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Balogh, A.; Dunlop, M. W.; Cowley, S. W. H.; Southwood, D. J.; Thomlinson, J. G.; Glaßmeier, K.‐H.; Musmann, G.; Lühr, H.; Buchert, Stephan; Acuña, M. H.; Fairfield, D. H.; Slavin, J. A.; Riedler, W.; Schwingenschuh, K.; Kivelson, M. G.

doi:10.1023/a:1004970907748

Cited by 356 publications

(167 citation statements)

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“…We will utilize data from two of the instruments on the Cluster satellites; the Electric Field and Wave Instrument (EFW) (Gustafsson et al, 1997), and the Fluxgate Magnetometer (FGM) (Balogh et al, 1997). The Cluster satellites were launched on 16 July and 9 August 2000 as a replacement of the original Cluster satellites which were lost due to a failure of the original launch in 1996.…”

Section: Event Overviewmentioning

confidence: 99%

Separating spatial and temporal variations in auroral electric and magnetic fields by Cluster multipoint measurements

Karlsson¹,

Marklund²,

Figueiredo³

et al. 2004

Ann. Geophys.

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Abstract. Cluster multipoint measurements of the electric and magnetic fields from a crossing of auroral field lines at an altitude of 4 R E are used to show that it is possible to resolve the ambiguity of temporal versus spatial variations in the fields. We show that the largest electric fields (of the order of 300 mV/m when mapped down to the ionosphere) are of a quasi-static nature, unipolar, associated with upward electron beams, stable on a time scale of at least half a minute, and located in two regions of downward current. We conclude that they are the high-altitude analogues of the intense return current/black auroral electric field structures observed at lower altitudes by Freja and FAST. In between these structures there are temporal fluctuations, which are shown to likely be downward travelling Alfvén waves. The periods of these waves are 20-40 s, which is not consistent with periods associated with either the Alfvénic ionospheric resonator, typical field line resonances or substorm onset related Pi2 oscillations. The multipoint measurements enable us to estimate a lower limit to the perpendicular wavelength of the Alfvén waves to be of the order of 120 km, which suggests that the perpendicular wavelength is similar to the dimension of the region between the two quasi-static structures. This might indicate that the Alfvén waves are ducted within a wave guide, where the quasi-static structures are associated with the gradients making up this waveguide.

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Section: Event Overviewmentioning

confidence: 99%

Separating spatial and temporal variations in auroral electric and magnetic fields by Cluster multipoint measurements

Karlsson¹,

Marklund²,

Figueiredo³

et al. 2004

Ann. Geophys.

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“…The k-filtering technique is a generalized minimum variance technique introduced into space science by Pinçon and Lefeuvre [1991]. This technique allows one to estimate the magnetic wave field energy distribution P(w, k) in the frequency and wave vector domain from data measured simultaneously at several points in space, under the assumption of (sufficient) stationarity of the time series (more details on this technique are given by Pinçon and Lefeuvre [1991], Pinçon and Motschmann [1998], Sahraoui et al [2003Sahraoui et al [ , 2010 [Balogh et al, 1997], and the Electric Fields and Waves (EFW) instrument provides 25 Hz electric field data [Gustafson et al, 1997]. Plasma data on ions and electrons (with 4 s resolution) were obtained from the Cluster Ion Spectrometry (CIS) and plasma electron and current experiment (PEACE) instruments, respectively [Rème et al, 2001;Johnstone et al, 1997].…”

Section: Introductionmentioning

confidence: 99%

Wave properties in the magnetic reconnection diffusion region with high β: Application of the k‐filtering method to Cluster multispacecraft data

et al. 2010

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[1] Magnetic reconnection is a crucial physical process in laboratory and astrophysical plasmas. Plasma waves are believed to provide the dissipation mechanism in magnetic reconnection. In this paper we analyze the properties of low-frequency waves in a magnetotail reconnection diffusion region with a small guide field and high b. Using the k-filtering method on the magnetic field data measured by Cluster spacecraft, we found that low-frequency waves in the diffusion region were highly oblique propagating mode. We compared the measured dispersion relation with theoretical ones calculated using the linear (hot) two-fluid and Vlasov-Maxwell theory. It is found that the observed waves in the diffusion region (with high plasma b) follow the dispersion relation of the Alfvén-Whistler wave mode. Comparisons with previous simulations and observational results are also discussed.

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“…The spectrogram was created by taking 1024 samples of the time series and transforming these data to the frequency domain by using a Fast Fourier Transform. The white line in each panel is the electron cyclotron frequency, as determined from the Fluxgate Magnetometer, FGM (see Balogh et al, 1997). Figure 1b shows a 25 msec line plot of the waveform beginning at 02:48:42.546 UT obtained by WBD on C4 (Cluster 4) from the 6-min interval seen in the spectrogram.…”

Section: Introductionmentioning

confidence: 99%

Isolated electrostatic structures observed throughout the Cluster orbit: relationship to magnetic field strength

et al. 2004

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Abstract. Isolated electrostatic structures are observed throughout much of the 4 R E by 19.6 R E Cluster orbit. These structures are observed in the Wideband plasma wave instrument's waveform data as bipolar pulses (one positive and one negative peak in the electric field amplitude) and tripolar pulses (two positive and one negative peak, or vice versa). These structures are observed at all of the boundary layers, in the solar wind and magnetosheath, and along auroral field lines at 4.5-6.5 R E . Using the Wideband waveform data from the various Cluster spacecraft we have carried out a survey of the amplitudes and time durations of these structures and how these quantities vary with the local magnetic field strength. Such a survey has not been carried out before, and it reveals certain characteristics of solitary structures in a finite magnetic field, a topic still inadequately addressed by theories. We find that there is a broad range of electric field amplitudes at any specific magnetic field strength, and there is a general trend for the electric field amplitudes to increase as the strength of the magnetic field increases over a range of 5 to 500 nT. We provide a possible explanation for this trend that relates to the structures being Bernstein-GreeneKruskal mode solitary waves. There is no corresponding dependence of the duration of the structures on the magnetic field strength, although a plot of these two quantities reveals the unexpected result that with the exception of the magnetosheath, all of the time durations for all of the other regions are comparable, whereas the magnetosheath time durations clearly are in a different category of much smaller time duration. We speculate that this implies that the structures are much smaller in size. The distinctly different pulse durations for the magnetosheath pulses indicate the possibility that the pulses are generated by a mechanism which is different from the mechanism operating in other regions.

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Cited by 356 publications

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Separating spatial and temporal variations in auroral electric and magnetic fields by Cluster multipoint measurements

Separating spatial and temporal variations in auroral electric and magnetic fields by Cluster multipoint measurements

Wave properties in the magnetic reconnection diffusion region with high β: Application of the k‐filtering method to Cluster multispacecraft data

Isolated electrostatic structures observed throughout the Cluster orbit: relationship to magnetic field strength

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