3.7. Magnetic fields in superclusters
Magnetic fields in the local supercluster are notoriously difficult to measure. In the absence of direct measurements it is the opinion of the author that these fields cannot be assumed to be small, i.e. << µ G. In this situation it seems useful to consider the possibility that these fields are large. In  this point of view has been taken in connection with the propagation of the most energetic cosmic rays. This approach is desirable since the (few) reliable claims of measurements of large-scale magnetic fields in the Local Supercluster seem to indicate that these fields are rather strong and more in the range of the µ G than in the range of the n G.
Recently  the possible existence, strength and structure of magnetic fields in the intergalactic plane, within the Local Supercluster, has been scrutinized. The local supercluster is centered approximately at the VIRGO cluster, about 18 Mpc from the Local Group. A statistically significant Faraday screen acting on the radio-waves coming from the most distance sources has been found. This analysis supports the existence of a regular magnetic field of 0.3 µ G in the Local Supercluster.
In the past detection of radio emission in the Coma supercluster has been reported . The plane of the Coma supercluster is defined by the Coma cluster and by the Abell cluster 1367. The observed magnetic field has been extimated to be of the order of 0.5 µ G.
In  using numerical simulations the spectrum of protons above 1019 eV has been determined under the assumption that the injection spectrum is determined by a discrete set of continuously emitting sources. The sources follow the profile of the local Supercluster. It has been shown that if || 0.05µ G the source distribution assumed in the Supercluster is inconsistent with the observations. On the other hand, if || 0.3 µ G, 10 sources in the local Supercluster would lead to spectra consistent with the observations. This analysis seems to fit with  and with the general arguments put forward in . In a complementary perspective, the authors of  claim to be able to simulate the evolution of large-scale magnetic fields from reasonably high red-shifts. The obtained results, according to , correctly reproduce the present large-scale structure of cluster and supercluster magnetic fields both in their observed and unobserved features.