Emission Of Jupiter Research Articles

Cyclotron mechanism of decameter radio emission of Jupiter

Cyclotron mechanism of decameter radio emission of Jupiter

Tsiklotronnyi mekhanizm dekametrovogo radioizlucheniya Yupitera

Tsiklotronnyi mekhanizm dekametrovogo radioizlucheniya Yupitera

Synoptic observations of Jupiter's radio emissions: Average statistical properties observed by Voyager

Observations of Jupiter's low‐frequency radio emissions collected over one‐month intervals before and after each Voyager encounter have been analyzed to provide a synoptic view of the average statistical properties of the emissions. Compilations of occurrence probability, average power flux density, and average sense of circular polarization are presented as a function of central meridian longitude, phase of Io, and frequency. The results are compared with ground‐based observations. The necessary geometrical conditions and preferred polarization sense for Io‐related decametric emission observed by Voyager from above both the dayside and nightside hemispheres are found to be essentially the same as those observed in earth‐based studies. On the other hand, there is a clear local time dependence in the Io‐independent decametric emission. The emission is prevalent at longitudes >200° when observed from over the dayside hemisphere but is dominant at longitudes <200° when observe from over the postmidnight sector. Decametric emission, which comprises the dynamic spectral lesser arcs near 10 MHz, displays a distinct, bimodal polarization pattern that is predominantly in the left‐hand sense at longitudes below 150° and in the right‐hand sense at longitudes above 150°. The central meridian longitude distributions of occurrence probability and average flux density at hectometric wavelengths appear to depend significantly on both the observer's latitude and local time. Io appears to have an influence on average flux density of the emission down to below 2 MHz. The average power flux density sectrum of Jupiter's emission has a broad peak near 9 MHz. Integration of the average spectrum over all frequencies and all longitudes gives a total radiated power for an equivalent isotropic source of 4 × 1011 W.

On the arc structure of the DAM Jupiter emission

An analysis of the dynamic spectra of the Jovian DAM emission (1.3–40 MHz) has been made from Voyager data; it appears that the different Jovian ‘sources’ can be defined by spectral characteristics, rather than by occurrence probability. The non‐Io emission consists of two families: vertex early arcs (VEA) and vertex late arcs (VLA). These two families are superimposed at all longitudes, but one is always more intense than the other. The characteristics of the two families are specified; in particular, it is shown that the VEA family is more stable in time than the VLA family. The Io‐controlled emission consists of the four sources already known from the ground‐based observations in addition to a new source, (Io‐A')sp, identified by its dynamic spectrum alone. All of the sources are partially superimposed on non‐Io emission. The (Io‐B)sp and (Io‐A')sp sources are made up of low‐curvature arcs having low‐frequency limits above 5 MHz. The high‐frequency limit of the (Io‐B)sp source is strongly modulated by Io‐phase. The (Io‐A)sp source has a spectrum similar to the non‐Io VLA emission. The other two sources, (Io‐C)sp and (Io‐D)sp, are not structured into well‐defined arcs. A comparison is made between the occurrence of these sources in the Io‐CML plane with the sources defined from ground observations by probability of occurrence. Local time effects are observed only in the non‐Io emission when compared before and after encounter. Before encounter, the VEA family is very weak and the VLA family very intense. After encounter, the opposite effect is observed. The Io‐controlled sources are not affected by these local time effects.

Arc structure in Saturn's radio dynamic spectra

The dynamic spectra of Saturn's kilometric radiation show arc structures whose main characteristics are described and compared with those observed in the decametre emission of Jupiter. The origin of the arcs is probably similar for the two planets.

