An analysis of the solar differential rotation in solar cycle No. 19 (1954-1964) determined using Kanzelhoehe sunspot group positions

Abstract

We study solar differential rotation (DR) for solar cycle No. 19 (1954-1964) by tracing sunspot groups on the sunspot drawings of Kanzelhoehe Observatory for Solar and Environmental Research (KSO). Our aim is to extend previous DR analysis from the KSO data (1964-2016) to the years prior to 1964 to create a catalog of sunspot group positions and DR parameters from KSO sunspot drawings and white light images. Synodic angular rotation velocities were first determined using the daily shift (DS) and robust linear least-squares fit (rLSQ) methods, then converted to sidereal velocities, and used to derive solar DR parameters. We compare the DR parameters obtained from different sources and analyse the north-south asymmetry of rotation for solar cycle No. 19. It has been shown that our results for the equatorial rotation velocity (parameter A) and the gradient of DR (parameter B) coincide with earlier results from the KSO data (performed with a different method), as well as with results from the Kodaikanal Solar Observatory (KoSO) and the Yunnan Observatories (YNAO). In contrast, the values of parameter A from three different earlier studies based on the Greenwich Photoheliographic Results (GPR) exhibit statistically significant differences when compared to the values of parameter A derived from KSO, KoSO and YNAO. These findings suggest that the GPR data have the largest inconsistency compared to the other three data sources, highlighting the need for further analysis to identify the causes of these discrepancies. The analysis of the north-south asymmetry in the solar rotation profile using two different methods shows that the DR parameters of the hemispheres coincide, indicating a rotational symmetry around the equator. This is consistent with previous results from KSO and YNAO data. However, all sources indicate slightly higher equatorial rotation velocities in the southern hemisphere.

References in corpus (12)

• The butterfly diagram in the 18th century
• Comparative analysis of Debrecen sunspot catalogues
• Hemispheric sunspot numbers 1874--2020
• Sunspot positions, areas, and group tilt angles for 1611-1631 from observations by Christoph Scheiner
• A Relationship between the Solar Rotation and Activity Analysed by Tracing Sunspot Groups
• Sunspot latitudes during the Maunder Minimum: a machine-readable catalogue from previous studies
• Solar differential rotation in the period 1964 - 2016 determined by the Kanzelhöhe data set
• Sunspot characteristics at the onset of the Maunder Minimum based on the observations of Hevelius
• Measurements of Solar Differential Rotation Using the Century Long Kodaikanal Sunspot Data
• Christian Horrebow's Sunspot Observations -- II. Construction of a Record of Sunspot Positions
• Kanzelhöhe Observatory: instruments, data processing and data products
• Variation in solar differential rotation and activity in the period 1964-2016 determined by the Kanzelhöhe data set