Interferometric Observations of the Extreme Solar Limb at 2.8 and 6 cm During the October 1977 Eclipse

1980 ◽  
pp. 61-64
Author(s):  
G. J. Hurford ◽  
K. A. Marsh ◽  
H. Zirin
Keyword(s):  
Solar Limb

July 11, 1991 Eclipse Corona Photometry by the Results of Electropolarimetric and CCD-Matrix Observations

1994 ◽  
Vol 144 ◽  
pp. 567-569
Author(s):  
V. Kulidzanishvili ◽  
D. Georgobiani
Keyword(s):  
Solar Corona ◽  
Observational Data ◽  
Solar Limb ◽  
Ccd Matrix

AbstractThe observational data of July 11, 1991 eclipse solar corona obtained by both electropolarimeter (EP) and CCD-matrix were processed. Using these data, the solar corona photometry was carried out. The results of EP data are compared with the ones of CCD data. It must be noted here that the CCD data give us only characteristics of the inner corona, while the EP data show the features of both the inner and middle corona up to 4R⊙. Standard flattening indexϵis evaluated from both data. The dependence of the flattening index on the distance from the solar limb is investigated. The isophotes in Na and Ca lines are plotted. Based on these data some ideas and conclusions on the type of the solar corona are presented.

Synoptic Charts of the Solar Eclipses of 1990 and 1991

1994 ◽  
Vol 144 ◽  
pp. 517-521
Author(s):  
Z. Mouradian ◽  
G. Buchholtz ◽  
G. Zlicaric
Keyword(s):  
Solar Limb ◽  
Active Regions ◽  
Solar Eclipses ◽  
Coronal Structures

AbstractThe synoptic charts of solar rotations 1831 and 1844 have been drawn up, corresponding to the eclipses of 22 July 1990 and 11 July 1991. These charts contain the active regions and the filaments, and show the position of the solar limb, at the time of the eclipse. They are for use in studying the coronal structures observed during these eclipses. The variation of these structures is given in the table. The last section of the article contains a formula for identifying the structures out of the limb.

scholarly journals Solar Irradiance Variability Due to Solar Flares Observed in Lyman-Alpha Emission

Solar Physics ◽  
2021 ◽  
Vol 296 (3) ◽  
Author(s):  
Ryan O. Milligan
Keyword(s):  
Solar Flares ◽  
Solar Spectrum ◽  
Neutral Hydrogen ◽  
Solar Limb ◽  
High Background ◽  
Superposed Epoch Analysis ◽  
Lyman Alpha ◽  
Alpha Emission ◽  
Epoch Analysis ◽  
Very High

AbstractAs the Lyman-alpha (Ly$\upalpha $ α ) line of neutral hydrogen is the brightest emission line in the solar spectrum, detecting increases in irradiance due to solar flares at this wavelength can be challenging due to the very high background. Previous studies that have focused on the largest flares have shown that even these extreme cases generate enhancements in Ly$\upalpha $ α of only a few percent above the background. In this study, a superposed-epoch analysis was performed on ≈8500 flares greater than B1 class to determine the contribution that they make to changes in the solar EUV irradiance. Using the peak of the 1 – 8 Å X-ray emission as a fiducial time, the corresponding time series of 3123 B- and 4972 C-class flares observed in Ly$\upalpha $ α emission by the EUV Sensor on the Geostationary Operational Environmental Satellite 15 (GOES-15) were averaged to reduce background fluctuations and improve the flare signal. The summation of these weaker events showed that they produced a 0.1 – 0.3% enhancement to the solar Ly$\upalpha $ α irradiance on average. For comparison, the same technique was applied to 453 M- and 31 X-class flares, which resulted in a 1 – 4% increase in Ly$\upalpha $ α emission. Flares were also averaged with respect to their heliographic angle to investigate any potential center-to-limb variation. For each GOES class, the relative enhancement in Ly$\upalpha $ α at the flare peak was found to diminish for flares that occurred closer to the solar limb due to the opacity of the line and/or foreshortening of the footpoints. One modest event included in the study, a C6.6 flare, exhibited an unusually high increase in Ly$\upalpha $ α of 7% that may have been attributed to a failed filament eruption. Increases of this magnitude have hitherto only been associated with a small number of X-class flares.

