A solar‐wind “trigger” for the outer heliosphere radio emissions and the distance to the terminal shock

Abstract

For roughly five years the Plasma Wave experiments on the two Voyager spacecraft have detected 2 to 3 kHz radio noise in the outer heliosphere. It has been suggested that this noise originates at the terminal shock of the solar wind, and this idea has been used to estimate the distance to the shock. We have examined the solar wind data from the Plasma Science experiment on the Voyager spacecraft to search for correlations with these radio emissions. We find that two anomalous high speed streams passed Voyager 2 before the noise was initially observed. We suggest that the interaction of these streams with the terminal shock may be responsible for the more intense emission. We estimate the distance to the shock using a time‐of‐flight argument as ∼70 A.U. ‐ 140 A.U.; the larger value is consistent with an estimate using Voyager data and a standard pressure balance argument.