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Register a new userThe contribution of cosmic rays to global warming
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A search has been made for a contribution of the changing cosmic ray intensity to the global warming observed in the last century. The cosmic ray intensity shows a strong 11 year cycle due to solar modulation and the overall rate has decreased since 1900. These changes in cosmic ray intensity are compared to those of the mean global surface temperature to attempt to quantify any link between the two. It is shown that, if such a link exists, the changing cosmic ray intensity contributes less than 8% to the increase in the mean global surface temperature observed since 1900.
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It has been claimed by others that observed temporal correlations of terrestrial cloud cover with `the cosmic ray intensity are causal. The possibility arises, therefore, of a connection between cosmic rays and Global Warming. If true, the implications would be very great. We have examined this claim to look for evidence to corroborate it. So far we have not found any and so our tentative conclusions are to doubt it. Such correlations as appear are more likely to be due to the small variations in solar irradiance, which, of course, correlate with cosmic rays. We estimate that less than 15% of the 11-year cycle warming variations are due to cosmic rays and less than 2% of the warming over the last 35 years is due to this cause.
The propagation of charged particles, including cosmic rays, in a partially ordered magnetic field is characterized by a diffusion tensor whose components depend on the particles Larmor radius $R_L$ and the degree of order in the magnetic field. Most studies of the particle diffusion presuppose a scale separation between the mean and random magnetic fields (e.g., there being a pronounced minimum in the magnetic power spectrum at intermediate scales). Scale separation is often a good approximation in laboratory plasmas, but not in most astrophysical environments such as the interstellar medium (ISM). Modern simulations of the ISM have numerical resolution of order 1 pc, so the Larmor radius of the cosmic rays that dominate in energy density is at least $10^{6}$ times smaller than the resolved scales. Large-scale simulations of cosmic ray propagation in the ISM thus rely on oversimplified forms of the diffusion tensor. We take the first steps towards a more realistic description of cosmic ray diffusion for such simulations, obtaining direct estimates of the diffusion tensor from test particle simulations in random magnetic fields (with the Larmor radius scale being fully resolved), for a range of particle energies corresponding to $10^{-2}lesssim R_L/l_c lesssim 10^{3}$, where $l_c$ is the magnetic correlation length. We obtain explicit expressions for the cosmic ray diffusion tensor for $R_L/l_c ll 1$, that might be used in a sub-grid model of cosmic ray diffusion. The diffusion coefficients obtained are closely connected with existing transport theories that include the random walk of magnetic lines.
The standard model of cosmic ray propagation has been very successful in explaining all kinds of the Galactic cosmic ray spectra. However, high precision measurement recently revealed the appreciable discrepancy between data and model expectation, from spectrum observations of $gamma$-rays, $e^+/e^-$ and probably the $B/C$ ratio starting from $sim$10 GeV energy. In this work, we propose that the fresh cosmic rays, which are supplied by the young accelerators and detained by local magnetic field, can contribute additional secondary particles interacting with local materials. As this early cosmic ray has a hard spectrum, the model calculation results in a two-component $gamma$-ray spectrum, which agree very well with the observation. Simultaneously, the expected neutrino number from the galactic plane could contribute $sim60%$ of IceCube observation neutrino number below a few hundreds of TeV. The same pp-collision process can account for a significant amount of the positron excesses. Under this model, it is expected that the excesses in $overline p/p$ and $B/C$ ratio will show up when energy is above $sim$10 GeV. We look forward that the model will be tested in the near future by new observations from AMS02, IceCube, AS$gamma$, HAWC and future experiments such as LHASSO, HiSCORE and CTA.
Sampling from a Boltzmann distribution is NP-hard and so requires heuristic approaches. Quantum annealing is one promising candidate. The failure of annealing dynamics to equilibrate on practical time scales is a well understood limitation, but does not always prevent a heuristically useful distribution from being generated. In this paper we evaluate several methods for determining a useful operational temperature range for annealers. We show that, even where distributions deviate from the Boltzmann distribution due to ergodicity breaking, these estimates can be useful. We introduce the concepts of local and global temperatures that are captured by different estimation methods. We argue that for practical application it often makes sense to analyze annealers that are subject to post-processing in order to isolate the macroscopic distribution deviations that are a practical barrier to their application.
One of the big problems of the age concerns Global Warming, and whether it is man-made or natural. Most climatologists believe that it is very likely to be the former but some scientists (mostly non-climatologists) subscribe to the latter. Unsurprisingly, the population at large is often confused and and is not convinced either way. Here we try to explain the principles of man-made global warming in a simple way. Our purpose is to try to understand the story which the climatologists are telling us through their rather complicated general circulation models. Although the effects in detail are best left to the climatologists models, we show that for the Globe as a whole the effects of man-made global warming can be demonstrated in a simple way. The simple model of only the direct heating from the absorption of infrared radiation, illustrates the main principles of the science involved. The predicted temperature increase due to the increase of greenhouse gases in the atmosphere over the last century describes reasonably well at least most of the observed temperature increase.
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