Apparently, the magnetic field of a star becomes significant only when
the stopping radius exceeds the radius of the star,
. We take the Alfven radius
for
, since it is the smallest of the two quantities
and
. Hence, we can estimate the lowest value of magnetic field of a star which
will influence the flow of matter

The case
,
is considered most frequently, and for this case we get the following numerical
estimations

or, equivalently,

Most presently observed NS have magnetic fields
G and dipole moments
G cm
, so the magnetic field must necessarily be taken into account when considering
interaction of matter with these stars.