Radio sources flickering and local interstellar medium (LISM) structure

A possibility of obtaining information on small-scale inhomogeneities of th e electron component of the local interstellar medium (LISM) was investigat ed using interstellar scintillations of extragalactic radio sources. We ana lysed Culgoora array observational variability data of 190 extragalactic ra dio sources, covering most of the sky, at 80 and 160 MHz. The variability a t time scales from 1 month to 15 years is interpreted as refractive interst ellar scintillations in fast-moving nearby (less than 150 pc) hot gas, near shock waves in the LISM. An all-sky map of scintillation indices, m, avera ged over three-five sources closest to one another, shows several m maxima. Two of the three most pronounced maxima are probably connected with Loop I ; the third one coincides with the soft X-ray (0.1-0.3 keV) background maxi mum near the South Galactic Pole. Other, less certain, m maxima probably co rrespond to the Orion star-formation region and to a soft X-ray maximum nea r the North Galactic Pole. The 'free-of-gas' tunnel in the direction l = 24 0 degrees corresponds to low values of In. The estimated time scale of inte rstellar scintillations on the above-mentioned LISM structures is in agreem ent with that of the observed radio-source variations. (C) 2000 Published b y Elsevier Science BN.