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Title:   Kandilli Rasathanesi'nde 1949 Ocak ayından 1951 Haziran ayına kadar yapılan Güneş leke resatları.
Authors:   Dizer, Muammer
Journal:   Istanbul, Milli Egitim Basimevi, 1953.
Publication Date:   00/1953
Origin:   LOC
LOC Keywords:   SUN-SPOTS
Comment:   LCCN: ne62-40(PREM); CALL NUMBER: QB525 .D56 (Orien Turk)
Bibliographic Code:   1953QB525.D56......

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Title:   Les observations des taches solaires faites a l'Observatoire de Kandilli DU 12 janvier 1949 AU 30 juin 1951.
Authors:   Dizer, Muammer
Journal:   Istanbul, Milli Egitim Basimevi, 1953.
Publication Date:   00/1953
Origin:   LOC
LOC Keywords:   SUN-SPOTS
Comment:   LCCN: 61-46363(PREM); CALL NUMBER: QB525 .D58
Bibliographic Code:   1953QB525.D58......

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Title:   Sur le cycle de 80 ans de l'activité solaire
Authors:   Dizer, Muammer
Journal:   Annales d'Astrophysique, Vol. 19, p.207
Publication Date:   01/1956
Origin:   ADS
Bibliographic Code:   1956AnAp...19..207D

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Title:   Long-lived filaments and geomagnetic storms
Authors:   Dizer, M.
Journal:   The Observatory, Vol. 82, p. 250-253 (1962)
Publication Date:   12/1962
Origin:   OBS
Bibliographic Code:   1962Obs....82..250D

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Title:   Kandilli Observatory, Istanbul
Authors:   Dizer, M.
Journal:   Solar Physics, Vol. 3, p.491 (SoPh Homepage)
Publication Date:   00/1968
Origin:   ADS
Bibliographic Code:   1968SoPh....3..491D

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Title:   A Typical Twisted Surge on November 10, 1967
Authors:   Dizer, M.
Journal:   Solar Physics, Vol. 4, p.99 (SoPh Homepage)
Publication Date:   00/1968
Origin:   ADS
Bibliographic Code:   1968SoPh....4...99D

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Title:   Isophotal Photometry and Morphological Changes in the Flares
Authors:   Dizer, M.
Journal:   Solar Physics, Vol. 10, p.416 (SoPh Homepage)
Publication Date:   00/1969
Origin:   ADS
Bibliographic Code:   1969SoPh...10..416D

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Title:   Isophotometric Measurements of Mercury
Authors:   Dizer, M.; Yazici, M. N.
Journal:   Astrophysics and Space Science, Vol. 13, p.106 (Ap&SS Homepage)
Publication Date:   00/1971
Origin:   ADS
Bibliographic Code:   1971Ap&SS..13..106D

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Title:   A loop prominence system observed on May 24, 1972
Authors:   Dizer, M.
Affiliation:   AA(Kandilli Observatory, Istanbul, Turkey)
Journal:   Solar Physics, vol. 59, Oct. 1978, p. 357-360. (SoPh Homepage)
Publication Date:   10/1978
Category:   Solar Physics
Origin:   STI
NASA/STI Keywords:   H ALPHA LINE, SOLAR FLARES, SOLAR PROMINENCES, SOLAR X-RAYS, SUNSPOTS, K LINES, SOLAR SPECTRA, X RAY SPECTRA
Bibliographic Code:   1978SoPh...59..357D

Abstract

A flare-loop prominence appeared over a complex sunspot group in McMath region No. 11895, on May 24, 1972. The evolution of the loop prominence and its relation to a flare were observed using H-alpha and Ca K filters. Soft X-ray emission between 0.5-20 A was found to be emitted from the flare-loop prominence system.

 

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Title:   International Symposium on the Observatories in Islam - Sep19-23,1977, 1980
Authors:   Dizer, Muammer
Journal:   International Symposium on the Observatories in Islam, September 19-23, 1977. Editor, Muammer Dizer; Publisher, Milli Egitim Basimevi, Istanbul, 1980. ISBN # NONE. LC # QB82.I8 I57 1977.
Publication Date:   00/1980
Origin:   ADS
Bibliographic Code:   1980isot.symp.....D

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Title:   Book-Review - on the Observatories in Islam - International Symposium 1977SEP19-23
Authors:   Dizer, M.; Kennedy, E. S.
Journal:   JOURNAL FOR THE HISTORY OF ASTRONOMY V. 13, P. 64, 1982
Publication Date:   00/1982
Origin:   KNUDSEN
Bibliographic Code:   1982JHA....13...64D

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Title:   A calculation method for the visibility curve of the new moon
Authors:   Dizer, Muammer
Journal:   [Istanbul] : Bosphorus University : Kandilli Observatory, [1984?]
Publication Date:   00/1984
Origin:   LOC
LOC Keywords:   NEW MOON: VISIBILITY: MEASUREMENT
Comment:   LCCN: 84-202758(BKS3); CALL NUMBER: QB588 .D59 1984
Bibliographic Code:   1984QB588.D59......

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Title:   Astronomi Hazineleri
Authors:   Dizer, Muammer
Journal:   [Istanbul] : Bogazici Universitesi, Kandilli Rasathanesi, 1986. 1. baski.
Publication Date:   00/1986
Origin:   LOC
LOC Keywords:   KANDILLI RASATHANESI, ASTRONOMICAL INSTRUMENTS: TURKEY: HISTORY, ASTRONOMICAL OBSERVATORIES: TURKEY: ISTANBUL
Comment:   LCCN: 87-968477(BKS3); CALL NUMBER: QB85 .D59 1986 
Bibliographic Code:   1986QB85.D59.......

