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Samuel Gissot - One of the best experts on this subject based on the ideXlab platform.
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a relationship between the Solar Rotation and activity in the period 1998 2006 analysed by tracing small bright coronal structures in soho eit images
Astronomy and Astrophysics, 2011Co-Authors: Rajka Jurdanasepic, Roman Brajša, Leif Svalgaard, H Wohl, A Hanslmeier, Ivana Poljancic, Samuel GissotAbstract:Aims. The study aims to find a relationship between the Rotation of the small bright coronal structures (SBCS) described by the Solar Rotation parameters and indices of Solar activity on monthly and yearly temporal scales. Methods. We analyse precise measurements of the Solar differential Rotation determined by tracing SBCS in SOHO-EIT images and compare the derived Solar Rotation parameters with the status of Solar activity in the period 1998−2006. Full-disc Solar images obtained with the Extreme ultraviolet Imaging Telescope (EIT) on board the Solar and Heliospheric Observatory (SOHO) were used to analyse Solar differential Rotation determined by tracing SBCS. An automatic method to identify and track the SBCS in EIT full-disc images with a six hour cadence is applied. We performed a statistical analysis of the monthly and yearly values of Solar sidereal Rotation velocity parameters A and B (corresponding to the equatorial Rotation velocity and the gradient of the Solar differential Rotation, respectively) as a function of various Solar activity indices. Results. The dependence of the Solar Rotation on the phase of the Solar cycle was found. It is clearly visible for the Solar Rotation parameter A, whilst the results are not conclusive for parameter B. The relationship between the Solar Rotation and activity, expressed by the monthly relative sunspot number, the smoothed monthly relative sunspot number, the yearly relative sunspot number, and the interdiurnal variability (IDV) index was investigated. The statistically significant correlation was found for the Solar Rotation parameter A, whilst a very low and insignificant correlation was obtained for the Rotation parameter B. Conclusions. During the maximum of the Solar cycle 23 and just after it, the equatorial Solar Rotation velocity was lower than in other phases of the cycle, when there was less activity. This is consistent with other observational findings, obtained by different tracers and methods.
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A relationship between the Solar Rotation and activity in the period 1998–2006 analysed by tracing small bright coronal structures in SOHO-EIT images
Astronomy and Astrophysics, 2011Co-Authors: Rajka Jurdana-Šepić, Roman Brajša, Hubertus Wöhl, Leif Svalgaard, A Hanslmeier, Ivana Poljančić, Samuel GissotAbstract:Aims. The study aims to find a relationship between the Rotation of the small bright coronal structures (SBCS) described by the Solar Rotation parameters and indices of Solar activity on monthly and yearly temporal scales. Methods. We analyse precise measurements of the Solar differential Rotation determined by tracing SBCS in SOHO-EIT images and compare the derived Solar Rotation parameters with the status of Solar activity in the period 1998−2006. Full-disc Solar images obtained with the Extreme ultraviolet Imaging Telescope (EIT) on board the Solar and Heliospheric Observatory (SOHO) were used to analyse Solar differential Rotation determined by tracing SBCS. An automatic method to identify and track the SBCS in EIT full-disc images with a six hour cadence is applied. We performed a statistical analysis of the monthly and yearly values of Solar sidereal Rotation velocity parameters A and B (corresponding to the equatorial Rotation velocity and the gradient of the Solar differential Rotation, respectively) as a function of various Solar activity indices. Results. The dependence of the Solar Rotation on the phase of the Solar cycle was found. It is clearly visible for the Solar Rotation parameter A, whilst the results are not conclusive for parameter B. The relationship between the Solar Rotation and activity, expressed by the monthly relative sunspot number, the smoothed monthly relative sunspot number, the yearly relative sunspot number, and the interdiurnal variability (IDV) index was investigated. The statistically significant correlation was found for the Solar Rotation parameter A, whilst a very low and insignificant correlation was obtained for the Rotation parameter B. Conclusions. During the maximum of the Solar cycle 23 and just after it, the equatorial Solar Rotation velocity was lower than in other phases of the cycle, when there was less activity. This is consistent with other observational findings, obtained by different tracers and methods.
