72 citations · 521 across the 25 of their papers we have counts for
25 papers
Solar oblateness & asphericities temporal variations: outstanding some unsolved issues
Jean P. Rozelot, Alexander G. Kosovichev, Ali Kilcik
Solar oblateness has been the subject of several studies dating back to the nineteenth century. Despite diffculties, both theoretical and observational, tangible results have been…
An outlook on the estimate of the solar quadrupole moment from relativistic gravitation contributions
Jean-Pierre Rozelot, Ali Kilcik, Zahra Fazel
Of all the solar fundamental parameters (mass, diameter, gravity at the surface,...), the gravitational moments have been quite often ignored in the past, mainly due to the great d…
Temporal and Periodic Variation of the MCMESI for the Last Two Solar Cycles; Comparison with the Number of Different Class X-Ray Solar Flares
A. Kilcik, P. Chowdhury, V. Sarp +4
In this study we compared the temporal and periodic variations of the Maximum CME Speed Index (MCMESI) and the number of different class (C, M, and X) solar X-Ray flares for the la…
Spatial Distribution of Origin of Umbral Waves in a Sunspot Umbra
Vasyl Yurchyshyn, Ali Kilcik, Seray Sahin +2
Umbral flashes (UFs) are emissions in the core of chromospheric lines caused by upward propagating waves steepening into shocks. UFs are followed by an expanding blue shifted umbra…
Physical Characteristics of Umbral Dots Derived from a High Resolution Observation
Ali Kilcik, Volkan Sarp, Vasyl Yurchyshyn +2
The aim of this study is revisit the physical parameters of umbral dots (UDs) with the latest high resolution observations and contribute to the scientific understanding of their f…
Nearly Century-scale Variation of the Sun's Radius
K. M. Hiremath, J. P. Rozelot, V. Sarp +3
The Kodaikanal Archive Program (India) is now available to the scientific community in digital form as daily digitized solar white light pictures, from 1923 to 2011. We present her…
Magnetic filed dynamics and varying plasma emission in large coronal loops
Seray Şahin, Vasyl Yurchyshyn, Pankaj Kumar +3
In this study we report detailed observations of magnetic environment at four footpoints of two warm coronal loops observed on 5 May 2016 in NOAA AR 12542 (Loop I) and 17 Dec 2015…
How big is the Sun: Solar diameter changes over time
J. P. Rozelot, A. G. Kosovichev, A. Kilcik
The measurement of the Sun's diameter has been first tackled by the Greek astronomers from a geometric point of view. Their estimation of ~1800", although incorrect, was not truly…
Critical frequencies of the ionospheric and layers during the last four solar cycles: sunspot group type dependencies
Erdal Yiğit, Ali Kilcik, Ana Georgina Elias +4
The long term solar activity dependencies of ionospheric F and F regions' critical frequencies ( and ) are analyzed for the last four solar cycles (1976--20…
The ratio between the number of sunspot and the number of sunspot groups
K. Georgieva, A. Kilcik, Yu. Nagovitsyn +1
Data from three solar observatories, Learmonth, Holloman, and San Vito, are used to study the variations in the average number of sunspots per sunspot group. It is found that the d…
Temporal and Periodic Variations of Sunspot Counts in Flaring and Non-flaring Active Regions
A. Kilcik, V. Yurchyshyn, B. Donmez +3
We analyzed temporal and periodic behavior of sunspot counts (SSCs) in flaring (C, M, or X class flares), and non-flaring active regions (ARs) for the almost two solar cycles (1996…
About the recalibration of the sunspot record
Katya Georgieva, Ali Kilcik, Yury Nagovitsyn +1
In 2015 the calculation of the International (Zurich) sunspot number was cancelled, and it was replaced by a new "recalibrated" series. A new data series was proposed also for the…
A brief history of the solar diameter measurements: a critical quality assessment of the existing data
Jean Pierre Rozelot, Alexander G. Kosovichev, Ali Kilcik
The size of the diameter of the Sun has been debated for a very long time. First tackled by the Greek astronomers from a geometric point of view, an estimate, although incorrect, h…
Temporal Offsets between Maximum CME Speed Index and Solar, Geomagnetic, and Interplanetary Indicators during Solar Cycle 23 and the Ascending Phase of Cycle 24
A. Özgüç, A. Kilcik, K. Georgieva +1
On the basis of morphological analysis of yearly values of the maximum CME (coronal mass ejection) speed index, the sunspot number and total sunspot area, sunspot magnetic field, a…
Active Latitude Oscillations Observed on the Sun
A. Kilcik, V. Yurchyshyn, F. Clette +2
We investigate periodicities in mean heliographic latitudes of sunspot groups, called active latitudes, for the last six complete solar cycles (1945-2008). For this purpose, the Mu…
Dynamics in Sunspot Umbra as Seen in New Solar Telescope and Interface Region Imaging Spectrograph Data
Vasyl Yurchyshyn, Valentyna Abramenko, Ali Kilcik
We analyse sunspot oscillations using Interface Region Imaging Spectrograph (IRIS) slit-jaw and spectral data and narrow-band chromospheric images from the New Solar Telescope (NST…
Sunspot Count Periodicities in Different Zurich Sunspot Group Classes since 1986
A. Kilcik, A. Ozguc, V. B. Yurchyshyn +1
In this study, we used two methods to investigate the periodic behavior of sunspot counts in four categories for the time period January 1986-October 2013. These categories include…
One Possible Reason for Double-Peaked Maxima in Solar Cycles: Is a Second Maximum of Solar Cycle 24 Coming?
Ali Kilcik, Atila Ozguc
We investigate solar activity by focusing on double maxima in solar cycles and try to estimate the shape of the current solar cycle (Cycle 24) during its maximum. We analyzed data…
Cyclic and Long-term Variation of Sunspot Magnetic Fields
Alexei A. Pevtsov, Luca Bertello, Andrey G. Tlatov +3
Measurements from the Mount Wilson Observatory (MWO) are used to study the long-term variations of sunspot field strengths from 1920 to 1958. Following a modified approach similar…
Transverse Motions of Chromospheric Type II Spicules Observed by the New Solar Telescope
V. Yurchyshyn, A. Kilcik, V. Abramenko
Using high resolution off-band \ha\ data from the New Solar Telescope and Morlet wavelet analysis technique, we analyzed transverse motions of type II spicules observed near the No…
Maximum Coronal Mass Ejection Speed as an Indicator of Solar and Geomagnetic Activities
A. Kilcik, V. B. Yurchyshyn, V. Abramenko +4
We investigate the relationship between the monthly averaged maximal speeds of coronal mass ejections (CMEs), international sunspot number (ISSN), and the geomagnetic Dst and Ap in…
Time Distributions of Large and Small Sunspot Groups Over Four Solar Cycles
A. Kilcik, V. B. Yurchyshyn, V. Abramenko +4
Here we analyze solar activity by focusing on time variations of the number of sunspot groups (SGs) as a function of their modified Zurich class. We analyzed data for solar cycles…
Properties of Umbral Dots as Measured from the New Solar Telescope Data and MHD Simulations
A. Kilcik, V. B. Yurchyshyn, M. Rempel +5
We studied bright umbral dots (UDs) detected in a moderate size sunspot and compared their statistical properties to recent MHD models. The study is based on high resolution data r…
Statistical Distribution of Size and Lifetime of Bright Points Observed with the New Solar Telescope
Valentyna Abramenko, Vasyl Yurchyshyn, Philip Goode +1
We present results of two-hour non-interrupted observations of solar granulation obtained under excellent seeing conditions with the largest aperture ground-based solar telescope -…