Decametric Radio Emission Research Articles

The Magnetic-Field Geometry of Jupiter and its Relation to Io-Modulated Jovian Decametric Radio Emission

The Magnetic-Field Geometry of Jupiter and its Relation to Io-Modulated Jovian Decametric Radio Emission

Modulation of Jupiter's Decametric Radio Emission by IO: Comments on a Paper by Goldreich and Lynden-Bell.

A d.c. circuit model has been proposed by Goldreich and Lynden-Bell to account for the modulation of Jupiter's decametric radio emission by Io. The model accounts for the observations only if the electrical resistance of Io is less than some critical resistance. These resistances are estimated and it is shown that Io's is probably the greater. It is also shown that the model probably cannot be applied to Amalthea.

Decametric Variability of Cas A and 3C 84

WE question the suggestion of Braude et al.1 that apparent variability of the decametric radio emission from Cas A and 3C 84 is intrinsic to the sources. Their suggestion, if correct, would have important consequences for theories of radio sources, but we argue that their reasons for discounting ionospheric phenomena as the cause of the variations may be insufficient. Furthermore, our own observations of 3C 84 at 10.03 MHz show no evidence of variability greater than that attributable to residual ionospheric effects.

Structured Events in the Dynamic Spectra of Jupiter's Decametric Radio Emission

view Abstract Citations (17) References (22) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Structured Events in the Dynamic Spectra of Jupiter's Decametric Radio Emission Riihimaa, Jornia J. Abstract High-resolution dynamic spectra of Jupiter's decametric radio bursts were studied. The decasecond bursts were found to resolve into patterns consisting of repeated ridges, tilted in the time-frequency plane. The sign of the slope of these patterns reverses at a CML close to 150 . The millisecond bursts form a distinct type of emission. They were not fully resolved in either frequency or time in the present experiment. Publication: The Astronomical Journal Pub Date: May 1968 DOI: 10.1086/110627 Bibcode: 1968AJ.....73..265R full text sources ADS |

Jupiter's Decametric Radio Emission and the Radiation Belts of Its Galilean Satellites

Many of the observed properties of Jupiter's decametric radiation may be explained by postulation that the inner Galilean satellites of Jupiter have magnetic properties that strongly distort Jupiter's magnetic field in the region of each satellite. Charged particles from Jupiter's radiation belts are trapped by these distorted fields and emit synchrotron radiation.

Electrodynamic Effects of Jupiter's Satellite Io

JUPITER'S satellite Io has remarkable control of Jovian decametric radio emission (recently reviewed1,2) and also a very high and possibly varying albedo3,4.

Decametric Radio Emission from Jupiter

Observations of the decametric radio emission from Jupiter establish the existence of a hitherto undetected sub-millisecond component. Bursts of between 0.2 and 10 msec are not due to interplanetary scintillation but come from the planet itself.

Dependence of Decametric Radio Emission from Jupiter on the Positions of the First Two Galilean Satellites

JOVIAN decametric radio emission is controlled by Io, the first Galilean satellite of the planet, and it has been assumed that the determining factor is the position of Io in its orbit as measured from superior geocentric conjunction1 or from superior heliocentric conjunction2. It has also been shown that the probability of emission is dependent on the position of Io with respect to the plane which contains the magnetic axis of the planet2,3.

Influence of the satellite Io on Jupiter’s decametric radio emission

An analysis of the influence of the satellite Io on Jupiter’s decametric radio emission was carried out utilizing observations recorded at Kodaikanal and Boulder. The influence is found to be complicated and is different at the three sources. It is suggested that the Io related emission can be due to Cerenkov radiation by fast electrons acting as a well-separated stream.

