Spatial Evidence for Transition Radiation in a Solar Radio Burst
Spatial Evidence for Transition Radiation in a Solar Radio Burst
复制标题
太阳射电暴中跃迁辐射的空间证据
DOI：
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发表时间：
2005
期刊：
影响因子：
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通讯作者：
G. Fleishman
中科院分区：
文献类型：
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作者：
G. Nita;D. Gary;G. Fleishman
微湍流，即，等离子体密度以及电场和磁场的增强的波动在天体物理等离子体中引起了极大的兴趣，但是发生在太小而不能通过遥感来分辨的空间尺度上，例如，在日冕中约1-100厘米处。这封信报告了空间分辨观测结果，这些观测结果为太阳耀斑中存在可疑的无线电发射机制（共振跃迁辐射）提供了强有力的支持，共振跃迁辐射与微湍流水平紧密耦合，并提供了分米空间尺度上波动存在和水平的直接诊断。虽然由射电资料得到的微湍流水平不是特别高，约为<$Δn2 <$/n2 ~ 10-5，但它足以影响带电粒子的扩散，产生有效的随机加速。这一发现具有非常广泛的天体物理学意义，因为现代复杂的数值模型预测在相对论性物体中会产生更强的湍流，例如，伽马射线爆发源。
Microturbulence, i.e., enhanced fluctuations of plasma density and electric and magnetic fields, is of great interest in astrophysical plasmas, but occurs on spatial scales far too small to resolve by remote sensing, e.g., at ~1-100 cm in the solar corona. This Letter reports spatially resolved observations that offer strong support for the presence in solar flares of a suspected radio emission mechanism, resonant transition radiation, which is tightly coupled to the level of microturbulence and provides direct diagnostics of the existence and level of fluctuations on decimeter spatial scales. Although the level of the microturbulence derived from the radio data is not particularly high, ⟨Δn2⟩/n2 ~ 10-5, it is large enough to affect the charged particle diffusion and give rise to effective stochastic acceleration. This finding has exceptionally broad astrophysical implications, since modern sophisticated numerical models predict generation of much stronger turbulence in relativistic objects, e.g., in gamma-ray burst sources.