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Title:   Rubu Tahtası
Authors:   Dizer, Muammer
Journal:   Istanbul : Bogazici Universitesi, 1987.
Publication Date:   00/1987
Origin:   LOC
LOC Keywords:   QUADRANT
Comment:   LCCN: 87-968781(BKS3); CALL NUMBER: QB105 .D59 1987 
Bibliographic Code:   1987QB105.D59......

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Title:   Spectral studies of the time-series of the geomagnetic activities
Authors:   Dizer, M.; Ozguc, A.
Affiliation:   AB(Kandilli Observatory, Istanbul, Turkey)
Journal:   Earth, Moon, and Planets (ISSN 0167-9295), vol. 43, Dec. 1988, p. 211-220. (EM&P Homepage)
Publication Date:   12/1988
Category:   Geophysics
Origin:   STI
NASA/STI Keywords:   GEOMAGNETISM, MAGNETIC EFFECTS, SPECTRUM ANALYSIS, TIME SERIES ANALYSIS, ANNUAL VARIATIONS, FOURIER TRANSFORMATION, POWER SPECTRA
Bibliographic Code:   1988EM&P...43..211D

Abstract

The geomagnetic effects of solar active centers and the seasonal variation of geomagnetic activity are examined. The periodicities of aa, Ci, and Ap indices are studied using discrete Fourier transforms. It is found that recurrent storm days do not significantly increase when the frequency of sporadic storm days increases as the active centers approach the sun-earth line.

 

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Title:   Periodicity and distribution of the sudden disappearances of solar prominences in the chromosphere
Authors:   Dizer, Muammer
Affiliation:   AA(Kandilli Observatory, Istanbul, Turkey)
Journal:   Astrophysics and Space Science (ISSN 0004-640X), vol. 173, no. 1, Nov. 1990, p. 127-144. (Ap&SS Homepage)
Publication Date:   11/1990
Category:   Solar Physics
Origin:   STI
NASA/STI Keywords:   CHROMOSPHERE, SOLAR PROMINENCES, POWER SPECTRA, SOLAR ATMOSPHERE, SYMMETRY
Bibliographic Code:   1990Ap&SS.173..127D

Abstract

The periodicity and the distribution of the sudden disappearance (SD) of the solar prominences on the chromosphere are studied. The spectral analysis of the SD, from 1039 to 1762 Carrington rotation number, shows a typical period at 138 (10.3 yr) solar rotations in the northern hemisphere and at 153 (11.4 yr) solar rotations in the southern hemisphere of the sun. The power-spectral analysis of the asymmetry index yields a primary peak at 155 (11.6 yr) solar rotations. By plotting the distribution of SD along the Carrington longitude, it can be seen that the distribution of the SD is nearly uniform.

 

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Title:   Periodicity in filamentary activity
Authors:   Dizer, Muammer
Affiliation:   AA(Kandilli Observatory, Istanbul, Turkey)
Journal:   Astrophysics and Space Science (ISSN 0004-640X), vol. 189, no. 2, March 1992, p. 289-301. (Ap&SS Homepage)
Publication Date:   03/1992
Category:   Solar Physics
Origin:   STI
NASA/STI Keywords:   PERIODIC VARIATIONS, SOLAR PROMINENCES, POWER SPECTRA, SOLAR ATMOSPHERE, SPECTRUM ANALYSIS
Bibliographic Code:   1992Ap&SS.189..289D

Abstract

This paper presents the results of the study on the periodicity in filament activity. The spectral analysis of the number of filaments shows a basic period at 141 (10.5 yr), at 138 (10.3 yr), and at 144 (10.7 yr) Carrington rotation in the Northern and Southern Hemisphere, respectively. The time series concerning the index of filament activity also shows a typical period at 135 Carrington rotation (about 10.1 yr) at 144 Carrington rotation (about 10.7 yr) and at 133 Carrington rotation (about 9.9 yr), respectively, in the Northern and Southern Hemisphere. The power spectrum analysis of the time series of the filamentary activity in the short-term also yields less pronounced but still noticeable peaks which are statistically significant.

 

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Title:   The relation between electric conductivity in faculae and in the Bilderberg model of the photosphere
Authors:   Kopeck?, M.; Soytürk, E.
Journal:   Bulletin of the Astronomical Institute of Czechoslovakia, vol. 22, p.154
Publication Date:   00/1971
Origin:   ADS
Bibliographic Code:   1971BAICz..22..154K

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Title:   North-south asymmetries in the green corona brightness between 1947 and 1976
Authors:   Ozguc, Atila; Ucer, Cumhure
Affiliation:   AB(Kandilli Observatory, Istanbul, Turkey)
Journal:   Solar Physics (ISSN 0038-0938), vol. 114, no. 1, 1987, p. 141-146. (SoPh Homepage)
Publication Date:   00/1987
Category:   Solar Physics
Origin:   STI
NASA/STI Keywords:   ASYMMETRY, BRIGHTNESS, PERIODIC VARIATIONS, POWER SPECTRA, SOLAR CORONA, SOLAR SPECTRA, PHOTOSPHERE, SOLAR ACTIVITY, SOLAR CYCLES, SUNSPOTS
Bibliographic Code:   1987SoPh..114..141O

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Title:   Kinematics of a twisted surge
Authors:   Ozguc, Atila; Duzgelen, Ayten
Affiliation:   AB(Kandilli Observatory, Istanbul, Turkey)
Journal:   Astrophysics and Space Science (ISSN 0004-640X), vol. 150, no. 2, Dec. 1988, p. 383-386. (Ap&SS Homepage)
Publication Date:   12/1988
Category:   Solar Physics
Origin:   STI
NASA/STI Keywords:   H ALPHA LINE, MAGNETOHYDRODYNAMICS, SOLAR PROMINENCES, SOLAR MAGNETIC FIELD, SOLAR RADIATION, TWISTING
Bibliographic Code:   1988Ap&SS.150..383O

Abstract

Using the H-alpha solar filtergrams taken at Kandilli Observatory, the motion of a twisted surge has been studied from the kinematic point of view. The Palus (1972) method has been applied to two knots of the twisted surge occurred at November 10, 1967. The results are discussed.

