Longitude Effects in Jovian Decametric Radio Emission.

Abstract

view Abstract Citations (3) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Longitude Effects in Jovian Decametric Radio Emission. Smith, Harlan J. Abstract The essential impossibility of directly resolving Jupiter's surface by any radio technique, other than microwave interferometry, forces decameter radio astronomers to use inferential approaches in localizing radio phenomena. The principal technique has been to determine a precise radio rotation period from the data, then to use this period to establish the frequency or probability of detection of decameter noise storms as a function of Jupiter's longitude of central meridian (LCM). Three principal LCM regions associated with (not necessarily the source of) emission have been suspected for some time. Douglas (Astron. J. 65, 487, 1960) has specified these as Regions 1 and 3 (A111= 1100 and 2800, respectively) and the principal Region 2 (2120). If emission frequency as a function of longitude is plotted as a polar histogram centered on Jupiter, the longitude-associated character of the decameter radiation stands out clearly as a lobe pattern the appearance of which supports the view that these regions correspond to integrated cones of emission. This paper summarizes evidence, from our own and other observers' data and conclusions, that: (a) for each cone, the emission cone angle is nearly independent of the intensity of the storm, (b) the basically trilobed character is strongly marked over the entire span of existing observations, (c) at a given frequency the three principal cones tend to be stable in position and angular width with time, (d) subsidiary cones may occasionally be observed, (e) certain phenomena are characteristic of phase with respect to the principal lobe, in particular the sense of frequency drift, and the polarization reversals and magnetic field inclination both of which are approximately aligned with the major lobe. These phenomena are generally consistent with models such as Warwick's in which the decameter radiation is produced at the local gyrofrequency in an obliquely rotating magnetic field. This work has been supported by the National Science Foundation and the National Aeronautics and Space Agency. Publication: The Astronomical Journal Pub Date: 1962 DOI: 10.1086/108662 Bibcode: 1962AJ.....67S.586S full text sources ADS |