Abstract
A possibility of ionization by precipitation of high energy particles is examined using phase records of the NLK radio signal (18.6 KHz) transmitted from Jim Creek, Washington, U.S.A.. The NLK is received on a path, about half of which goes near the polar cap region, and often shows anomalous phase changes (SPA's) during geomagnetic storm periods. SPA's are investigated by using data obtained from the reception of NLK during 25 months from August 1970 to December 1973 with a point of view of associating SPA's at night with 24 geomagnetic storms whose horizontal components are greater than 100 γ observed at the Memanbetsu Magnetic Observatory of Japan . The results obtained for nocturnal periods are; a) Phase of NLK wave are advanced by 10 μs associated with decrease of horizontal component of 70 γ at the main phase. b) Phase change occurs 2 hours later than the main phase of a geomagnetic storm and continues for about 2 days but weak effect continues for about 5 days .