 

 
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Title:   Spectral studies of the time-series of the geomagnetic activities
Authors:   Dizer, M.; Ozguc, A.
Affiliation:   AB(Kandilli Observatory, Istanbul, Turkey)
Journal:   Earth, Moon, and Planets (ISSN 0167-9295), vol. 43, Dec. 1988, p. 211-220. (EM&P Homepage)
Publication Date:   12/1988
Category:   Geophysics
Origin:   STI
NASA/STI Keywords:   GEOMAGNETISM, MAGNETIC EFFECTS, SPECTRUM ANALYSIS, TIME SERIES ANALYSIS, ANNUAL VARIATIONS, FOURIER TRANSFORMATION, POWER SPECTRA
Bibliographic Code:   1988EM&P...43..211D

Abstract

The geomagnetic effects of solar active centers and the seasonal variation of geomagnetic activity are examined. The periodicities of aa, Ci, and Ap indices are studied using discrete Fourier transforms. It is found that recurrent storm days do not significantly increase when the frequency of sporadic storm days increases as the active centers approach the sun-earth line.

 

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Title:   Solar rotation rate from stable sunspot tracings
Authors:   Ozguc, Atila; Saglamsaatci, Mualla
Affiliation:   AB(Kandilli Observatory, Istanbul, Turkey)
Journal:   Astrophysics and Space Science (ISSN 0004-640X), vol. 153, no. 2, March 1989, p. 345-349. (Ap&SS Homepage)
Publication Date:   03/1989
Category:   Solar Physics
Origin:   STI
NASA/STI Keywords:   ANGULAR VELOCITY, SOLAR ROTATION, SUNSPOTS, LEAST SQUARES METHOD, LONG TERM EFFECTS, NORTHERN HEMISPHERE, POSITION (LOCATION), SOUTHERN HEMISPHERE
Bibliographic Code:   1989Ap&SS.153..345O

Abstract

Positions of sunspots between 1966 and 1976 as observed at Kandilli Observatory were used to determine the differential rotation of the sun. A total of 202 sunspot groups which were E, F, G, H, and J-types were chosen, and a least-squares solution was calculated with their daily rotations. A gradient difference was found between the two hemispheres of the sun.

 

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Title:   Distribution of LDE flares on the sun during solar cycles 20 and 21
Authors:   Ozguc, Atila; Duzgelen, Ayten
Affiliation:   AB(Kandilli Observatory, Cengelkoy, Turkey)
Journal:   Astrophysics and Space Science (ISSN 0004-640X), vol. 162, no. 1, Dec. 1989, p. 27-33. (Ap&SS Homepage)
Publication Date:   12/1989
Category:   Solar Physics
Origin:   STI
NASA/STI Keywords:   SOLAR CYCLES, SOLAR FLARES, PROBABILITY DISTRIBUTION FUNCTIONS, SOLAR X-RAYS
Bibliographic Code:   1989Ap&SS.162...27O

Abstract

The latitude and longitude (northern and southern hemispheric) distributions based on 2277 LDE flares observed during the period from 1966 to 1986 have been studied. It is found that there exist active zones, in which the LDE flare occurrence rate is much higher. Latitudinal belts between 11-20 deg and longitudinal belts around 80-100 deg are the most prolific places to produce LDE flares. During cycles 20 and 21 these active zones produced 36 percent of the total number of LDE flares by occupying only 6 percent area of the sun.

 

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Title:   78-day periodicity in the solar 1-8 A X-ray index during the ascending branch of cycle 21
Authors:   Ozguc, Atila
Affiliation:   AA(Kandilli Observatory, Cengelkoy, Turkey)
Journal:   Astrophysics and Space Science (ISSN 0004-640X), vol. 162, no. 1, Dec. 1989, p. 123-127. (Ap&SS Homepage)
Publication Date:   12/1989
Category:   Solar Physics
Origin:   STI
NASA/STI Keywords:   SOLAR ACTIVITY, SOLAR CYCLES, SOLAR X-RAYS, FOURIER TRANSFORMATION, POWER SPECTRA
Bibliographic Code:   1989Ap&SS.162..123O

Abstract

The time series of 1-8 A X-ray index for the time interval between January 1977 to September 1981 has been analyzed by calculating the power spectrum using the discrete Fourier transform. A 78-day periodicity, which is one-half of the period found from various solar parameters of cycles 20 and 21 by various authors, was found. This periodicity is thought to be related to the 152-day periodicity.

 

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Title:   Periodic behavior of solar flare index during solar cycles 20 and 21
Authors:   Ozguc, Atila; Atac, Tamer
Affiliation:   AB(Kandilli Observatory, Istanbul, Turkey)
Journal:   Solar Physics (ISSN 0038-0938), vol. 123, no. 2, 1989, p. 357-365. (SoPh Homepage)
Publication Date:   00/1989
Category:   Solar Physics
Origin:   STI
NASA/STI Keywords:   PERIODIC VARIATIONS, SOLAR CYCLES, SOLAR FLARES, FACULAE, SOLAR ACTIVITY, SUNSPOT CYCLE
Bibliographic Code:   1989SoPh..123..357O

Abstract

Short-term periodicities of solar activity were studied with the flare index by using Discrete Fourier Transform for the time interval 1966-1986. Two noticeable periodicities (18.5 and 5 months) have been found. The existence of these periodicities comparing with the early findings is discussed.

