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the intra - cluster medium ( icm ) in clusters of galaxies is known to possess magnetic fields whose origin and properties are not yet well known . the presence of cluster magnetic fields is demonstrated by a ) the existence of diffuse cluster - wide radio emission ( radio halo ) as revealed in some clusters ( e.g. coma , see giovannini et al . 1993 , and references therein ) , b ) the detection of inverse compton hard x - ray emission ( bagchi et al . 1998 , fusco - femiano et al . 1998 ) , c ) the study of variations of the faraday rotation of background sources shining through different lines of sight across the clusters , d ) the analysis of faraday rotation gradients in extended sources embedded within the cluster . kim et al . ( 1991 ) analyzed the rotation measure ( rm ) of radio sources in a sample of abell clusters and found that @xmath0 g level fields are widespread in the icm , regardless whether they do or do not have a strong radio halo . stronger magnetic fields , from about 5 up to the extreme value of 30 @xmath0 g ( as in 3c  295 , perley & taylor 1991 ; and hydra a , taylor & perley 1993 ) have been found in `` cooling flow '' clusters where extremely large faraday rotations have been revealed , suggesting that the generation of very strong icm magnetic fields may be connected with the cooling flow process ( soker & sarazin 1990 , godon et al . 1998 ) . in the coma cluster , a magnetic field of about 6@xmath1 @xmath0 g was found by feretti et al . ( 1995 ) from the analysis of the rotation measure in the cluster radio galaxy ngc  4869 . this large value is comparable to the magnetic field strength observed in cooling flow clusters , and it is considerably larger than the `` equipartition '' field derived by the radio data of the diffuse radio halo coma c , permeating the coma cluster center . the icm magnetic field can be tangled on scales much smaller than the typical galaxy size . crusius - wtzel et al . ( 1990 ) , studying the depolarization in 5 strong double sources , found tangling on smaller scales ( 1 - 4 kpc ) . this is confirmed by the results of feretti et al . ( 1995 ) on the coma cluster . the knowledge of the properties of the large - scale magnetic fields in clusters is important to study the cluster formation and evolution , and has significant implications for primordial star formation ( pudritz & silk 1989 ) . it has been suggested that strong fields can originate either by large scale dynamo amplification ( ruzmaikin 1989 ) or by turbulence following a cluster merger ( tribble 1993 ) . these magnetic fields can be traced by studying the rotation measures of radio sources located within or behind the cluster .    [ cols= " < , < , < , < , < , < " , ]     caption . column 1 : source name ; column 2 : maximum absolute value of rm ; column 3 : average value of rm ; column 4 : rm dispersion ; column 5 : average depolarization defined as m@xmath2/m@xmath3 ; column 6 : distance from the cluster center in units of core radii .    in the case of a tangled magnetic field , with cells of uniform size , same strength , and random orientation , the observed rm along any given line of sight will be generated by a random walk process , and the distribution of rm results in a gaussian with zero mean , and the dispersion related to the number of cells along the line of sight . the source will also depolarize at long wavelength , if the external faraday screen is not fully resolved by the observing beam . the good @xmath4 fits to the polarization angle favour the interpretation that external faraday rotation is the dominant mechanism in the present sources . in table [ polar ] we summarize the results for the present radio galaxies . the most striking result is the trend of rm dispersion and depolarization with distance from the cluster center . the innermost source , 0053 - 015 , has the largest @xmath5 , the highest absolute values of rm , and the highest depolarization at long wavelengths . the source 0053 - 016 , located just beyond 1 core radius from the cluster center , still shows high values of rm , but lower than in 0053 - 015 , and also the depolarization is lower . finally , the peripheral source 3c  29 shows little rm and little depolarization . this result points to the interpretation that the external faraday screen is the same for all 3 sources , i.e. it is the intergalactic medium in a  119 , which plays different roles according to how much magneto - ionized medium is crossed by the polarized emission . this is consistent with the two nat s being really located in the inner cluster region , and not simply projected onto it . as suggested by tribble ( 1991 ) , unresolved external rm fluctuations produce a fall - off of the polarization degree with @xmath6 . a consistent picture is thus that the structure of the intergalactic magnetic field is tangled on small scales , this accounting for the observed depolarization . from the polarization degree of 0053 - 015 and 0053 - 016 ( see sect . 3 ) , there is evidence that the 3.5   observing beam does not fully resolve the screen . thus , we can argue that the scale of tangling of the magnetic field is @xmath74 kpc . moreover , field reversals must take place . the indirect detection of the magnetic field associated with the intergalactic medium of a  119 is an important result , since so far a significant intergalactic magnetic field has been only found at the center of clusters with strong cooling flows ( ge & owen 1993 , taylor et al . 