  Recent EUV spectroscopic observations indicate that slow magnetosonic waves
are present in active region (AR) loops. Some of the spectral data were also
interpreted as evidence of fast (~100-300 km/s) quasi-periodic flows. We have
performed three-dimensional magnetohydrodynamic (3D MHD) modeling of a bipolar
AR that contains impulsively generated waves and flows in coronal loops. The
model AR is initiated with a dipole magnetic field and gravitationally
stratified density, with an upflow driven steadily or periodically in localized
regions at the footpoints of magnetic loops. The resulting flows along the
magnetic field lines of the AR produce higher density loops compared to the
surrounding plasma by injection of material into the flux-tubes and the
establishment of siphon flow. We find that the impulsive onset of flows with
subsonic speeds result in the excitation of damped slow magnetosonic waves that
propagate along the loops and coupled nonlinearly driven fast mode waves. The
phase speed of the slow magnetosonic waves is close to the coronal sound speed.
When the amplitude of the driving pulses is increased we find that slow
shock-like wave trains are produced. When the upflows are driven periodically,
undamped oscillations are produced with periods determined by the periodicity
of the upflows. Based on the results of the 3D MHD model we suggest that the
observed slow magnetosonic waves and persistent upflows may be produced by the
same impulsive events at the bases of ARs.