 

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Title:   On the Latitudinal Distribution of the Solar Surges
Authors:   Ozguc, A.
Journal:   SOLAR PHYSICS V.123, NO. 2, P.381, 1989 (SoPh Homepage)
Publication Date:   00/1989
Origin:   KNUDSEN
Bibliographic Code:   1989SoPh..123..381O

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Title:   Distribution of solar surges
Authors:   Ozguc, A.; Yesilyaprak, H.; Duzgelen, A.
Affiliation:   AC(Kandilli Observatory, Istanbul, Turkey)
Journal:   Astronomy and Astrophysics (ISSN 0004-6361), vol. 241, no. 1, Jan. 1991, p. 209-211. (A&A Homepage)
Publication Date:   01/1991
Category:   Solar Physics
Origin:   STI
NASA/STI Keywords:   SOLAR ACTIVITY EFFECTS, SOLAR FLARES, SOLAR TERRESTRIAL INTERACTIONS, ANNUAL VARIATIONS, MAGNETIC DISTURBANCES, SUNSPOTS, SURGES
Bibliographic Code:   1991A&A...241..209O

Abstract

Latitudinal and longitudinal (northern and southern hemispheric) distributions were studies, based on 1456 flare-related solar surges observed during the period from 1980 to 1988. It is found that there exist some active longitude belts where the surge production is more profuse in each hemisphere of the sun. Latitudinal belts between + or - 11 deg and + or - 20 deg and longitudinal belts around 0 - 10 deg and 270 - 280 deg are the most prolific zones to produce surges. During the period 1980-1988 those active zones produced 22 percent of the total number of surges while occupying less than 10 percent of the solar surface. There is good correlation with earlier findings of active longitudes.

 

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Title:   Intermediate-term periodicities in the green corona brightness of the sun
Authors:   Ozguc, Atila
Affiliation:   AA(Kandilli Observatory, Istanbul, Turkey)
Journal:   Astrophysics and Space Science (ISSN 0004-640X), vol. 187, no. 2, Jan. 1992, p. 197-207. (Ap&SS Homepage)
Publication Date:   01/1992
Category:   Solar Physics
Origin:   STI
NASA/STI Keywords:   EMISSION SPECTRA, IRRADIANCE, PERIODIC VARIATIONS, SOLAR CORONA, SOLAR SPECTRA, FOURIER TRANSFORMATION, SOLAR ACTIVITY, SOLAR CYCLES
Bibliographic Code:   1992Ap&SS.187..197O

Abstract

Intermediate-term periodicities in the green corona were analyzed by dividing 10-deg latitudinal belts for the solar cycles 18, 19, and 20 (1947-1976). Discrete Fourier transform technique was used and three noticeable periodicities (3.48, 2.57, and 2.27 yr) were found. The period of 3.48-yr period is the strongest one, and the 17.6-m periodicity was found only around the +40-deg belt while 155-d periodicity was not revealed.

 

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Title:   The 73-day periodicity of the flare index during the current solar cycle 22
Authors:   Ozguc, Atila; Atac, Tamer
Affiliation:   AABogazici University, Istanbul, Turkey ABBogazici University, Istanbul, Turkey
Journal:   Solar Physics, vol. 150, no. 1-2, p. 339-346 (SoPh Homepage)
Publication Date:   03/1994
Category:   Solar Physics
Origin:   STI
NASA/STI Keywords:   GAMMA RAY ASTRONOMY, GAMMA RAY BURSTS, LIGHT (VISIBLE RADIATION), PERIODIC VARIATIONS, PHOTOSPHERE, SOLAR ACTIVITY, SOLAR CORONA, SOLAR CYCLES, SOLAR FLARES, SOLAR PROTONS, SOLAR X-RAYS, SUNSPOTS, X RAY ASTRONOMY, BRIGHTNESS, CORRELATION, FALSE ALARMS, FOURIER ANALYSIS, FOURIER TRANSFORMATION, POWER SPECTRA, PROBABILITY THEORY, RANDOM NOISE, SPECTRUM ANALYSIS, TIME SERIES ANALYSIS
Bibliographic Code:   1994SoPh..150..339O

Abstract

The flare index of the current solar cycle 22 is analysed to detect periodicities. Power spectral analysis of the time series of solar flare index data reveals a periodicity around 73 and 53 days. We find that a periodicity of 73 days was in operation from November 1988 to the end of December 1991. We also find that when the 73-day periodicity or the 154-day periodicity is in operation the flare index is well correlated with the relative sunspot numbers.

 

 
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Title:   The 73-DAY Periodicity of the Flare Index during the Current SOLAR-CYCLE-22
Authors:   Ozguc, A.; Atac, T.
Journal:   SOLAR PHYSICS V.152, NO. 1/JUN, P.318, 1994 (SoPh Homepage)
Publication Date:   06/1994
Origin:   KNUDSEN
Bibliographic Code:   1994SoPh..152..318O

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Title:   Confirmation of the 25.5-Day Fundamental Period of the Sun Using the North-South Asymmetry of the Flare Index
Authors:   Ozguc, Atila; Atac, Tamer
Journal:   Solar Physics, v. 163, p. 183-191. (SoPh Homepage)
Publication Date:   01/1996
Origin:   KLUWER
Bibliographic Code:   1996SoPh..163..183O

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Title:   Longitudinal Distribution of Flares in the Late Phase of Active Regions
Authors:   Ozguc, Atila; Altas, Levent
Journal:   Solar Physics, v. 163, p. 327-333. (SoPh Homepage)
Publication Date:   02/1996
Origin:   KLUWER
Bibliographic Code:   1996SoPh..163..327O

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Title:   North-South Asymmetry in the Solar Flare Index
Authors:   Atac, Tamer; Ozguc, Atila
Journal:   Solar Physics, v. 166, p.201 (SoPh Homepage)
Publication Date:   06/1996
Origin:   ADS
Bibliographic Code:   1996SoPh..166..201A

