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the investigation of the dynamics of solar activity and regularity of its cyclicing is of great importance for the astrophysics .
correspondingly the study of those intervals when solar activity is sharply changed is of particular significance .
examples of such interesting periods are : 1100 - 1250 yy `` maximum of middle ages '' , in 1282 - 1342 yy `` volf minimum '' , 1416 - 1534 yy `` shperer minimum '' , 1645 - 1715 yy `` maunder minimum '' .
the period of the maunder minimum has attracted an additional attention because it puts forward a lot of new and unexpected problems . indeed , for a long time scientists consider spots on the sun surface as main characteristics of the solar activity .
therefore , the notes about the disappearance of the sunspot is reliable , but due to the absence of regular observations it is difficult to determine level of solar activity in the mentioned period .    it should be noted that the anomalies are found in differential rotation of the sun surface at the beginning of the maunder minimum .
according of the different authors , it might indicate that global characteristics of the inner parts of the sun change to such at extant that even the `` dynamo '' mechanisms is stopped . in this connection
the following questions arise : how to characterize the sun activity and the radioactive state in the earth s space in that epoch ? what is main processes which cause such a drastic fall of solar activity ? to what extent our insight into the solar activity correct in general ?    for solving mentioned problems
physicist direct their special attention to cosmogenic isotopes @xmath4 @xmath5 , @xmath6 @xmath7 .
the study of these isotopes may give a lot of information about the dynamics of solar activity .    at present
the most complete data about the solar activity and the intensity of cosmic rays are obtained by means of the above mentioned cosmogenic isotopes ( @xmath8 and @xmath6 ) formed in the earth s atmosphere .
the main peculiarity of these isotopes and advantage as compared with others is the fact that there exist objects in nature ( e. g. tree rings , arctic and antarctic ices , algae with long life time , etc . ) which can `` fix '' i.e. `` memorize '' annual concentration of the mentioned isotopes , during period that prevails it s half - life time .
to study the influence of solar activity ( modu1ation ) in the earth atmosphere on radiocarbon concentration during the maunder minimum we use experimental data obtained at the laboratory of nuclear physics of the tsu @xcite ( fig .
first of all , it should be noted that experimental data cover the maunder minimum itself ( 1645 - 1720 yy ) ( fig .
2 ) and its neighboring periods ( 1600 - 1645 and 1715 - 1800 yy ) too .
the measurements in @xcite were performed with one - year step , i.e. for every calendar year @xmath4 concentration is measured in the corresponding tree ring .
the experimental samples of tree rings were obtained in lithuania .
the value of @xmath4 concentration in relation to the international standard scale is calculated by the following formula @xmath9 where @xmath10 , @xmath11,@xmath12 represents measured activities of the sample ( s ) , standard ( st ) and background ( b ) , respectively . experimental error
does not exceed 0.2 - 0.3% . in order to extract variations of @xmath4
concentration originated only from the `` cosmic '' sources , it is necessary to exclude the influence of the earth s magnetic field .
this influence has been widely discussed and to date the most accurate estimation is that : global change of geomagnetic field with period of 10 thousand years causes about 10% change in @xmath4 data .
the following expression accounts for the geomagnetic field effect in @xmath4 concentration @xmath13 , \ ] ] where t is current calendar year ( t is negative b.c . ) .
as we mentioned above the effective tool for studying the solar activity dynamics during the maunder minimum is to reveal the cyclings in @xmath4 time dependence ( i.e. periodicities in experimental data given in fig.2 ) . for this purpose
the method of spectral analysis has been used @xcite . the calculated power spectrum is shown in fig.3 . according to fig.3 the main peak at frequency 0.05 lies in high reliability interval ( 95% ) ( corresponding period @xmath2 year ) .
small peak is observed at frequency 0.12 ( corresponding period @xmath3 year ) though it s reliability is comparatively low .
1 .   using the method of spectral analysis
we have revealed variations in cosmogenic radiocarbon concentration in the earth atmosphere during the maunder minimum .
periodicities of two types have been revealed in experimental data .
3 .   the reason of the mentioned periodicities is the solar activity .
this means that in the maunder minimum period modulating action of the sun was weak , nevertheless cycling is preserved
. it can be also said that in period of the maunder minimum the mechanism of solar dynamo still works .
reduction of the number of the sunspots may be caused by the coincidence of the minima of any other long - term periodicities at the moment of the maunder minimum .
kocharov , i.v .
zhorzholiani , z.v .
lomtatidze , r.y .
metskvarishvili , s.l .
tsereteli , radiocarbon , 1992 , v.34 , n2,p .
213 - 217 .
kocharov , y. n. markov , r.y .
metskvarishvili , s. l. tsereteli .
materials of the seminar `` intensity of cosmic rays and cosmogen isotopes '' . 1983 .
l. 101.[in russian ] i.v .
zhorzholiani , p. g. kereselidze , et al .
materials of intern .
seminar `` experimental methods of astrophysical and geophysical phenomena study '' . 1988 .
l. 114.[in russian ] g. m. jenkins , d. g. watts `` spectral analysis and its applications '' , holden - day , san francisco , cambridge , london , amsterdam 1969 .
catalog of indices of solar and geliomagnetic activity .
obninsk 1976.[in russian ]
variations of radiocarbon concentration have been studied in annual rings for the last 350 years @xmath0 on the basis of our experimental research using methods of spectral analysis . from this interval of time special attention 
 is paid to the so - called period of the maunder minimum @xmath1 of solar activity . in the experimental series of corresponding period two types of periodicity 
 are revealed : @xmath2 year and @xmath3 year .    
 tbilisi state university , georgia , 0128 . 
 tbilisi , chavchavadze av . 
 3 + email : bochorishvili@ictsu.tsu.edu.ge