Tilt Angles of Solar Filaments over the Period of 1919 – 2014

Abstract

The spatial and temporal distributions of solar filaments were analyzed using data from the Meudon Observatory for the period of 1919 -2003 and the Kislovodsk Mountain Astronomical Station for the period of 1979 -2014. We scanned Hα solar synoptic charts on which the filaments were identified and digitized. The data on each filament comprise its location, length, area, and other geometrical characteristics. The temporal distributions of the number and total length of the filaments were obtained. We also found latitudinal migration of filament locations with the solar cycle and analyzed the latitudinal distribution and asymmetry of filaments in the northern and southern hemispheres as well as other properties of their distribution. The tilt angles of filaments with respect to the solar equator (τ ) were analyzed. On average, the eastern tips of filaments are closer to the poles than the western ones (τ ≈ 10 • ). On the other hand, the filaments in the polar regions (latitude |θ | > 50 • ) usually have negative tilts (τ < 0 • ). The tilt angles vary with the phase of the 11-year sunspot cycle and show their highest values in the activity maximum. In the century-long modulation of the solar activity (Gleissberg cycle), the mean tilt angles of filaments in the mid-latitude zone (θ ≈ ±40 • ) were largest in the middle of the 20th century in Solar Cycles 18 -19. We hereby propose that these statistical properties of solar filaments can be used as a coherent measure of the solar cycle that covers all latitudes and for which an almost century-long systematically calibrated data series is available.

The Association of Filaments, Polarity Inversion Lines, and Coronal Hole Properties with the Sunspot Cycle: An Analysis of the McIntosh Database

“…Despite the presence of data gaps, our analysis of 442 Carrington maps spread over 36 years establishes some important trends. We find a cyclic behavior of total filament length with the time that is consistent with earlier reports (Hao et al 2015;Tlatov et al 2016). The variation of the total PIL lengths with time shows a cyclic behavior similar to the solar cycle.…”

“…The high concentration at low latitudes indicates that filaments are closely associated with the magnetic activity occurring around the active region belts in both the hemispheres. These results are consistent with the earlier findings by Hao et al (2015) and Tlatov et al (2016) who have used different data sources. We further show that the longitudinal positions of filaments' centroids are evenly distributed over 360 • through Figure 3…”

“…In general, filaments are distributed over all possible latitudes (from the equator to the poles) and longitudes on the solar surface throughout a solar cycle. However, Hao et al (2015), Tlatov et al (2016), and Chatterjee et al (2017) reported that the temporal variation of the latitudinal positions of filaments' geometric centers forms a butterfly-like pattern with a spread much larger as compared to the sunspot butterfly diagram (which is usually confined within ±45 • latitudes). Their work also includes statistical analysis of filaments' tilt angle distribution.…”

Time‐Latitude Distribution of Prominences for 10 Solar Cycles: A Study Using Kodaikanal, Meudon, and Kanzelhohe Data

“…To the best of our knowledge this is probably the first detailed result presented for century‐long prominence observation for about eight cycles from Kodaikanal and three cycles from Meudon and Kanzelhohe. All previous studies which contain long‐term prominence detection from the early 1900s either considered hand‐drawn data sets (Tlatov et al, ) or semiautomated detection methods (Rybák et al, ). Time‐latitude distribution of detected prominences has been produced depicting a clear signature of polar rush for 10 cycles starting from 1906 till April 2018 with initial ones mimicking those presented in Ananthakrishnan () from same data set. Cycle 20 was seen to have two northern polar branches with the second one being fainter and having higher migration rate.…”

“…To the best of our knowledge this is probably the first detailed result presented for century-long prominence observation for about eight cycles from Kodaikanal and three cycles from Meudon and Kanzelhohe. All previous studies which contain long-term prominence detection from the early 1900s either considered hand-drawn data sets (Tlatov et al, 2016) or semiautomated detection methods (Rybák et al, 2011). 3.…”