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Title:   Examination of the solar cycle variation of foF2 by using solar flare index for the cycle 21
Authors:   Özgüç, A.; Tulunay, Y.; Ataç, T.
Affiliation:   AA(Kandilli Observatory, Bog˘azi çi University, Çengelköy Istanbul, Turkey), AB(Middle East Technical University, Dept. of Aeronautical Eng. 06531 Ankara, Turkey), AC(Kandilli Observatory, Bog˘aziçi University, Çengelköy Istanbul, Turkey)
Journal:   Advances in Space Research, Volume 22, Issue 1, p. 139-142. (AdSpR Homepage)
Publication Date:   00/1998
Origin:   ELSEVIER
Abstract Copyright:   (c) 1998 Elsevier Science B.V. All rights reserved.
Bibliographic Code:   1998AdSpR..22..139O

Abstract

For solar cycle 21 (1976 - 1986) the variation of monthly mean values of noon-time foF2 at Slough, Rome, and Manila are examined by using solar flare index and geomagnetic Ap index. A single regression analysis for dependence of foF2 on solar flare index shows better matching. Moreover, less hysteresis effect is seen when we use solar flare index instead of other solar indices. Thus, for making prediction, one needs to take into account just the solar flare index and not the solar flare index and geomagnetic Ap index simultaneously.

 

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Title:   Flare Index of Solar Cycle 22
Authors:   Atac, Tamer; Ozguc, Atila
Journal:   Solar Physics, v. 180, Issue 1/2, p. 397-407. (SoPh Homepage)
Publication Date:   06/1998
Origin:   KLUWER
Bibliographic Code:   1998SoPh..180..397A

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Title:   The last total solar eclipse of the millennium in Turkey
Authors:   Ozguc, A.; Atac, T.; Altas, L.
Journal:   Contributions of the Astronomical Observatory Skalnate Pleso, vol. 28, no. 3, p. 285-289. (CoSka Homepage)
Publication Date:   03/1999
Origin:   COSKA
Keywords:   THE SUN, SOLAR ECLIPSE
Bibliographic Code:   1999CoSka..28..285O

Abstract

The last total solar eclipse of the millennium will be observed from Turkey which bridges two continents and has been the cradle of so many past civilizations. Wouldn't you like to witness this magnificent event in the mystic ambiance of central Anatolia which offers its guests Turkish hospitality and a lot of historical examples of paganism, Christianity and Islam. Among the countries from which the eclipse will be visible, Turkey seems to be one of the most suitable countries in terms of its climate and observational facilities. Kandilli Observatory and Earthquake Research Institute has arranged fieldwork on the eclipse path to determine the suitable points for the observations. The shadow of the moon will be first seen from the Black Sea coast at 14:20 L.T. It will then pass through central Anatolia and will leave Turkey from south-east at 14:42 L.T.

 

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Title:   The Last Total Eclipse of the Millennium
Authors:   Livingston, W.; Özgüc, A.
Journal:   The Publications of the Astronomical Society of the Pacific, Volume 111, Issue 766, pp. 1597-1597. (PASP Homepage)
Publication Date:   12/1999
Origin:   UCP
PASP Keywords:   CONFERENCE HIGHLIGHTS
Abstract Copyright:   (c) 1999: The Astronomical Society of the Pacific
Bibliographic Code:   1999PASP..111.1597L

Abstract

Conference was held in Istanbul, Turkey, in 1999 August. Proceedings will be edited by W. Livingston and A. Özgüc and published in the ASP Conference Series.

 

 
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Title:   Preparations for the Last Total Solar Eclipse of the Millenium in Turkey
Authors:   Özgüç, A.; Ataç, T.; Altas, L., Rusin, V.
Journal:   Third Advances in Solar Physics Euroconference: Magnetic Fields and Oscillations, ASP Conference Series vol.184, p. 348-352. Eds. B. Schmieder, A. Hofmann, J. Staude. ISBN: 1-58381-010-2(1999)
Publication Date:   09/1999
Origin:   AUTHOR
Keywords:   SUN, SOLAR ECLIPSE
Bibliographic Code:   1999tasp.conf..348O

Abstract

The last total solar eclipse of the millennium will be observed from Turkey which bridges two continents and has been the cradle of so many past civilizations. Among the countries from which the eclipse will be visible, Turkey seems to be one of the most suitable countries in terms of its climate and observational facilities. Kandilli Observatory and Earthquake Research Institute has organised a survey along the eclipse path to determine the suitable sites for the observations. The shadow of the moon will be first seen from the Black Sea coast at 14:20 L.T. It will then pass through central Anatolia and will leave Turkey from south-east at 14:42 L.T. A list of the suitable observing sites along the eclipse path is given.

 

 
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Title:   Effects of hysteresis of some solar indices
Authors:   Özgüç, A.; Ataç, T.; Antalova, A.
Affiliation:   AA(Kandilli Observatory, Istanbul, Turkey)
Journal:   Recent Insights into the Physics of the Sun and Heliosphere: Highlights from SOHO and other Space Missions, International Astronomical Union. Symposium no. 203. Manchester, England, August 2000.
Publication Date:   00/2000
Origin:   AUTHOR
Bibliographic Code:   2000IAUS..203E..72O

Abstract

During the past two cycles, researchers have been monitoring solar irradiance at many selected wavelengths in addition to maintaining more traditional indices such as sunspot number and the 10.7cm flux. Certain pairs of these indices exhibit hysteresis, solar cycle dependent differences in their relative variations. We study this hysteresis effect by using smoothed time series of some indices of solar activity including the solar flare index and LDE flare index. The solar flare index and LDE flare index are newly calculated by the authors for the cycles 21 and 22. Further we try to find that hysteresis effect is indeed a feature of solar activity during the past two cycles.