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a precise measurement of the Solar differential Rotation by tracing small bright coronal structures in soho eit images results and comparisons for the period 1998 2006
Astronomy and Astrophysics, 2010Co-Authors: H Wohl, A Hanslmeier, R Brajsa, Samuel GissotAbstract:Aims. We precisely determine the Solar Rotation velocity during most of the 23rd Solar cycle, in the years 1998-2006. We measure the Solar differential Rotation by tracing small bright coronal structures (SBCS) in SOHO-EIT images. Methods. The 28.4 nm EIT channel was used and positions of more than 55 000 structures were measured applying an interactive and improved automatic method of data reduction. Results. We achieve the closest representation of the observational data when all three Solar differential Rotation parameters are used and obtain the formula ω ( b ) = 14.499 ( ± 0.006) – 2.54 ( ± 0.06) sin 2 b – 0.77 ( ± 0.09) sin 4 b . This result represents the sidereal Rotation velocity in deg day -1 and is produced by the automatic method applied in 1998-2006. A north-south Rotational asymmetry and a rigid component of the Solar Rotation at high latitudes were found. Conclusions. A more differential Rotation profile of SBCS than of sunspots and sunspot groups was found. The Rotation velocity of SBCS is very similar to those obtained by small photospheric magnetic features. The north-south Rotational asymmetry of SBCS was interpreted with a model of the relationship between Solar Rotation and activity. The rigid component of the Solar Rotation at high latitudes, identifiable only from the results of the automatic method, was related to larger structures mostly identified by that method, in contrast to the interactive method, which detected smaller structures.
Roman Brajša - One of the best experts on this subject based on the ideXlab platform.
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An analysis of the Solar Rotation velocity by tracing coronal features
2020Co-Authors: Roman Brajša, Bojan Vršnak, V. Ruždjak, Dragan Roša, D. Hržina, H. Woehl, Frédéric Clette, Jean-françois HochedezAbstract:Full-disc Solar images in the extreme ultraviolet part of the spectrum from the SOHO spacecraft (EIT) are used to identify various coronal structures appropriate for the Solar Rotation determination (e.g. bright points and coronal holes). From the time differences in tracer positions (more than 1 image per day) Solar Rotation velocities are measured, primarily by well-defined tracers, such as coronal bright points, whose large number and broad coverage of latitudes may provide an unique opportunity for a Solar Rotation analysis. The analysis started using the SOHO data from 1997-1999 and preliminary experiences obtained measuring Solar Rotation from the full-disc images in soft X-rays from the YOHKOH (SXT) satellite were taken into account. - this work is connected to the SOHO EIT Proposal Brajsa_206
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An Analysis of the Solar Rotation Velocity by Tracing Coronal Features
Symposium - International Astronomical Union, 2020Co-Authors: Roman Brajša, Bojan Vršnak, V. Ruždjak, Dragan Roša, D. Hržina, Frédéric Clette, Hubertus Wöhl, Jean-françois HochedezAbstract:The Solar Rotation is determined tracing coronal EUV and soft X-ray bright points, active regions, parts of coronal holes and foot points of coronal loops. Full-disc Solar images in the EUV part of the spectrum from the SOHO spacecraft (EIT, Fe XV, 28.4 nm) and from the Yohkoh satellite (SXT, 2 nm) are used.
