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Carr, T. D.

Publications and source records attributed to Carr, T. D..

At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

Modulation of the Jovian emission below 8 MHz

RAE-1 data on Jovian decametric emission between 1 and 8 MHz are analyzed to investigate modulation of the emission with respect to the rotation phase of the planet and Io phase as well as a possible variation with flux density of the rotation-phase and Io-phase control below 8 MHz. Attention is given to the observing interval, identification of Jovian emission, orbital-phase constraint, and calculated emission occurrence probabilities. Five frequencies are selected for the analysis (6550, 4700, 3930, 2200, and 1310 kHz), and System III coordinates are used to illustrate the rotation-phase behavior. The spectral distribution of peak flux density is examined along with the overall occurrence probability, the individual modulations, theoretical implications of invariance of active Io phases, and possible modulation by Europa. The results show that Io exerts a suprisingly high degree of control at the low frequencies, that rotation-phase control is only marginal, and that the manner in which Io control is found to vary with flux density is consistent with previous findings at higher frequencies.

Desch, M. D.↗
NASA NTRS1976

Recent decametric and hectometric observations of Jupiter

Observational results on Jupiter's high-frequency radiation, for the range 1-35 MHz (10 to 100 m), obtained over the past six years with the aid of orbited telescopes, are surveyed. Spectral distributions, periodic effects, burst waveforms and dynamic spectra of storms, polarization effects, high-resolution interferometry, and possible correlations with solar activity are discussed. Related spacecraft experiments are described. Close attention is given to long-term accumulation of occurrence probability data as functions of time and frequency (synoptic monitoring) on Jovian HF emission, and to dominating effects of the Jovian satellite Io, as well as modulation of periodicities by the 11.9-year orbital motion period of Jupiter. Possible effects of the other four Jovian satellites immersed in the Jovian magnetosphere are also taken into consideration. Absence of a Jovian Faraday effect and polarization of fine burst structure are discussed.

Carr, T. D.↗
NASA NTRS1975

Observations of Jupiter at 26.3 MHz using a large array

A 640 element phase-steerable dipole array has been used to make highly sensitive observations of the planet Jupiter during the 1973 apparition. The satellite Io is found to have very little influence at the low flux levels, whereas the definition of sources A and B appears to be relatively flux independent. A two-dimensional analysis of the data in the Jupiter-Io plane has revealed considerable source B activity at low intensities which is not influenced by Io.

Desch, M. D.↗
NASA NTRS1974

Dekametric and hectometric observations of Jupiter from the RAE-1 satellite

Analysis of RAE-1 satellite data has revealed the presence of radio bursts from Jupiter in the frequency range from 4700 kHz to 450 kHz. Variations in the activity with respect to the planet's system III longitude are presented at seven frequencies. A merge of ground-based and satellite-acquired data indicates that the long-sought-for peak in Jupiter's low-frequency flux spectrum occurs at about 8 MHz.

Desch, M. D.↗
NASA NTRS1974

An analysis of Jupiter data from the RAE-1 satellite

The analysis of Radio Astronomy Explorer Satellite data are presented. Radio bursts from Jupiter are reported in the frequency range 4700 KHz to 45 KHz. Strong correlations with lo were found at 4700, 3930, and 2200 KHz, while an equally strong Europa effect was observed at 1300, 900, and 700 KHz. Histograms indicating the relative probability and the successful identification of Jupiter activity were plotted, using automatic computer and visual search techniques.

Carr, T. D.↗
NASA NTRS1974

Radio observations of two clusters of galaxies

Maps including the Coma and Hercules clusters of galaxies were made at 195, 318, and 611 MHz, and were compared with optical counts of galaxies in the clusters. An extended region of radio emission approximately 20 minutes in diameter was observed at the center of the Coma cluster. A distributed source region was also observed which appears to include the Hercules cluster, although the possibility that it is just an irregularity in the galactic foreground radiation cannot be completely ruled out.

Donivan, F. F., Jr.↗
NASA NTRS1972

Nonthermal radio observations of the major planets.

The complex and intriguing source of emission over the entire radio spectrum that Jupiter represents is reviewed in the light of ground radio observation data gathered over a period of seventeen years. The observations indicate the presence of intense radiation belts and a strong magnetic field inclined to the axis of rotation. At decametric wavelengths, several remarkably powerful sources are correlated with the rotation of the planet and the orbital motion of the satellite Io. There is at most marginal evidence of nonthermal emission from Saturn, and no such evidence as yet from Uranus and Neptune.

Smith, A. G.↗
NASA NTRS1972

Information from Jupiter's decametric radiation

Radiation associated with decametric bursts are observed from about 39.5 MHz downwards, and its occurrence probability depends partly on the central meridian longitude of Jupiter. Three central meridian longitude regions of emission are designated as Sources A, B, and C. Emissions from B and C regions are also dependent on Io's phase. The frequency band of noise storms drifts slowly up or down the spectrum. Pulses with durations of 20 microseconds display drifts at the rate of 1000 MHz/sec. Decametric data are used to estimate Jupiter's surface magnetic field strength to be 10 gauss; however, if the maximum emission, about 10 MHz, is the electron gyrofrequency at Io's orbit, the surface field strength would be about 800 gauss. A model of the emission beam control exercised by Io is summarized. Data are presented which indicate that the width of source A emissions results from the changes in the angle of Jovicentric declination of the earth. One of two recent theories places the plasmapause at least 50 Jupiter radii from the surface on the sunward side, and the other places it within Io's orbit.

Carr, T. D.↗
NASA NTRS1972

Nonthermal radio observations of the major planets

Seventeen years of observations have shown that Jupiter is a complex and intriguing source of emission over the entire radio spectrum accessible from the ground. The observations indicate the presence of intense radiation belts and a strong magnetic field inclined to the axis of rotation. At decametric wavelengths, several remarkably powerful sources are correlated with the rotation of the planet and the orbital motion of the satellite Io. Longer-term variations of these sources may be associated with the sunspot cycle, with Jupiter's orbital motion, or with changes in the internal structure of the planet. There is at most marginal evidence of nonthermal emission from Saturn, and as yet no evidence for such radiation from Uranus or Neptune.

Smith, A. G.↗
NASA NTRS1972

Jupiter's decametric rotation period and the source-A emission beam

Determinations of the average decametric rotation period for the planet Jupiter are discussed. Mean rotation periods for a twelve year span are plotted as a function of the mean epochs. Two lesser peaks in the longitude histograms were resolved in addition to the main peak. The three peaks, which are believed to result from emission beams oriented in different directions relative to the corotating magnetic field of the planet, are designated Sources A, B, and C in decreasing order of prominence at frequencies in the vicinity of 18 MHz.

Carr, T. D.↗
NASA NTRS1969

Jupiter's decametric rotation period.

Rotation period of Jupiter based on decametric component of radio emission, suggesting anticorrelation with sunspot number for drift observed

Carr, T. D.↗