Primordial magnetic fields (PMF) damp at scales smaller than the photon diffusion and free-streaming scale. This leads to heating of ordinary matter (electrons and baryons), which affects both the ...thermal and ionization history of our Universe. Here, we study the effect of heating due to ambipolar diffusion and decaying magnetic turbulence. We find that changes to the ionization history computed with recfast are significantly overestimated when compared with CosmoRec. The main physical reason for the difference is that the photoionization coefficient has to be evaluated using the radiation temperature rather than the matter temperature. A good agreement with CosmoRec is found after changing this aspect. Using Planck 2013 data and considering only the effect of PMF-induced heating, we find an upper limit on the rms magnetic field amplitude of B
0 ≲ 1.1 nG (95 per cent c.l.) for a stochastic background of PMF with a nearly scale-invariant power spectrum. We also discuss uncertainties related to the approximations for the heating rates and differences with respect to previous studies. Our results are important for the derivation of constraints on the PMF power spectrum obtained from measurements of the cosmic microwave background anisotropies with full-mission Planck data. They may also change some of the calculations of PMF-induced effects on the primordial chemistry and 21cm signals.
Context.
In the last few decades, increasing evidence has been found in both numerical studies and high-resolution in situ data that magnetic turbulence spontaneously generates coherent structures ...over a broad range of scales. Those structures play a key role in energy conversion because they are sites where magnetic energy is locally dissipated in plasma heating and particle energization. How much turbulent energy is dissipated via processes such as magnetic reconnection of thin coherent structures, namely current sheets, remains an open question.
Aims.
We aim to develop semi-automated methods for detecting reconnection sites over multiple spatial scales. This is indeed pivotal in advancing our knowledge of plasma dissipation mechanisms and for future applications to space data.
Methods.
By means of hybrid–Vlasov–Maxwell 2D–3V simulations, we combine three methods based on the partial variance of increments measured at a broad range of spatial scales and on the current density, which together, and in a synergistic way, provide indications as to the presence of sites of magnetic reconnection. We adopt the virtual satellite method, which in upcoming works will allow us to easily extend this analysis to in situ time-series.
Results.
We show how combining standard threshold analysis to a 2D scalogram based on magnetic field increments represents an efficient diagnostic for recognizing reconnecting structure in 1D spatial- and time-series. This analysis can serve as input to automated machine-learning algorithms.
We study the contribution of a stochastic background (SB) of primordial magnetic fields (PMFs) on the anisotropies in temperature and polarization of the cosmic microwave background (CMB) radiation. ...A SB of PMF modelled as a fully inhomogeneous component induces non-Gaussian scalar, vector and tensor metric linear perturbations. We give the exact expressions for the Fourier spectra of the relevant energy–momentum components of such a SB, given a power-law dependence parametrized by a spectral index nB for the magnetic field power spectrum cut at a damping scale kD. For all the values of nB considered here, the contribution to the CMB temperature pattern by such a SB is dominated by the scalar contribution and then by the vector one at higher multipoles. We also give an analytic estimate of the scalar contribution to the CMB temperature pattern.
ABSTRACT
We update and extend our previous cosmic microwave background anisotropy constraints on primordial magnetic fields through their dissipation by ambipolar diffusion and magnetohydrodynamic ...decaying turbulence effects on the post-recombination ionization history. We derive the constraints using the latest Planck 2018 data release which improves on the E-mode polarization leading to overall tighter constraints with respect to Planck 2015. We also use the low-multipole E-mode polarization likelihood obtained by the SROLL2 map making algorithm and we note how it is compatible with larger magnetic field amplitudes than the Planck 2018 baseline, especially for positive spectral indices. The 95 per cent confidence level constraints on the amplitude of the magnetic fields from the combination of the effects is $\sqrt{\langle B^2 \rangle } \lt 0.69 (\lt 0.72)$ nG for Planck 2018 (SROLL2) by marginalizing on the magnetic spectral index. We also investigate the impact of a damping scale allowed to vary and the interplay between the magnetic field effects and the lensing amplitude parameter.
We study the energy-momentum tensor and helicity of gauge fields coupled through g ϕ F ˜ F / 4 to a pseudoscalar field ϕ driving inflation. Under the assumption of a constant time derivative of the ...background inflaton, we compute analytically divergent and finite terms of the energy density and helicity of gauge fields for any value of the coupling g . We introduce a suitable adiabatic expansion for mode functions of physical states of the gauge fields which correctly reproduces ultraviolet divergences in average quantities and identifies corresponding counterterms. Our calculations shed light on the accuracy and the range of validity of approximated analytic estimates of the energy density and helicity terms previously existed in the literature in the strongly coupled regime only, i.e., for g ˙ ϕ / ( 2 H ) ≫ 1 . We discuss the implications of our analytic calculations for the backreaction of quantum fluctuations onto the inflaton evolution.
This Voyage 2050 paper highlights the unique science opportunities using spectral distortions of the cosmic microwave background (CMB). CMB spectral distortions probe many processes throughout the ...history of the Universe, delivering novel information that complements past, present and future efforts with CMB anisotropy and large-scale structure studies. Precision spectroscopy, possible with existing technology, would not only provide key tests for processes expected within the cosmological standard model but also open an enormous discovery space to new physics. This offers unique scientific opportunities for furthering our understanding of inflation, recombination, reionization and structure formation as well as dark matter and particle physics. A dedicated experimental approach could open this new window to the early Universe in the decades to come, allowing us to turn the long-standing upper distortion limits obtained with
COBE
/FIRAS some 25 years ago into clear detections of the expected standard distortion signals and also challenge our current understanding of the laws of nature.
The parity symmetry of the cosmic microwave background (CMB) pattern as seen by Wilkinson Microwave Anisotropy Probe 7 yr (WMAP 7 yr) is tested jointly in temperature and polarization at large ...angular scale. A quadratic maximum likelihood (QML) estimator is applied to the WMAP 7-yr low-resolution maps to compute all polarized CMB angular power spectra. The analysis is supported by 10 000 realistic Monte Carlo realizations. We confirm the previously reported parity anomaly for TT in the range δℓ=2, 22 at >99.5 per cent C.L. No anomalies have been detected in TT for a wider ℓ range (up to ℓmax= 40). No violations have been found for EE, TE and BB which we test here for the first time. The cross-spectra TB and EB are found to be consistent with zero. We also forecast Planck capabilities in probing parity violations on low-resolution maps.
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