interval on only one satellite pass but were not present 24 hours earlier or later, suggesting that the peaks might have been observed as a result of drift dispersion from an impulsive event.