1994 ) . moreover , direct evidence of a cluster magnetic field is provided in the few clusters containing a radio halo ( see e.g. feretti & giovannini 1996 ) . the magnetic field present in a  119 is spread on a size larger at least than one cluster core radius . the existence of a magnetic field component in the intergalactic medium therefore seems to be a common feature in clusters of galaxies . the determination of the strength of the magnetic field in a  119 depends on the model for the x - ray gas distribution and on several assumptions , including the rm structure function , and the field structure .    in the simplest case that a constant magnetic field fills the whole cluster , using the central gas density and a core radius as the path - length , eq . ( 2 ) requires @xmath8 = 1.2 @xmath0 g . we have found , however , that the magnetic field is likely to be tangled on scales of the order of a few kpc . in this case , the intensity of magnetic field is larger by the square root of the number of cells crossed by the line of sight .    a more realistic approach is to assume a magnetic field in randomly oriented cells of uniform size and strength , and a gas density distribution given by the hydrostatic isothermal model . the gas density @xmath9 has the functional form @xmath10 where the parameters have the same meaning as in eq . ( 1 ) . in this case , the rm dispersion at different projected distance from the cluster center was evaluated by felten ( 1996 ) by solving the integral of eq . ( 2 ) : @xmath11 where @xmath12 is the gamma function , @xmath13 is the core radius in kpc , and @xmath14 is the size of each cell in kpc ; the central gas density @xmath15 is in @xmath16 and @xmath8 is in @xmath0 g . the constant @xmath17 depends on the integration path over the gas density distribution : @xmath17 = 624 , if the source lies completely beyond the cluster , and @xmath17 = 441 if it is as distant from the observer as the cluster center . for the cluster a  119 , using @xmath17 = 441 and the gas parameters given in table [ clusd ] , the previous formula becomes @xmath18 the values of @xmath5 obtained for the 2 nat s of a  119 fit fairly well in the model described above and are consistent with a magnetic field strength in the range 9.6 - 13.6 @xmath0 g , for a cell size between 2 and 4 kpc . the rm of the peripheral source 3c  29 is also consistent with the previous model . however , the magnetic field probably can not be constant over 4 core radii ( @xmath19 1.5 mpc ) , otherwise the magnetic pressure would exceed the thermal pressure in the outer parts of the cluster . so it is reasonable to believe that the very low rm of 3c  29 derives not only from the low density of the foreground medium , but also from a weaker magnetic field in this region . the model used to derive the magnetic field strength is very simplified : first , the two radio galaxies can be at different locations along the line of sight ; second , the cluster shows possible substructures both in optical and in x - rays , and therefore the model used for the gas density distribution may be inaccurate ; third , the magnetic field structure could be more complicated than assumed . we can not exclude the possibility that the cell size of the magnetic field in the region around the radio galaxies would be smaller than that of the the cluster - wide magnetic field , due to the interaction between the radio sources themselves and the intergalactic medium . with cells of 10 - 20 kpc , the magnetic field derived from eq . ( 5 ) is 4.5 - 6.1 @xmath0 g .    even allowing for the uncertainties related to the previous computations , the observational evidence favours the existence of a strong magnetic field in the intergalactic medium of a  119 , over a scale larger than the cluster core radius . a plausible range for the magnetic field strength is about 5 - 10 @xmath0 g . three radio galaxies belonging to the cluster abell 119 , located at different projected distance from the cluster center , are studied in total intensity and polarization . the two radio galaxies closer to the cluster center show similar nat structure , while the most peripheral radio galaxy is a classical fri source . the spectra of the nat radio galaxies progressively steepen with the distance , as expected under the effect of synchrotron energy losses . the electron lifetimes inferred from the spectral curvature lead to drift velocities of @xmath194000 - 4500 km s@xmath20 . still higher values are obtained if the magnetic field is different from the equipartion value . such large values of the velocities can derive from projection effects , or from the existence of reacceleration processes within the tails , or bulk motions along the tails and/or in the integalactic medium . we also note that non - 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we present new , multiwavelength very large array observations of the 3 radio galaxies in the cluster abell 119 : 0053 - 015 , 0053 - 016 and 3c  29 . 
 the first two radio galaxies , which lie close to the cluster center , show a narrow - angle - tailed structure , with many twists in the tails . 
 the third radio source is located at the cluster periphery , and shows an undistorted fri morphology . 
 all three radio sources are strongly polarized at the highest frequencies , and all three show both more depolarization and higher faraday rotation measures with increasing proximity to the cluster center . 
 we interpret this polarization behaviour as induced by the magneto - ionized intracluster medium , whose magnetic field is estimated to be in the range 5 - 10 @xmath0 g . 
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