Horizontal Flows in the Photosphere and Subphotosphere of Two Active Regions
Yang Liu Submitted: 2012-07-23 11:57
We compare horizontal flow fields in the photosphere and subphotosphere
a layer of 0.5 Mm below the photosphere in two solar active regions:
AR11084 and AR11158. AR11084 is a mature, simple active region without
significant flaring activities, and AR11158 is a multipolar, complex active region
with magnetic flux emerging during the period studied. Flows in the photosphere
are derived by applying the method of Differential Affine Velocity Estimator for
Vector Magnetograms (DAVE4VM) on HMI observed vector magnetic fields,
and the subphotospheric flows are inferred by time ? distance helioseismology
using HMI observed Doppergrams. Similar flow patterns are found for both
layers for AR11084: inward flows in sunspot umbra and outward flows surrounding
the sunspot. The boundary between the inward and outward flows,
which is slightly different in the photosphere and the subphotosphere, is within
the sunspot penumbra. The area having inward flows in the subphotosphere is
larger than that in the photosphere. For AR11158, flows in these two layers
show great similarities in some areas and significant differences in other areas.
Both layers exhibit consistent outward flows in the areas surrounding sunspots.
On the other hand, most well-documented flux-emergence-related flow features
seen in the photosphere do not have their counterparts in the subphotosphere.
This implies that the horizontal flows caused by flux emergence do not extend
deeply into the subsurface.
Authors: Yang Liu, Junwei Zhao, Peter W. Schuck
Publication Status: Accepted by Solar Physics
Last Modified: 2012-07-24 11:02