Heliospheric current sheet effect on propagation of type II interplanetary radio bursts from coronal mass ejections

In this paper, we present our hypothesis that a disturbed heliospheric current sheet and heliospheric plasma sheet can exert a very strong influence on propagation of type II radio waves through interplanetary space. We make a conjecture that these layers become more dense and the critical frequency becomes higher, so radio emission induced in the bow shock region in front of the coronal mass ejection is reflected or deflected more strongly. The idea is illustrated by two examples of type II radio bursts: in January 1997 and in May 1997. In the first case, the effect of the heliospheric current sheet and heliospheric plasma sheet was minimal because they were some 30° below the ecliptic plane and did not play an important role in the propagation of radio waves to the Earth, while during the second event the layers were located in the way of radio waves, and attenuated them strongly.