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it has been 20 years since the discovery of the nonthermal radio filaments ( nrfs ) associated with the galactic center arc was first reported ( yusef - zadeh , morris , & chance 1984 ) . these observations showed evidence of linear , magnetized features running perpendicular to the galactic plane . a number of nrfs with similar characteristics to the prototype nrfs have been discovered in the intervening years ( yusef - zadeh 2003 and references therein ) . several models have suggested that the filaments trace the illuminated component of a large - scale poloidal magnetic field pervasive throughout the galactic center region . however , the presence of a number of filaments oriented at large angles to the normal to the galactic plane does not support the above interpretation and indicates a different origin . unlike most models that predict a global , static geometry of the magnetic field around the galactic center , the model described here argues for a local origin . in the proposed picture , the nrfs originate in star - forming regions . the filaments behave like jets extracting mass and energy from embedded young stars or clusters of stars as the jets propagate in a dense ism of the galactic center region . a more detailed account of this model will be given elsewhere . recent observations of a number of radio filaments found in the galactic center region show a wide range of morphological structures ( nord et al . 2003 ; yusef - zadeh , hewitt , & cotton 2004 ) . the new images show structures that suggest nrfs are interacting with their surrounding medium as described here briefly : ( i ) the distortion of the filaments from a straight geometry ; ( ii ) sub - filamentation at the point where the filaments are most distorted ; ( iii ) an increase in the surface brightness in the middle of the filaments ; ( iv ) a gentle curvature and a widening of the filaments ; ( v ) gaps along the length of the filaments . the interaction hypothesis implies the flow of high velocity nonthermal material along the filaments . this interpretation is in contrast to earlier models in which the strong preexisting organized magnetic field lines are illuminated by relativistic particles propagating at the alfvn speed . many of the morphological characteristics described above have also been observed in fr i sources . the presumably supersonic and super - alfvnic jets of fr i sources are known to propagate and interact with a denser material of their ambient medium ( ferrari 1998 ) . for example , the decollimation of some of the filaments and their gentle curvature are analogous to the morphology of bent jets , which has been interpreted in terms of collisions with clouds . the widening of one of the isolated nrfs is shown in figure 1 [ right panel ] as the filament n2 runs almost perpendicular to the galactic plane ; this widening could be explained either by the negative pressure gradient expected in the direction away from the galactic plane or by entrainment of ambient material into the jet . another example is the lack of bright shocked emission from a hot spot at the terminus of the filament ; this can be interpreted in terms of the deceleration of light jets by the surrounding medium , in similar fashion to fr i sources . yet another example is the brightness of many nrfs peaking in the middle of the filaments . in the context of the jet model , the location of the enhanced surface brightness is where the jet changes its course as a result of an encounter with an obstacle ; this in turn may lead to shocks , particle acceleration , and a change in the spectral and magnetic properties ( clarke , burns , & feigelson 1986 ) . lastly , the bundles of filaments that make up the arc and sgr c are examples in which the filaments broaden and appear more diffuse with a steeper spectral index in the direction away from the galactic plane ( tsuboi et al . 1986 ) . in analogy with fr i jets , we believe that these so - called lobes ( see fig . 1 , left panel ) are produced when jets with a low internal - to - ambient density ratio get decelerated and disrupted as they propagate away from the galactic plane ( see fig . 9a of ferrari 1998 ) .
protostellar sources in star forming regions are responsible for driving jets with flow velocities ranging between 300 and 400 km s@xmath0 . 
 this class of jets consists of highly collimated outflows which include thermal knots with number densities estimated to be greater than that of their ambient medium . 
 on the other hand , extragalactic fr i jets consist of light fluid with low mach number burrowing through a denser medium as the magnetized jets radiate nonthermal emission . both protostellar and extragalactic jets are believed to be launched by accretion disks . 
 here we consider a jet model in which the characteristics common to both protostellar and extragalactic jets are used to explain the origin of nonthermal filaments in the galactic center region . 
 we argue that these filaments are analogous to fr i extragalactic sources but are launched by embedded young stars or clusters of stars in star - forming regions .