 

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Title:   Characteristics of Flares with Hα Emission Protruding over Major Sunspot Umbrae
Authors:   Vrsnak, B.; Ruzdjak, V.; Brajsa, R.; Zlobec, P.; Altas, L.; Özgüç, A.; Aurass, H.; Schroll, A.
Affiliation:   AA(Hvar Observatory, Faculty of Geodesy, Kaciceva 26, HR-10000 Zagreb, Croatia), AB(Hvar Observatory, Faculty of Geodesy, Kaciceva 26, HR-10000 Zagreb, Croatia), AC(Hvar Observatory, Faculty of Geodesy, Kaciceva 26, HR-10000 Zagreb, Croatia), AD(Osservatorio Astronomico di Trieste, Via G.B. Tiepolo 11, I-34131 Trieste, Italy), AE(Kandilli Observatory, TR-81220 Çengelköy-Istanbul, Turkey), AF(Kandilli Observatory, TR-81220 Çengelköoy-Istanbul, Turkey), AG(Astrophysikalisches Institut Potsdam, An der Sternwarte 16, D-14482 Potsdam, Germany), AH(Sonnenobservatorium Kanzelhöhe, Universität Graz, A-9521 Treffen, Austria)
Journal:   Solar Physics, v. 194, Issue 2, p. 285-303 (2000). (SoPh Homepage)
Publication Date:   06/2000
Origin:   KLUWER
Abstract Copyright:   (c) 2000 Kluwer Academic Publishers
Bibliographic Code:   2000SoPh..194..285V

Abstract

A sample of 47 importance >= 1 flares whose Hα emission occurred or protruded over umbrae of major sunspots (so called Z-flares) was studied to investigate characteristics of the associated dm-m radio, microwave and soft X-ray emission as the energy release site permeats into regions of strong magnetic fields. A close time association was found between the microwave burst peak and the `contact' of the Hα emission with the sunspot umbra. The Hα emission attained maximum close to or a few minutes after the contact. The soft X-ray bursts were delayed more, attaining maximum 0-10 min after the contact. The onset of bursts in the dm-m wavelength range was associated with the period of growth or the peak of the microwave burst. Two categories of type III and IV bursts could be recognized: the ones starting some ten minutes before the microwave peak, and those that begin close to the microwave burst peak. Type III bursts occur preferably when the microwave burst peaks simultaneously with or after the contact. The results are explained presuming that the contact reveals a permeation of the energy release process into a region of strong magnetic fields, where the process intensifies, and where the accelerated particles have access to magnetic field lines extending to large coronal heights. Different manifestations of the energy release process in various magnetic field topologies are considered to account for the various time sequences observed.

 

 
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Title:   Observations of the Total Solar Eclipse August 11, 1999
Authors:   Özgüç, A.; Rusin, V.; Rybansk?, M.; Livingston, W.
Journal:   Last Total Solar Eclipse of the Millennium, ASP Conference Series, Vol. 205. Edited by W. Livingston and A. Ozque. ISBN: 1-58381-032-3 (2000), p.184
Publication Date:   00/2000
Origin:   ADS
Bibliographic Code:   2000ltse.conf..184O

Abstract

Not Available

 

 
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Title:   Variation of Cosmic Ray Intensity During the Solar Eclipse August 11, 1999
Authors:   Kandemir, G.; Güçlü, M. C.; Geçkinli, M.; Firat, C.; Boydag, S.; Özgüç, A.; Yasar, T.
Journal:   Last Total Solar Eclipse of the Millennium, ASP Conference Series, Vol. 205. Edited by W. Livingston and A. Ozque. ISBN: 1-58381-032-3 (2000), p.202
Publication Date:   00/2000
Origin:   ADS
Bibliographic Code:   2000ltse.conf..202K

Abstract

Not Available
 
 
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Title:   Statistical relationship between sunspots and major flares
Authors:   Atac, T.
Affiliation:   AA(B.U. Kandilli Observatory, Istanbul, Turkey)
Journal:   Astrophysics and Space Science (ISSN 0004-640X), vol. 129, no. 1, Jan. 1987, p. 203-208. (Ap&SS Homepage)
Publication Date:   01/1987
Category:   Solar Physics
Origin:   STI
NASA/STI Keywords:   SOLAR FLARES, STATISTICAL ANALYSIS, SUNSPOTS, MAGNETIC FLUX, SOLAR CYCLES
Bibliographic Code:   1987Ap&SS.129..203A

Abstract

In this study, the statistical relationship between sunspots and major flares observed in the descending branch of the 20th and in the ascending branch of the 21st solar cycle is evaluated. It is found that the sunspots which produced these major flares are of the type Dki or Eki with magnetic class D and the largest magnetic field strength between 1600 and 2500 G.

 

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Title:   Time variation of the flare index during the 21st solar cycle
Authors:   Atac, T.
Affiliation:   AA(B. U. Kandilli Observatory, Istanbul, Turkey)
Journal:   Astrophysics and Space Science (ISSN 0004-640X), vol. 135, no. 1, July 1987, p. 201-205. (Ap&SS Homepage)
Publication Date:   07/1987
Category:   Solar Physics
Origin:   STI
NASA/STI Keywords:   PERIODIC VARIATIONS, SOLAR CYCLES, SOLAR FLARES, CHROMOSPHERE, SOLAR ACTIVITY, SOLAR TERRESTRIAL INTERACTIONS, SPATIAL DISTRIBUTION
Bibliographic Code:   1987Ap&SS.135..201A

Abstract

In this study, the flare index during the solar activity cycle 21 is calculated for every day from January 1, 1976 to March 31, 1986. It is determined that the chromospheric activity for the whole disc was significantly higher during the 21st solar cycle as compared to the preceding cycle. It is found that the activity began and reached its maximum earlier on the northern hemisphere. Finally, it is determined that the time variation of the flare indices for the eastern and western hemispheres are in good agreement.

