  The simulations of the formation of cosmological structure allows to
determine the spatial inhomogeneity of cosmic magnetic fields. Such
simulations, however, do not give an absolute number for the strength of the
magnetic field due to insufficient spatial resolution. Combining these
simulations with observations of the Rotation Measure to distant radio sources
allows then to deduce upper limits for the strength of the magnetic field.
These upper limits are of order 0.2 - 2 muG along the filaments and sheets of
the galaxy distribution. In one case, the sheet outside the Coma cluster, there
is a definitive estimate of the strength of the magnetic field consistent with
this range. Such estimates are almost three orders of magnitude higher than
hitherto assumed usually. High energy cosmic ray particles can be either
focussed or strongly scattered in such magnetic filaments and sheets, depending
on the initial transverse momentum. The cosmological background in radio and
X-ray wavelengths will have contributions from these intergalactic filaments
and sheets, should the magnetic fields really be as high as 0.2 - 2 muG.
