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The evolution equation


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 tex2html_wrap_inline9832 is a specific angular momentum applied by the accretion matter to the rotator. This quantity is given by


      where tex2html_wrap_inline9343 is the radius of the inner disk edge, tex2html_wrap_inline9836 is the rotational frequency of the binary system, and tex2html_wrap_inline9838 (Illarionov and Sunyaev, 1975[76]). The values of dimensionless factor tex2html_wrap_inline9479 , characteristic radius tex2html_wrap_inline9842 and the accretion rate tex2html_wrap_inline9166 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 tex2html_wrap_inline9846 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. 


Mike E. Prokhorov
Sat Feb 22 18:38:13 MSK 1997