The M dwarf V374 Peg ( M4 ) is believed to lie near the theoretical mass threshold for fully convective interiors .
Its rapid rotation ( P = 0.44 days ) along with its intense magnetic field point toward magneto-centrifugal acceleration of a coronal wind .
In this work , we investigate the structure of the coronal wind of V374 Peg by means of three-dimensional magnetohydrodynamical ( MHD ) numerical simulations .
For the first time , an observationally derived surface magnetic field map is implemented in MHD models of stellar winds for a low mass star .
By self-consistently taking into consideration the interaction of the outflowing wind with the magnetic field and vice versa , we show that the wind of V374 Peg deviates greatly from a low-velocity , low-mass-loss rate solar-type wind .
We have found general scaling relations for the terminal velocities , mass-loss rates , and spin-down times of highly magnetized M dwarfs .
In particular , for V374 Peg , our models show that terminal velocities across a range of stellar latitudes reach u _ { \infty } \simeq ( 1500 – 2300 ) n _ { 12 } ^ { -1 / 2 } ~ { } { km~ { } s } ^ { -1 } , where n _ { 12 } is the coronal wind base density in units of 10 ^ { 12 } ~ { } { cm } ^ { -3 } , while the mass-loss rates are about \dot { M } \simeq 4 \times 10 ^ { -10 } n _ { 12 } ^ { 1 / 2 } ~ { } { M } _ { \odot } ~ { } { yr } ^ { -1 } .
We also evaluate the angular-momentum loss of V374 Peg , which presents a rotational braking timescale \tau \simeq 28 { n _ { 12 } ^ { -1 / 2 } } Myr .
Compared to observationally derived values from period distributions of stars in open clusters , this suggests that V374 Peg may have low coronal base densities ( \lesssim 10 ^ { 11 } ~ { } { cm } ^ { -3 } ) .
We show that the wind ram pressure of V374 Peg is about 5 orders of magnitude larger than for the solar wind .
Never the less , a small planetary magnetic field intensity ( \sim 0.1 G ) is able to shield a planet orbiting at 1 ~ { } AU against the erosive effects of the stellar wind .
However , planets orbiting inside the habitable zone of V374 Peg , where the wind ram pressure is higher , might be facing a more significant atmospheric erosion .
In that case , higher planetary magnetic fields of , at least , about half the magnetic field intensity of Jupiter , are required to protect the planet ’ s atmosphere .