 

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Title:   Relation of the fluctuations of some of the solar activity indices
Authors:   Atac, T.
Affiliation:   AA(B.U. Kandilli Observatory, Istanbul, Turkey)
Journal:   Astrophysics and Space Science (ISSN 0004-640X), vol. 153, no. 1, March 1989, p. 173-176. (Ap&SS Homepage)
Publication Date:   03/1989
Category:   Solar Physics
Origin:   STI
NASA/STI Keywords:   SOLAR ACTIVITY, SOLAR CORONA, CORRELATION COEFFICIENTS, SOLAR ATMOSPHERE, SUNSPOTS
Bibliographic Code:   1989Ap&SS.153..173A

Abstract

The fluctuation curves from the differences of unsmoothed and smoothed values of the different solar activity indices are obtained. The patterns of fluctuations of these curves are compared. Using monthly mean values of each index, the degree of correlation between the pairs of indices during the selected time intervals is studied.

 

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Title:   On the short term variations of solar activity during solar cycle 21
Authors:   Atac, Tamer
Affiliation:   AA(Kandilli Observatory, Cengelkoy, Turkey)
Journal:   Earth, Moon, and Planets (ISSN 0167-9295), vol. 47, Nov. 1989, p. 165-170. (EM&P Homepage)
Publication Date:   11/1989
Category:   Solar Physics
Origin:   STI
NASA/STI Keywords:   SOLAR ACTIVITY, SOLAR CYCLES, TEMPORAL DISTRIBUTION, FORBIDDEN TRANSITIONS, SOLAR CORONA, SOLAR FLARES, VARIABILITY
Bibliographic Code:   1989EM&P...47..165A

Abstract

Short-term variations of the last solar activity cycle were studied by the flare and coronal indices using Gleissberg method. Systematic short-term variations are found from their course during the 21st solar activity cycle. Comparison of their autocorrelograms constructed by the new set of data obtained from the magnitude of the fluctuations showed the existence of the phase shift between the temporal variations of the two indices.

 

 
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Title:   On the SID durations
Authors:   Atac, Tamer
Affiliation:   AA(Kandilli Observatory, Istanbul, Turkey)
Journal:   Astrophysics and Space Science (ISSN 0004-640X), vol. 181, no. 1, July 1991, p. 157-159. (Ap&SS Homepage)
Publication Date:   07/1991
Category:   Geophysics
Origin:   STI
NASA/STI Keywords:   SOLAR FLARES, SOLAR TERRESTRIAL INTERACTIONS, SOLAR X-RAYS, SUDDEN IONOSPHERIC DISTURBANCES, D REGION, GOES SATELLITES, SOLAR PHYSICS
Bibliographic Code:   1991Ap&SS.181..157A

Abstract

This Letter is based on analysis of data on SID listed in Solar Geophysical Data. The mean durations of 1272 SIDs taken from the SGD lists were calculated with respect to their associated X-ray flares. In general, all of the present calculated mean durations showed a large scatter in the mean values. The comparison of the present values by the estimated Solar Geophysical Data Center SID durations indicated an apparent discrepancy in the mean duration relative to that estimated by SGD for the case of low levels of SID importance. This apparent discrepancy suggests a need for a correction in SGD's assumptions in the importance range from -1 to +1.

 

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Title:   Low-frequency analysis of the sunspot cycles
Authors:   Boelge, H.; Altas, L.
Journal:   Astron. Astrophys. 288, 967-972 (1994) (A&A Homepage)
Publication Date:   08/1994
Origin:   A&A via CDS; KNUDSEN
A&A Keywords:   SUN: ACTIVITY, SUNSPOTS
Abstract Copyright:   (c) 1994: Astronomy & Astrophysics
Bibliographic Code:   1994A&A...288..967B

Abstract

The low-frequency components of the solar cycles were analysed to understand the complex amplitude modulation of the cycles. The antisymmetrical sideband distribution around the fundamental frequency (the Hale frequency) supports the idea that there are frequencies which beat the fundamental frequency. All the results were based on a linear relationship between the modulated wave and the relative sunspot numbers, but the sharpness of the cycles and the appearance of a third harmonic in the spectra shows a lack of strict proportionality between these two quantities
 
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Title:   Carbon, nitrogen, and oxygen abundances in Procyon, sun, and Arcturus
Authors:   Altas, L.
Affiliation:   AA(B.U. Kandilli Observatory, Istanbul, Turkey)
Journal:   Astrophysics and Space Science (ISSN 0004-640X), vol. 134, no. 1, June 1987, p. 85-94. (Ap&SS Homepage)
Publication Date:   06/1987
Category:   Astrophysics
Origin:   STI
NASA/STI Keywords:   ABUNDANCE, CARBON, NITROGEN, OXYGEN, STELLAR COMPOSITION, SUN, INFRARED SPECTRA, LINE SPECTRA, NEAR INFRARED RADIATION, STELLAR LUMINOSITY, STELLAR SPECTRA, STELLAR TEMPERATURE
Bibliographic Code:   1987Ap&SS.134...85A

Abstract

CI, NI, and OI permitted and forbidden lines in the near-infrared spectra of Procyon (F5 IV-V), the sun (G2 V), and Arcturus (K2 IIIp) have been analyzed to determine their carbon, nitrogen, and oxygen abundances. Procyon is found to have normal abundances, while Arcturus is found to have an enhanced nitrogen abundance by a factor of 1.03 dex relative to the sun. The dependence of the derived abundances on the effective temperature and luminosity is investigated.