X-ray imaging of a solar limb flare on 1982 January 22

Solar Physics ◽  
1986 ◽  
Vol 107 (1) ◽  
pp. 109-121 ◽  
Author(s):  
T. Takakura ◽  
K. Tanaka ◽  
N. Nitta ◽  
K. Kai ◽  
K. Ohki
Keyword(s):  
Solar Limb ◽  
X Ray ◽  
X Ray Imaging ◽  
Limb Flare

Theoretical explanation of the solar limb effect

1971 ◽  
Vol 19 (6) ◽  
pp. 659-667 ◽  
Author(s):  
Cs. Ferencz ◽  
Gy. Tarcsai
Keyword(s):  
Solar Limb ◽  
Theoretical Explanation ◽  
Limb Effect

The variation of solar brightness at the extreme solar limb at centimetre radio waves

Solar Physics ◽  
1979 ◽  
Vol 63 (2) ◽  
Author(s):  
P. Lantos ◽  
E. F�rst ◽  
W. Hirth
Keyword(s):  
Solar Limb ◽  
Radio Waves ◽  
Solar Brightness

scholarly journals Solar radius determined from PICARD/SODISM observations and extremely weak wavelength dependence in the visible and the near-infrared

2018 ◽  
Vol 616 ◽  
pp. A64 ◽  
Author(s):  
M. Meftah ◽  
T. Corbard ◽  
A. Hauchecorne ◽  
F. Morand ◽  
R. Ikhlef ◽  
...  
Keyword(s):  
Inflection Point ◽  
Near Infrared ◽  
Solar Limb ◽  
Wavelength Dependence ◽  
Uncertainty Budget ◽  
Solar Radius ◽  
Absolute Calibration ◽  
Point Position ◽  
Near Ultraviolet ◽  
Venus Transit

Context. In 2015, the International Astronomical Union (IAU) passed Resolution B3, which defined a set of nominal conversion constants for stellar and planetary astronomy. Resolution B3 defined a new value of the nominal solar radius (R⊙N = 695 700 km km) that is different from the canonical value used until now (695 990 km). The nominal solar radius is consistent with helioseismic estimates. Recent results obtained from ground-based instruments, balloon flights, or space-based instruments highlight solar radius values that are significantly different. These results are related to the direct measurements of the photospheric solar radius, which are mainly based on the inflection point position methods. The discrepancy between the seismic radius and the photospheric solar radius can be explained by the difference between the height at disk center and the inflection point of the intensity profile on the solar limb. At 535.7 nm (photosphere), there may be a difference of ∼330 km between the two definitions of the solar radius. Aims. The main objective of this work is to present new results of the solar radius in the near-ultraviolet, the visible, and the near-infrared from PICARD space-based and ground-based observations. Simulations show the strong influence of atmosphere effects (refraction and turbulence) on ground-based solar radius determinations and highlight the interest of space-based solar radius determinations, particularly during planet transits (Venus or Mercury), in order to obtain more realistic and accurate measurements. Methods. Solar radius observations during the 2012 Venus transit have been made with the SOlar Diameter Imager and Surface Mapper (SODISM) telescope on board the PICARD spacecraft. We used the transit of Venus as an absolute calibration to determine the solar radius accurately at several wavelengths. Our results are based on the determination of the inflection point position of the solar limb-darkening function (the most common solar radius definition). A realistic uncertainty budget is provided for each solar radius obtained with the PICARD space-based telescope during the 2012 Venus transit. The uncertainty budget considers several sources of error (detection of the centers of Venus and Sun in PICARD images, positions of Sun and Venus from ephemeris (planetary theory), PICARD on-board timing, PICARD spacecraft position, and optical distortion correction from PICARD images). Results. We obtain new values of the solar radius from the PICARD mission at several wavelengths and in different solar atmosphere regions. The PICARD spacecraft with its SODISM telescope was used to measure the radius of the Sun during the Venus transit in 2012. At 535.7 nm, the solar radius is equal to 696 134 ± 261 km (combined standard uncertainty based (ξ) on the uncertainty budget). At 607.1 nm, the solar radius is equal to 696 156 ± 145 km (ξ), and the standard deviation of the solar radius mean value is ±22 km. At 782.2 nm, the solar radius is equal to 696 192 ± 247 km (ξ). The PICARD space-based results as well as PICARD ground-based results show that the solar radius wavelength dependence in the visible and the near-infrared is extremely weak. The differences in inflection point position of the solar radius at 607.1 nm, 782.2 nm, and 1025.0 nm from a reference at 535.7 nm are less than 60 km for the different PICARD measurements.

scholarly journals EUV Sprays: Jet-like eruptive activity on the solar limb

2001 ◽  
Vol 379 (1) ◽  
pp. 324-335 ◽  
Author(s):  
R. A. Harrison ◽  
P. Bryans ◽  
R. Bingham
Keyword(s):  
Solar Limb ◽  
Eruptive Activity

Solar limb brightening and enhancement measurements at 1.2 mm

Solar Physics ◽  
1969 ◽  
Vol 6 (1) ◽  
pp. 56-66 ◽  
Author(s):  
R. A. Newstead
Keyword(s):  
Solar Limb
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