Magneto-rotational instability in the solar core and Ap star envelopes
Seminar Room 1, Newton Institute
The radiative core of the Sun rotates uniformly as suggested by helioseismological observations. It also rotates as slow as the average surface rotation. The pre-main squence Sun probably rotated much faster. If surface breaking has slowed down the Sun, a fast angular-momentum transport would be necessary to reduce the rotation rate of the core, too. Pure microscopic viscosiy is not sufficient. The problem of slow-down and equalizing of the core rotation is attributed to the magneto-rotational instability. Time-scales of 10-100 mill yr are found. A similar scenario may be possible in the radiative envelopes of Ap stars. Given their shorter life-times, the redistribution of angular momentum must be an ongoing process.