Bibcode
Lites, B.; Martinez Pillet, V.
Referencia bibliográfica
American Astronomical Society, 188th AAS Meeting, #33.13; Bulletin of the American Astronomical Society, Vol. 28, p.870
Advertised on:
5
1996
Número de citas
0
Número de citas referidas
0
Descripción
We have carried out quantitative observations of the vector magnetic
field during the emergence of three small bipolar active regions in
June, 1992, July 1993, and September 1994 using the Advanced Stokes
Polarimeter (ASP). The region of horizontal magnetic field at the actual
site of emergence is always characterized by low magnetic field strength
(i.e. considerably less than 1000 Gauss). We find a strong relationship
between field strength and inclination in these regions. This suggests
that 1) flux emerging from below the photosphere does not coalesce into
strong flux tubes until it reaches the photosphere, becomes nearly
vertical as a result of magnetic buoyancy, and is then acted upon by
convective collapse, and 2) the field strength of flux rising through
the convection zone may be in rough equipartition with the fluid
motions. We find the flux emergence zone to be characterized by highly
variable (both spatially and temporally) fill factors for the magnetic
field, suggesting that the flux below the surface is filamentary, that
it rises rapidly through the photosphere to form a magnetic canopy above
the emergence region. Sequences of Hα on- and off-band images
obtained with the ASP reveal the accompanying development of the
arch-filament system, and suggest that the material within the Hα
structures is supplied by a siphon flow as evidenced by apparent
chromospheric red shifts on the sides of the loops closest to a large
pore, and blue shifts where the fields anchor in plage regions. Proper
motions of the magnetic flux images throughout a day's observation
indicate the presence of a persistent vortex flow on a small scale (a
few arcseconds). The National Center for Atmospheric Research is
sponsored by the National Science Foundation.