The Solar Wind and Jovian Decametric Radio Emission

Abstract

Spaced-receiver observations of the 19·7 MHz radio emission from Jupiter during 1963 and 1964 demonstrate that many of the so-called bursts with quasiperiods of 1-10 sec are caused by the sweeping of an interplanetary diffraction pattern across the receiver by the motion of scattering irregularities in the solar wind. Measurements made on these scintillations include arrival time differences at spaced receivers, scintillation rate, angular position scintillation, and the width of the scattered angular power spectrum.The derived properties of the scattering irregularities are as follows. (1) The solar wind is radially directed with respect to the Sun and possesses an average velocity V s """ 600 km sec-i. (2) (6) The irregularities in electron density with dimensions of hundreds of kilometres are relatively weak (-10%) in oomparison with the average eleotron density.Theoretical restriotions on source size are used to derive an upper limit of -0·6 sec of arc to the angular diameter of the deoametrio source on Jupiter. It is shown that the intensity sointillations are significantly reduced when the line of sight pa.sses within 60° of the Sun; if this is due to the finite source size, a. lower limit of -0·1 sec of arc oan be assigned to the source diameter.. I. INTRODUOTION Shortly after the discovery of the Jovian decametric radio emission by Burke and Franklin (1955) it was realized that some, if not all, of the intensity variations may be imposed on an essentially steady intrinsic emission by propagation effects . between the planet and observer. Such considerations led Gardner and Shain (1958) to record bursts simultaneously at sites separated by 25 km, observations that showed the presence of considerable differences between the time variations at the two receivers. Subsequent spaced-receiver experiments by Smith et al. (1960) and Douglas and Smith (1961) over baselines varying in length from 15 to 7000 km showed that all degrees of burst correlation could be experienced; the differences were usually ascribed to the effects of ionospheric scintillations which, from discrete radio source observations, were known to be poorly correlated over distances greater than about 5 km.

L-bursts in Jupiter's decametric radio spectra

“…It seems evident, however, that the lanes are not produced by an actual frequency drift of emission, but are superimposed on the spectra for some other reason (Riihimaa, 1971). A co-rotating screen consisting of successive pass and stop zones could be adapted to the phenomenology of the lanes (Riihimaa, 1971;Smith, 1973). The possible nature of the screen cannot be identified.…”

From the Solar Corona to Clusters of Galaxies: The Radio Astronomy of Bruce Slee

“…This result turned the Radiophysics Jovian decametric project in a new direction: what had started as a quest for emission source size now became an investigation of scattering by the interplanetary medium. Slee and Higgins (1968) then used 1963-1964 data on burst arrival times, burst rates, angular position scintillations and apparent angular size to successfully investigate interplanetary diffraction patterns and electron irregularities in the solar wind. Slee's final foray into Jovian decametric emission occurred in 1965-1966 while he was based at the RRE.…”