Analysis of the nature of interaction of a magnetized star with the
surrounding plasma allows us to write an approximate evolution equation
for the angular momentum of a magnetic rotator in the general form (Lipunov,
1982a[98])

where
is a specific angular momentum applied by the accretion matter to the rotator.
This quantity is given by

where
is the radius of the inner disk edge,
is the rotational frequency of the binary system, and
(Illarionov and Sunyaev, 1975[76]).
The values of dimensionless factor
, characteristic radius
and the accretion rate
in different regimes are presented in Table 3.

The evolution equation (4.10.2)
is approximate. In practice, the situation with propellers
and superpropellers is not yet clear. In Table 3
is the size of a magnetosphere whose value at the propeller
stage is not known accurately and which may differ significantly from the
standard expressions for the Alfvén radius.