Bursts of type N in Jupiter's decametric radio spectra

Dynamic spectra of Jupiter's decametric emission often display narrow-band features, referred to as events of type N (Carr et al., 1983). The average bandwidth of these emissions is in the vicinity of 200 kHz, their durations are typically in the decasecond range, and their f-t slopes are small and random. Although the N-bursts can be described as narrow-band L-bursts, it seems that they are realted to S-bursts in their area of occurrence in the Io-B region, the durations of the emission envelopes, and their bandwidths. Possible implications are discussed.     

Interaction of S- and L-bursts in Jupiter's decametric radio spectra

Dynamic spectra of Jupiter's decametric emission are observed with a high-resolution radio spectrograph. Certain events observed in region Io-B display interaction effects between the S- and L-emissions. The effect appears as a gap in the L-emission after a passage of an S-burst. In a typical case the L-emission has a relatively narrow bandwidth, the S-burst appears as a sloping line crossing it, and the duration of the emission gap is a substantial fraction of a second. The gap has sharp, sloped edges; its leading edge has anf-t slope which is the same as that of the S-burst while the slope of the trailing edge is lower. A kind of tilted V-pattern is thus formed. It is suggested that some more complicated spectral patterns may also be produced this way. It seems that an emission model consisting of S-bursts from bunches of gyrofrequency-emitting electrons ascending a flux tube and interacting with L-emitting bunches of electrons having more stationary guiding centers is inadequate to explain the complex S-L interactions.Contribution of No. 36 of the Department of Astronomy, University of Florida, U.S.A.     

Solar energy cycle and its relation to geomagnetic activity

It is suggested that recurrent and nonrecurrent geomagnetic disturbances which are related to the release of solar magnetic energy in the form of unipolar and bipolar magnetic regions respectively, are connected with the variations in the solar energy source. The true beginning of the solar cycle takes place when unipolar magnetic regions start to develop, i.e, when nuclear energy generation becomes dominant over the neutrino energy loss according to the photon-neutrino coupling theory.     

Beaming of Jupiter's decametric emission

Dynamic spectra of a Jovian non-Io-A storm recorded simultaneously by the Voyager 1 spacecraft and by the Kiiminki radio spectrograph are compared. It seems that the emission beam of the storm co-rotates with the planet and has a sloped leading edge, in accordance with the result of Maeda and Carr (1984).     

Night-time reception of solar radio bursts over wide bandwidths

Spectra of night-time solar radio bursts observed over wide bandwiths are described. The bursts covered frequency ranges of 20–30 and 24–33 MHz without displaying any abrupt frequency structures. It seems that a scatter mechanism of some kind is involved in the night-time propagation.     

Summary results from a pilot study conducted around an oil production platform on the Northwest Shelf of Australia

The Australian Institute of Marine Science (AIMS) conducted a pilot study around the Harriet A oil production platform on the Northwest Shelf of Australia. We evaluated hepatic ethoxyresorufin-O-deethylase (EROD) activity, fluorescent aromatic compounds (FACs) in bile and immunodetection of CYP1A-like proteins in two Australian tropical fish species, Gold-Spotted Trevally (Carangoides fulvoguttatus) and Bar-Cheeked Coral Trout (Plectropomus maculatus) to assess exposure to petroleum hydrocarbons associated with produced formation water (PFW). Additionally, the incidence of hydrocarbon-degrading bacteria isolated from the liver and bile of all fish captured was examined. Low EROD activity was found in both species, with EROD activity in C. fulvoguttatus showing significant site differences. FACs and CYP1A protein levels in C. fulvoguttatus showed a clear trend in hydrocarbon exposure consistent with hydrocarbon chemistry data: Harriet A>Harriet C>reference site. P. maculatus showed elevated levels of FACs at Harriet A as compared to the reference site and demonstrated detectable levels of CYP1A-like proteins at these two sites. Hydrocarbon-degrading bacteria were found in the liver and bile of both species, yet there was no correlation by sites. Our results demonstrate that C. fulvoguttatus and P. maculatus have potential as indicator species for assessing the effects from exposure to petroleum hydrocarbons. Both FACs and CYP1A are providing warning signs that there is potential for biological effects on fish populations exposed to PFW around the Harriet A production platform.     