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STATISTICAL WEIGHTS AND SELECTIVE HEIGHT CORRECTIONS IN THE DETERMINATION OF THE Solar Rotation VELOCITY
Solar Physics, 2020Co-Authors: Roman Brajša, Bojan Vršnak, V. Ruždjak, Hubertus Wöhl, Silja Pohjolainen, S. UproAbstract:Observations of the Sun performed at 37 GHz with the 14-m radio telescope of the Metsahovi Radio Observatory were analyzed. Rotation velocities were determined, tracing Low Temperature Regions (LTRs) in the years 1979–1980, 1981–1982, 1987–1988, and 1989–1991. Statistical weights were ascribed to the determined Rotation velocities of LTRs, according to the number of tracing days. Measured changes of the Rotation velocity during the Solar activity cycle, as well as a north–south Rotation asymmetry, are discussed. The results obtained with and without the statistical weights procedure are compared, and it was found that the statistical significance of the Solar differential Rotation parameters' changes is higher when the statistical weights procedure is applied. A selective application of the height correction on LTR's positions has not removed the cycle-related changes nor the north–south asymmetry of the Solar Rotation measured tracing LTRs. So, projection effects cannot explain these changes. The differential Rotation of LTRs is more rigid than the differential Rotation obtained tracing magnetic features and measuring Doppler shifts, which can be explained by the association rate of the LTRs' positions with rigidly rotating `pivot points'. The observed cycle-related changes and the north–south asymmetry of the Rotation velocity of LTRs are consistent with the cycle-related changes and the north–south asymmetry of the association rate between LTRs and pivot points.
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a relationship between the Solar Rotation and activity in the period 1998 2006 analysed by tracing small bright coronal structures in soho eit images
Astronomy and Astrophysics, 2011Co-Authors: Rajka Jurdanasepic, Roman Brajša, Leif Svalgaard, H Wohl, A Hanslmeier, Ivana Poljancic, Samuel GissotAbstract:Aims. The study aims to find a relationship between the Rotation of the small bright coronal structures (SBCS) described by the Solar Rotation parameters and indices of Solar activity on monthly and yearly temporal scales. Methods. We analyse precise measurements of the Solar differential Rotation determined by tracing SBCS in SOHO-EIT images and compare the derived Solar Rotation parameters with the status of Solar activity in the period 1998−2006. Full-disc Solar images obtained with the Extreme ultraviolet Imaging Telescope (EIT) on board the Solar and Heliospheric Observatory (SOHO) were used to analyse Solar differential Rotation determined by tracing SBCS. An automatic method to identify and track the SBCS in EIT full-disc images with a six hour cadence is applied. We performed a statistical analysis of the monthly and yearly values of Solar sidereal Rotation velocity parameters A and B (corresponding to the equatorial Rotation velocity and the gradient of the Solar differential Rotation, respectively) as a function of various Solar activity indices. Results. The dependence of the Solar Rotation on the phase of the Solar cycle was found. It is clearly visible for the Solar Rotation parameter A, whilst the results are not conclusive for parameter B. The relationship between the Solar Rotation and activity, expressed by the monthly relative sunspot number, the smoothed monthly relative sunspot number, the yearly relative sunspot number, and the interdiurnal variability (IDV) index was investigated. The statistically significant correlation was found for the Solar Rotation parameter A, whilst a very low and insignificant correlation was obtained for the Rotation parameter B. Conclusions. During the maximum of the Solar cycle 23 and just after it, the equatorial Solar Rotation velocity was lower than in other phases of the cycle, when there was less activity. This is consistent with other observational findings, obtained by different tracers and methods.
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A relationship between the Solar Rotation and activity in the period 1998–2006 analysed by tracing small bright coronal structures in SOHO-EIT images
Astronomy and Astrophysics, 2011Co-Authors: Rajka Jurdana-Šepić, Roman Brajša, Hubertus Wöhl, Leif Svalgaard, A Hanslmeier, Ivana Poljančić, Samuel GissotAbstract:Aims. The study aims to find a relationship between the Rotation of the small bright coronal structures (SBCS) described by the Solar Rotation parameters and indices of Solar activity on monthly and yearly temporal scales. Methods. We analyse precise measurements of the Solar differential Rotation determined by tracing SBCS in SOHO-EIT images and compare the derived Solar Rotation parameters with the status of Solar activity in the period 1998−2006. Full-disc Solar images obtained with the Extreme ultraviolet Imaging Telescope (EIT) on board the Solar and Heliospheric Observatory (SOHO) were used to analyse Solar differential Rotation determined by tracing SBCS. An automatic method to identify and track the SBCS in EIT full-disc images with a six hour cadence is applied. We performed a statistical analysis of the monthly and yearly values of Solar sidereal Rotation velocity parameters A and B (corresponding to the equatorial Rotation velocity and the gradient of the Solar differential Rotation, respectively) as a function of various Solar activity indices. Results. The dependence of the Solar Rotation on the phase of the Solar cycle was found. It is clearly visible for the Solar Rotation parameter A, whilst the results are not conclusive for parameter B. The relationship between the Solar Rotation and activity, expressed by the monthly relative sunspot number, the smoothed monthly relative sunspot number, the yearly relative sunspot number, and the interdiurnal variability (IDV) index was investigated. The statistically significant correlation was found for the Solar Rotation parameter A, whilst a very low and insignificant correlation was obtained for the Rotation parameter B. Conclusions. During the maximum of the Solar cycle 23 and just after it, the equatorial Solar Rotation velocity was lower than in other phases of the cycle, when there was less activity. This is consistent with other observational findings, obtained by different tracers and methods.
