22 research outputs found
Ca II K Spectral Study of an Emerging Flux Region using Domeless Solar Telescope in Hida Observatory
A cooperative observation with Hida observatory and Hinode satellite was
performed on an emerging flux region. The successive Ca II K spectro-heliograms
of the emerging flux region were taken by the Domeless Solar Telescope of Hida
observatory. Hinode observed the emerging flux region with Ca II H and Fe I
Stokes IQUV filtergrams. In this study, detailed dynamics and temporal
evolution of the magnetic flux emergence was studied observationally. The event
was first detected in the photospheric magnetic field signals. 3 minutes later,
the horizontal expansion of the dark area was detected. And then, 7 minutes
later than the horizontal expansion, the emerging loops were detected with the
maximal rise speed of 2.1 km/s at chromospheric heights. The observed dynamics
of emerging magnetic flux from the photosphere to the upper chromosphere is
well consistent with the results of previous simulation works. The gradual
rising phase of flux tubes with a weak magnetic strength was confirmed by our
observation.Comment: 14 pages, 7 figure
Can High Frequency Acoustic Waves Heat the Quiet Sun Chromosphere?
We use Hinode/SOT Ca II H-line and blue continuum broadband observations to
study the presence and power of high frequency acoustic waves at high spatial
resolution. We find that there is no dominant power at small spatial scales;
the integrated power using the full resolution of Hinode (0.05'' pixels, 0.16''
resolution) is larger than the power in the data degraded to 0.5'' pixels
(TRACE pixel size) by only a factor of 1.2. At 20 mHz the ratio is 1.6.
Combining this result with the estimates of the acoustic flux based on TRACE
data of Fossum & Carlsson (2006), we conclude that the total energy flux in
acoustic waves of frequency 5-40 mHz entering the internetwork chromosphere of
the quiet Sun is less than 800 W m, inadequate to balance the radiative
losses in a static chromosphere by a factor of five.Comment: 6 pages, 8 figures, accepted for publication in PASJ (special Hinode
issue
Observations of Sunspot Oscillations in G band and Ca II H line with Solar Optical Telescope on Hinode
Exploiting high-resolution observations made by the Solar Optical Telescope
onboard Hinode, we investigate the spatial distribution of power spectral
density of oscillatory signal in and around NOAA active region 10935. The
G-band data show that in the umbra the oscillatory power is suppressed in all
frequency ranges. On the other hand, in Ca II H intensity maps oscillations in
the umbra, so-called umbral flashes, are clearly seen with the power peaking
around 5.5 mHz. The Ca II H power distribution shows the enhanced elements with
the spatial scale of the umbral flashes over most of the umbra but there is a
region with suppressed power at the center of the umbra. The origin and
property of this node-like feature remain unexplained.Comment: 7 pages, 8 figures, accepted for publication in PASJ (Hinode Special
Issue
Spicule Dynamics over Plage Region
We studied spicular jets over a plage area and derived their dynamic
characteristics using Hinode Solar Optical Telescope (SOT) high-resolution
images. The target plage region was near the west limb of the solar disk. This
location permitted us to study the dynamics of spicular jets without the
overlapping effect of spicular structures along the line of sight.
In this work, to increase the ease with which we can identify spicules on the
disk, we applied the image processing method `MadMax' developed by Koutchmy et
al. (1989). It enhances fine, slender structures (like jets), over a diffuse
background. We identified 169 spicules over the target plage. This sample
permits us to derive statistically reliable results regarding spicular
dynamics.
