Electron temperature from topside plasma resonance observations

Warnock, J. M.; McAfee, J. R.; Thompson, Thomas L.

doi:10.1029/ja075i034p07272

Cited by 23 publications

(8 citation statements)

References 11 publications

(17 reference statements)

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“…The difference in frequency between the two is about a kilohertz, so that an observable beat is produced in a sounder system by using amplitude detection. Quantitative comparisons between predicted and observed beat patterns yield convincing agreement [Warnock et al, 1970; Feldstein and Gra#, 1972]. This paper describes a rocket-borne sounder experiment.…”

supporting

confidence: 60%

Rocket observation of topside resonances

McAfee¹,

Thompson²,

Calvert³

et al. 1972

J. Geophys. Res.

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In a recent rocket experiment designed to resolve the slow-wave echoes comprising the resonances excited by topside sounders the plasma, the upper hybrid resonance, and the first three electron cyclotron resonances were observed. In particular, the variation of echo frequency versus delay was observed for the upper hybrid resonance. The good agreement ' found between the observed and the predicted frequency delay function confirms the slowwave propagation nature of the phenomenon. The frequency of all three electron cyclotron resonances are consistent with the Pogo (3/68) magnetic-field model within its stated accuracy. Observations of resonances in the ionosphericplasma have been made by topside sounders since 1961 [Lockwood, 1963; Calvert and Goe, 1963; Calvert and McA•ee, 1969]. The experiments consist of exciting the plasma in the vicinity of the spacecraft with a short RF pulse and observing the response with a radio receiver. A resonance consists of an apparent ringing signal lasting a few milliseconds when the system is tuned to certain frequencies. The principal resonances occur at the plasma frequency f•, the upperhybrid frequency f•, and the electron cyclotron frequency fn and its harmonics nfn. Current explanations of the resonances involve the propagation, reflection, and reception of slow waves [McA]ee, 1968, 1969a, b, 1970a, b; Bitoun et al.A continuum of such slow-wave echoes can be found with a specific frequency delay relationship. This could produce a trace on a topside ionogram analogous to the normal electromagnetic-wave traces. However, the range of frequencies contributing to the resonance during a normal listening period is considerably narrower than either the rec.eiver bandwidth or the spectrum of the transmitter pulse. Therefore the echoes from a single pulse cover all delays to produce the apparent ringing signal. Previous satellite experiments were incapable of observing this frequency variation with delay within the receiver bandwidth because of on board signal detection.Previous evidence favoring the echo .explanation has relied on the prediction that two separate sets of echoes can occur when the appropriate conditions are met. One corresponds to waves launched with propagation vector components generally parallel to the spacecraft velocity, and the other to waves in the opposite direction. These two echoes may have different frequency delay variations, and, furthermore, they would experience different Doppler shifts. The difference in frequency between the two is about a kilohertz, so that an observable beat is produced in a sounder system by using amplitude detection. Quantitative comparisons between predicted and observed beat patterns yield convincing agreement [Warnock et al., 1970; Feldstein and Gra#, 1972]. This paper describes a rocket-borne sounder experiment. designed specifically to observe the slow-wave echoes comprising a resonance and reports the major results. EXPERIMENTThe rocket sounder consisted of a frequency synthesizer, a pulsed transmitter, a receiver, a transm...

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supporting

confidence: 60%

Rocket observation of topside resonances

McAfee¹,

Thompson²,

Calvert³

et al. 1972

J. Geophys. Res.

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“…However, the present study confirms the systematic, but unexplained, existence of a phenomenon already pointed out by Warnock et al [1970] and Feldstein and Graff[1972]. The curve representing the beat frequency as a function of time delay shows oscillations superimposed on the smooth curve predicted by theory.…”

Section: R Feldstein's (Private Communication 1972) Computer Prograsupporting

confidence: 90%

“…This theory predicts a spike modulation resulting from the interference between two echoes that differ slightly in frequency. Such frequency beats have been observed and compared successfully with theory by Warnock et al [1970] and Feldstein and Graff[1972]. However, such modulations do not appear on all the observed spikes.…”

supporting

confidence: 66%

Antenna dependence of plasma resonance patterns

Fleury¹,

Petit²

1974

J. Geophys. Res.

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The oblique echo theory is well verified experimentally when the calculated beat times are compared with those observed on the plasma frequency resonance spikes. Yet one point remains unclear: the behavior of the spikes strongly depends upon the antenna orientation, for, in a large number of cases, the beats disappear and the duration of the resonances shortens. It is the purpose of this report to give a simple explanation of this phenomenon by taking into account the finite size of the antenna and its orientation with respect to the static magnetic field.

