A. Kilcik

Akdeniz University · Department of Space Sciences and Technologies

The process of producing information about dynamic land use/land cover and ecosystem health in a short time with high accuracy and low cost is important. This information is one of the basic data used for sustainable land management. For this purpose, remote sensing technologies are generally used, and sampling points are mostly assigned. Determina...

We studied the temporal and periodic variations of the monthly solar flare index (FI) and selected geomagnetic-activity parameters (Ap, Dst, Scalar B, and aa) measured during Solar Cycles 21 – 24 (from January 1, 1975 to December 31, 2020) and report the following findings: 1) all data sets except the FI peak values gradually decreased after 1992,...

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 difficulty to get a reliable estimate. Even though the order of magnitude of the solar quadrupole moment $J_2$ is now known to be $10^{-7}$, its accurate value is still di...

The sunspot cycle waxes and wanes over a period of about 11 years and modulates ‘space weather’. Therefore, predicting the maximum amplitude of the solar cycle is an important goal for both solar physics and space weather. It is clear nowadays that cyclic variations of the Sun are non-linear processes, and thus the above-mentioned goal is difficult...

In this study, we used the flare index (FI) data taken from Kandilli Observatory for the period of 2009–2020. The data sets are analyzed in three categories as Northern Hemisphere, Southern Hemisphere, and total FI data sets. Total FI data set is obtained from the sum of Northern and Southern Hemispheric values. In this study, the periodic variatio...

Ionizing radiation sources such as Solar Energetic Particles and Galactic Cosmic Radiation may cause unexpected errors in imaging and communication systems of satellites in the Space environment, as reported in the previous literature. In this study, the temporal variation of the speckle values on Sentinel 1 satellite images were compared with the...

In this study we compared the temporal and periodic variations of the Maximum CME Speed Index (MCMESI) and the the number of different class (C, M, and X) solar X-ray flares for the last two solar cycles (Solar Cycles 23 and 24). To obtain the correlation between the MCMESI and solar flare numbers the cross-correlation analysis was applied to month...

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 last two solar cycles (Cycle 23 and 24). To obtain the correlation between the MCMESI and solar flare numbers the cross correlation analysis was applied to monthly data set...

The technique of acquiring information about objects with measurements from any distance without physical contact with the objects develops in parallel with technological developments. In this context, remote sensing and geographical information systems are preferred by many professional disciplines. High-quality information is obtained in a short...

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 umbral wave (UW) and red-shifted plasma returning to the initial state. Here we use 5 s cadence images acquired at $\pm$0.04~nm off the Halpha line center by the Visible Imagi...

The aim of this study is to revisit the physical parameters of umbral dots (UDs) with the latest high-resolution observations and contribute to the scientific understanding of their formation and evolution. In this study, we applied a particle tracking algorithm for detecting UDs in NOAA AR 12384 observed on June 14, 2015 by the Goode Solar Telesco...

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 formation and evolution. In this study, we applied a particle tracking algorithm for detecting UDs in NOAA AR12384 observed on June 14, 2015 by the Goode Solar Telescope (...

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 here the solar radius data, obtained after a painstaking effort to remove all effects that contribute to the error in their measurements (limb darkening, distortion of the o...

In this article, we investigate temporal and periodic variations of the hemispheric sunspot number using sunspot data from Kanzelhöhe Solar Observatory (KSO) for the time period of 1944 – 2017, which covers Solar Cycles 18 to 23 and almost the entire Solar Cycle 24 (2009 – 2017). The KSO data set was verified against the International Sunspot Numbe...

We analyzed modulation of cosmic-ray intensities (CRIs) during Solar Cycles 23 and 24 by using the international sunspot numbers (ISSN) and the maximum CME speed index (MCMESI) as proxies for solar activity. Temporal variations, cross-correlations, and hysteresis patterns of CRI, MCMESI, and ISSN data were investigated. As a result, we concluded th...

Solar oblateness has been the subject of several studies dating back to the nineteenth century. Despite difficulties, both theoretical and observational, tangible results have been achieved. However, variability of the solar oblateness with time is still poorly known. How the solar shape evolves with the solar cycle has been a challenging problem....

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 in NOAA AR 12470 (Loop II). These loops were connecting a plage region with sunspot periphery (Loop I) and a sunspot umbra (Loop II). We used Solar Dynamics Observatory (...