Periodicities in Jupiter's decametric radiation

A systematic search for periodicities in Jupiter's decametric radio emission and methods of assessing their statistical and physical significances are described. It is shown that no independent effects of the satellites Ganymede (III), Callisto (IV), and Amalthea (V) are detectable, while Europa (II) has a small apparent effect, reducing the emission when the satellite is 40° past the Sun-Jupiter line. Claims that simultaneous conjunctions of satellites, I, II and III, or that the magnetic longitude of Io (I), have an effect upon the emission are shown to be questionable. A hypothesis of the origin of the radiation is presented which is designed to explain the partially independent influences on it of Io and the magnetic field.

Observations of Jupiter's decametric radio emissions

Observations of the mean power of Jupiter's decametric radio emissions at six frequencies, 4.7, 15.7, 18.7, 21.5, 24.5 and 28.0 Mc/s, have been used to prepare histograms of relative power and probability of occurrence at each frequency. The variation of the mean flux density of the emissions was determined as a function of frequency, and was found to increase monotonically with decreasing frequency down to 4.7 Mc/s. The spectrum consists of two parts, one having a spectral index of −2.5 between 4.7 Mc/s and 20 Mc/s, and the other a spectral index of −13.7 between 24 and 30 Mc/s. The location of Jupiter's magnetic poles is discussed. The 4.7 Mc/s data is consistent with Jupiter's north magnetic pole being located near 175° system III longitude, while the higher frequency results indicate slightly lower longitudes. The data at 4.7, 15.7, 24.5 and 28.0 Mc/s was examined for influence of the Jovian Satellite Io and contour diagrams of the emission were plotted.

Short-Term Correlations of Decameter Radio Emission from Jupiter and Solar Activity.

view Abstract Citations (1) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Short-Term Correlations of Decameter Radio Emission from Jupiter and Solar Activity. Sastry, Ch. V. Abstract An analysis of decameter radio emission from Jupiter and solar activity over the past 10 yr by the Chree method of superposed epochs showed that there is a significant increase in the radio emission from Jupiter following enhanced solar activity during the past sunspot maximum. The indices used to represent solar activity are (1) geomagnetic planetary index Ap, (2) solar radio flux at centimeter wavelengths. It is pointed out that due to the directivity of the source on Jupiter, the effect of the satellite lo and the observing procedures the Jupiter data contain periodicities which are not inherent in the source. These periodicities are estimated in the following way. A two-dimensional histogram giving the occurrence probability as a function of LCM (system III) and the position of the satellite lo is calculated using all the available data. For an assumed 4 h observing function each day the theoretical probability of ohserving Jupiter based on the two-dimensional histogram is calculated for a number of days. A power spectrum analysis of these theoretical probabilities showed that there can be a number of periodicities in Jupiter data with periods ranging from 2 to 30 days. It is well known that solar data exhibit similar periodicities. The observed correlations may be due to the existence of similar periodicities in both time series. To test this hypothesis the probability of observing Jupiter for each day, for which observing times are available, during the period 1957 through 1961 is calculated using the two-dimensional histogram. These theoretical probabilities are correlated with the solar indices for the same period. The correlation curves thus obtained are similar to the correlation curves obtained by using the days on which Jupiter emission is detected. On the basis of these results it is suggested that there is no conclusive evidence that decameter radio emission from Jupiter and solar activity are related. Publication: The Astronomical Journal Pub Date: February 1966 DOI: 10.1086/110086 Bibcode: 1966AJ.....71R.179S full text sources ADS |

A New Search for Visual Aurorae on Jupiter.