Copernicus measurements of the Lyman-alpha albedo of Jupiter

view Abstract Citations (18) References (17) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Copernicus measurements of the Lyman-alpha albedo of Jupiter Bertaux, J. L. ; Festou, M. ; Barker, E. S. ; Jenkins, E. B. Abstract Measurements of the Lyman alpha emission of Jupiter were made at 0.06-A resolution in January and August/September 1976 with the Princeton spectrometer of Copernicus. Simultaneous measurements of the L-alpha emission of the geocorona allow the derivation of the albedo of the planet, regardless of the exact value of the exciting solar flux, and of the exact calibration factor of the instrument. Comparison of the measured albedo with previous theoretical calculations allows a determination of a total H column density above the absorbing lower boundary ranging between 2.5 x 10 to the 16th and 3.1 x 10 to the 17th/sq cm. The measured line width is consistent with this determination. There is some evidence of H column density variation on the scale of one month from Copernicus measurements, whereas comparison with other measurements (Pioneer 10 and Voyager 1) establishes without doubt a large variability of the upper atmosphere of Jupiter. Publication: The Astrophysical Journal Pub Date: June 1980 DOI: 10.1086/158080 Bibcode: 1980ApJ...238.1152B Keywords: Albedo; Jupiter Atmosphere; Lyman Alpha Radiation; Ultraviolet Astronomy; Astronomical Spectroscopy; Geocoronal Emissions; Oao 3; Upper Atmosphere; JUPITER; LYMAN-ALPHA RADIATION; ALBEDO; EMISSIONS; SPECTROMETER; DATA; COMPARISONS; THEORETICAL STUDIES; ATMOSPHERE; ULTRAVIOLET; SPECTRUM; WAVELENGTHS; OBSERVATIONS; PARAMETERS; ABSORPTION; FLUX; MODELS; REFLECTIVITY; DOPPLER OBSERVATIONS; INTENSITY; VOYAGER 1; PIONEER 10; Lunar and Planetary Exploration; Jupiter full text sources ADS | data products MAST (1)

Induced emission of Jupiter's decametric radiation by Io-accelerated electrons

A source mechanism for the Io-modulated component of the Jovian decametric radiation is proposed on the basis of the model where electrons in the Io flux tube (IFT) can be accelerated by Io's sheath. It is suggested that a significant fraction of the Io-sheath-accelerated electrons can have pitch angles greater than the atmospheric loss cone and therefore become trapped in the IFT. These electrons have flat helical orbits near their mirror points and can give rise to induced emission of extraordinary-mode radiation with frequencies close to the local electron gyrofrequency. The excitation mechanism is primarily due to the interaction of electromagnetic waves with the electrons via a relativistic gyroresonance which arises because of the momentum dependence of the gyrofrequency. Emphasis is put on the case of nearly perpendicular propagation because it is consistent with the observed source regions and beaming pattern of the decametric emissions. The energy requirement is satisfied within the context of the theory. It is also shown that emission occurs in regions close to the planet above the ionosphere.

On the possibility of nonlinear phase bunching effects in the extraordinary mode decametric radio emission of Jupiter

Electron phase bunching can become important on a millisecond time scale in coherent extraordinary mode waves of the amplitude estimated for the Jovian and terrestrial radio emissions, assuming that the emission frequency is slightly above the local cyclotron frequency. Through a coherent interaction a significant fraction of the energy of cyclotron resonant electrons can be transferred to such waves. If the in situ wave fields are sufficiently coherent, phase bunching effects may control the high-resolution dynamic spectrum of the emissions. Field gradients may prevent such phase bunching in the terrestrial magnetosphere, but not in the Jovian decametric source region. Phase-coherent theories suggest two possible explanations of the frequency drift of Jovian millisecond radio bursts. (AIP)

Jupiter Emission Observed Near 1 MHz

Emission from Jupiter has been observed by the IMP-6 spacecraft at 19 frequencies between 600 and 9900 kHz covering the period 1971 April to 1972 October. The Jovian bursts were identified in the IMP-6 data through the phase of the observed modulated signal detected from the spinning dipole antenna. Initial data reduction has isolated 177 events over a span of 500 days. These events persisted over a period between 1 and 60 minutes. Of these events at least 48 occurred during times in which Jupiter emission was being observed at either 16.7 or 22.2 MHz by ground-based instruments of the Goddard Space Flight Center Jupiter monitoring system. Large bursts were detectable from 9900 kHz down to 600 kHz, while smaller bursts ranged down to 1030 kHz. Subject headings: Jupiter - radio radiation, planetary

The Position and Stokes Parameters in the Integrated 21-CENTIMETER Radio Emission of Jupiter and Their Variation with Epoch and Central Meridian Longitude

The Position and Stokes Parameters in the Integrated 21-CENTIMETER Radio Emission of Jupiter and Their Variation with Epoch and Central Meridian Longitude

Physical Sciences: Fine Structure of the Jupiter Radio Bursts

SHORT pulses with a time scale of milliseconds and fractions of a millisecond have been observed in the radio emissions of Jupiter at wave frequencies near 20 MHz since 1956 (refs. 1 and 2). Little is known about these “S” bursts, however, although it has been established3 that their occurrence depends strongly on the orbital position of the satellite Io. Further, Gordon and Warwick4 were able to show from a small set of observations that the bursts may have a relatively narrow radio frequency bandwith (<50 kHz) and that their centre frequency may change rapidly with time at the rate 25–35 MHz s−1, at least near 26 MHz.

