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The Spatio-Temporal Analysis of Field Fluctuations (STAFF) experiment is one of five experiments which together comprise the Wave Experiment Consortium (WEC). STAFF consists of a three-axis search coil magnetometer to measure magnetic fluctuations at frequencies up to 4 kHz, and a spectrum analyser to calculate in near-real time aboard the spacecraft, the complete auto- and cross-spectral matrices using the three magnetic and two electric components of the electromagnetic field. The magnetic waveform at frequencies below either 10 Hz or 180 Hz is also transmitted. The sensitivity of the search coil is adapted to the phenomena theo be studied: the values 3 × 10-3 nT Hz-1/2 and 3 × 10-5 nT Hz-1/2 are achieved respectively at 1 Hz and 100 Hz. The dynamic range of the STAFF instruments is about 96 dB in both waveform and spectral power, so as to allow the study of waves near plasma boundaries. Scientific objectives of the STAFF investigations, particularly those requiring four point measurements, are discussed. Methods by which the wave data will be characterised are described with emphasis on those specific to four-point measurements, including the use of the Field Energy Distribution function.

This paper describes the RETE (Research on Electrodynamic Tether Effects) experiment mounted on board the TSS (Tethered-Satellite System) satellite which was deployed on a cable from the space Shuttle Atlantis during the TSS mission flown in August 1992. The experiment layout and its modes of operation are described in detail. To give an idea of RETE capabilities and actual performance during the mission, samples of measurements are also presented.

There have been many reports of the terrestrial foreshock as a source of freely propagating electromagnetic (e.m.) radiation1–7, identified as plasma emission at twice the solar-wind plasma frequency, 2fp. The 2fp source is close behind the curved surface defined by the interplanetary magnetic field lines tangent to the Earth's bow shock. Electrons accelerated at the shock over a wide range of energies propagate along these field lines where, from a time-of-flight effect6, they have a distribution that is unstable to the production of Langmuir waves6,8. These Langmuir waves9,10 and the unstable electron distributions11,12 have been observed. The mechanism suggested for generating the 2fp radiation5,6,13,14 by the terrestrial foreshock is closely related to present models of type III solar radio emission and rely on some of the energy in the Langmuir waves converting to e.m. waves. The e.m. emission of type III bursts is known to be produced in the solar wind at both the fundamental and second harmonic15, and whether fundamental emission is produced in the terrestrial foreshock is of considerable interest. Comparison of nearby fundamental and harmonic emissions and the Langmuir wave energy density in the source will help discriminate between the different conversion models8,14,16. We present here unambiguous measurements made with the sounder experiment aboard the International Sun–Earth Explorer-1 (ISEE-1) and the radio experiment on ISEE-3 of simultaneous fundamental and second harmonic e.m. emission from the Earth's foreshock.

The authors review the techniques available for finding out the location and polarization of a radio source using antennas with low directivity, that is, electric or magnetic antennas with dimensions less than the wavelength. The use of such antennas is imposed by the combination of the low frequency of observation and of the dynamical constraints upon the antenna length particularly in the case of planetary probes. First they summarize the relationship of an arbitrary antenna to the parameters describing the radiation field, emphasizing the importance of the antenna polarization vector. The application of these results defines precisely the limited information available using short electric antennas. In principle, it is possible to determine the direction (except for the sense) and also the polarization of a point source, using either three such antennas on a three-axis stabilized spacecraft or two antennas on a spinning spacecraft. With a single antenna which is neither parallel nor perpendicular to the spin axis it is possible to determine the source direction with a πambiguity but not its complete polarization. If the single antenna is perpendicular to the spin axis (as is usually the case) only the great circle containing the source direction and the spin axis can be obtained, and this at the expense of assumptions about the source polarization. Source localization requires, in addition to the direction, either observations from another spacecraft or some assumption about the source mechanism and the spatial distribution of the relevant plasma parameters. The application of these methods to the observations of solar radio bursts and terrestrial kilometric radiations is presented.

Plasma, electric-field and magnetic-field data from several experiments on board the spacecraft ISEE 1 and 2 have been analysed in the interaction region upstream of the Earth's bow shock. Upstream waves which are known to be associated with diffuse distributions of backstreaming protons are shown to correlate also with variability in the distribution of the incoming solar-wind protons. Both phenomena are also clearly connected with the presence of enhanced electric-field turbulence. On the basis of these relations, a preliminary discussion can be given of the complex nonlinear plasma processes occurring in the foreshock region.

MANY experiments to measure the radio noise intensity in the topside ionosphere have found an intense “band” of noise in the range of frequency between the plasma frequency and the upper hybrid resonance frequency1–4. Various explanations have been suggested, including plasma instability, radiation by energetic particles5 and anomalous behaviour of the antenna impedance4. Data received by the UK-2 (Ariel 2) satellite suggest that the energy for this noise comes from the particles trapped in the inner Van Allen radiation belt.

ON April 17, 1949, during the course of a survey of the shore known as the Gates at the southern tip of Lundy, a piece of a Floridean alga, too small to identify with certainty, was collected in order that its population of epiphytic red algae might be examined. It occurred in a pool very near extreme low water springs, the spring tides at this period being some of the biggest of the year.

An attempt is made to explain the observed frequency-time profiles of type III solar radiobursts in terms of a rapid plasma wave decay rate combined with the exciter model recently proposed by the author. The decay rate is assumed to be sufficiently rapid for the plasma wave energy density profile to be similar to the excitor power density time profile; this is consistent with the exciter model, the rapid decay being caused by Landau damping on the electrons of the modified high energy tail of the ambient plasma electron velocity distribution. The model is compared with radio observations by making simple assumptions about the dependence of the radio intensity upon the plasma wave energy. A comparison is made with simultaneous radio and electron observations by further assuming a simple power-law velocity distribution for the electrons at their point of ejection from the Sun.