view Abstract Citations (6) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A New Search for Visual Aurorae on Jupiter. Dulk, George A. ; Eddy, John A. Abstract The nature of decametric radio emission from Jupiter and the known properties of its magnetic field suggest that energetic electrons frequently impinge on its upper atmosphere. These events, occurring at the time of decametric emission, should ionize atmospheric constituents and cause a visible recoml~ination emission spectrum. This Jupiter auroral emission has long been suspected but never observed. Past attempts to observe the effect in hydrogen-~ have mostly used filter monochromators, with bandpass 15-20 A, or low-dispersion spectrographs. The best previous search (Smi4~, Rodman, and Sloan. Astron. J. 68, 79, 1963) could have detected a 100 kilo- rayleigh aurora in HCL, had one occurred in their field of view. The recent finding that lo controls much of the radio emission (Bigg, Natttro 203, 10C8, 1964) enables one to predict the time and place of probable aurorae on Jupiter (Dulk, Science 148, 1585. 1965) and thus increases the chance of detection. Anroral activity is likely to occur on magnetic field lines connecting lo to Jupiter, at times and places favorable for detection several times per week, with duration 3 to 5 h. The authors have reinitiated the optical search for these events using the coude' spectrograph at the 84-in. telescope at the Kitt Peak National Observatory. Auroral emission expected is a narrow, weak perturbation in the reflected absorption lines, Doppler-shifted from line center by planetary rotation. With spectral resolution of 0.1 A, a 1.2 kilo- rayleigh aurora should be detectable in HCL, and approximately 10 kilorayleigh aurora elsewhere in the spectrum. Spectra were obtained on three favorable nights in November 1965 with negative results. We conclude that either no aurora brighter than 1.2 kilorayleigh was present or the spectrograph slit was incorrectly placed on the planet. Nearly concurrent filtergrams were obtained with a 5 A HCL interference filter which has a 1000 kilorayleigh auroral threshold. Publication: The Astronomical Journal Pub Date: February 1966 DOI: 10.1086/110070 Bibcode: 1966AJ.....71R.160D full text sources ADS |

Periodicities in the Jovian Decametric Radio Emission.

Periodicities in the Jovian Decametric Radio Emission.

Faraday rotation on decametric radio emissions from jupiter : Warwick, James W., and George A. Dulk, High Altitude Observatory Lab, Boulder, Colorado, Reprint, Science, 145, No. 3630, July 1964, 4 p.

Faraday rotation on decametric radio emissions from jupiter : Warwick, James W., and George A. Dulk, High Altitude Observatory Lab, Boulder, Colorado, Reprint, Science, 145, No. 3630, July 1964, 4 p.

Jupiter, as observed at long radio waves, the decametric radio emissions of Jupiter

Jupiter, as observed at long radio waves, the decametric radio emissions of Jupiter

Io-Related Radio Emission from Jupiter

As evidenced by spectra of Jupiter's decametric radio emissions from 1960 through 1964, Jupiter's satellite Io acts to induce much of the emission and influences the spectral character of the emission. The emission pattern of Io-related emission is derived, and possible interaction mechanisms to explain the Io effect are discussed.

Faraday Rotation on Decametric Radio Emissions from Jupiter

Some decametric radio emissions from Jupiter observed recently exhibit effects which are attributable to Faraday rotation within the earth's ionosphere. We present the evidence for the presence of Faraday rotation and discuss its origin. Identification of the magnetoionic mode in which the emission is generated at Jupiter appears possible, although near the limit of accuracy of our present observations. The emission seems to be generated in the extraordinary mode.

High-resolution Spectral Observations of Jupiter's Decametric Radio Emission

DURING the 1963 apparition of Jupiter, an experiment was carried out relating to the fine structure in the dynamic spectra of Jovian decametric radiation. The equipment used was a sweep-frequency receiver1, operated between 20 and 18 Mc/s with a repetition frequency of 10/sec. The 3 and 20 db. intermediate frequency band-widths were 80 and 150 kc/s, respectively, and the post-detection time constant 0.1 msec. The dynamic spectra were recorded photographically from the intensity-modulated cathode-ray tube display. The aerial installation consisted of four identical three-element Yagi aerials, two of them connected in parallel to the spectrograph and two others, separated by 7.5 wave-lengths, to a phase-switching interferometer on 19.3 Mc/s driving a pen recorder. All the Yagi aerials were directed 30° west of the meridian.

Repeatability of Jupiter's Decametric Radio Emission

Repeatability of Jupiter's Decametric Radio Emission