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Woolliscroft, L. J. C.; Alleyne, H.; Dunford, C.; Sumner, A.E.; Thompson, J. A.; Walker, S. N.; Yearby, K. H.; Buckley, A M; Chapman, Sandra C.; Gough, M. P.

doi:10.1023/a:1004914211866

Cited by 34 publications

(17 citation statements)

References 3 publications

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“…The acquisition intervals are placed 13.3 ms apart. Successive electric field magnitude frequency spectra, calculated by FFT (fast Fourier transform) every 13.3 ms, are accumulated on board by the DWP (Digital Wave Processing) instrument, bin to bin, to form a single "accumulated" spectrum (Woolliscroft et al, 1997;Trotignon et al, 2010). Due to different operating capabilities of WHISPER instruments on board C3 and C4 (the latter having lost a memory word in year 2003), "accumulated" spectra are available more frequently on C3 (32 individual spectra accumulated every 0.426 s) than on C4 (64 individual spectra accumulated every 0.852 s).…”

Section: Measured Quantitiesmentioning

confidence: 99%

Remote sensing of a NTC radio source from a Cluster tilted spacecraft pair

Décréau¹,

Kougblénou²,

Lointier³

et al. 2013

Ann. Geophys.

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Abstract. The Cluster mission operated a "tilt campaign" during the month of May 2008. Two of the four identical Cluster spacecraft were placed at a close distance (∼ 50 km) from each other and the spin axis of one of the spacecraft pair was tilted by an angle of ∼ 46 • . This gave the opportunity, for the first time in space, to measure global characteristics of AC electric field, at the sensitivity available with long boom (88 m) antennas, simultaneously from the specific configuration of the tilted pair of satellites and from the available base of three satellites placed at a large characteristic separation (∼ 1 R E ). This paper describes how global characteristics of radio waves, in this case the configuration of the electric field polarization ellipse in 3-D-space, are identified from in situ measurements of spin modulation features by the tilted pair, validating a novel experimental concept. In the event selected for analysis, non-thermal continuum (NTC) waves in the 15-25 kHz frequency range are observed from the Cluster constellation placed above the polar cap. The observed intensity variations with spin angle are those of plane waves, with an electric field polarization close to circular, at an ellipticity ratio e = 0.87. We derive the source position in 3-D by two different methods. The first one uses ray path orientation (measured by the tilted pair) combined with spectral signature of magnetic field magnitude at source. The second one is obtained via triangulation from the three spacecraft baseline, using estimation of directivity angles under assumption of circular polarization. The two results are not compatible, placing sources widely apart. We present a general study of the level of systematic errors due to the assumption of circular polarization, linked to the second approach, and show how this approach can lead to poor triangulation and wrong source positioning. The estimation derived from the first method places the NTC source region in the dawn sector, at a large L value (L ∼ 10) and a medium geomagnetic latitude (35 • S). We discuss these untypical results within the frame of the geophysical conditions prevailing that day, i.e. a particularly quiet long time interval, followed by a short increase of magnetic activity.

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Section: Measured Quantitiesmentioning

confidence: 99%

Remote sensing of a NTC radio source from a Cluster tilted spacecraft pair

Décréau¹,

Kougblénou²,

Lointier³

et al. 2013

Ann. Geophys.

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“…For E pow parameters, the corresponding time resolutions are 213 ms and 13 ms, respectively (Décréau et al, 1997). Further details on different operational modes of WEC and WHISPER are described elsewhere (Pedersen et al, 1997;Décréau et al, 1997;Woolliscroft et al, 1997).…”

Section: Data Selection and Analysis Proceduresmentioning

confidence: 99%

On nonstationarity and rippling of the quasiperpendicular zone of the Earth bow shock: Cluster observations

et al. 2008

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Abstract. A new method for remote sensing of the quasiperpendicular part of the bow shock surface is presented. The method is based on analysis of high frequency electric field fluctuations corresponding to Langmuir, upshifted, and downshifted oscillations in the electron foreshock. Langmuir waves usually have maximum intensity at the upstream boundary of this region. All these waves are generated by energetic electrons accelerated by quasiperpendicular zone of the shock front. Nonstationary behavior of the shock, in particular due to rippling, should result in modulation of energetic electron fluxes, thereby giving rise to variations of Langmuir waves intensity. For upshifted and downshifted oscillations, the variations of both intensity and central frequency can be observed. For the present study, WHISPER measurements of electric field spectra obtained aboard Cluster spacecraft are used to choose 48 crossings of the electron foreshock boundary with dominating Langmuir waves and to perform for the first time a statistical analysis of nonstationary behavior of quasiperpendicular zone of the Earth's bow shock. Analysis of hidden periodicities in plasma wave energy reveals shock front nonstationarity in the frequency range 0.33 f Bi

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“…Because the amplitudes of Langmuir waves in the Earth's foreshock can change on time scales of 1 ms or less, the 0.1 s time period of the Digital Wave Processor (DWP) (Woolliscroft et al, 1997) gain update clock results in occasional clipping of the waveform peaks when the wave amplitudes exceed the maximum range for a particular gain state. On 17 February 2002, the WBD receiver on spacecraft 4 was operated with the gain manually set to 0 dB.…”

Section: Instrumentationmentioning

confidence: 99%

Statistical behavior of foreshock Langmuir waves observed by the Cluster wideband data plasma wave receiver

Sigsbee

Kletzing²,

Gurnett³

et al. 2004

Ann. Geophys.

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Abstract. We present the statistics of Langmuir wave amplitudes in the Earth's foreshock using Cluster Wideband Data (WBD) Plasma Wave Receiver electric field waveforms from spacecraft 2, 3 and 4 on 26 March 2002. The largest amplitude Langmuir waves were observed by Cluster near the boundary between the foreshock and solar wind, in agreement with earlier studies. The characteristics of the waves were similar for all three spacecraft, suggesting that variations in foreshock structure must occur on scales greater than the 50-100 km spacecraft separations. The electric field amplitude probability distributions constructed using waveforms from the Cluster WBD Plasma Wave Receiver generally followed the log-normal statistics predicted by stochastic growth theory for the event studied. Comparison with WBD receiver data from 17 February 2002, when spacecraft 4 was set in a special manual gain mode, suggests nonoptimal auto-ranging of the instrument may have had some influence on the statistics.

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Cited by 34 publications

References 3 publications

Remote sensing of a NTC radio source from a Cluster tilted spacecraft pair

Remote sensing of a NTC radio source from a Cluster tilted spacecraft pair

On nonstationarity and rippling of the quasiperpendicular zone of the Earth bow shock: Cluster observations

Statistical behavior of foreshock Langmuir waves observed by the Cluster wideband data plasma wave receiver

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