H Wohl - One of the best experts on this subject based on the ideXlab platform.
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a relationship between the Solar Rotation and activity in the period 1998 2006 analysed by tracing small bright coronal structures in soho eit images
Astronomy and Astrophysics, 2011Co-Authors: Rajka Jurdanasepic, Roman Brajša, Leif Svalgaard, H Wohl, A Hanslmeier, Ivana Poljancic, Samuel GissotAbstract:Aims. The study aims to find a relationship between the Rotation of the small bright coronal structures (SBCS) described by the Solar Rotation parameters and indices of Solar activity on monthly and yearly temporal scales. Methods. We analyse precise measurements of the Solar differential Rotation determined by tracing SBCS in SOHO-EIT images and compare the derived Solar Rotation parameters with the status of Solar activity in the period 1998−2006. Full-disc Solar images obtained with the Extreme ultraviolet Imaging Telescope (EIT) on board the Solar and Heliospheric Observatory (SOHO) were used to analyse Solar differential Rotation determined by tracing SBCS. An automatic method to identify and track the SBCS in EIT full-disc images with a six hour cadence is applied. We performed a statistical analysis of the monthly and yearly values of Solar sidereal Rotation velocity parameters A and B (corresponding to the equatorial Rotation velocity and the gradient of the Solar differential Rotation, respectively) as a function of various Solar activity indices. Results. The dependence of the Solar Rotation on the phase of the Solar cycle was found. It is clearly visible for the Solar Rotation parameter A, whilst the results are not conclusive for parameter B. The relationship between the Solar Rotation and activity, expressed by the monthly relative sunspot number, the smoothed monthly relative sunspot number, the yearly relative sunspot number, and the interdiurnal variability (IDV) index was investigated. The statistically significant correlation was found for the Solar Rotation parameter A, whilst a very low and insignificant correlation was obtained for the Rotation parameter B. Conclusions. During the maximum of the Solar cycle 23 and just after it, the equatorial Solar Rotation velocity was lower than in other phases of the cycle, when there was less activity. This is consistent with other observational findings, obtained by different tracers and methods.
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a precise measurement of the Solar differential Rotation by tracing small bright coronal structures in soho eit images results and comparisons for the period 1998 2006
Astronomy and Astrophysics, 2010Co-Authors: H Wohl, A Hanslmeier, R Brajsa, Samuel GissotAbstract:Aims. We precisely determine the Solar Rotation velocity during most of the 23rd Solar cycle, in the years 1998-2006. We measure the Solar differential Rotation by tracing small bright coronal structures (SBCS) in SOHO-EIT images. Methods. The 28.4 nm EIT channel was used and positions of more than 55 000 structures were measured applying an interactive and improved automatic method of data reduction. Results. We achieve the closest representation of the observational data when all three Solar differential Rotation parameters are used and obtain the formula ω ( b ) = 14.499 ( ± 0.006) – 2.54 ( ± 0.06) sin 2 b – 0.77 ( ± 0.09) sin 4 b . This result represents the sidereal Rotation velocity in deg day -1 and is produced by the automatic method applied in 1998-2006. A north-south Rotational asymmetry and a rigid component of the Solar Rotation at high latitudes were found. Conclusions. A more differential Rotation profile of SBCS than of sunspots and sunspot groups was found. The Rotation velocity of SBCS is very similar to those obtained by small photospheric magnetic features. The north-south Rotational asymmetry of SBCS was interpreted with a model of the relationship between Solar Rotation and activity. The rigid component of the Solar Rotation at high latitudes, identifiable only from the results of the automatic method, was related to larger structures mostly identified by that method, in contrast to the interactive method, which detected smaller structures.