Metabolic activation of polycyclic aromatic hydrocarbons by fish liver cytochrome P-450

The incidence of hepatoma, epidermal and other forms of cancerous growths in fish is well documented (Halver, 1967; Matsushima & Sugimura, 1976; Dawe et al., 1964). In fish, as in mammals, cancer may be a result of metabolically activated carcinogens. In mammals the primary enzyme system involved in the activation of environmental carcinogens is the cytochrome P-450 linked mixed-function oxidase (MFO). The hepatic microsomes of the species offish studied contain variable levels of cytochrome P-450. Liver microsomes of the trout Salmo trutta lacustris are surprisingly active in metabolising benzo-[a]pyrene (BP) and other compounds preferentially metabolised by polycyclic aromatic hydrocarbon (PAH)-specific cytochrome P-450. This finding may be significant, because it is apparent that the detrimental effects of PAHs require metabolic activation.We have studied the production of reactive intermediates of BP by following their binding to DNA and by measuring the specific nucleotide-BP metabolite complexes by chromatography. Untreated S. trutta liver microsomes catalyse the production of reactive intermediates of BP which bind to nucleotides of DNA at a rate that is 3–4 times higher than that catalysed by control rat liver microsomes. The most prominent DNA-BP metabolite adducts produced by trout liver microsomes are the nucleoside adduct of BP-7, 8-diol-9,10-epoxide and 9-OH-BP-4,5-oxide and other phenol oxides. In contrast to the trout, another fish species, roach (Rutilus rutilus), has extremely low activity. Although the in vitro binding of BP to DNA is not strictly correlated to in vivo binding or biological effects, our results show that reactive intermediates are formed by trout liver and thus the prerequisite for chemical carcinogenesis or mutagenesis is ful filled. This is further supported by the fact that in Ames's test, trout liver preparations produce mutagenic products from promutagens.     

Evolution of the spectral fine structure of Jupiter's decametric S-storms

High-resolution spectra of Jupiter's decametric S-storms are studied with an acousto-optical radio spectrograph operating over the frequency range 20–30 MHz. In 1985–1989 20 S-storms were recorded in the Io-B region. There is only a slight average zoning effect of certain types of fine structure in the Io-B region, with sporadic S-bursts occurring most often in the early CML values, and S-trains in the late values. Emissions of type N and its variants occur at lower values of the Io phase than S-emissions and their variants. There is no exact storm-to-storm correspondence, nor any Io-B-centered zones in which the various types of fine structure could be accurately placed. Every storm is different and has a signature of its own. An important exception is formed by the wide-range quasi-periodic FDS-S storms that occur at the edge of the Io-B region with Io phase values greater than 80 . These are outstanding storms in which the individual bursts may extend across the full spectral width of 20–30 MHz and be repeated in rapid succession at quasi-periodic rates of 20–40 s^–1. It is suggested that these be referred to as type Q storms. It is estimated that only 10% of the S-burst types are recorded so far.     

Changes in solar rotation due to the solar energy generation cycle of 11 years

It is suggested that the observed differences in the periods of variation of some solar phenomena (solar brightness, appearance of sunspot maximum and interplanetary sector structure) occurring close to 27 days are due to differences in the rotation periods of the solar regions in which these phenomena are originated. Changes in periods during the solar cycle can be attributed to changes in the solar energy generation. On the basis of these considerations changes in the sign of the gradient of the Sun's angular velocity can be expected.     

S-bursts in Jupiter's decametric radio spectra

Dynamic spectra of Jupiter's S-bursts are observed with sweep-frequency and multi-channel receivers operating at frequency ranges 21–30 and 20.85–23.20 MHz, respectively. Spectra obtained with time resolutions of 0.2, 0.02, and 0.004 s are compared, the frequency resolution being 50 kHz. The most normal appearance of S-bursts is in trains with a frequency range of the order of 1 MHz. Narrow-band Strains also occur. Narrow-band L-emissions in region B are often associated with S-bursts, obviously in the manner described by Flagget al. (1976). Synoptic spectral observations indicate that region B for S-bursts exhibits a drift in longitude similar to that for L-bursts. The Io phase profile for S-bursts has a maximum in the vicinity of 80° in region B and 230° in region C. S-bursts observed in 1976 have higher drift rates than those compiled by Krauscheet al. (1976). Region C bursts have simpler spectra and lower drift rates than region B bursts.