Predicting the solar activity is an important task for space weather and solar physics. There are various approaches to predict the solar activity and these predictions are used in various areas such as planning space missions, approximating the mechanism of solar dynamo, etc. In this paper, a non-linear prediction algorithm based on delay-time and...

According to the modified Zurich classification, sunspot groups are classified into seven different classes (A, B, C, D, E, F and H) based on their morphology and evolution. In this classification, classes A and B, which are small groups, describe the beginning of sunspot evolution, while classes D, E and F describe the large and evolved groups. Cl...

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 called into question for several centuries. The first pioneer works for measuring the Sun's diameter with an astrometric precision were made around the year 1660 by Gabri...

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 through 2016). Our main findings are as follows: i) The temporal variation of monthly means of daily total SSCs in flaring and non-flaring ARs are different and these di...

Solar activity is a chaotic process and there are various approximations to forecast its long term and short term variations. But there is no prediction method that exactly predicts the solar activity. In this study, a nonlinear prediction model was applied to sunspot numbers and the model performance was tested for the last 5 cycles. According to...

Solar activity is a chaotic process and there are various approximations to forecast its long term and short term variations. But there is no prediction method that predicts the solar activity exactly. In this study, a nonlinear prediction approach was applied to international sunspot numbers and performance of predictions was tested for the last 5...

Two x-ray solar flare parameters (number of flares and peak flux) are compared to geomagnetic and space weather activity indices. The first solar flare parameter, X-ray solar flare number (SFN), is the total number of solar flares observed in a given month. The second one is the monthly maximum of X-ray solar flare peak fluxes (SFP). In order to co...

The long term solar activity dependencies of ionospheric F$_1$ and F$_2$ regions' critical frequencies ($f_0F_1$ and $f_0F_2$) are analyzed for the last four solar cycles (1976--2015). We show that the ionospheric F$_1$ and F$_2$ regions have different solar activity dependencies in terms of the sunspot group (SG) numbers: F$_1$ region critical fre...

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 different types of sunspot groups and the number of sunspots in these groups have different solar cycle and cycle to cycle variations. The varying ratio between the averag...

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 Group sunspot number. As a result, these two series which originally differed mainly in their long-term trends, were "reconciled", and the long-term trends in both of the...

We investigated the possible morphological variations observed in sunspot groups on the day before aring activity occurred between January 1996 and November 2014. We found that 77% of all aring sunspot groups were large and complex (D, E, and F modified Zurich classes). In addition, the Zurich classification of A, B, and C class sunspot groups chan...

The long-term relationship between solar (sunspot counts in different Zurich sunspot groups, International Sunspot Number (ISSN), solar wind, and X-Ray solar flare index and geomagnetic indices (Ap and Dst) is investigated. Data sets used in this study cover a time period from January 1996 to March 2014. Our main findings are as follows: 1) The bes...

In this study, we analyzed different types (C, M, and X classes) of X-Ray solar flares occurring in sunspot groups. The data cover 1996-2014 time interval, and a total of 4262 active regions (ARs) were included in the data set. We defined the solar flare production potential as the ratio of the total number of flares observed in a sunspot group to...

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, has been determined, not truly called into question for several centuries. The French school of astronomy, under the impetus of Mouton and Picard in the XVIIth century can...

We studied the relationship between X-Ray flare numbers (C, M, and, X class flares) and sunspot counts in four categories (Simple (A + B), Medium (C), Large (D + E + F), and End (H)). All data sets cover the whole Solar Cycle 23 and the ascending and maximum phases of Cycle 24 (1996-2014). Pearson correlation analysis method was used to investigate...

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, and solar flare index, the solar wind speed and interplanetary magnetic field strength, and the geomagnetic Ap and Dst indices, we point out the particularities of solar a...

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 Multi Taper Method and Morlet Wavelet analysis methods were used. We found the following: 1) Solar rotation periodicities (26-38 days) are present in active latitudes of bo...

We studied the relationship between X-Ray flare numbers (C, M, and, X class flares) and previously reported four sunspot categories (Simple (A and B), Medium (C), Large (D+E+F), and End (H)). All data sets cover the whole Solar Cycle 23 and the ascending phase of Cycle 24 (1996-2014). The Pearson Correlation Method was used to obtain the degree of...

