Bibcode
Lites, B. W.; Skumanich, A.; Martinez Pillet, V.
Referencia bibliográfica
Astronomy and Astrophysics, v.333, p.1053-1068 (1998)
Fecha de publicación:
5
1998
Revista
Número de citas
111
Número de citas referidas
96
Descripción
Several small emerging bipolar regions have been observed with the
Advanced Stokes Polarimeter (ASP), including extensive time series
measurements of one small region. Both new and previously recognized
properties of the actual site of first emergence, where the magnetic
field is nearly horizontal to the surface, are revealed by these
observations. They provide the most complete and accurate observational
description to date of newly emerging vector magnetic fields. We find
that: 1) the strength of the magnetic field at the site of the emergence
(where the vector field is nearly parallel to the solar surface) ranges
from about 200 to 600 G, 2) as individual flux elements migrate rapidly
away from the emergence zone, they attain kiloGauss strengths only after
becoming oriented nearly vertically, 3) the emergence zone is dotted by
small, transient, upward rising ( ~ 1 km s(-1) ) horizontal magnetic
elements as indicated by the Doppler shift of the polarized spectral
profiles, 4) the leading polarity flux coalesces immediately into a
compact region which forms a pore, but the emerging following polarity
flux is spatially much less compact, 5) some ``moving magnetic
features'' having the same magnetic polarity as the growing pore, but on
the opposite side of the pore from the emergence zone, coalesce with the
pore during the observation period, and 6) the observations suggest a
low canopy of weak horizontal magnetic fields arches over the emergence
zone. These observations support a widely accepted picture of emerging
bipolar flux: the buoyantly rising flux transports mass from the
photosphere into the chromosphere, where it then may drain downward
along arched magnetic loops. The observed formation of a pore suggests
that emergence of subsurface structure, not organized flows near the
surface, is largely responsible for the apparent coalescence of sunspots
from more diffuse fields viewed at the solar surface. These observations
neither confirm nor refute the operation of convective collapse of flux
tubes.