283 research outputs found
A new type of small-scale downflow patches in sunspot penumbrae
A sunspot penumbra is observationally examined to reveal properties of
small-scale flow structures and how they are related to the filamentary
magnetic structures and the Evershed flow. We also study how the photospheric
dynamics is related to chromospheric activities. The study is based on data
analysis of spectro-polarimetric observations of photospheric Fe I lines with
the Solar Optical Telescope aboard Hinode in a sunspot penumbra at different
heliocentric angles. Vector magnetic fields and velocities are derived using
the spectro-polarimetric data and a Stokes inversion technique. An observation
with a Ca II H filtergram co-spatial and co-temporal with the
spectro-polarimetric one is also used to study possible chromospheric
responses. We find small patches with downflows at photospheric layers. The
downflow patches have a size of 0.5" or smaller and have a geometrical
configuration different from that of the Evershed flow. The downflow velocity
is about 1 km/s at lower photspheric layers, and is almost zero in the upper
layers. Some of the downflow patches are associated with brightenings seen in
Ca II H images. The downflows are possible observational signatures of downward
flows driven by magnetic reconnection in the interlaced magnetic field
configuration, where upward flows make brightenings in the chromosphere.
Another possibility is that they are concentrated downward flows of overturning
magnetoconvection.Comment: 9 pages, 7 figures, accepted for publication in Astronomy &
Astrophysic
Orphan penumbrae: Submerging horizontal fields
We investigate the properties of orphan penumbrae, which are photospheric
filamentary structures observed in active regions near polarity inversion lines
that resemble the penumbra of regular sunspots but are not connected to any
umbra. We use Hinode data from the Solar Optical Telescope to determine the
properties of orphan penumbrae. Spectropolarimetric data are employed to obtain
the vector magnetic field and line-of-sight velocities in the photosphere.
Magnetograms are used to study the overall evolution of these structures, and
G-band and Ca II H filtergrams are to investigate their brightness and apparent
horizontal motions. Orphan penumbrae form between regions of opposite polarity
in places with horizontal magnetic fields. Their magnetic configuration is that
of -shaped flux ropes. In the two cases studied here, the
opposite-polarity regions approach each other with time and the whole structure
submerges as the penumbral filaments disappear. Orphan penumbrae are very
similar to regular penumbrae, including the existence of strong gas flows.
Therefore, they could have a similar origin. The main difference between them
is the absence of a "background" magnetic field in orphan penumbrae. This could
explain most of the observed differences. The fast flows we detect in orphan
penumbrae may be caused by the siphon flow mechanism. Based on the similarities
between orphan and regular penumbrae, we propose that the Evershed flow is also
a manifestation of siphon flows.Comment: 15 pages, 15 figure
Evaluating Pain Response of Metritic versus Healthy Cows
Agriculture/Environmental Science (The Ohio State University Denman Undergraduate Research Forum)Metritis is a uterine infection commonly affecting dairy cows around parturition and little work has been done evaluating the pain associated with this disease. Physiological changes, such as back arching, are indicative of pain and tissue palpation has been shown to be an effective evaluation of visceral pain. The objective of this study was to evaluate the pain response through rectal palpation in cows diagnosed with metritis as compared to clinically healthy cows through rectal palpation. A systematic health check were performed on postpartum Holstein cows (n= 52) between 3 and 15 d in milk to determine health status. The health check consisted of a passive rectal palpation where the examiner’s hand was placed above the area of the uterus in a stand-still position to evaluate the response to visceral pain, followed by a vaginal examination. Vaginal discharge (VD) scoring was used to diagnosis metritic cases by the following scale no mucus or clear mucus, no odor = 0; cloudy mucus, with some pus or blood, no odor = 1; mucopurulent, foul smell= 2; purulent, foul smell = 3; and putrid= 4. A total of 23 metritic cows (VD ≥ 2) occurred, and thus there were 29 healthy cows used in the study. The back arch was recorded using video recording and computer programing was used to determine back arch area (cm2). Metritic cows on the day of diagnosis had an average vaginal discharge score of 3.48 versus healthy cows with an average score of 0.86 (P < 0.0001). The back arch of metritic cows was higher than healthy cows during the passive rectal palpation (566 cm2 vs. 771 cm2, P < 0.01). As expected, the VD was greater for metritic than healthy cows. In addition, it was determined that passive rectal palpation provides an indication of pain associated with metritis.Academic Major: Animal Science
Comparison of theoretical and observed Ca~{\sc ii}~8542 Stokes profiles in quiet regions at the centre of the solar disc
Interpreting the Stokes profiles observed in quiet regions of the solar
chromosphere is a challenging task. The Stokes Q and U profiles are dominated
by the scattering polarisation and the Hanle effect, and these processes can
only be correctly quantified if 3D radiative transfer effects are taken into
