­Long-Term Variation of Latitudinal Distribution of Coronal Holes B. Chargeishvili,1 D. Japaridze,1 T. Mdzinarishvili,1 B. M. Shergelashvili2,1,3 1 Abastumani Astrophysical Observatory at Ilia State University, University St. 2, Tbilisi, Georgia 2 Space Research Institute, Austrian Academy of Sciences, Schmiedlstrasse 6, 8042 Graz, Austria 3 Combinatorial Optimization and Decision Support, KU Leuven campus Kortrijk, E. Sabbelaan 53, 8500 Kortrijk, Belgium Observational Data and Methodology : EIT 171 Å data from May 1996 to February 2017 – 6376 daily FITS files; SSW IDL special code – automatic intensity thresholding detection of coronal holes (CH); fast processing of FITS file series; The code scans the solar disk within the ranges ±90 latitudes and ±80 longitudes both with spans of 0.5 degrees and gets data from 361x321 points of a disk from each daily FITS file; Presence factor (PF) - a longitudinal average of the inverted emission intensities at each latitude multiplied on cosine of the latitude 361X6376 data matrix for the CH presence factors

­Long-Term Variation of Latitudinal Distribution of Coronal Holes The temporal evolution of the CH activity latitudinal distribution manifests a clear butterfly pattern. Polar and mid-latitude zones apparently have different properties. Along with the 11-year solar activity cycle, the quasi-annual periodic variation is also evident (solid line depicts the motion of the line-of-sight solar disk central point with respect to ecliptics)

­Long-Term Variation of Latitudinal Distribution of Coronal Holes Latitudinal distribution of PF averaged over all the period studied CH activity in different latitudinal zones Side minima come on ±55 degrees, that are taken for separation of latitudinal zones. NP and SP – Northern and Southern polar zones NM and SM – Northern and Southern middle zones

­Long-Term Variation of Latitudinal Distribution of Coronal Holes Comparison of activity curves for magnitudes of sunspot numbers (SILSO), middle latitudinal coronal hole PFs. and the absolute value of the general magnetic field strength (WSO, USA). Comparison of CH and magnetic field temporal variations in polar (a) northern and b) southern) latitudinal zones. Solid lines depict magnitudes of CH PFs and dashed lines the magnitudes of the magnetic field The peak of CH activity lags that of sunspots by about a year. It shows the causal dependence of two different features of the Sun. CHs should have some connections with sunspot magnetic field evolution.

­Long-Term Variation of Latitudinal Distribution of Coronal Holes Main results Presence factor, the new effective tool for coronal hole activity assessment is introduced. PF should be also useful for study of other solar features; Fine structure of temporal variation of CH activity latitudinal distribution is obtained; The oscillation shape of coronal hole distribution is explained by periodic overlapping of open-structured magnetic features by closed ones, which are caused by annual variations in the position angle of disk center with respect to line-of-sight; Periods for all latitudinal zone that were extracted by Fourier analyses are most known from the previous studies. Among them are synodic period about 26 days, well-known Rieger period about 160 days, annual period, so-called quasi-biennial oscillation period about two years and other. It must be mentioned the period about 1.3 years that is widely observed in the solar wind; Distribution and other features of activity of coronal holes show a strong correlation with long-term data of the general magnetic field and daily hemispheric sunspots numbers.