Physics – Space Physics
Scientific paper
Dec 1994
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994jgr....9923505c&link_type=abstract
Journal of Geophysical Research (ISSN 0148-0227), vol. 99, no. A12, p. 23,505-23,513
Physics
Space Physics
6
Cyclotron Frequency, Electromagnetic Radiation, Emission, Fine Structure, Harmonic Radiation, Interplanetary Magnetic Fields, Plasma Frequencies, Plasma Waves, Solar Wind, Earth Magnetosphere, International Sun Earth Explorers, Magnetosheath, Solar Activity, Solar Radio Bursts
Scientific paper
Novel observations are presented of intrunsic fine structure in the frequency spectrum of electomagnetic (EM) radiation and plasma waves near the electron plasma frequency fp during a period of unusually high interplanetary magnetic field strength. Measured using the wideband receiver on the International Sun-Earth Explorer (ISEE) 1 spacecraft, fine-structured emissions are observed both in the solar wind and the foreshock, The fine structure is shown to correspond to emissions spaced above fp near half harmonies of the electon cyclotron frequency fce, i.e., near fp + nfce/2. These appear to be the first space physics observations of emissions spaced by fce/2. Indirect but strong arguments are used to discriminate between EM and electrostatic (ES) signals, to identify whether ISEE 1 is in the solar wind or the foreshock, and to determine the relative frequencies of the emissions and the local fp. The data are consistent with generation of the ES and EM emissions in the foreshock, with subsequent propagation of the EM emissions into the solar wind. It remains possible that some emissions currently identified as ES have significant EM character. The ES and EM emisions often merge into one another with minimal changes in frequency, arguing that their source regions and generation mechanisms are related and imposing significant constraints on theories. The fce/2 ES and EM fine structures observed may be intrinsic to the emission mechanisms or to superposition of two series of signals with fce spacing that differ in starting frequency by fce/2. Present theories for nonlinear wave coupling processes, cyclotron maser emission, and other linear instability processes are all unable to explain multiple EM and/or ES components spaced by approximately fce/2 above fp for fp/fce much greater than 1 and typical for shock beams parameters. Suitable avenues for further theoretical research are identified. Empirically, the observed fine structures appear very similar to those in split band and multiple-lane type II solar radio bursts; interpretation of both these type II fine structures in terms of fce/2 splitting is suggested, thereby supporting and generalizing a suggestion by Wild (1950). A possible application to continuum radiation is mentioned. The ubiquity of these fine structures in the Earth's fp radiation and foreshock waves remains unknown. Only the ISEE 1 wideband receiver has sufficient frequency resolution (approximately less than or equal to 100 Hz) to perform a dedicated search. Further study of the ubiquity of these fine structures, of how reliably the splitting corresponds to fce/2, and of the other interpretations above is necessary.
No associations
LandOfFree
Fine structure in plasma waves and radiation near the plasma frequency in Earth's foreshock does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Fine structure in plasma waves and radiation near the plasma frequency in Earth's foreshock, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Fine structure in plasma waves and radiation near the plasma frequency in Earth's foreshock will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1411724