A Hanslmeier - One of the best experts on this subject based on the ideXlab platform.
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a relationship between the Solar Rotation and activity in the period 1998 2006 analysed by tracing small bright coronal structures in soho eit images
Astronomy and Astrophysics, 2011Co-Authors: Rajka Jurdanasepic, Roman Brajša, Leif Svalgaard, H Wohl, A Hanslmeier, Ivana Poljancic, Samuel GissotAbstract:Aims. The study aims to find a relationship between the Rotation of the small bright coronal structures (SBCS) described by the Solar Rotation parameters and indices of Solar activity on monthly and yearly temporal scales. Methods. We analyse precise measurements of the Solar differential Rotation determined by tracing SBCS in SOHO-EIT images and compare the derived Solar Rotation parameters with the status of Solar activity in the period 1998−2006. Full-disc Solar images obtained with the Extreme ultraviolet Imaging Telescope (EIT) on board the Solar and Heliospheric Observatory (SOHO) were used to analyse Solar differential Rotation determined by tracing SBCS. An automatic method to identify and track the SBCS in EIT full-disc images with a six hour cadence is applied. We performed a statistical analysis of the monthly and yearly values of Solar sidereal Rotation velocity parameters A and B (corresponding to the equatorial Rotation velocity and the gradient of the Solar differential Rotation, respectively) as a function of various Solar activity indices. Results. The dependence of the Solar Rotation on the phase of the Solar cycle was found. It is clearly visible for the Solar Rotation parameter A, whilst the results are not conclusive for parameter B. The relationship between the Solar Rotation and activity, expressed by the monthly relative sunspot number, the smoothed monthly relative sunspot number, the yearly relative sunspot number, and the interdiurnal variability (IDV) index was investigated. The statistically significant correlation was found for the Solar Rotation parameter A, whilst a very low and insignificant correlation was obtained for the Rotation parameter B. Conclusions. During the maximum of the Solar cycle 23 and just after it, the equatorial Solar Rotation velocity was lower than in other phases of the cycle, when there was less activity. This is consistent with other observational findings, obtained by different tracers and methods.
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A relationship between the Solar Rotation and activity in the period 1998–2006 analysed by tracing small bright coronal structures in SOHO-EIT images
Astronomy and Astrophysics, 2011Co-Authors: Rajka Jurdana-Šepić, Roman Brajša, Hubertus Wöhl, Leif Svalgaard, A Hanslmeier, Ivana Poljančić, Samuel GissotAbstract:Aims. The study aims to find a relationship between the Rotation of the small bright coronal structures (SBCS) described by the Solar Rotation parameters and indices of Solar activity on monthly and yearly temporal scales. Methods. We analyse precise measurements of the Solar differential Rotation determined by tracing SBCS in SOHO-EIT images and compare the derived Solar Rotation parameters with the status of Solar activity in the period 1998−2006. Full-disc Solar images obtained with the Extreme ultraviolet Imaging Telescope (EIT) on board the Solar and Heliospheric Observatory (SOHO) were used to analyse Solar differential Rotation determined by tracing SBCS. An automatic method to identify and track the SBCS in EIT full-disc images with a six hour cadence is applied. We performed a statistical analysis of the monthly and yearly values of Solar sidereal Rotation velocity parameters A and B (corresponding to the equatorial Rotation velocity and the gradient of the Solar differential Rotation, respectively) as a function of various Solar activity indices. Results. The dependence of the Solar Rotation on the phase of the Solar cycle was found. It is clearly visible for the Solar Rotation parameter A, whilst the results are not conclusive for parameter B. The relationship between the Solar Rotation and activity, expressed by the monthly relative sunspot number, the smoothed monthly relative sunspot number, the yearly relative sunspot number, and the interdiurnal variability (IDV) index was investigated. The statistically significant correlation was found for the Solar Rotation parameter A, whilst a very low and insignificant correlation was obtained for the Rotation parameter B. Conclusions. During the maximum of the Solar cycle 23 and just after it, the equatorial Solar Rotation velocity was lower than in other phases of the cycle, when there was less activity. This is consistent with other observational findings, obtained by different tracers and methods.
