Context. The average Doppler shift shown by spectral lines formed from the chromosphere to corona reveals important information on mass and energy balance of solar atmosphere, providing an observational constraint any models corona. Previous spectroscopic observations vacuum ultra-violet (VUV) have revealed a persistent wavelength at temperatures up 1 MK. At higher temperatures, behaviour is still essentially unknown.

Here, we developed a complex network of solar active regions (ARs) to study various local and global properties the network. The values Hurst exponent ($0.8-0.9$) were evaluated by both detrended fluctuation analysis rescaled range applied on time series AR numbers. findings suggest that ARs can be considered as system self-organized criticality. We constructed growing based locations, occurrence times, lifetimes 4,227 recorded from 1 January 1999 14 April 2017. behaviour clustering...

Abstract In this study, the properties of wave functions MHD oscillations for a single and system straight flux tubes are investigated. Magnetic with magnetic field longitudinal density stratification were considered in zero‐ β approximation. A three‐dimensional equation (eigenvalue problem) is solved component perturbed using finite element method. Wave (eigenfunction equation) categorized into sausage, kink, helical fluting modes. Exact recognition frequencies can be used coronal...

The moss is the area at footpoint of hot (3 to 5 MK) loops forming core active region where emission believed result from heat flux conducted down transition loops. Studying variation Doppler shift as a function line formation temperatures over can give clues on heating mechanism in regions. We investigate absolute lines formed between 1 MK and 2 within NOAA 11243 using novel technique that allows determining EUV by combining observations SUMER EIS spectrometers. inner (brighter denser) part...

A Crescent shaped prominence Structure (CS), over the solar west limb is studied using EIS/HINODE and AIA/SDO. First, time varying positions of top below borders CS, along with its central axis are derived. Time evolutions Doppler shifts, Line width Fe~{\scriptsize \rm XII} 195.119 line CS borders. Transverse kink oscillations observed both in Solar-Y direction shifts observers' LOS. One explanation could be oscillatory main wave build an angle observers This calculated to equal 27 degrees...

The influence of longitudinal structuring on the fast kink modes coronal loops is investigated. Analytical dispersion relations and mode profiles are derived for second-order ordinary differential equation governing z- component perturbation in magnetic field, $δB_z$. All other components given terms Deviations from frequencies homogenous as functions density scale height. effects fixed variable column masses, negative heights, contrasts inside outside studied. frequency ratios, profiles,...

Magnetic elements of the solar surface are studied in magnetograms recorded with high-resolution Solar Dynamics Observatory / Helioseismic and Imager . To extract some statistical physical properties these (e.g., filling factors, magnetic flux, size, lifetimes), Yet Another Feature Tracking Algorithm (YAFTA), a region-based method, is employed. An area 400$^{\prime\prime}\times$400$^{\prime\prime}$ was selected to investigate characteristics during year 2011. The correlation coefficient...

Recognition of the appropriate locations for ground-based observations Sun with high angular resolution depends on factors such as seeing, meteorological and astronomical parameters. Seeing is one most effective parameters that could limit quality observations. Therefore, to have an accurate observation, needs estimation this parameter. Using Solar Differential Image Motion Monitor (S-DIMM) method, day-time seeing parameter estimated first time at Optical Observatory University Zanjan, Iran....