Identification of natural plasma emissions observed close to the plasmapause by the Cluster-Whisper relaxation sounder

Canu, P.; Décréau, Pierrette; Trotignon, Jean-Gabriel; Rauch, Jean-Louis; Séran, H. C.; Fergeau, P.; Lévèque, M.; Martin, Ph.; Sené, F. X.; Guirriec, E. Le; Alleyne, H.; Yearby, K. H.

doi:10.5194/angeo-19-1697-2001

Cited by 30 publications

(30 citation statements)

References 32 publications

(55 reference statements)

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“…In the passive mode, natural wave bands between two successive harmonics of the electron gyro-frequency can be observed. We used these active and passive measurements to obtain the electron density through the method specified by Canu et al (2001) and Trotignon et al (2001Trotignon et al ( , 2003. The density derived from the local measurement provided by WHISPER along the spacecraft orbit was used to derive the density along L shells using an R −4 model for the electron density (Persoon et al, 1983;Gallagher et al, 2000).…”

Section: Simulation Results: the Ray-tracing Techniquementioning

confidence: 99%

Cluster observations of ELF/VLF signals generated by modulated heating of the lower ionosphere with the HAARP HF transmitter

et al. 2004

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Abstract.It is now well known that amplitude modulated HF transmissions into the ionosphere can be used to generate ELF/VLF signals using the so-called "electrojet antenna". Although most observations of the generated ELF/VLF signals have been made on the ground, several low and highaltitude satellite observations have also been reported (James et al., 1990). One of the important unknowns in the physics of ELF/VLF wave generation by ionospheric heating is the volume of the magnetosphere illuminated by the ELF/VLF waves. In an attempt to investigate this question further, ground-satellite conjunction experiments have recently been conducted using the four Cluster satellites and the HF heater of the High-Frequency Active Auroral Research Program (HAARP) facility in Gakona, Alaska. Being located on largely closed field lines at L≈4.9, HAARP is currently also being used for ground-to-ground type of ELF/VLF waveinjection experiments, and will be increasingly used for this purpose as it is now being upgraded for higher power operation. In this paper, we describe the HAARP installation and present recent results of the HAARP-Cluster experiments. We give an overview of the detected ELF/VLF signals at Cluster, and a possible explanation of the spectral signature detected, as well as the determination of the location of the point of injection of the HAARP ELF/VLF signals into the magnetosphere using ray tracing.

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Section: Simulation Results: the Ray-tracing Techniquementioning

confidence: 99%

Cluster observations of ELF/VLF signals generated by modulated heating of the lower ionosphere with the HAARP HF transmitter

et al. 2004

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“…Intense chorus was observed by the WBD, STAFF, and Whisper wave instruments. Plasma density of a few particles per cm 3 , indicative of magnetospheric regions outside the plasmasphere, was estimated from the Whisper data (P. Canu, private communication, 2002;Canu et al, 2001). The WBD instruments measured continuous waveforms with pass-band filters between 50 Hz and 9.5 kHz, mainly using the 88-m electric double-sphere antennas (for short periods of time, signals from magnetic search coil antennas were transmitted-these data are not shown here).…”

Section: Time-frequency Characteristics Of Chorus In the Source Regionmentioning

confidence: 99%

Multipoint investigation of the source region of storm-time chorus

2004

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Abstract. In this case study we investigate the source region of whistler-mode chorus located close to the geomagnetic equator at a radial distance of 4.4 Earth radii. We use measurements from the four Cluster spacecraft at separations of less than a few hundreds of km, recorded during the geomagnetic storm of 18 April 2002. The waveforms of the electric field fluctuations were obtained by the WBD instruments in the frequency range 50 Hz-9.5 kHz. Using these data, we calculate linear and rank correlation coefficients of the frequency averaged power-spectral density measured by the different spacecraft. Those coefficients have been recently shown to decrease with spacecraft separation distance perpendicular to the static magnetic field (Santolík and Gurnett, 2003) with a characteristic scale length of 100 km. We find this characteristic scale varying between 60 and 200 km for different data intervals inside the source region. We examine possible explanations for the observed large scatter of the correlation coefficients, and we suggest a simultaneously acting effect of random positions of locations at which the individual chorus wave packets are generated. The statistical properties of the observations are approximately reproduced by a simple 2-D model of the source region, assuming a perpendicular half-width of 35 km (approximately one wavelength of the whistler-mode waves) for the distribution of power radiated from individual active areas.

