shadishacker said:Dear all,
Can anyone give me a time scale/ redshift range as an estimate for the formation of magnetic fields in the universe?
Could you please give me a redshift scale?wolram said:Hope this helps shadishacker.
http://arxiv.org/abs/astro-ph/0009061
This review concerns the origin and the possible effects of magnetic fields in the early Universe. We start by providing to the reader with a short overview of the current state of art of observations of cosmic magnetic fields. We then illustrate the arguments in favour of a primordial origin of magnetic fields in the galaxies and in the clusters of galaxies. We argue that the most promising way to test this hypothesis is to look for possible imprints of magnetic fields on the temperature and polarization anisotropies of the cosmic microwave background radiation (CMBR). With this purpose in mind, we provide a review of the most relevant effects of magnetic fields on the CMBR. A long chapter of this review is dedicated to particle physics inspired models which predict the generation of magnetic fields during the early Universe evolution. Although it is still unclear if any of these models can really explain the origin of galactic and intergalactic magnetic fields, we show that interesting effects may arise anyhow. Among these effects, we discuss the consequences of strong magnetic fields on the big-bang nucleosynthesis, on the masses and couplings of the matter constituents, on the electroweak phase transition, and on the baryon and lepton number violating sphaleron processes. Several intriguing common aspects, and possible interplay, of magnetogenesis and baryogenesis are also dicussed.
cristo said:I guess the answer is that we don't really know. There are various mechanisms for generation of magnetic fields, but there is not one definitive agreed upon solution. Generally, since magnetic fields appear to be correlated on large scales, and appear in voids, it is expected that they are cosmic in origin - that is, they were created in the very early universe, or during inflation. Additionally, magnetic fields can be created from phase transitions in the very early universe.
cristo said:since magnetic fields appear to be correlated on large scales, and appear in voids.
See, e.g., A. Neronov and I. Vovk, Science 328, 73 (2010) [http://arxiv.org/abs/1006.3504] . Distant photons traveling through the void interact with background light and produce electron/positron pairs. These pairs would travel in the same direction as the initial photon, however in the presence of a magnetic field are deflected, and the emission off this secondary cascade is suppressed. This has been observed in many distant TeV blazars, which is therefore good evidence of the existence of magnetic fields in voids.Hornbein said:How might an astronomer detect a magnetic field in a void?
The origin of the magnetic field in the early universe is still a topic of debate among scientists. Some theories suggest that it was generated by cosmic inflation, while others propose that it was created by the motion of charged particles in the plasma of the early universe.
The strength of the magnetic field in the early universe is difficult to determine, as it has been distorted and amplified by various processes throughout cosmic history. However, some studies estimate its strength to be around 10^-22 gauss, which is incredibly weak compared to the magnetic field on Earth.
Yes, the magnetic field in the early universe is believed to have played a role in the formation of galaxies. It could have affected the motion of gas and dust, influencing the collapse of these materials into galaxies. Additionally, the magnetic fields of galaxies today are thought to have originated from the primordial magnetic field.
Scientists study the magnetic field in the early universe through a combination of observational data and theoretical models. They use telescopes and other instruments to measure the magnetic fields in distant galaxies and compare them to predictions from models of the early universe. Additionally, experiments are conducted in labs to simulate the conditions of the early universe and test different theories.
There is currently no evidence to suggest that the magnetic field in the early universe has any direct connection to dark matter. However, some theories propose that dark matter particles could have interacted with the magnetic field in the early universe, leaving behind imprints that could potentially be detected in the cosmic microwave background radiation.