  We present a spectroscopic analysis of over 38,000 low-mass stars from the
Sloan Digital Sky Survey (SDSS) Data Release 5 (DR5). 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. We also present evidence
for a possible decrease in the metallicity as a function of height above the
Galactic Plane. In addition to our activity analysis, we provide line
measurements, molecular band indices, colors, radial velocities, 3-D space
motions and mean properties as a function of spectral type for the SDSS DR5
low-mass star sample.
