SDSS-DR5 low-mass star spectroscopic sample

Analysis of this unprecedentedly large sample confirms the previously detected decrease in the fraction of magnetically active stars (as traced by H{alpha} emission) as a function of vertical distance from the Galactic Plane. The magnitude and slope of this effect varies as a function of spectral type.

Using simple 1-D dynamical models, we demonstrate that the drop in activity fraction can be explained by thin disk dynamical heating and a rapid decrease in magnetic activity. The timescale for this rapid activity decrease changes according to the spectral type. By comparing our data to the simulations, we calibrate the age-activity relation at each M dwarf spectral type.