Radio observations of PKS2314 + 03 during occultation by comet Halley

Abstract

Strong interplanetary scintillations (IPS) were recorded at 103 MHz at Thaltej (23°02'N, 72°36'E) between 18 and 20 December 1985, when the quasar PKS2314 +03 was occulted by the ion tail of comet Halley. The scintillation periodicities were near 1 s and their amplitudes decreased progressively as the source approached the end of the tail. The scintillating flux density on these days was 18.2, 11.4 and 4.7 Jy when the source was ~86° from the Sun. The r.m.s. density variations were 10, 6 and 3 electrons cm⁻³ on 18,19 and 20 December respectively, and varied with distance r from cometary nucleus as r ^−3.3. Assuming an ion velocity of 100 km s⁻¹, we show here that the observed periodicity of 1 s implies ion density inhomogeneities of the order of 100 km.