The properties of plage spicules can be summarized as follows: (1) In a plage
area, we clearly identified spicular jet features. (2) They were shorter in
length than the quiet region limb spicules, and followed ballistic motion under
constant deceleration. (3) The majority (80%) of the plage spicules showed the
cycle of rise and retreat, while 10% of them faded out without a complete
retreat phase. (4) The deceleration of the spicule was proportional to the
velocity of ejection (i.e. the initial velocity).Comment: 12 pages, 9 figures, accepted for publication in PAS
Initial Helioseismic Observations by Hinode/SOT
Results from initial helioseismic observations by Solar Optical Telescope
onboard Hinode are reported. It has been demonstrated that intensity
oscillation data from Broadband Filter Imager can be used for various
helioseismic analyses. The k-omega power spectra, as well as corresponding
time-distance cross-correlation function that promises high-resolution
time-distance analysis below 6-Mm travelling distance, were obtained for G-band
and CaII-H data. Subsurface supergranular patterns have been observed from our
first time-distance analysis. The results show that the solar oscillation
spectrum is extended to much higher frequencies and wavenumbers, and the
time-distance diagram is extended to much shorter travel distances and times
than they were observed before, thus revealing great potential for
high-resolution helioseismic observations from Hinode.Comment: 6 pages, accepted for publication in PAS
Emergence of a Helical Flux Rope Under an Active Region Prominence
Continuous observations were obtained of active region 10953 with the Solar
Optical Telescope (SOT) on board the \emph{Hinode} satellite during 2007 April
28 to May 9. A prominence was located over the polarity inversion line (PIL) in
the south-east of the main sunspot. These observations provided us with a time
series of vector magnetic fields on the photosphere under the prominence. We
found four features: (1) The abutting opposite-polarity regions on the two
sides along the PIL first grew laterally in size and then narrowed. (2) These
abutting regions contained vertically-weak, but horizontally-strong magnetic
fields. (3) The orientations of the horizontal magnetic fields along the PIL on
the photosphere gradually changed with time from a normal-polarity
configuration to a inverse-polarity one. (4) The horizontal-magnetic field
region was blueshifted. These indicate that helical flux rope was emerging from
below the photosphere into the corona along the PIL under the pre-existing
prominence. We suggest that this supply of a helical magnetic flux into the
corona is associated with evolution and maintenance of active-region
prominences.Comment: 10 pages, 2 figures, accepted for publication in ApJ Letter
Polarimetric calibration of a spectropolarimeter instrument with high precision: Sunrise chromospheric infrared spectropolarimeter (SCIP) for the sunrise iii balloon telescope
The Sunrise chromospheric infrared spectropolarimeter (SCIP) installed in the international balloon experiment sunrise iii will perform spectropolarimetric observations in the near-infrared band to measure solar photospheric and chromospheric magnetic fields simultaneously. The main components of SCIP for polarization measurements are a rotating wave plate, polarization beam splitters, and CMOS imaging sensors. In each of the sensors, SCIP records the orthogonal linearly polarized components of light. The polarization is later demodulated on-board. Each sensor covers one of the two distinct wavelength regions centered at 770 and 850 nm. To retrieve the proper circular polarization, the new parameter , defined as the 45° phase shifted component of Stokes in the modulation curve, is introduced. SCIP is aimed at achieving high polarization precision (1<3×10−4 of continuum intensity) to capture weak polarization signals in the chromosphere. The objectives of the polarization calibration test presented in this paper are to determine a response matrix of SCIP and to measure its repeatability and temperature dependence to achieve the required polarization precision. Tolerances of the response matrix elements were set after considering typical photospheric and chromospheric polarization signal levels. We constructed a feed optical system such that a telecentric beam can enter SCIP with the same -number as the light distribution instrument of the sunrise iii telescope. A wire-grid linear polarizer and achromatic wave plate were placed before SCIP to produce the known polarization. The obtained response matrix was close to the values expected from the design. The wavelength and spatial variations, repeatability, and temperature dependence of the response matrix were confirmed to be smaller than tolerances. © 2022 Optica Publishing Group.Japan Society for the Promotion of Science KAKENHI (JP18H05234); Max Planck Foundation; National Aeronautics and Space Administration (#80NSSC18K0934); ISAS/JAXA Small Mission-of Opportunity Program; Spanish Research Agency (RTI2018-096886-B-C5); Centro de Excelencia Severo Ochoa Program (SEV-2017-0709).Peer reviewe