||Magnetic Braking in Convective Stars
||447, Evolution of Compact Binaries
||Hussain, G. A. J.
||Magnetic braking causes the spin-down of single stars as they evolve
on the main sequence. Models of magnetic braking can also explain the evolution of
close binary systems, including cataclysmic variables.
The well-known period gap in the orbital period distribution of
cataclysmic variable systems indicates that
magnetic braking must be significantly disrupted in secondaries that are
However, activity studies show that
fully convective stars are some of the most active stars
observed in young open clusters.There is therefore conflicting evidence about what
happens to magnetic activity in fully convective stars.
Results from spectro-polarimetric studies of cool stars have found that
the field morphologies and field strengths are dependent on spectral type
and rotation rate. While rapidly rotating stars with radiative cores
show strong, complex magnetic fields, they have relatively weak dipole components.
Fully convective stars that are rapidly rotating also possess strong magnetic
fields, but their configurations are much simpler; often close to dipole fields.
How this change in field geometry affects the stellar wind is the focus of
several ongoing modelling efforts. Initial results suggest that rapidly rotating active dwarfs drive much stronger winds, about two orders of magnitude larger than
those on the Sun.