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“…and Goe, 1963]. Their further theoretical interpretation as oblique echoes in the cases of f•v and fr [McAfee, 1969;Graff, 1971] have led to the measurement of the electron temperature T e from the fine structure of the resonance signals [ Warnock et al, 1970;Feldstein and Graff, 1972]. However, the original Alouette data, which gave only the envelope and not the waveform of the signals, do not provide a rigorous check on the theoretical interpretation at f•v and fr; an extra structure is systematically superimposed upon the theoretical ones, and it remains unexplained ].…”

mentioning

confidence: 99%

“…The spectrum labelled segment 11 is that obtained from The fringe patterns observed on some of the f•v spikes obtained from the Alouette-ISIS data[Calvert and McAfee, 1969] are interpreted byMcAfee [1969] as the beats of the two oblique echo signals. This interpretation is used byWarnock et al [ 1970]…”

mentioning

confidence: 99%

Small‐scale irregularities of electron density in the F region from ƒ_N resonances observed by a rocket‐borne relaxation sounding experiment

Higel¹

1978

Radio Science

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The plasma resonance phenomena observed near the plasma frequency ƒN through active experiments of relaxation sounding have been experimentally investigated within the range 100‐500 km in the ionosphere by means of the three rocket launches of the EIDI payloads (Experiment on the Impedance of a Dipole in the Ionosphere). The design of the EIDI relaxation sounders has been improved with respect to that of previous topside sounding experiments (Alouette and ISIS programs) in that it records both the envelope and the waveform of the resonance signals in a large dynamic range. This allows the study of spectral features of the plasma resonance phenomena. The data of EIDI 3 are first used to point out the accuracy and the reliability of relaxation sounding experiments for the measurement of the ionospheric electron density; the electron density profile obtained is typical of a midlatitude, winter, nighttime ionosphere. Secondly, the spectral features of the ƒN resonance signals are investigated. Their comparison with those predicted by the theory of oblique echoes for the ƒN resonances leads to a disagreement, although the waves received are shown to be the electrostatic slow ones used in this theory. However, a correlation processing between the Fourier spectra of the ƒN resonance signals observed in sequence allows us to point out the existence of small‐scale irregularities of the electron density. This result is inconsistent with the theoretical hypothesis of a linear density variation versus altitude. By taking these irregularities into account, the features of the resonance signals can then be qualitatively explained. The properties deduced from the data regarding the size and the amplitude of the density irregularities are in agreement with those obtained under comparable ionospheric conditions through another kind of experiment for measuring the irregularities (Retarding Potential Analyzer on the OGO 6 satellite). Moreover, the unexplained phenomena of beat frequency oscillations observed on the Alouette and ISIS ƒN resonance data are tentatively interpreted in a similar way through the existence of sinusoidal irregularities of the electron density. Finally, it is pointed out that the relaxation sounding experiment on‐board the GEOS satellite has been designed to provide an effective measurement of the electron density irregularities in the magnetosphere.

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Electron temperature from topside plasma resonance observations

Cited by 23 publications

References 11 publications

Rocket observation of topside resonances

Rocket observation of topside resonances

Antenna dependence of plasma resonance patterns

Small‐scale irregularities of electron density in the F region from ƒ_N resonances observed by a rocket‐borne relaxation sounding experiment

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Electron temperature from topside plasma resonance observations

Cited by 23 publications

References 11 publications

Rocket observation of topside resonances

Rocket observation of topside resonances

Antenna dependence of plasma resonance patterns

Small‐scale irregularities of electron density in the F region from ƒN resonances observed by a rocket‐borne relaxation sounding experiment

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Small‐scale irregularities of electron density in the F region from ƒ_N resonances observed by a rocket‐borne relaxation sounding experiment