Interference fringes detected by OEDIPUS C

James, H. G.; Calvert, W.

doi:10.1029/98rs00446

Cited by 25 publications

(41 citation statements)

References 12 publications

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“…The forward payload carried a digitally controlled radio transmitter called the high-frequency exciter (HEX), whose signals could be fed into two pairs of 19-m tipto-tip V-shaped dipoles or into the tether [James and Calvert, 1998]. The V shape was adapted to produce linearly polarized fields in the antenna plane perpendicular to B.…”

Section: Instrumentation and Experimental Backgroundmentioning

confidence: 99%

Electron acceleration by megahertz waves during OEDIPUS C

Huang¹,

Burke²,

Hardy³

et al. 2001

J. Geophys. Res.

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Abstract. Observations of Electric Field Distributions in the Ionospheric Plasma-A Unique Strategy (OEDIPUS C) was a tethered mother-son experiment that was launched northward from the Poker Flat rocket range at 0638 UT on November 7, 1995, across a sequence of a. uroral structures. During the flight's upleg the magnetically aligned tether was deployed to a separation of ,,•1.2 km and then cut at both ends. The forward payload contained a 50-kHz to 8-MHz steppedfrequency transmitter. Receivers were carried on both forward and aft payloads. The transmitter swept through the frequency range every 0.5 s. During each of the 3-ms steps the transmitter emitted only for the first 0.3 ms. The scientific complement also included multiangular electrostatic analyzers on both payloads that were sensitive to fluxes of electrons with energies from 20 eV to 20 keV. The durations of sampling and frequency steps were matched. During the flight the electron gyrofrequency was approximately twice the plasma frequency. When the transmitter swept through the lo½•1 gyrofrequency, the particle detectors on both payloads detected sounder-accelerated electrons (SAEs) independent of the energy steps being sampled. In addition, SAEs were detected at the aft payload out to separations of several hundred meters for wa,ve emissions at harmonics of the electron gyrofrequency as well as in the upper hybrid and whistler bands. As the vehicle separation increased, significant time differences developed between the wave-emission pulses a, nd the onsets/durations of SAE detections. The data indicate that electrons were heated through strong wa, ve-partic]e interactions. However, a simple resonant-interaction explana, tion •ppears inadequate. We outline requirements for any models purporting to explain OEDIPUS C measurements.

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Section: Instrumentation and Experimental Backgroundmentioning

confidence: 99%

Electron acceleration by megahertz waves during OEDIPUS C

Huang¹,

Burke²,

Hardy³

et al. 2001

J. Geophys. Res.

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“…[8] The reader is referred to previous publications about OC for more detailed descriptions of the principal features of the OC suborbital flight and the operational modes of the HEX-REX combination [James and Calvert, 1998;James et al, 1999].…”

Section: Experiments Descriptionmentioning

confidence: 99%

“…Figure 1b gives the history of the angle d between the subpayload separation vector r and B, and of the separation magnitude jrj = S T . Figure 1c is a plot of the electron density local to the payload, as scaled from ionograms [James and Calvert, 1998]. …”

Section: Experiments Descriptionmentioning

confidence: 99%

Electromagnetic whistler‐mode radiation from a dipole in the ionosphere

James

2003

Radio Science

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[1] Dipole-antenna radiation theory has been tested for electromagnetic whistler-mode waves in the frequency range 0.1-1.3 MHz using data from the two-point rocket experiment Observations of Electric-field Distributions in the Ionospheric Plasma; a Unique Strategy (OEDIPUS) C. Waves were emitted from a double-V dipole on a transmitting subpayload and received at a distance of about 1200 m on a similar dipole connected to a synchronized receiver. The magnitudes of transmitted signals predicted by a theory for short dipoles have been found to be in good agreement with observations. The agreement is very good in the top two thirds of the frequency range where the dispersion relation and the geometry provide only one saddle-point solution with the required group direction. In this part of the parameter space studied, the transmitterreceiver separation is at least 10 wavelengths. This is not always true at the lowest frequencies, where the expected effects of interference of multiple saddle-point rays and of the oblique resonance cone are observed.

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“…Distributions in the Ionospheric Plasma--A Unique Strategy A (OEDIPUS-A) [James, 1991[James, , 1993 and OEDIPUS-C [James and Calvert, 1998] bistatic rocket payloads carried out a variety of active and passive experiments that give a different perspective on plasma wave and EM-wave propagation in the ionosphere than that provided by monostatic sounders. In addition, the bistatic HF Paper number 1999JA900427.…”

Section: The Observations Of Electric-fieldmentioning

confidence: 99%

“…Figure 3d gives the history of the electron density at the payload. These values that are scaled from the ionograms using characteristic cutoff frequencies of the cold plasma theory [James and Calvert, 1998], reached the instrumental lower limit of -100 cm -3. Near apogee, extremely low densities are observed, such that fp/fc -< O.…”

Section: Geophysical Conditions On November 7 1995mentioning

confidence: 99%

OEDIPUS‐C topside sounding of a structured auroral E region

Prikryl¹,

James²,

Knudsen³

et al. 2000

J. Geophys. Res.

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Abstract. The Observations of Electric-field Distributions in the Ionospheric Plasma--A Unique Strategy C (OEDIPUS-C) rocket payload was launched from Poker Flat, Alaska, into an evening aurora at 0638 UT, on November 7, 1995. The payload included a tethered HF transmitter-receiver pair which acted as a topside sounder. The bistatic (twopoint) configuration allowed an in situ calibration of the radiated power. The conditions in the magnetosphere and ionosphere during the experiment were monitored by a groundbased network of instruments and by instruments on the GOES 7 satellite in a geosynchronous orbit. In this paper we present results of the data analysis of topside ionograms that were obtained during the down-leg flight of OEDIPUS-C (OC). The relatively low altitudes through which OC carried out topside sounding make the resulting ionograms a novel data set. Ionospheric reflections of the 10-W transmissions were detected at payload heights between 780 and 160 km on the down leg. Near apogee at 824 km, extremely low electron densities (-100 cm -3) were observed. The monotonic rise in electron density at the payload from apogee to reentry clearly showed that there was no ionospheric F layer peak. The topside-sounding echoes came from all heights between the payload and the E layer peak around 100 km altitude. Strong X-mode ionospheric reflections plus strong O-mode ground reflections were observed. OC thus has provided a close-hand view of a thick, highly structured, auroral E layer sounded at small ranges. The RF signal was efficiently guided along the magnetic field aligned density depletions that were located at the equatorward edges of auroral arcs. Large pulse-to-pulse variations in the amplitude of the ionospheric reflection are not explained by ducting in the geometricoptics sense.

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Interference fringes detected by OEDIPUS C

Cited by 25 publications

References 12 publications

Electron acceleration by megahertz waves during OEDIPUS C

Electron acceleration by megahertz waves during OEDIPUS C

Electromagnetic whistler‐mode radiation from a dipole in the ionosphere

OEDIPUS‐C topside sounding of a structured auroral E region

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