Astrophysical magnetic fields decay primarily via two processes, namely ambipolar diffusion and turbulence. Constraints on the strength and the spectral index of nonhelical magnetic fields have been derived earlier in the literature through the effect of the above-mentioned processes on the cosmic microwave background (CMB) radiation. A helical component of the magnetic field is also produced in various models of magnetogenesis, which can explain larger coherence length magnetic field. In this study, we focus on studying the effects of post-recombination decay of maximally helical magnetic fields through ambipolar diffusion and decaying magnetic turbulence and the impact of this decay on CMB. We find that helical magnetic fields lead to changes in the evolution of baryon temperature and ionization fraction which in turn lead to modifications in the CMB temperature and polarization anisotropy. These modifications are different from those arising due to nonhelical magnetic fields with the changes dependent on the strength and the spectral index of the magnetic field power spectra.

中文翻译：

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螺旋磁场复合后耗散在宇宙微波背景辐射上的印记

天体物理磁场主要通过两个过程衰减，即双极扩散和湍流。通过上述过程对宇宙微波背景 (CMB) 辐射的影响，文献较早已经得出了对非螺旋磁场强度和光谱指数的约束。在各种磁发生模型中也产生了磁场的螺旋分量，这可以解释更大的相干长度磁场。在这项研究中，我们专注于研究通过双极扩散和衰减磁湍流对最大螺旋磁场的复合后衰减的影响以及这种衰减对 CMB 的影响。我们发现螺旋磁场会导致重子温度和电离分数的演变发生变化，进而导致 CMB 温度和极化各向异性的改变。这些修改不同于由非螺旋磁场引起的修改，其变化取决于磁场功率谱的强度和光谱指数。