STUDY OF MERIDIONAL FLOW USING Ca-K LINE PROFILES DURING SOLAR CYCLES 22 AND 23

Abstract

The analysis of Ca-K line spectra as a function of solar latitude and integrated over longitudes taken during the period of 1989-2011 indicates that the K 1 width attains maximum amplitude at various latitude belts at different phases of the solar cycle. The FWHM of the K 1 distribution at different latitudes shows that its width varies by about 30% for the equatorial belt (<30 •) and 11% for the polar region (>70 •) latitudes. Interestingly, the K 1 width varies by ∼6% only in the 40-60 • latitude belts during the solar cycle. The analysis of cross-correlation coefficients of the K 1 width between the 35 • latitude and other latitude belts as a function of phase differences indicates that the activity representing toroidal field shifted at a uniform rate of about 5.1 m s −1 in the northern hemisphere from mid-latitudes toward the equator. In the southern hemisphere, activity shifted at a faster rate, ∼14 m s −1 , in the beginning of the cycle and the speed decreased with time, yielding an average speed of 7.5 m s −1 toward the equator. The shift of activity in the higher latitude belts showed complex behavior, indicating poleward and equatorward migration. These findings, especially the fewer variations in mid-latitude belts as compared to polar regions, asymmetry in the speed of the shift in the activity in both hemispheres, and complex variation in the direction of the shift in the activity representing poloidal fields in mid-latitude belts, will have an important implication on the modeling of the solar dynamo.

Variation of Chromospheric Features as a Function of Latitude and Time Using Ca-K Spectroheliograms for Solar Cycles 15 – 23: Implications for Meridional Flow

“…The amplitude values in the table indicate that the fractional area of EN, AN and QN follows a similar trend as a function of latitude. Thus, it can be said that variations in the fractional area of plage, EN, AN and QN with time are maximum around 20 • and minimum around 50 • latitude belts, which agrees with the findings of Sindhuja, Singh, and Ravindra (2014). They reported that there is minimum variation in the Ca-K 1 width around 50 • latitude belt.…”

“…These magnetic features have cyclic variations (Oliver, Ballester, and Baudin, 1998;Gopalswamy, 2008 and references cited therein). From the spectroscopic observations of the Ca-K profiles, Sindhuja, Singh, and Ravindra (2014) reported that variations in the Ca-K line parameters can be used to study the meridional flows. The movement of solar activity towards lower latitudes has been studied by using sunspots and related high magnetic field indices.…”

“…Using these images we see pole-and equator-ward shift in the activity; thereby the meridional flows have been studied. The magnetic images of the Sun for the earlier times are not available but other types such as Ca-K, Hα are available since the beginning of 20th century (Oliver, Ballester, and Baudin, 1998;Gopalswamy, 2008;Sindhuja, Singh, and Ravindra, 2014;Priyal et al, 2019 and the references cited therein). The cyclic variations of these features are known as the solar cycle.…”

“…Their results shows the flux transport towards pole and also reported that the meridional circulation responsible for the flux transport slows down before reaching to pole. The equatorial and pole-ward transport of the flux was recently presented in the study of Sindhuja, Singh, and Ravindra (2014). They have used the Kodaikanal Ca-K line spectra data for the Solar Cycle 22 -23.…”

Long-term Variations in the Intensity of Plages and Networks as Observed in Kodaikanal Ca-K Digitized Data

“…The flow of material in the meridional plane direction, from the solar equator toward poles and from poles towards the equator deep inside the Sun, plays a significant role in the solar magnetic dynamo (Choudhuri, Schussler, and Dikpati, 1995;Charbonneau, 2007). The pattern of change in surface magnetic field, sunspots, Hα filaments, Ca-K features and other solar activity indices, and its variation with time has implication for the study of meridional flows (Jiang et al, 2010;Jin and Wang, 2012;Sindhuja, Singh, and Ravindra, 2014).…”