Weibel不稳定性驱动的再电离期间种子磁场
Weibel Instability-Driven Seed Magnetic Fields during Reionization
AI总结：
研究再电离期间Weibel不稳定性如何通过各向异性生成种子磁场。
摘要：
宇宙再电离是一个高度非平衡事件，影响了整个星系际介质，使其成为天体物理产生星系际磁场的候选者。在再电离期间，第一颗恒星和星系电离了周围大部分中性介质，形成了不断扩大的外壳。来自源的一侧的光电离结合光电离截面的四极角依赖性，导致电子速度分布的各向异性。我们研究再电离前沿的不稳定性作为产生种子磁场的机制。Weibel不稳定性有潜力从这些各向异性中产生磁场。我们计算了模拟再电离前沿中各向同性和各向异性分布的幅度。我们发现，各向异性分数可以增长到离子化前沿中间的6×10⁻³。我们展示了Weibel不稳定性线性增长时间尺度比离子化前沿的交叉时间（约2×10⁵秒）快。我们简要推测了不稳定性可能的非线性演化及其对宇宙磁生成的含义。
英文摘要：
Cosmological reionization was a highly out-of-equilibrium event that affected every parcel of the intergalactic medium, making it a candidate for astrophysical generation of intergalactic magnetic fields. During reionization, the first stars and galaxies ionized the surrounding, largely neutral, medium in ever-expanding envelopes. Photoionization from sources on one side of the front, combined with the quadrupolar angular dependence of the photoionization cross section, leads to an anisotropic electron velocity distribution. We investigate instabilities in these reionization fronts as a mechanism to generate seed magnetic fields. The Weibel instability has the potential to create a magnetic field from these anisotropies. We calculate the magnitude of the isotropic and anisotropic distribution within a simulated reionization front. We find that the fractional anisotropy can grow to $6\times 10^{-3}$ toward the middle of the ionization front. We show that the linear growth timescale of the Weibel instability is fast compared to the crossing time of the ionization front ($\sim 2\times 10^5$ seconds). We briefly speculate on the possible non-linear evolution of the instability and the implications for cosmological magnetogenesis.
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