D. R. Japaridze

Investigation of the solar differential rotation by hydrogen filaments in 1976–1986

Based on observational data on chromosphere filaments, certain characteristics of solar differential rotation during solar activity cycle No. 21 are determined at Abastumani Astrophysical Observatory.In the northern hemisphere of the Sun, propagation of a quasi-bi-annual impulse of the rotation residual from high latitudes to the equator is found in 1979–1981. It is supposed that this phenomenon might be related to the polarity reversal in the northern hemisphere of the Sun in 1981.0.

N–S asymmetry in the differential rotation of the sun and its variation with the solar activity cycles

Abstract Peculiarities in the characteristics of the solar differential rotation are investigated using hydrogen filaments as tracers. The existence of North–South (N–S) asymmetry in hydrogen filaments rotation is confirmed statistically. The connection of asymmetry with the solar activity cycles is established. It is found that the northern hemisphere rotates faster during the even cycles (Cycles 20 and 22) while the rotation of southern hemisphere dominates in odd one (Cycle 21). The mechanism of the solar activity should be responsible for the N–S asymmetry of the solar differential rotation.

Investigation of the Differential Rotation by Hα Filaments and Long-Lived Magnetic Features for Solar Activity Cycles 20 and 21

For solar activity Cycles 20 and 21 (1966 – 1985) the solar differential rotation has been investigated using Hα filaments and relatively small-scale long-lived magnetic features with negative and positive polarities. We used annual averaged angular velocities of quiescent Hα filaments from Hα photoheliograms of the Abastumani Astrophysical Observatory film collection and selected long-lived magnetic features from the McIntosh atlas (McIntosh, Willock, and Thompson, Atlas of Stackplots, NGDC, 1991). We have determined coefficients of Faye’s formulas for Hα filaments as well as for long-lived magnetic features and have found that for Solar Cycles 20 and 21 the Hα filaments have lower rotation rates and rotated more differentially than the long-lived magnetic features.

Propagation of a quasi bi-annual impulse close to the moment of the solar magnetic field polarity changing

Some particular features of solar differential rotation have been recently revealed in Abastumani Astrophysical Observatory: in the northern hemisphere of the Sun a propagation of a quasi bi-annual impulse of the rotation residual from the high latitudes to the equator, during the time interval of 1979–1981, was statistically demonstrated. Japaridze and Gigolashvili (1992) proposed that this event might be related with the change of magnetic polarity in the northern hemisphere of the Sun in 1981.To prove this hypothesis an investigation of the MHD equations in the local system of coordinates has been carried out. A homogeneous equation with partial derivatives in the linear approximation was obtained. Its solution is presented analytically. The disturbance of velocity enhances especially at the moment of reversal of magnetic field polarity.

Statistical properties of coronal hole rotation rates: Are they linked to the solar interior?

The present paper discusses results of a statistical study of the characteristics of coronal hole (CH) rotation in order to find connections to the internal rotation of the Sun. The goal is to measure CH rotation rates and study their distribution over latitude and their area sizes. In addition, the CH rotation rates are compared with the solar photospheric and inner layer rotational profiles. We study coronal holes observed within

Evidence for Precursors of the Coronal Hole Jets in Solar Bright Points

\pm 60

N–S Asymmetry in the Solar Differential Rotation During 1957–1993

latitude and longitude degrees from the solar disc centre during the time span from the 1 January 2013 to 20 April 2015, which includes the extended peak of solar cycle 24.We used data created by the Spatial Possibilistic Clustering Algorithm (SPoCA), which provides the exact location and characterisation of solar coronal holes using SDO=AIA 193 {\AA} channel images. The CH rotation rates are measured with four-hour cadence data to track variable positions of the CH geometric centre. North-south asymmetry was found in the distribution of coronal holes: about 60 percent were observed in the northern hemisphere and 40 percent were observed in the southern hemisphere. The smallest and largest CHs were present only at high latitudes. The average sidereal rotation rate for 540 examined CHs is

Investigation of the N–S asymmetry of the differential rotation of Hα filaments and large-scale magnetic elements

13:86 (\pm 0:05)

Variations of the Solar Differential Rotation Associated with Polarity Reversal

degrees/d. Conclusions. The latitudinal characteristics of CH rotation do not match any known photospheric rotation profile. The CH angular velocities exceed the photospheric angular velocities at latitudes higher than 35-40 degrees. According to our results, the CH rotation profile perfectly coincides with tachocline and the lower layers of convection zone at around 0.71

Investigation of the differential rotation of the large-scale magnetic elements for the solar activity cycles 20 and 21

R_{\odot}