 

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Title:   Major flare effects on the intensity of the green Corona and geomagnetic activity
Authors:   Altas, Levent
Affiliation:   AA(Kandilli Observatory, Istanbul, Turkey)
Journal:   Earth, Moon, and Planets (ISSN 0167-9295), vol. 46, Aug. 1989, p. 127-134. (EM&P Homepage)
Publication Date:   08/1989
Category:   Solar Physics
Origin:   STI
NASA/STI Keywords:   MAGNETIC VARIATIONS, SOLAR ACTIVITY EFFECTS, SOLAR CORONA, SOLAR FLARES, SOLAR TERRESTRIAL INTERACTIONS, MAGNETOACTIVITY, SOLAR CYCLES, SOLAR RADIO BURSTS, SOLAR WIND VELOCITY
Bibliographic Code:   1989EM&P...46..127A

Abstract

The effects of the solar major flares indicated by the intensive radio bursts, high velocity streams or shock waves, coronal and ionospheric disturbances on the geomagnetic and coronal activities are investigated during the near the maximum phase of 21st solar cycle, in detail. The significant and the weak increases in the level of the geomagnetic and coronal activities indices were observed, respectively, after the occurrence of these events.

 

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Title:   The duration of spotless flares
Authors:   Barlas, Oryal; Altas, Levent
Affiliation:   AB(Kandilli Observatory, Istanbul, Turkey)
Journal:   Astrophysics and Space Science (ISSN 0004-640X), vol. 197, no. 2, p. 337-341. (Ap&SS Homepage)
Publication Date:   11/1992
Category:   Solar Physics
Origin:   STI
NASA/STI Keywords:   BRIGHTNESS DISTRIBUTION, H ALPHA LINE, SOLAR FLARES, SOLAR PROTONS, TYPE 2 BURSTS
Bibliographic Code:   1992Ap&SS.197..337B

Abstract

The mean durations of spotless H-alpha flares, SFs were calculated as a function of their importance. Totally 3569 SFs chosen from the Quarterly Bulletin and Solar Geophysical Data were used in the present analysis for the period 1947-1990. The detailed analysis of average life and rise times of SFs is discussed.
 
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Title:   Spotless flare activity
Authors:   Altas, Levent
Affiliation:   AABogazici Univ., Istanbul, Turkey
Journal:   Solar Physics, vol. 151, no. 1, p. 169-176 (SoPh Homepage)
Publication Date:   04/1994
Category:   Solar Physics
Origin:   STI
NASA/STI Keywords:   SOLAR FLARES, SPATIAL DISTRIBUTION, SUNSPOTS, SOLAR PHYSICS, SUN
Bibliographic Code:   1994SoPh..151..169A

Abstract

The distribution of spotless flares (SFs) covering the time interval between 1947 and 1990 was investigated. The (11-20 deg) latitude zone was found as the most prolific region for the occurrence of SFs. The longitudinal distribution of SFs occurred most frequently at six or more places on the solar surface. In addition, the asymmetry of SF activity on the solar disk was also studied in this paper. The variation of the asymmetry was compared with other solar activity manifestations. The existence of secondary maxima of SFs appears to be an important result of our analysis. A one-year shift was found when the number of events was plotted versus the year.
 
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Title:   The Bright Surge-Like Spike at the Solar Limb September 24, 1991
Authors:   Altas, L.; Duzgelen, A.
Journal:   Solar Physics, v. 171, Issue 1, p. 145-153. (SoPh Homepage)
Publication Date:   03/1997
Origin:   KLUWER
Bibliographic Code:   1997SoPh..171..145A

Abstract

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Title:   The Determination of the Reduction Factor for Sunspot Observations and its Variation with Meteorological Parameters
Authors:   Altas, L.; Duzgelen, A.; Barlas, O.
Journal:   Solar Physics, v. 178, Issue 2, p. 267-270. (SoPh Homepage)
Publication Date:   00/1998
Origin:   KLUWER
Bibliographic Code:   1998SoPh..178..267A

Abstract

Not Available

 

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Title:   Flare Index During the Rising Phase of Solar Cycle 23
Authors:   Ataç, Tamer; Özgüç, Atila
Affiliation:   AA(atac@boun.edu.tr), AB(atac@boun.edu.tr)
Journal:   Solar Physics, v. 198, Issue 2, p. 399-407 (2001). (SoPh Homepage)
Publication Date:   02/2001
Origin:   KLUWER
Abstract Copyright:   (c) 2001 Kluwer Academic Publishers
Bibliographic Code:   2001SoPh..198..399A

Abstract

A brief description and results of the flare index (FI) as a measure of solar activity for cycle 23 are given. The calculation of the daily flare index was determined using the final solar flare tables from the National Geophysical Data Center A. The final data of FI are presented in graphical form over the rising activity phase of solar cycle 23. Daily calculated values are available for general use in Kandilli observatory's and NGDC's anonymous ftp servers. The pattern of similar activity indices that arise under different physical conditions during the rising activity phase are compared with the flare index. The north-south asymmetry in the daily flare index data was studied.

 

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Title:   Effects of hysteresis of some solar indices
Authors:   Özgüç, A.; Ataç, T.; Antalova, A.
Affiliation:   AA(Kandilli Observatory, Istanbul, Turkey)
Journal:   Recent Insights into the Physics of the Sun and Heliosphere: Highlights from SOHO and other Space Missions, International Astronomical Union. Symposium no. 203. Manchester, England, August 2000.
Publication Date:   00/2000
Origin:   AUTHOR
Bibliographic Code:   2000IAUS..203E..72O

Abstract

During the past two cycles, researchers have been monitoring solar irradiance at many selected wavelengths in addition to maintaining more traditional indices such as sunspot number and the 10.7cm flux. Certain pairs of these indices exhibit hysteresis, solar cycle dependent differences in their relative variations. We study this hysteresis effect by using smoothed time series of some indices of solar activity including the solar flare index and LDE flare index. The solar flare index and LDE flare index are newly calculated by the authors for the cycles 21 and 22. Further we try to find that hysteresis effect is indeed a feature of solar activity during the past two cycles.