This paper introduces and describes the radio and plasma wave investigation on the STEREO Mission: STEREO/WAVES or S/WAVES. The S/WAVES instrument includes a suite of state-of-the-art experiments that provide comprehensive measurements of the three components of the fluctuating electric field from a fraction of a hertz up to 16 MHz, plus a single frequency channel near 30 MHz. The instrument has a direction finding or goniopolarimetry capability to perform 3D localization and tracking of radio emissions associated with streams of energetic electrons and shock waves associated with Coronal Mass Ejections (CMEs). The scientific objectives include: (i) remote observation and measurement of radio waves excited by energetic particles throughout the 3D heliosphere that are associated with the CMEs and with solar flare phenomena, and (ii) in-situ measurement of the properties of CMEs and interplanetary shocks, such as their electron density and temperature and the associated plasma waves near 1 Astronomical Unit (AU). Two companion papers provide details on specific aspects of the S/WAVES instrument, namely the electric antenna system (Bale et al., Space Sci. Rev., 2007) and the direction finding technique (Cecconi et al., Space Sci. Rev., 2007).
Abstract. Some interplanetary shocks associated with coronal mass ejections (CMEs) generate type II radio emissions at the local plasma frequency and/or its harmonic. These type II radio emissions provide a means of remotely studying and tracking CMEs from the solar corona to 1 AU and beyond. New analysis techniques that inherently reveal the dynamics of a CME as it propagates through the interplanetary medium are used for tracking the CME-associated radio emissions. The techniques make use of dynamic spectra of the radio intensity plotted as a function of inverse frequency and time. When in situ measurements are also available, the analyses determine unequivocally whether the type II radio emissions occurred at the fundamental or harmonic of the local plasma frequency in the upstream or downstream regions of the CME-driven shock. These new analysis techniques are applied to three type II radio bursts that were observed by the WAVES radio experiment on the Wind spacecraft on May 13-14, November 4-5, and November 6-7, 1997; each event corresponded to a CME observed by SOHO LASCO (large angle and spectrometric coronagraph), and each event was observed in situ by Wind. We find that the type II radio emissions for each of the three events were generated at both the fundamental and harmonic of the plasma frequency in the upstream region of the CMEdriven shock, that the type II emissions appear, in general, to originate in regions along the shock front of higher than normal densities, and that the radio emission sites along the shock front change with time. In one case, additional radio tracking, provided by the directionfinding analysis, was used to locate the sites of the radio emission along the shock front.
A new class of kilometer wavelength solar radio bursts has been observed with the ISEE‐3 Radio Astronomy Experiment. These events resemble groups of ordinary type III bursts but have some unique properties. They are very intense and have durations considerably longer than groups of type III bursts. The new class of events do not necessarily occur at the times of reported meter wavelength type III activity and therefore do not appear to be the continuation of such activity to long wavelengths. Instead they occur at the reported times of type II events, which are indicative of a shock wave. An examination of records from the Culgoora Radio Observatory shows that the associated type II bursts have fast drift elements emanating from them i.e. herringbone structure. It is proposed that the new class of bursts are the long wavelength continuation of herringbone structure and it seems probable that the electrons producing the radio emission are accelerated by shocks. The new type of events will be referred to as shock accelerated (SA) events. The characteristics of SA events are discussed.
Abstract. Radio triangulation from the widely separated Ulysses and Wind spacecraft is used to reconstruct the trajectory of a type III radio burst in the three-dimensional heliosphere. The derived radio trajectory follows a (Parker) spiral path corresponding to a solar wind speed of ---200 km/s and progresses to the south of the ecliptic plane. These remote radio observations also measure the interplanetary plasma density along the path of the radio source. The derived average density-distance scale is very similar to the previously derived RAE density scale, which was determined in a different way. The results of the radio triangulation combined with a drift rate analysis give an average electron exciter speed of---0.3c. The radio source size and the brightness temperature as viewed from Ulysses and Wind are determined and compared as a function of observing frequency. IntroductionInterplanetary ( Kilometric (wavelength) type III radio bursts have been observed and intensively studied for the past 25 years or so. By tracking these radio bursts through interplanetary space, space-borne radio observations made with spinning dipole antennas were expected to provide remote mapping of the interplanetary magnetic field topology. Initial results [Fainberg et al., 1972] confirmed the Archimedean spiral form of the interplanetary magnetic fields. The full potential of this technique, however, was not previously realized for a number of reasons. Since the direction-finding techniques from single spacecraft yield only the direction of arrival of the radiation, an assumption had to be made about the distance to the radio source. It was customarily assumed that the interplanetary density falls off uniformly in all directions so that, at a given frequency, the radio source must lie somewhere on a sphere of constant plasma density whose radius is fixed by the value of the density and hence the radio frequency. The radio source at a given frequency is then located as the point where the line of sight from the spacecraft intersects this sphere of constant density. In this way the type III radio source could be tracked through Copyright 1998 by the American Geophysical Union. Paper number 97JA02646.0148-0227/98/97JA-02646509.00 interplanetary space as a function of the observing frequency. In this approach, spatial and temporal variations of the interplanetary plasma were ignored. For some techniques developed to circumvent some of these difficulties, see Reiner and Stone [1986, 1988] and Reiner et al. [1995]. This latter reference utilized the position of the Ulysses spacecraft high above the ecliptic plane (---78 ø ecliptic latitude at a heliocentric distance of 2 AU) to derive type III radio trajectories directly from the direction finding analysis, without the necessity of making any assumptions about the falloff of the interplanetary density.Another difficulty with remote radio tracking is that the type III source, at a given frequency, is quite large; its average angular radius increases with decreasing frequency roughl...
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