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| Paper: |
Sources and Removal of Magnetic Flux in the Solar Atmosphere |
| Volume: |
455, 4th Hinode Science Meeting: Unsolved Problems and Recent Insights |
| Page: |
91 |
| Authors: |
Moreno-Insertis, F. |
| Abstract: |
Recent advances in the observation and numerical modeling of magnetic
flux emergence on small-scales are reviewed. The high-resolution limit
of solar photospheric observations has reached scales of order
0".2, or 100–200 km, in recent years. Observations with that
resolution show individual flux tubes emerging within single granules
in the quiet Sun as small bipolar features of flux as low as 1016
Mx. Also, high-resolution observations of emerging ephemeral active
regions have been carried out simultaneously at heights from the
photosphere to the corona using different instruments in space and on
the ground, and providing views of the emergence process with
unprecedented detail. This paper starts with a brief review of some
of the highest-resolution flux emergence observations. On the theory
side, there is an increasing number of realistic numerical simulations
of flux emergence that solve the equations of magnetohydrodynamics and
radiation transfer. Various groups have studied different aspects of
the radiation-MHD modeling of flux emergence, but their simulations in
part cover the same processes. In this paper, a number of conclusions
of the models are discussed with special focus on the comparison
between the results of the different groups. The removal of magnetic
fields from the surface is a less explored field than the inverse
process, both observationally and theoretically. Yet, there is a good
number of observations of flux disappearance from the photosphere and
other atmospheric layers, typically in the form of cancellation of
colliding flux elements of opposite polarity. On the simulation side,
various numerical experiments of emerging flux regions find clear
instances of flux cancellation and removal in the runs. In those
cases, reconnection of field lines of opposite polarity is taking
place and leads to phenomena akin to those reported in some of the
observations. In this review a number of recent results from theory
and observation are discussed which help understand the removal of
flux from the solar atmosphere. |
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