Abstract:
Continuous high-cadence and high
spatial resolution Dopplergrams allow us to study subsurface dynamics that
may be further extended to explore precursors of visible solar activity on the surface. Since the
p
-mode power is
absorbed in the regions of high magnetic
fi
eld, the inferences in these regions are often presumed to have large
uncertainties. In this paper, using the Dopplergrams from space-borne Helioseismic Magnetic Imager, we compare
horizontal
fl
ows in a shear layer below the surface and the photospheric layer in and around active regions. The
photospheric
fl
ows are calculated using the local correlation tracking
(
LCT
)
method, while the ring-diagram
technique of helioseismology is used to infer
fl
ows in the subphotospheric shear layer. We
fi
nd a strong positive
correlation between
fl
ows from both methods near the surface. This implies that despite the absorption of acoustic
power in the regions of strong magnetic
fi
eld, the
fl
ows inferred from the helioseismology are comparable to those
from the surface measurements. However, the magnitudes are signi
fi
cantly different; the
fl
ows from the LCT
method are smaller by a factor of 2 than the helioseismic measurements. Also, the median difference between the
direction
of corresponding vectors is 49
°
.
