中子星磁层相对论磁化激波中的辐射反作用
Radiation Reaction in Relativistic Magnetized Shocks of Neutron Star Magnetospheres
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中文总结 AI 辅助
本研究通过多流体模型和粒子模拟，发现辐射反作用不抑制磁星怪物激波的前驱辐射，仅将光谱峰值移至更高频率，且亮度由驱动波亮度和转换效率决定。
中文摘要 AI 辅助
磁星内磁层中快磁声波的陡化可产生怪物激波，其前驱辐射可能解释快速射电暴（FRB）。对于足够亮的暴，穿越激波的粒子在单个回旋周期内辐射其能量，这引发了一个问题：辐射反作用如何影响激波结构及其相干辐射。我们利用推广至包含朗道-利夫希茨辐射反作用力的稳态多流体模型，并结合怪物激波动力学的粒子模拟，研究了强冷却、相对论磁化激波。我们表明，动力学尺度激波过渡仅由两个无量纲参数控制：阿尔芬马赫数和一个冷却参数$\tau$，后者衡量一个回旋周期内的辐射损失。相干前驱辐射在超过一个随$\tau$增加而增大的临界马赫数时被触发，此时束动力学变得混沌。在此阈值之上，辐射冷却将前驱辐射的峰值频率移至更高值，按$\tau^{2/7}$标度变化。值得注意的是，即使在强辐射冷却下，怪物激波仍远高于发射阈值。因此，辐射反作用不会抑制前驱辐射；相反，它主要将光谱峰值移至动力学区域。前驱波的亮度仅由驱动千赫兹波的亮度和转换效率$\epsilon_X\sim 10^{-3} - 10^{-2}$决定。
英文摘要
The steepening of fast magnetosonic waves in the inner magnetospheres of magnetars can produce monster shocks, whose precursor emission may account for fast radio bursts (FRBs). For sufficiently bright bursts, particles crossing the shock radiate their energy within a single gyration period, raising the question of how radiation reaction affects the shock structure and its coherent emission. We investigate strongly cooled, relativistically magnetized shocks using a stationary multifluid model generalized to include the Landau-Lifshitz radiation-reaction force, together with particle-in-cell simulations of monster-shock dynamics. We show that the kinetic-scale shock transition is governed by only two dimensionless parameters: the Alfvénic Mach number and a cooling parameter $τ$ that measures radiative losses over a gyration period. Coherent precursor emission is triggered above a critical Mach number that increases with $τ$, at which the beam dynamics becomes chaotic. Above this threshold, radiative cooling shifts the peak frequency of the precursor to higher values, scaling as $τ^{2/7}$. Remarkably, monster shocks remain far above the emission threshold even under strong radiative cooling. Radiation reaction therefore does not quench the precursor emission; instead, it primarily shifts the spectral peak into the kinetic regime. The luminosity of the precursor wave is determined solely by the luminosity of the driving kHz wave and the conversion efficiency, $ε_X\sim 10^{-3} - 10^{-2}$.
发表机构
- Observatoire de Paris, Sorbonne Université, Université PSL, CNRS, LUX（巴黎天文台，索邦大学，巴黎文理研究大学，法国国家科学研究中心，LUX）
- School of Physics and Astronomy, Tel Aviv University（特拉维夫大学物理与天文学学院）
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