137 research outputs found
Absolute intensity calibrations of solar K line profiles
Individual K-line profiles from elements of fine structure on the surface of the sun are calibrated absolutely. The continuum calibrations of Labs and Neckel and of Houtgast and Namba are considered, and the average K-profile is scaled to that of White and Suemoto. The ranges of intensities across a high-resolution spectrogram are tabulated for various parts of the line profile. Although the spatially-averaged value for K3 of 4.2% of the continuum corresponds to a brightness temperature of 4155 deg K, minimum and maximum values were 3980 and 4360 K, respectively. Similarly, K2v ranges from 4200 to 4560 K, and K2r from 4180 to 4460 K in small elements about 1 arc sec across
A Comparison of the Red and Green Coronal Line Intensities at the 29 March 2006 and the 1 August 2008 Total Solar Eclipses: Considerations of the Temperature of the Solar Corona
During the total solar eclipse at Akademgorodok, Siberia, Russia, in 1 August
2008, we imaged the flash spectrum with a slitless spectrograph. We have
spectroscopically determined the duration of totality, the epoch of the 2nd and
3rd contacts and the duration of the flash spectrum (63 s during ingress and 48
s during egress). Here we compare the 2008 flash spectra with those that we
similarly obtained from the total solar eclipse of 29 March 2006, at
Kastellorizo, Greece. Any changes of the intensity of the corona emission
lines, in particularly those of [Fe X] and [Fe XIV], could give us valuable
information about the energy content of the solar corona and the temperature
distribution of the corona. The results show that the high-ionization state,
the [Fe XIV] emission line, was much weaker during the 2008 eclipse, indicating
that following the long, inactive period during the solar minimum, there was a
drop in the overall temperature of the solar corona.Comment: 10 color figures of spectra, 3 b/w figure
The 2008 August 1 Eclipse Solar-Minimum Corona Unraveled
We discuss results stemming from observations of the white-light and [Fe XIV]
emission corona during the total eclipse of the Sun of 2008 August 1, in
Mongolia (Altaj region) and in Russia (Akademgorodok, Novosibirsk, Siberia).
Corresponding to the current extreme solar minimum, the white-light corona,
visible up to 20 solar radii, was of a transient type with well-pronounced
helmet streamers situated above a chain of prominences at position angles 48,
130, 241 and 322 degrees. A variety of coronal holes, filled with a number of
thin polar plumes, were seen around the poles. Furthering an original method of
image processing, stars up to 12 magnitude, a Kreutz-group comet (C/2008 O1),
and a coronal mass ejection (CME) were also detected, with the smallest
resolvable structures being of, and at some places even less than, 1 arcsec.
Differences, presumably motions, in the corona and prominences are seen even
with the 19-min time difference between our sites. In addition to the
high-resolution coronal images, which show the continuum corona (K-corona) that
results from electron scattering of photospheric light, images of the
overlapping green-emission-line (530.3 nm, [Fe XIV]) corona were obtained with
the help of two narrow-passband filters (centered on the line itself and for
the continuum in the vicinity of 529.1 nm, respectively), each with FWHM of
0.15 nm. Through solar observations, on whose scheduling and details we
consulted, with the Solar and Heliospheric Observatory, Hinode's XRT and SOT,
TRACE, and STEREO, as well as Wilcox Solar Observatory and SOHO/MDI
magnetograms, we set our eclipse observations in the context of the current
unusually low and prolonged solar minimum.Comment: Accepted in The Astrophysical Journal, 6 July 200
Spectroscopic Coronal Observations during the Total Solar Eclipse of 11 July 2010
The flash spectrum of the solar chromosphere and corona was measured with a
slitless spectrograph before, after, and during the totality of the solar
eclipse, of 11 July 2010, at Easter Island, Chile. This eclipse took place at
the beginning of the Solar Cycle 24, after an extended minimum of solar
activity. The spectra taken during the eclipse show a different intensity ratio
of the red and green coronal lines compared with those taken during the total
solar eclipse of 1 August 2008, which took place towards the end of the Solar
Cycle 23. The characteristic coronal forbidden emission line of forbidden Fe
XIV (5303 {\AA}) was observed on the east and west solar limbs in four areas
relatively symmetrically located with respect to the solar rotation axis.
Subtraction of the continuum flash-spectrum background led to the
identification of several extremely weak emission lines, including forbidden Ca
XV (5694 {\AA}), which is normally detected only in regions of very high
excitation, e.g., during flares or above large sunspots. The height of the
chromosphere was measured spectrophotometrically, using spectral lines from
light elements and compared with the equivalent height of the lower
chromosphere measured using spectral lines from heavy elements.Comment: 14 pages, 8 figures, 1 table; Solar Physics, 2012, Februar
The application of a Trous wave filtering and Monte Carlo analysis on SECIS 2001 solar eclipse observations
8000 images of the Solar corona were captured during the June 2001 total
Solar eclipse. New software for the alignment of the images and an automated
technique for detecting intensity oscillations using multi scale wavelet
analysis were developed. Large areas of the images covered by the Moon and the
upper corona were scanned for oscillations and the statistical properties of
the atmospheric effects were determined. The a Trous wavelet transform was used
for noise reduction and Monte Carlo analysis as a significance test of the
detections. The effectiveness of those techniques is discussed in detail.Comment: 17 pages, 8 figures, accepted by Solar Physics Journal for
publication in Topical Issue: "Frontiers in Solar Image Processing
Charon's radius and density from the combined data sets of the 2005 July 11 occultation
The 2005 July 11 C313.2 stellar occultation by Charon was observed by three
separate research groups, including our own, at observatories throughout South
America. Here, the published timings from the three data sets have been
combined to more accurately determine the mean radius of Charon: 606.0 +/- 1.5
km. Our analysis indicates that a slight oblateness in the body (0.006 +/-
0.003) best matches the data, with a confidence level of 86%. The oblateness
has a pole position angle of 71.4 deg +/- 10.4 deg and is consistent with
Charon's pole position angle of 67 deg. Charon's mean radius corresponds to a
bulk density of 1.63 +/- 0.07 g/cm3, which is significantly less than Pluto's
(1.92 +/- 0.12 g/cm3). This density differential favors an impact formation
scenario for the system in which at least one of the impactors was
differentiated. Finally, unexplained differences between chord timings measured
at Cerro Pachon and the rest of the data set could be indicative of a
depression as deep as 7 km on Charon's limb.Comment: 25 pages including 4 tables and 2 figures. Submitted to the
Astronomical Journal on 2006 Feb 0
Explosive events - swirling transition region jets
In this paper, we extend our earlier work to provide additional evidence for
an alternative scenario to explain the nature of so-called `explosive events'.
The bi-directed, fast Doppler motion of explosive events observed
spectroscopically in the transition region emission is classically interpreted
as a pair of bidirectional jets moving upward and downward from a reconnection
site. We discuss the problems of such a model. In our previous work, we focused
basically on the discrepancy of fast Doppler motion without detectable motion
in the image plane. We now suggest an alternative scenario for the explosive
events, based on our observations of spectral line tilts and bifurcated
structure in some events. Both features are indicative of rotational motion in
narrow structures. We explain the bifurcation as the result of rotation of
hollow cylindrical structures and demonstrate that such a sheath model can also
be applied to explain the nature of the puzzling `explosive events'. We find
that the spectral tilt, the lack of apparent motion, the bifurcation, and a
rapidly growing number of direct observations support an alternative scenario
of linear, spicular-sized jets with a strong spinning motion.Comment: 9 pages, 3 figures, accepted for publication in Solar Physic
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