Proton cyclotron echo: a phenomenon of wave-wave and wave-particle interactions in topside sounding of the ionosphere
Date
2018-07-09
Authors
Chen, Guang-Ming
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
Proton cyclotron echoes are phenomena related to the proton cyclotron frequency
discovered On topside sounder swept-frequency ionograms from the Canadian
satellite Alouette II in 1969. Subsequent studies were also limited to the
use of the swept-frequency ionograms and devoted only to these so called regular
proton cyclotron echoes. The regular proton cyclotron echoes occur on the
swept-frequency ionograms at constant apparent ranges predominantly at frequencies
below the electron plasma frequency fN and slightly above the electron
cyclotron frequency fH. In this dissertation over 2000 topside sounder ionograms
(both swept-frequency mode and fixed-frequency mode) obtained from
the Alouette II, ISIS I and II satellites of the Alouette-ISIS program are used
to investigate proton cyclotron echoes in detail.
Examination of the combined swept-frequency and fixed ionograms indicates
that the proton cyclotron echoes are also observed on the fixed-frequency ionograms,
In addition to some features, such as constant apparent ranges and
higher order multiple echoes, which have been already observed on the swept frequency
ionograms and also occur on the fixed-frequency ionograms, under
some Conditions non-constant apparent ranges and modulations in intensity of
the proton cyclotron echoes on the fixed-frequency ionograms are observed.
Usually the proton cyclotron echoes on the fixed-frequency ionogram can
be observed for a much longer time than on the swept-frequency ionograms
due to the fixed sounding frequencies. A proton cyclotron echo can be under
observation for several spin periods of the satellite if the plasma parameters
encountered by the sounder are appropriate, The modulation in intensity of the
proton cyclotron echo by antenna orientation is evident. In terms of analysis of
the combined swept-frequency and fixed-frequency ionograms, and the satellite
orbital parameters and spin axis attitude, effects on proton cyclotron echoes of
antenna orientation with respect to the earth’s magnetic field are examined. It
is found that higher intensity and higher harmonics of proton cyclotron echoes
occur when the sounding antenna is parallel to the earth’s magnetic field.
A new class of proton cyclotron echoes was discovered, which occur on electron
plasma resonances. The proton cyclotron echoes on the fH, nfH (n = 2, 3, 4), fQ3 and fD have been observed- The first three are checked in more detail.
The proton cyclotron echoes observed on the fH, 4fH, fQ3 and fD resonances
exhibit doublet, on the 2fH resonance triplex and on 3fH resonance single while
the regular proton cyclotron echoes are always single. A frequency difference of
about 5-10 Hz exists between subechoes in a doublet or triplex. The regular
proton cyclotron echo seems to correspond to the first echo of the double or
triple proton cyclotron echoes. No echo minus exists and most proton cyclotron
echoes on the electron plasm a resonances are observed at dip angles whose magnitudes
are less than 8°. This new class of proton cyclotron echoes is attributed
to the results of nonlinear interactions of ion and electron Bernstein waves or ion
Bernstein waves and DKO mode electromagnetic waves (for the fH resonance).
Absorption phenomena on the 3fH, 4fH and fQ3 resonance spikes near the proton
cyclotron period on swept-frequency ionograms are observed occasionally,
but not yet understood.
A theory based on nonlinear interaction of two waves is suggested to interpret
proton cyclotron echoes. Many observational features of proton cyclotron echoes
can be interpreted by this nonlinear interaction model of two waves.
Description
Keywords
Protons, Cyclotrons, Ionosphere, Wave-particle duality