406 research outputs found
The pre-penumbral magnetic canopy in the solar atmosphere
Penumbrae are the manifestation of magnetoconvection in highly inclined (to the vertical direction)
magnetic field. The penumbra of a sunspot tends to form, initially, along the arc of the umbra
antipodal to the main region of flux emergence. The question of how highly inclined magnetic field
can concentrate along the antipodal curves of umbrae, at least initially, remains to be answered.
Previous observational studies have suggested the existence of some form of overlying magnetic canopy
which acts as the progenitor for penumbrae. We propose that such overlying magnetic canopies are
a consequence of how the magnetic field emerges into the atmosphere and are, therefore, part of the
emerging region. We show, through simulations of twisted flux tube emergence, that canopies of
highly inclined magnetic field form preferentially at the required locations above the photosphere
IRIS observations of magnetic interactions in the solar atmosphere between pre-existing and emerging magnetic fields. II. UV emission properties
Multi-wavelength ultraviolet (UV) observations by the IRIS satellite in
active region NOAA 12529 have recently pointed out the presence of long-lasting
brightenings, akin to UV bursts, and simultaneous plasma ejections occurring in
the upper chromosphere and transition region during secondary flux emergence.
These signatures have been interpreted as evidence of small-scale, recurrent
magnetic reconnection episodes between the emerging flux region (EFR) and the
pre-existing plage field. Here, we characterize the UV emission of these
strong, intermittent brightenings and we study the surge activity above the
chromospheric arch filament system (AFS) overlying the EFR. We analyze the
surges and the cospatial brightenings observed at different wavelengths. We
find an asymmetry in the emission between the blue and red wings of the Si IV
1402 \AA{} and Mg II k 2796.3 \AA{} lines, which clearly outlines the dynamics
of the structures above the AFS that form during the small-scale eruptive
phenomena. We also detect a correlation between the Doppler velocity and
skewness of the Si IV 1394 \AA{} and 1402 \AA{} line profiles in the UV burst
pixels. Finally, we show that genuine emission in the Fe XII 1349.4 \AA{} line
is cospatial to the Si IV brightenings. This definitely reveals a pure coronal
counterpart to the reconnection event.Comment: 19 pages, 8 figures + 3 figures in the Appendix; accepted in Ap
HINODE Observations of Chromospheric Brightenings in the Ca II H Line during small-scale Flux Emergence Events
\ion{Ca}{2} H emission is a well-known indicator of magnetic activity in the
Sun and other stars. It is also viewed as an important signature of
chromospheric heating. However, the \ion{Ca}{2} H line has not been used as a
diagnostic of magnetic flux emergence from the solar interior. Here we report
on Hinode observations of chromospheric \ion{Ca}{2} H brightenings associated
with a repeated, small-scale flux emergence event. We describe this process and
investigate the evolution of the magnetic flux, G-band brightness, and
\ion{Ca}{2} H intensity in the emerging region. Our results suggest that energy
is released in the chromosphere as a consequence of interactions between the
emerging flux and the pre-existing magnetic field, in agreement with recent 3D
numerical simulations.Comment: 12 Pages, 6 Figures, Accepted for publication in ApJ Letter
Satellite observations of reconnection between emerging and pre-existing small-scale magnetic fields
We report multi-wavelength ultraviolet observations taken with the IRIS
satellite, concerning the emergence phase in the upper chromosphere and
transition region of an emerging flux region (EFR) embedded in the unipolar
plage of active region NOAA 12529. The photospheric configuration of the EFR is
analyzed in detail benefitting from measurements taken with the
spectropolarimeter aboard the Hinode satellite, when the EFR was fully
developed. In addition, these data are complemented by full-disk, simultaneous
observations of the SDO satellite, relevant to the photosphere and the corona.
In the photosphere, magnetic flux emergence signatures are recognized in the
fuzzy granulation, with dark alignments between the emerging polarities,
cospatial with highly inclined fields. In the upper atmospheric layers, we
identify recurrent brightenings that resemble UV bursts, with counterparts in
all coronal passbands. These occur at the edges of the EFR and in the region of
the arch filament system (AFS) cospatial to the EFR. Jet activity is also found
at chromospheric and coronal levels, near the AFS and the observed brightness
enhancement sites. The analysis of the IRIS line profiles reveals the heating
of dense plasma in the low solar atmosphere and the driving of bi-directional
high-velocity flows with speeds up to 100 km/s at the same locations.
Furthermore, we detect a correlation between the Doppler velocity and line
width of the Si IV 1394 and 1402 \AA{} line profiles in the UV burst pixels and
their skewness. Comparing these findings with previous observations and
numerical models, we suggest evidence of several long-lasting, small-scale
magnetic reconnection episodes between the emerging bipole and the ambient
field. This process leads to the cancellation of a pre-existing photospheric
flux concentration of the plage with the opposite polarity flux patch of the
EFR. [...]Comment: 4 pages, 2 figures, to be published in "Nuovo Cimento C" as
proceeding of the Third Meeting of the Italian Solar and Heliospheric
Communit
Description of Anteon seramense (Hymenoptera. Dryinidae), a new species from Indonesia
Anteon seramense sp. nov. is described from Seram Island (Indonesia). Seram is an island
situated in a transition area between the Oriental and the Australian regions. Anteon seramense
can be distinguished from the related Australian species A. giluwense Olmi and
A. chelogynoides (Perkins) by the different sculpture of the scutum (granulated in A. seramense,
punctate and unsculptured among punctures in A. giluwense and A. chelogynoides)
and the different distal apex of the protarsal segment 5 (deeply hollow in A. seramense,
not hollow in A. giluwense and A. chelogynoides). Anteon seramense sp. nov. can be distinguished
from the related Oriental species A. heppneri Olmi and A. thai Olmi by the different
shape of the protarsal segment 5 (basal part slightly longer than distal part in A. seramense,
much longer in A. heppneri and A. thai)
The 2013 February 17 sunquake in the context of the active region's magnetic field configuration
© 2017. The American Astronomical Society. All rights reserved. Sunquakes are created by the hydrodynamic response of the lower atmosphere to a sudden deposition of energy and momentum. In this study, we investigate a sunquake that occurred in NOAA active region 11675 on 2013 February 17. Observations of the corona, chromosphere, and photosphere are brought together for the first time with a nonlinear force-free model of the active region's magnetic field in order to probe the magnetic environment in which the sunquake was initiated. We find that the sunquake was associated with the destabilization of a flux rope and an associated M-class GOES flare. Active region 11675 was in its emergence phase at the time of the sunquake and photospheric motions caused by the emergence heavily modified the flux rope and its associated quasi-separatrix layers, eventually triggering the flux rope's instability. The flux rope was surrounded by an extended envelope of field lines rooted in a small area at the approximate position of the sunquake. We argue that the configuration of the envelope, by interacting with the expanding flux rope, created a “magnetic lens” that may have focussed energy on one particular location of the photosphere, creating the necessary conditions for the initiation of the sunquake
Description of Bocchus irwini sp. nov. from Madagascar (Hymenoptera Dryinidae)
Bocchus irwini sp. nov. is described from a male collected in Analagnambe forest,
Mahajanga Province, Madagascar. The new species is similar to Bocchus watshami Olmi 1987.
Keys to the Afrotropical species of Bocchus are modified to include the new species
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