account. Forward-modelling of the intensity and polarisation of spectral lines
using a 3D model atmosphere is a suitable approach in order to statistically
compare the theoretical and observed line profiles. Our aim is to present novel
observations of the Ca 8542 line profiles in a quiet region at the centre of
the solar disc and to quantitatively compare them with the theoretical Stokes
profiles. We aim at estimating the reliability of the 3D model atmosphere using
not only the line intensity but the full vector of Stokes parameters. We used
data obtained with the ZIMPOL instrument at the IRSOL and compared the
observations with the theoretical profiles computed with the PORTA radiative
transfer code, using as solar model atmosphere a 3D snapshot taken from a
radiation-magnetohydrodynamics simulation. The synthetic profiles were degraded
to match the instrument and observing conditions. The degraded theoretical
profiles of the Ca 8542 line are qualitatively similar to the observed ones. We
confirm that there is a fundamental difference in the widths of all Stokes
profiles: the observed lines are wider than the theoretical lines. We find that
the amplitudes of the observed profiles are larger than those of the
theoretical ones, which suggests that the symmetry breaking effects in the
solar chromosphere are stronger than in the model atmosphere. This means that
the isosurfaces of temperature, velocity, and magnetic field strength and
orientation are more corrugated in the solar chromosphere than in the currently
available 3D radiation-magnetohydrodynamics simulation
Recent advancements in the EST project
The European Solar Telescope (EST) is a project of a new-generation solar
telescope. It has a large aperture of 4~m, which is necessary for achieving
high spatial and temporal resolution. The high polarimetric sensitivity of the
EST will allow to measure the magnetic field in the solar atmosphere with
unprecedented precision. Here, we summarise the recent advancements in the
realisation of the EST project regarding the hardware development and the
refinement of the science requirements.Comment: accepted to Advances in Space Researc
Atmosphere above a large solar pore
A large solar pore with a granular light bridge was observed on October 15,
2008 with the IBIS spectrometer at the Dunn Solar Telescope and a 69-min long
time series of spectral scans in the lines Ca II 854.2 nm and Fe I 617.3 nm was
obtained. The intensity and Doppler signals in the Ca II line were separated.
This line samples the middle chromosphere in the core and the middle
photosphere in the wings. Although no indication of a penumbra is seen in the
photosphere, an extended filamentary structure, both in intensity and Doppler
signals, is observed in the Ca II line core. An analysis of morphological and
dynamical properties of the structure shows a close similarity to a
superpenumbra of a sunspot with developed penumbra. A special attention is paid
to the light bridge, which is the brightest feature in the pore seen in the Ca
II line centre and shows an enhanced power of chromospheric oscillations at 3-5
mHz. Although the acoustic power flux in the light bridge is five times higher
than in the "quiet" chromosphere, it cannot explain the observed brightness.Comment: 6 pages, 3 figures, accepted in Journal of Physics: Conference Serie
A Novel Method for Epileptic Seizure Detection Using Coupled Hidden Markov Models
We propose a novel Coupled Hidden Markov Model to detect epileptic seizures
in multichannel electroencephalography (EEG) data. Our model defines a network
of seizure propagation paths to capture both the temporal and spatial evolution
of epileptic activity. To address the intractability introduced by the coupled
interactions, we derive a variational inference procedure to efficiently infer
the seizure evolution from spectral patterns in the EEG data. We validate our
model on EEG aquired under clinical conditions in the Epilepsy Monitoring Unit
of the Johns Hopkins Hospital. Using 5-fold cross validation, we demonstrate
that our model outperforms three baseline approaches which rely on a classical
detection framework. Our model also demonstrates the potential to localize
seizure onset zones in focal epilepsy.Comment: To appear in MICCAI 2018 Proceeding
Heating of the solar photosphere during a white-light flare
The \ion{Fe}{i} lines observed by the Hinode/SOT spectropolarimeter were
always seen in absorption, apart from the extreme solar limb. Here we analyse a
unique dataset capturing these lines in emission during a solar white-light
flare. We analyse the temperature stratification in the solar photosphere
during a white-light flare and compare it with the post-white-light flare
state. We used two scans of the Hinode/SOT spectropolarimeter to infer, by
means of the LTE inversion code Stokes Inversion based on Response function
(SIR), the physical properties in the solar photosphere during and after a
white-light flare. The resulting model atmospheres are compared and the changes
are related to the white-light flare. We show that the analysed white-light
flare continuum brightening is probably not caused by the temperature increase
at the formation height of the photospheric continuum. However, the photosphere
is heated by the flare approximately down to and this
results in emission profiles of the observed \ion{Fe}{i} lines. From the
comparison with the post-white-light flare state of the atmosphere, we estimate
that the major contribution to the increase in the continuum intensity
originates in the heated chromosphere
- …