SOUNDING THE FLANKS OF THE EARTHS BOW SHOCK TO -230 R-E - ISEE-3 OBSERVATIONS OF TERRESTRIAL RADIO-SOURCES DOWN TO 1.3 TIMES THE SOLAR-WINDPLASMA FREQUENCY

We sound the Earth's bow shock and magnetosheath to X(GSE) similar or equal to-230 R-E by analyzing the propagation of low-frequency terrest rial radio emissions through these regions to ISEE 3 in the interplane tary (IP) medium in the 0300-0400 LT sector less than 200 R-E from Ear th. Two sources are seen tailward of the Earth's direction, the farthe r the lower the frequency and sometimes away from the shock: the spike of low-frequency (LF) bursts from 1.3 to 2f(p.sw) (f(p.sw) is the sol ar wind plasma frequency) and the auroral kilometric radiation (AKR) a bove 2f(p.sw). IP Scattering can help explaining how radiation can rea ch the spacecraft while traveling sunward from X similar or equal to-2 30 R-E; but only if the whole of the apparent source on the shock flan k is far enough tailward. The minimum frequency at which the spike can be located is in most cases within 10% of the maximum plasma frequenc y f(max.sh) across the shock calculated from the Rankine-Hugoniot equa tions. Models of the bow shock-magnetosheath density distribution (f(m ax.sh)(X)) are thus built so that the LF radiation becomes occulted fo r X < X-occ as f decreases thus explaining some very remote apparent s ources. However these new models do not account so well as our previou s ones [Steinberg and Hoang, 1993] for the apparent direction of the A KR source at f greater than or similar to 2f(p.sw) which appears close r to Earth than the burst spike. This probably implies that the aurora l and the LF burst spike radiations cross the shock at about the same time but at different places.