Recent solar radius determinations from space observations of Mercury and Venus transits have been made by different teams in 2003, 2006, 2012, and 2014. Seemingly the results are not consistent: the authors interpreted the discrepancies as caused by the different methods of analysis. However, looking at the wavelength dependence and adding other a...

The possibility that the Sun's radius is changing, even at a faint level, has been discussed over a long time. As the solar radius is certainly one of the most important basic pieces of astrophysical information, it is crucial to determine the physical mechanisms that may cause shrinking or expansion of the solar envelope. The wavelength dependence...

Here, we analyzed solar flare production potential of each sunspot groups since 1996. For this purpose about 4260 NOAA active region data were checked; about 12330 flares were counted then flare production potential of each sunspot groups were calculated. In result of our analysis we found that the flare production potential of an A, B, C, D, E, F,...

The possible effects of cosmic ray intensity and solar activity variations on the rainfall over Turkey and Azerbaijan (middle-latitude Turkey-Caucasus/Caspian Sea region) and Caspian Sea level changes are investigated. Rainfall data for Turkey and Azerbaijan as climate parameter and sunspot number and cosmic ray intensity data as space weather indi...

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) for the main sunspot in NOAA AR 11836. We report that the difference between the shock arrival times as measured the Mg II k 2796.35\AA\ and Si IV 1393.76\AA\ line form...

Here, we analyze different sunspot group (SG) behaviors from the points of view of both the sunspot counts (SSCs) and the number of SGs, in four categories, for the time period of 1982 January-2014 May. These categories include data from simple (A and B), medium (C), large (D, E, and F), and decaying (H) SGs. We investigate temporal variations of a...

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 the counts from simple (A and B), medium (C), large (D, E, and F), and final (H) sunspot groups. We used: i) the Multi-taper Method with red noise approximation, and ii)...

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 for Solar Cycle 24 by using Learmonth Solar Observatory sunspot group data since 2008. All sunspot groups (SGs) recorded during this time interval were separated into two...

Measurements from the Mount Wilson Observatory (MWO) were used to study the long-term variations of sunspot field strengths from 1920 to 1958. Following a modified approach similar to that presented in Pevtsov et al. (Astrophys. J. Lett. 742, L36, 2011), we selected the sunspot with the strongest measured field strength for each observing week and...

The paper considers the relationship between the cyclic variations in the velocity of coronal mass ejections (CME) and the large-scale magnetic field structure (LSMF) in cycles 21 – 23. To characterize a typical size of the LSMF structure, we have used the index of the effective solar multipole (ESMI). The cyclic behavior of the CME occurrence rate...

Using the smoothed time series of maximum CME speed index for solar cycle 23, it is found that this index, analyzed jointly with six other solar activity indicators, shows a hysteresis phenomenon. The total solar irradiance, coronal index, solar radio flux (10.7 cm), Mg ii core-to-wing ratio, sunspot area, and Hα flare index follow different paths...

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 North Pole of the Sun. Our new findings are that i) some of the observed type II spicules display kink or an inverse "Y" features, suggesting that their origin may be due t...

We studied oscillations of type II spicules observed near the north pole of the sun. The study is based on high-resolution data recorded by the New Solar Telescope at the Big Bear Solar Observatory. The spicule oscillations were probed by applying the global wavelet method to a 34 min continuous time series of off-band Halpha images. The main findi...

We used historical synoptic data the Mount Wilson Observatory (MWO) to study long-term changes in sunspot magnetic field strengths over the period of 1920-1959. By selecting sunspots with the strongest field strength for each observing day, we find that the average field strengths in sunspots vary with solar cycle with amplitude of a few hundred Ga...

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 recorded by the New Solar Telescope at the Big Bear Solar Observatory and 3D MHD simulations of sunspots. Observed UDs, living longer than 150 s, were detected and tracked...

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 2023 by using Rome (cycles 2021) and Learmonth Solar Observatory (cycles 2223) SG numbers. All SGs recorded during these time intervals were separated into two groups. Th...

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 indices covering the 1996-2008 time interval (solar cycle 23). Our new findings are as follows. (1) There is a noteworthy relationship between monthly averaged maximum CME...