170 research outputs found
Variations of flaring kernel sizes in various parts of the H-alpha line profile
We analyze the temporal variations of the sizes and emission intensities of
thirtyone flaring kernels in various parts of the H{\alpha} line profile. We
have found that the areas of all kernels decrease systematically when observed
in consecutive wavelengths toward the wings of the H{\alpha} line, but their
areas and emission intensity vary in time. Our results are in agreement with
the commonly accepted model of the glass-shaped lower parts of the magnetic
flaring loops channelling high energy variable particle beams toward the
chromospheric plasma. High time resolution spectral-imaging data used in our
work were collected using the Large Coronagraph and Horizontal Telescope
equipped with the Multi-channel Subtractive Double Pass Spectrograph and the
Solar Eclipse Coronal Imaging System (MSDP-SECIS) at the Bia{\l}k\'ow
Observatory of the University of Wroc{\l}aw, Poland
Sizes of flaring kernels in various parts of the H-alpha line profile
In this paper we present new results of spectraphotometrical investigations
of the flaring kernels sizes and their intensities measured simultaneously in
various parts of the H-alpha line profile. Our investigations were based on the
very high temporal resolution spectral-imaging observations of the solar flares
collected with Large Coronagraph (LC), Multi-channel Subtractive Double Pass
Spectrograph and Solar Eclipse Coronal Imaging System (MSDP-SECIS) at Bialkow
Observatory (University of Wroclaw, Poland). We have found that the areas of
the investigated individual flaring kernels vary in time and in wavelengths as
well as the intensities and areas of the H-alpha flaring kernels decreased
systematically when observed in consecutive wavelengths toward the wings of the
H-alpha line. Our result could be explained as an effect of the cone-shaped
lower parts of the magnetic loops channeling high energy particle beams
exciting chromospheric plasma.Comment: Paper accepted to print in Annales Geophysicae (Special Issue: SOHO
20 Solar Conference); 6 pages, 7 figure
A Search for High-Frequency Coronal Brightness Variations in the 21 August 2017 Total Solar Eclipse
We report on a search for short-period intensity variations in the green-line
FeXIV 530.3 nm emission from the solar corona during the 21 August 2017 total
eclipse viewed from Idaho in the United States. Our experiment was performed
with a much more sensitive detection system, and with better spatial
resolution, than on previous occasions (1999 and 2001 eclipses), allowing fine
details of quiet coronal loops and an active-region loop system to be seen. A
guided 200-mm-aperture Schmidt-Cassegrain telescope was used with a
state-of-the-art CCD camera having 16-bit intensity discrimination and a
field-of-view 0.43 degree x 0.43 degree that encompassed approximately one
third of the visible corona. The camera pixel size was 1.55 arcseconds, while
the seeing during the eclipse enabled features of approx. 2 arcseconds (1450 km
on the Sun) to be resolved. A total of 429 images were recorded during a 122.9
second portion of the totality at a frame rate of 3.49 images per second. In
the analysis, we searched particularly for short-period intensity oscillations
and travelling waves, since theory predicts fast-mode magneto-hydrodynamic
(MHD) waves with short periods may be important in quiet coronal and
active-region heating. Allowing first for various instrumental and photometric
effects, we used a wavelet technique to search for periodicities in some 404
000 pixels in the frequency range 0.5-1.6 Hz (periods: 2 second to 0.6 second).
We also searched for travelling waves along some 65 coronal structures.
However, we found no statistically significant evidence in either. This
negative result considerably refines the limit that we obtained from our
previous analyses, and it indicates that future searches for short-period
coronal waves may be better directed towards Doppler shifts as well as
intensity oscillations
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