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“…Trotignon et al (2001) explains how the WHISPER measurements can be used to determine electron density, and Canu et al (2001) discuss the natural plasma emissions observed close to the plasmapause. WHISPER data are extremely rich and the subject of ongoing interpretation, but the basic resonances observed in the ambient plasma include the plasma, electron gyro-, upper-hybrid, and Bernstein's mode frequencies.…”

Section: Cluster Satellite Observationsmentioning

confidence: 99%

An auroral westward flow channel (AWFC) and its relationship to field-aligned current, ring current, and plasmapause location determined using multiple spacecraft observations

Parkinson

Wild²,

Waters³

et al. 2007

Ann. Geophys.

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Abstract. An auroral westward flow channel (AWFC) is a latitudinally narrow channel of unstable F-region plasma with intense westward drift in the dusk-to-midnight sector ionosphere. AWFCs tend to overlap the equatorward edge of the auroral oval, and their life cycle is often synchronised to that of substorms: they commence close to substorm expansion phase onset, intensify during the expansion phase, and then decay during the recovery phase. Here we define for the first time the relationship between an AWFC, large-scale field-aligned current (FAC), the ring current, and plasmapause location. The Tasman International Geospace Environment Radar (TIGER), a Southern Hemisphere HF Super-DARN radar, observed a jet-like AWFC during ∼08:35 to 13:28 UT on 7 April 2001. The initiation of the AWFC was preceded by a band of equatorward expanding ionospheric scatter (BEES) which conveyed an intense poleward electric field through the inner plasma sheet. Unlike previous AWFCs, this event was not associated with a distinct substorm surge; rather it occurred during an interval of persistent, moderate magnetic activity characterised by AL∼ −200 nT. The four Cluster spacecraft had perigees within the dusk sector plasmasphere, and their trajectories were magnetically conjugate to the radar observations. The Waves of High frequency and Sounder for Probing Electron density by Relaxation (WHISPER) instruments on board Cluster were used to identify the plasmapause location. The Imager for Magnetopause-to-Aurora Global Exploration (IM-AGE) EUV experiment also provided global-scale observations of the plasmapause. The Cluster fluxgate magnetometers (FGM) provided successive measurements specifying the relative location of the ring current and filamentaryCorrespondence to: M. L. Parkinson (m.parkinson@latrobe.edu.au) plasma sheet current. An analysis of Iridium spacecraft magnetometer measurements provided estimates of large-scale ionospheric FAC in relation to the AWFC evolution. Peak flows in the AWFC were located close to the peak of a Region 2 downward FAC, located just poleward of the plasmapause. DMSP satellite observations confirmed the AWFC was located equatorward of the nightside plasmasheet, sometimes associated with ∼10 keV ion precipitation.

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Identification of natural plasma emissions observed close to the plasmapause by the Cluster-Whisper relaxation sounder

Cited by 30 publications

References 32 publications

Cluster observations of ELF/VLF signals generated by modulated heating of the lower ionosphere with the HAARP HF transmitter

Cluster observations of ELF/VLF signals generated by modulated heating of the lower ionosphere with the HAARP HF transmitter

Multipoint investigation of the source region of storm-time chorus

An auroral westward flow channel (AWFC) and its relationship to field-aligned current, ring current, and plasmapause location determined using multiple spacecraft observations

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