Analytical determination of propagation paths near gyroharmonics

Self Cite

The waveforms and envelopes of resonance signals observed in the ionosphere at 2, 3, 4, and 5fH by rocket experiment are compared with the analytical results provided by a spatial ray‐tracing procedure which takes the gradient of Earth's magnetic field into account. An approximate calculation yields the algebraic expression of the wave damping from whence the decrease of the received signals is deduced versus time as well as their frequency variations.

“…As the difference between 0 and xr/2 is shown to be less than 1 ø [Bitoun, 1974] ---2(N-1)½toHkz/(k2y + kz 2)…”

Section: Gyroharmonicsmentioning

confidence: 95%

“…Theoretical equations obtained in a preceding paper [Bitoun, 1974] are generalized here to a three-dimensional reference system. The main features of the basic hypotheses are discussed briefly, and we point out the quantitative determination of wave damping.…”

Section: Introductionmentioning

confidence: 99%

Theoretical study of gyroresonances with application to rocket experiments

Bitoun¹,

Fleury²,

Higel³

1975

Self Cite

“…(It should be noted, however, that these observational differences in signal time duration and intensity between the 2fu and Q3 waves may be partly due to their different propagational characteristics. The Q3 signal is attributed to sounder-generated electrostatic waves that have a group velocity nearly matched to the satellite velocity[Muldrew, 1972a], whereas the 2fu signal is usually attributed to sounder-generated electrostatic waves that are reflected in the ambient plasma and returned to the sounder antenna as demonstrated numerically for the 3fH wave byMuldrew [ 1972b] and analytically for the nfu waves with n > 1 byBitoun [1974] and Bitoun et al [1975]; this analytical treatment, while not successful in explaining satellite 2fH resonance observations [Benson and Bitoun, 1979], has been successful in explaining rocket 2fu resonance observations [Bitoun et al, 1975].) The original argument by Oya [1971], that the Q3 resonance was of fundamental importance in the process of maintaining the long time duration of the D1 resonance, was based on the observed strong coupling of the variations of the frequenciesfa 3 andfo• on a diagram like Figure 3, i.e.,f Q3 --•foi + 2ftt.…”

mentioning

confidence: 99%

Stimulated plasma instability and nonlinear phenomena in the ionosphere

Benson¹

1982

Several hundred topside ionograms, corresponding to both high‐ and low‐power sounder operation, were used to investigate stimulated wave‐particle interactions in the ionosphere. The investigation combined the benefits of high frequency resolution Alouette 2 analog sounder data with modern digital graphics techniques. One of the main conclusions of the study is that the sounder pulse can cause significant plasma heating when the plasma parameter ƒN/ƒH is confined to specific ranges, where ƒN is the plasma frequency and ƒH is the electron cyclotron frequency. This heating is indicated by a variety of diffuse plasma signal returns that appear to be generated in a plasma which is driven into a state of turbulence by the sounder pulse. The signals are observed primarily in the range of ƒz ≲ nƒH ≲ ƒT where ƒT is the upper hybrid frequency, ƒz is the cutoff of the electromagnetic z wave (the lower‐frequency branch of the extraordinary mode), and n is an integer ≥ 1. The case n = 1 corresponds to a newly discovered diffuse resonance observed at a frequency designated by ƒDNT which is confined between ƒN and ƒT. It is observed over nearly the complete limits of the above frequency range, i.e.,ƒz ≲ ƒH ≲ ƒT. The characteristics of the ƒDNT resonance reveal a dramatic change as the ambient plasma parameter ƒN/ƒH increases from ƒN/ƒH < 1 to ƒN/ƒH > 1. The phenomena associated with n > 1 (some reported here for the first time) are restricted to narrower frequency limits of nƒH within the ƒz to ƒT range. Such restrictions of the stimulated phenomena to certain ƒN/ƒH values suggest that the source of the heating is the absorption of energy from slowly propagating sounder‐stimulated plasma waves rather than directly from the RF fields associated with the brief sounder pulse. The sequence of diffuse resonances observed at frequencies below ƒT and between the nƒH harmonics has previously been attributed to a sounder‐initiated instability combined with a nonlinear sustaining mechanism. Several theories have been proposed. The present observations provide strong support for the Harris instability generation process and the nonlinear Landau damping maintaining process for the long‐duration diffuse resonances, and indicate that the nonlinear three‐wave interaction process may be important for the short‐duration diffuse resonances. The so‐called Q resonances observed at frequencies above ƒT and between the nƒH harmonics have previously been attributed to nearly pure Bernstein mode waves stimulated by the sounder pulse. The present observations, however, indicate that these resonances have some characteristics which imply that generation processes in a sounder‐stimulated plasma turbulence may be involved. These Q resonances, which are often observed to ‘float’ away from the zero time delay baseline, are here found to occasionally have nonfloating subsidiary components. The short‐time‐duration resonances observed at the harmonics and sum and differrence frequencies of the long‐duration plasma resonances at ƒN, ƒT, ƒH, and 2ƒH were found t...

“…In this case, the HEX-REX separation (<100 m) may be small enough to permit the aft payload to detect the ES waves directly. Ray tracing results for frequencies near nfc [Muldrew, 1972;Bitoun, 1974] show that the least damped ES waves have raypaths largely along the magnetic field axis, travelling distances up to about 1 km. The absence of positive ES wave WAVES ON OEDIPUS A 69 signatures after about the 100-m separation may be caused by the thermal damping of these waves.…”

Section: Connectionsmentioning

confidence: 99%

Sheath waves observed on OEDIPUS A

James¹,

Balmain²,

Bantin³

et al. 1995

An important novel feature of the tethered sounding rocket experiment OEDIPUS A (Observations of Electric‐field Distributions in the Ionospheric Plasma—A Unique Strategy) was its direct excitation and detection of electromagnetic waves on conductors in space plasmas. We present quantitative evidence about sheath waves excited in the ionosphere by a high‐frequency transmitter on one end of the 1‐km tether and detected by a synchronized receiver on the other end. An important characteristic of sheath waves is their sequence of sharply defined passbands and stop bands in the frequency range 0.1–5 MHz. The lowest passband is between 0.1 MHz and the plasma frequency near 2 MHz, the bandwidth where existing theory predicts sheath waves. Resonance fringes in this band have been scaled to determine the phase and group refractive indices of sheath waves. These agree reasonably well with the theory, considering the approximations therein. Passbands and stop bands observed in the range between 2 and 5 MHz are not expected on the basis of the current theory. In this range, band limits have clear signatures of the interaction of the tether fields with electrostatic cyclotron waves. Finite wire moment method modeling of the payload shows that in the low‐frequency passband, RF coupling along the tether is increased by 20 dB over vacuum conditions. Similarly, isolation is greater than vacuum isolation in the stop bands. Because sheath waves at frequencies up to 2 MHz are guided efficiently along conductors in plasma, they are a significant design issue in the electromagnetic compatibility of avionics at frequencies up to HF on large metal space structures.