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a precise measurement of the Solar differential Rotation by tracing small bright coronal structures in soho eit images results and comparisons for the period 1998 2006
Astronomy and Astrophysics, 2010Co-Authors: H Wohl, A Hanslmeier, R Brajsa, Samuel GissotAbstract:Aims. We precisely determine the Solar Rotation velocity during most of the 23rd Solar cycle, in the years 1998-2006. We measure the Solar differential Rotation by tracing small bright coronal structures (SBCS) in SOHO-EIT images. Methods. The 28.4 nm EIT channel was used and positions of more than 55 000 structures were measured applying an interactive and improved automatic method of data reduction. Results. We achieve the closest representation of the observational data when all three Solar differential Rotation parameters are used and obtain the formula ω ( b ) = 14.499 ( ± 0.006) – 2.54 ( ± 0.06) sin 2 b – 0.77 ( ± 0.09) sin 4 b . This result represents the sidereal Rotation velocity in deg day -1 and is produced by the automatic method applied in 1998-2006. A north-south Rotational asymmetry and a rigid component of the Solar Rotation at high latitudes were found. Conclusions. A more differential Rotation profile of SBCS than of sunspots and sunspot groups was found. The Rotation velocity of SBCS is very similar to those obtained by small photospheric magnetic features. The north-south Rotational asymmetry of SBCS was interpreted with a model of the relationship between Solar Rotation and activity. The rigid component of the Solar Rotation at high latitudes, identifiable only from the results of the automatic method, was related to larger structures mostly identified by that method, in contrast to the interactive method, which detected smaller structures.
Rajka Jurdanasepic - One of the best experts on this subject based on the ideXlab platform.
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a relationship between the Solar Rotation and activity in the period 1998 2006 analysed by tracing small bright coronal structures in soho eit images
Astronomy and Astrophysics, 2011Co-Authors: Rajka Jurdanasepic, Roman Brajša, Leif Svalgaard, H Wohl, A Hanslmeier, Ivana Poljancic, Samuel GissotAbstract:Aims. The study aims to find a relationship between the Rotation of the small bright coronal structures (SBCS) described by the Solar Rotation parameters and indices of Solar activity on monthly and yearly temporal scales. Methods. We analyse precise measurements of the Solar differential Rotation determined by tracing SBCS in SOHO-EIT images and compare the derived Solar Rotation parameters with the status of Solar activity in the period 1998−2006. Full-disc Solar images obtained with the Extreme ultraviolet Imaging Telescope (EIT) on board the Solar and Heliospheric Observatory (SOHO) were used to analyse Solar differential Rotation determined by tracing SBCS. An automatic method to identify and track the SBCS in EIT full-disc images with a six hour cadence is applied. We performed a statistical analysis of the monthly and yearly values of Solar sidereal Rotation velocity parameters A and B (corresponding to the equatorial Rotation velocity and the gradient of the Solar differential Rotation, respectively) as a function of various Solar activity indices. Results. The dependence of the Solar Rotation on the phase of the Solar cycle was found. It is clearly visible for the Solar Rotation parameter A, whilst the results are not conclusive for parameter B. The relationship between the Solar Rotation and activity, expressed by the monthly relative sunspot number, the smoothed monthly relative sunspot number, the yearly relative sunspot number, and the interdiurnal variability (IDV) index was investigated. The statistically significant correlation was found for the Solar Rotation parameter A, whilst a very low and insignificant correlation was obtained for the Rotation parameter B. Conclusions. During the maximum of the Solar cycle 23 and just after it, the equatorial Solar Rotation velocity was lower than in other phases of the cycle, when there was less activity. This is consistent with other observational findings, obtained by different tracers and methods.