Low-Frequency Radio Emission from Jupiter

Radio observations of Jupiter obtained at frequencies between 3 and 8 MHz are described. it is found that radiation may be received whatever the longitude of the central meridian (LCM), but the emission is stronger and more likely when LCM is near 30 , 170 , or 3300. Furthermore, it is found that the flux density decreases below 5 MHz, and that Jupiter's emission appears strongest at about 8 to 10 MHz.

A Jupiter Model of Pulsars

A precedent to the recently-discovered pulsed radio sources or ‘pulsars’ exists in our own solar system. Jupiter could be thought of as a very slow ‘pulsar’ having a period of about 10 h or 35 000 s. Like pulsars, this emission period is known to a high order of accuracy (about 1 in 106). One difference is that Jupiter emission is received over an appreciable part of this period (1/4 to 1/2 or more) compared with about 1/30 of a typical pulsar period (about 40 ms in 1.3 s). Both pulsar and Jupiter bursts have a microstructure of the order of milliseconds, suggesting similar sizes of instantaneous emission regions. In both, the intensity observed varies from period to period. Emissions from both have relatively strong circular-polarization components at times.

Internal Structure and Energy Emission of Jupiter

Jupiter emits much more energy than it absorbs. Explanations of the source of this heat depend upon our knowledge of its interior and of the behaviour of condensed matter at very high temperatures and pressures.

Apparent changes in the rotation rate of Jupiter

The apparent change of Jupiter's rotation rate derived from decameter emission probability histograms is shown to differ from the change derived by comparing dynamic spectra of the radiation. The dynamic spectra indicate that the two major “sources” of radiation shifted longitudes in opposite directions over the period from 1960 through 1965. The drift of histogram features and the drift of spectral features is attributed partly to emission beam divergence as the Earth's declination changes, and partly to a slightly incorrect System III period. The observations are explained by a model in which much of Jupiter's emission (especially the Io-related emission) is beamed in a thin conical sheet from Jupiter's northern hemisphere. On Earth, we observe the two regions where the sheet crosses the ecliptic plane.

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 |

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

Modulation of Jupiter decametric emission by the satellite Io

A re-analysis of Jupiter emission data strongly supports Bigg's finding that it is controlled by the satellite Io.

Thermal infrared emission of the Jovian disk

The 8–14 micron infrared emission of Jupiter has been observed on six nights in December 1963 using the 200-inch Hale telescope. The new observations possess twice the resolution of those obtained in 1962. The brightness temperature at the center of the disk appears to be nearly constant at 129°K. With some slight ambiguity, the light bands are about 0.5° cooler in appearance than the dark bands. There is some suggestion of morning-evening asymmetry in one of the bands. The Great Red Spot is found to be from 1.5° to 2.0° cooler than the surrounding disk at the newer resolution.

Mapping the Brightness-Temperature Distribution of Jupiter at 10 μ.

view Abstract Citations (1) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Mapping the Brightness-Temperature Distribution of Jupiter at 10 μ. Wildey, Robert L. Abstract The 8-14 ~ infrared emission of Jupiter has been observed on six nights in December of 1963 using the 200-in. Hale telescope. The new observations possess twice the resolution of those obtained in 1962. The brightness temperature at the center of the disk appears to be closely constant at 1290K. With some slight ambiguity, the light bands are about 0?5 cooler in appearance than the dark bands. There is some suggestion of morning-evening asymmetry in one of the bands. The Great Red Spot is found to be from 1?5 to 2?0 cooler than the surrounding disk at the newer resolution. The observations were collected with a photometer employing a mercury-doped germanium photoconductor utilized as a 180 cps transducer through the use of a simple articulated double mirror spatial filter which eliminates a large portion of sky-telescope background from the signal. The present limitations to these maps arise from the nonstationary nature of part of the noise. In the future, noise-suppressed maps may be possible without superposition of several maps, which may then remove some of the ambiguity of the present interpretation. These observations will be presented in greater detail in the current issue of the Journal of Geophysical Research. Publication: The Astronomical Journal Pub Date: 1965 DOI: 10.1086/109843 Bibcode: 1965AJ.....70T.696W full text sources ADS |