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the anisotropic models occup an important place among various realistic models for study of the dynamical evolution of globular clusters . in frame of this models
it have been work out the many evolution theories of the kinematics and dynamics of spherical self - gravitating systems ( e.g. , bettwieser & spurzem 1986 ; spurzem 1996 ; louis 1990 ; solanes & salvador - sole 1990 ; takahashi 1996 ) . at the same time
have been accumlated many observational data .
these data mostly concerned star counts and surface brightness profiles , proper motions , stellar radial velocity dispersion , etc .
( meylan & heggie 1997 ) . despite of the presence such great quantity information ,
still there are difficulties in comparision problem the observational data with results of numerical simulations in the frame work of anisotropic models .
one of causes of this phenomenon perhaps is concluded in that for their performe we must have at least the value of the anisotropy parameter @xmath0 , where @xmath1 and @xmath2 are radial and tangential components of velocity dispersion respectively ( @xmath3 ) . in general case it depends on radial distance and time .
the aim of this work is to determine the value of anisotropy parameter for 10 globular clusters , to try find out the its dependence on limiting magnitude and on radial distance .
we have used the method that was proposed by agekian and petrovskaya ( 1962 ) .
let us assume : 1 ) the star ensemble has an equal - mass spectrum ; 2 ) the cluster is spherically symmetric and is in stationary state in the regular force - field ; 3 ) the cluster consists of single stars ; 4 ) @xmath4 and @xmath5 along radius ( so @xmath6 ) .
then the cluster is described by means of the equation @xmath7 where @xmath8 and @xmath9 are undimensional radial distance and undimensional spatial density .
a theoretical surface mass density profile is determined as @xmath10 where @xmath11 and @xmath12 are scale factors , @xmath13 is constant taking into account the infinity radius of the model and @xmath14 is the solution of ( 1 ) . from assumption 1 ) it follows that @xmath15 , where n is spatial number star density .
then @xmath16 is theoretical surface number density of stars . here
constants @xmath11 , @xmath12 and @xmath13 are determined by minimization of the function @xmath17 ^ 2 $ ] where n is number of star counts zones and @xmath18 is observed surface number density of stars .
that value of @xmath19 that gives minimum @xmath20 is adopted as most probable value of a.
we determined the value of anisotropy parameter @xmath19 for following 10 globular clusters : m3 , m12 , m13 , m15 , m55 , m56 , palomar 3 , palomar 14 , ngc5139 ( @xmath21 cen ) and ngc6535 .
the results are given in table 1 .
for most clusters we have @xmath22 , i.e. they have almost isotropic velocity distribution .
it is interesting that for all clusters theoretical number density profiles are in good agreement with observational ones .
but the theoretical density profile in the halo almost in all cases is lower than observational one .
perhaps the cause is in the assumption about equal - mass .
the fact is , as a result of mass segregation the low - mass stars prevail in the halo and consequently we overestimated mass density in this region . in reality
the mass density less than we suppose .
for m56 at limiting magnitude @xmath23 we found @xmath24 .
hence in this cluster the velocity distribution is strongly anisotropic yet .
besides in order to find out an influence of limiting magnitude to value of @xmath19 , we calculated it at @xmath25 and found @xmath26 , i.e. if in this case the limiting magnitude decreases , then the anisotropy parameter decreases also .
perhaps it is because , in first case ( @xmath23 ) it is expected the influence of low - mass stars to value of @xmath19 that generally are in halo and move along elongated orbits .    in order to find out the possible dependence of the anisotropy parameter on the radial distance we performed for ngc5139 ( @xmath21 cen ) additional calculations in three separate regions .
the results show that in the central region @xmath22 , in middle region @xmath27 and in the halo @xmath26 . in this case
the agreement of the theoretical and observational density profiles essentially was improved than one for whole cluster .
ccccc cluster & a & limit .
& source of & note + & & or exp .
time & observational data & + m3 & 0 & 10 min & king et al .
1968 & + m12 & 0 & 9 min & king et al .
1968 & + m13 & 0 & 10 min & king et al .
1968 & + m15 & 0 & 30 min & king et al .
1968 & + m55 & 0 & 2 min & king et al .
1968 & + pal 3 & 0 & 30 min & king et al .
1968 & + pal 14 & 0 & v=224 & harris & & + & & & van den berg 1984 & + ngc6535 & 0 & b=200 & peykov & & + & & & roussev 1988 & + m56 & 0.8 & b=215 & peykov & & + & & & roussev 1986 & + -//- & 0.3 & b=190 & peykov & & + & & & roussev 1986 & + ngc5139 & 0 & 30 min & king et al .
1968 & @xmath28 + -//- & 0 & -//- & king et al .
1968 & @xmath29 + -//- & 0.1 & -//- & king et al .
1968 & @xmath30 + -//- & 0.3 & -//- & king et al .
1968 & @xmath31 +    we think this way allowes to solve partly the problem of dependence of the anisotropy parameter on radial distance for any globular cluster .
if we will make use of the more precise observational data , e.g. surface brightness profile recevied from hubble space telescope , then we can find the more precisely dependence of anisotropy parameter on radial distance in the concrete observed globular cluster .
further we plan to study nostationary effects .
the problem of determination of the velocity anisotropy parameter from star density profiles in globular clusters is considered . 
 the calculations are performed for 10 globular clusters . 
 the simple way for study of the dependence of anisotropy parameter on radial distance is used .    
 # 1_#1 _ # 1_#1 _ =    # 1 1.25 in .125 in .25 in