VLF LINE RADIATION OBSERVED BY SATELLITE

VLF line radiation received by the ISIS 1 and 2 satellites over New Ze aland is found to fall into two distinct classes, The first of these c onsists of magnetospheric lines (MLs) which are characterized by a bro adband appearance and by frequency drifts of a few tens of hertz per m inute, similar to those reported elsewhere, Both their initial frequen cies and their frequency spacings were, however, found to be essential ly random rather than multiples of 50 or 60 Hz. The hourly variation i n ML occurrence showed no correlation with electrical load in possible electrical mains systems sources. No clear decrease in occurrence on weekends was evident, This first satellite survey with significant num bers of MLs found no evidence of a relationship with power line harmon ics, The second class of satellite-received VLF lines consists of ''tr am lines'' (TLs) which are characterized by their very narrow bandwidt h and zero frequency drift, TLs appear to lie close to harmonics of 50 or 60 Hz, An example of this class is presented.