An explanation for the fine structure of MF burst emissions
An explanation for the fine structure of MF burst emissions
复制标题
对中频爆发发射精细结构的解释
DOI：
10.1029/2010gl046218
复制
发表时间：
2011
影响因子：
5.2
通讯作者：
J. Labelle
中科院分区：
文献类型：
--
作者：
J. Labelle
中频爆发（Medium Frequency Burst，MFB）是在极光亚暴开始时在地面观测到的宽带极光射电辐射。最近的高分辨率测量表明，它是由精细结构组成的，当显示为频率-时间谱图时，具有“向后七”形的前缘。利用一个简单的一维模型，可以通过调整顶侧密度分布，使起源于F区顶侧并线性转换为L模式的朗缪尔波的群延迟与前缘的形状相匹配，但对于合理的密度分布，拟合意味着相对低能量的电子束（几百keV）。如果这种机制解释了发射，那么它将与亚暴开始期间向极扩展的极光弧前缘相对低能量的阿尔文加速电子束的激发相一致。
Medium Frequency Burst (MFB) is a broadband auroral radio emission observed at ground‐level at the onset of auroral substorms. Recent high‐resolution measurements show it to be composed of fine structures with “backwards seven”‐shaped leading edges when displayed as a frequency‐time spectrogram. With a simple one‐dimensional model, the group delay of Langmuir waves originating on the F‐region topside and converting linearly to L‐mode can be made to match the shape of the leading edge by adjusting the topside density profile, but for plausible density profiles the fit implies relatively low energy electron beams (few hundred keV). If this mechanism explains the emissions, it would be consistent with their excitation by relatively low energy Alfvénically accelerated electron beams in the leading edges of poleward‐expanding auroral arcs during substorm onset.