The Radio Plasma Imager Investigation on the Image Spacecraft

Reinisch, B. W.; Haines, D. M.; Bibl, K.; Cheney, G.; Galkin, I. A.; Huang, Xin; Myers, S. H.; Sales, Gary S.; Benson, Robert F.; Fung, S. F.; Green, J. L.; Boardsen, S. A.; Taylor, William W.; Bougeret, Jean‐Louis; Manning, Robert M.; Meyer‐Vernet, N.; Moncuquet, M.; Carpenter, D. L.; Gallagher, D. L.; Reiff, P. H.

doi:10.1007/978-94-011-4233-5_11

Cited by 121 publications

(135 citation statements)

References 22 publications

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“…Figure 7 shows continuous AKR spectra observed on a day in the northern winter (left panel) and on a day in the northern summer (right panel). In winter, the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) satellite [Reinisch et al, 2000], which has an eccentric polar orbit over the Northern Hemisphere, observed AKR of the form sin ot (Figure 7a). The GEOTAIL satellite in the equatorial magnetosphere also observed AKR (Figure 7b), which showed similar frequency variation as did the northern AKR observed by IMAGE.…”

Section: Observationmentioning

confidence: 99%

Universal time control of AKR: Earth is a spin‐modulated variable radio source

et al. 2013

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[1] Auroral kilometric radiation (AKR) is known to be transient emissions generated by rapidly accelerated electrons together with sudden auroral activation in the polar magnetosphere. In contrast, the characteristics and relationship with the auroral acceleration of rather continuous AKR emissions are not well understood. We examine the emission using long-term data and report that the continuous AKR emission frequency changes with universal time (UT) as the Earth rotates, indicating that the Earth is a spin-modulated variable radio source. The observed UT variation of AKR frequency means that the acceleration altitude changes periodically with planetary rotation. The observations indicate that the diurnal wobble of the tilted geomagnetic field in the solar wind flow alters the magnetosphere-ionosphere (M-I) coupling state in the polar magnetosphere, giving rise to periodic variation of auroral particle acceleration altitude. These observations of planetary radio wave properties provide insight into the physics of planetary particle acceleration.

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Section: Observationmentioning

confidence: 99%

Universal time control of AKR: Earth is a spin‐modulated variable radio source

et al. 2013

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“…The design and measurement characteristics of RPI have been described in detail by Reinisch et al (2000).…”

Section: Radio Observations In Space With Image/rpimentioning

confidence: 99%

CLUSTER and IMAGE: New Ways to Study the Earth’s Plasmasphere

et al. 2009

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Ground-based instruments and a number of space missions have contributed to our knowledge of the plasmasphere since its discovery half a century ago, but it is fair to say that many questions have remained unanswered. Recently, NASA's IMAGE and ESA's CLUSTER probes have introduced new observational concepts, thereby providing a nonlocal view of the plasmasphere. IMAGE carried an extreme ultraviolet imager producing global pictures of the plasmasphere. Its instrumentation also included a radio sounder for remotely sensing the spacecraft environment. The CLUSTER mission provides observations at four nearby points as the four-spacecraft configuration crosses the outer plasmasphere on every perigee pass, thereby giving an idea of field and plasma gradients and of electric current density. This paper starts with a historical overview of classical single-spacecraft data interpretation, discusses the non-local nature of the IMAGE and CLUSTER measurements, and emphasizes the importance of the new data interpretation tools that have been developed to extract non-local information from these observations. The paper reviews these innovative techniques and highlights some of them to give an idea of the flavor of these methods. 8 J. De Keyser et al.In doing so, it is shown how the non-local perspective opens new avenues for plasmaspheric research.

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“…More recent satellite missions reported observations of waves related to the local F lh resonance, and discussed their generation, in particular by excitation via ordinary electromagnetic whistler-mode waves, both of natural and man-made origin (Bell et al, 1991, and references therein;Shklyar et al, 2010). Recently, F lh has been determined from the cut-offs of whistler-mode echoes of sounder-transmitted waves by the Radio Plasma Imager (RPI) (Reinish et al, 2000) on the IMAGE satellite when RPI is sounding from 6 to 63 kHz (Sonwalkar et al, 2008;see plasmagrams in Fig. 5, Sonwalkar et al, 2011a).…”

Section: Introductionmentioning

confidence: 99%

Lower hybrid resonances stimulated by the four CLUSTER relaxation sounders deep inside the plasmasphere: observations and inferred plasma characteristics

Kougblénou¹,

Lointier²,

Décréau³

et al. 2011

Ann. Geophys.

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Abstract. The frequency range of the WHISPER relaxation sounder instrument on board CLUSTER, 4-80 kHz, has been chosen so as to encompass the electron gyro-frequency, F ce , and the electron plasma frequency, F p , in most regions to be explored. Measurement of those frequencies, which are triggered as resonances by the sounder, provides a direct estimation of in situ fundamental plasma characteristics: electron density and magnetic field intensity. In the late mission phase, CLUSTER penetrated regions deep inside the plasmasphere where F ce and F p are much higher than the upper frequency of the sounder's range. However, they are of the right order of magnitude as to place the lower hybrid frequency, F lh , in the 4-15 kHz band. This characteristic frequency, placed at a resonance of the medium, is triggered by the sounder's transmitter and shows up as an isolated peak in the received spectrum, not present in spectra of naturally occuring VLF waves. This paper illustrates, from analysis of case events, how measured F lh values give access to a plasma diagnostic novel of its kind. CLUSTER, travelling along its orbit, encounters favourable conditions where F ce is increasing and F p decreasing, such that F ce /F p increases from values below unity to values above unity. Measured F lh values thus give access, in turn, to the effective mass, M eff , indicative of plasma ion composition, and to the core plasmasphere electron density value, a parameter difficult to measure. The analysed case events indicate that the estimated quantities (M eff in the 1.0-1.4 range, N e in the 5 × 10 2 -10 4 cm −3 range) are varying with external factors (altitude, L value, geomagnetic activity) in a plausible way. Although covering only a restricted region (mid-latitude, low altitude inner plasmasphere), these measurements are available, sinceCorrespondence to: S. Kougblénou (sena.kougblenou@cnrs-orleans.fr) late 2009, for all CLUSTER perigee passes not affected by eclipses (on average, roughly a third of a total of ∼200 passes per year) and offer multipoint observations previously unavailable in this region.

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The Radio Plasma Imager Investigation on the Image Spacecraft

Cited by 121 publications

References 22 publications

Universal time control of AKR: Earth is a spin‐modulated variable radio source

Universal time control of AKR: Earth is a spin‐modulated variable radio source

CLUSTER and IMAGE: New Ways to Study the Earth’s Plasmasphere

Lower hybrid resonances stimulated by the four CLUSTER relaxation sounders deep inside the plasmasphere: observations and inferred plasma characteristics

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