The absence of thermal instability in the high/soft state of black hole X-ray binaries , in disagreement with the standard thin disk theory , is a long-standing riddle for theoretical astronomers .
We have tried to resolve this question by studying the thermal stability of a thin disk with magnetically driven winds in the \dot { M } - \Sigma plane .
It is found that disk winds can greatly decrease the disk temperature and thus help the disk become more stable at a given accretion rate .
The critical accretion rate \dot { M } _ { crit } corresponding to the thermal instability threshold is increased significantly in the presence of disk winds .
For \alpha = 0.01 and B _ { \phi } = 10 B _ { { } _ { p } } , the disk is quite stable even for a very weak initial poloidal magnetic field [ \beta _ { p, 0 } \sim 2000 , \beta _ { p } = ( P _ { gas } + P _ { rad } ) / ( B _ { p } ^ { % 2 } / 8 \pi ) ] .
But when B _ { \phi } = B _ { { } _ { p } } or B _ { \phi } = 0.1 B _ { { } _ { p } } , a somewhat stronger ( but still weak ) field ( \beta _ { p, 0 } \sim 200 or \beta _ { p, 0 } \sim 20 ) is required to make the disk stable .
Nevertheless , despite the great increase of \dot { M } _ { crit } , the luminosity threshold corresponding to instability remains almost constant or even decreases slowly with increasing \dot { M } _ { crit } due to the decrease of gas temperature .
The advection and diffusion timescales of the large-scale magnetic field threading the disk are also investigated in this work .
We find that the advection timescale can be smaller than the diffusion timescale in a disk with winds , because the disk winds take away most of the gravitational energy released in the disk , resulting in the decrease of the magnetic diffusivity \eta and the increase of the diffusion timescale .