Measurement of the Electric Fluctuation Spectrum of Magnetohydrodynamic Turbulence

Bale, S. D.; Kellogg, P. J.; Mozer, F. S.; Horbury, T. S.; Rème, H.

doi:10.1103/physrevlett.94.215002

Cited by 506 publications

(581 citation statements)

References 19 publications

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“…The electric field follows a −1/2 power law, and the magnetic field follows a −2.15 power law between 0.35 and 3 Hz. Similar observations have been reported in the solar wind and in the magnetotail [Bale et al, 2005;Chaston et al, 2009;Sahraoui et al, 2009].…”

Section: Overview Of the Cluster Observationssupporting

confidence: 89%

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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Section: Overview Of the Cluster Observationssupporting

confidence: 89%

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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“…However, observations of power law spectra at k ⊥ ρ p 1 (Sahraoui et al, , 2010Alexandrova et al, 2009;Kiyani et al, 2009) suggest a continuation of the cascade that is consistent with the theoretical picture of KAWs (Bale et al, 2005;Schekochihin et al, 2009;Sahraoui et al, 2010). It has been envisaged that the nonlinear evolution and related wavenumber spectra in the range below k ⊥b are dominated by MHD-type nonlinear interactions among Alfvén waves, and that the spectra for k ⊥ > k ⊥b are determined by KAW properties (Schekochihin et al, 2009).…”

Section: Introductionsupporting

confidence: 57%

“…There are numerous observational and theoretical indications that MHD Alfvén turbulence in the solar wind cascades towards high k ⊥ and eventually reaches the KAW wavenumber range at the proton gyroradius scales, k ⊥ ρ p ∼ 1 Bale et al, 2005;Alexandrova et al, 2008a;Sahraoui et al, 2009Sahraoui et al, , 2010. It is not yet certain what happens next with these KAWs: do they dissipate by heating the plasma , or do they interact nonlinearly among themselves and cascade further towards higher k ⊥ , ultimately reaching electron scales (Sahraoui et al, , 2010Alexandrova et al, 2009).…”

Section: Introductionmentioning

confidence: 99%

“…In these conditions, satellites measure perpendicular wavenumber spectra, f ∝ k ⊥ , except for rare cases of B 0 V SW , where frequency measures parallel wavenumber, f ∝ k z . The spectral break f b is often associated with one of the proton kinetic scales, the proton gyroradius ρ p or the proton inertial length δ p = V A / p , such that the observed frequency of the break is 2πf b V SW /ρ p or V SW /δ p Bale et al, 2005;Alexandrova et al, 2010;Sahraoui et al, 2010). Perri et al (2010) show, however, that the break position is not sensitive to the radial dependence of the ion scales, whereas Markovskii et al (2008) argue that the break position depends upon a combination of the scale and the turbulent amplitudes at that scale.…”

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confidence: 99%

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Turbulent spectra and spectral kinks in the transition range from MHD to kinetic Alfvén turbulence

Voitenko

Keyser

2011

Nonlin. Processes Geophys.

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Abstract.A weakly dispersive range (WDR) of kinetic Alfvén turbulence is identified and investigated for the first time in the context of the MHD/kinetic turbulence transition. We find perpendicular wavenumber spectra ∝ k −3 ⊥ and ∝ k −4 ⊥ formed in WDR by strong and weak turbulence of kinetic Alfvén waves (KAWs), respectively. These steep WDR spectra connect shallower spectra in the MHD and strongly dispersive KAW ranges, which results in a specific doublekink (2-k) pattern often seen in observed turbulent spectra. The first kink occurs where MHD turbulence transforms into weakly dispersive KAW turbulence; the second one is between weakly and strongly dispersive KAW ranges. Our analysis suggests that partial turbulence dissipation due to amplitude-dependent non-adiabatic ion heating may occur in the vicinity of the first spectral kink. The threshold-like nature of this process results in a conditional selective dissipation that affects only the largest over-threshold amplitudes and that decreases the intermittency in the range below the first spectral kink. Several recent counter-intuitive observational findings can be explained by the coupling between such a selective dissipation and the nonlinear interaction among weakly dispersive KAWs.

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“…4b. The corresponding power-spectrum-density (PSD) is calculated by using the wavelet method, which is similar to the method used by Bale et al (2005) to analyze the PSD of electromagnetic fields in the solar wind. One peak of the PSD profile at a period of about 5 min is clearly shown in Fig.…”

Section: Chromospheric Activities In the Source Regionmentioning

confidence: 99%

Intermittent outflows at the edge of an active region – a possible source of the solar wind?

He¹,

Marsch²,

Tu³

et al. 2010

A&A

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Context. It has already been established that the solar wind may originate at the edges of active regions (ARs), but the key questions of how frequently these outflows occur, and at which height the nascent solar wind originates have not yet been addressed. Aims. We study the occurrence rate of these intermittent outflows, the related plasma activities beneath in the low solar atmosphere, and the interplanetary counterparts of the nascent solar wind outflow. Methods. We use the observations from XRT/Hinode and TRACE to study the outflow patterns. The occurrence frequency of the intermittent outflow is estimated by counting the occurrences of propagating intensity enhancements in height-time diagrams. We adopt observations of SOT/Hinode and EIS/Hinode to investigate the phenomena in the chromosphere associated with the coronal outflows. The ACE plasma and field in-situ measurements near Earth are used to study the interplanetary manifestations. Results. We find that in one elongated coronal emission structure, referred to as strand, the plasma flows outward intermittently, about every 20 min. The flow speed sometimes exceeds 200 km s −1 , which is indicative of rapid acceleration, and thus exceeds the coronal sound speed at low altitudes. The inferred flow speed of the soft-X-ray-emitting plasma component seems a little higher than that of the Fe ix/x-emitting plasma component. Chromospheric jets are found to occur at the root of the strand. Upflows in the chromosphere are also confirmed by blue-shifts of the He ii line. The heliospheric plasma counterpart close to the Earth is found to be an intermediate-speed solar wind stream. The AR edge may also deliver some plasmas to a fraction of the fast solar wind stream, most of which emanate from the neighboring CH. Conclusions. The possible origin of the nascent solar wind in the chromosphere, the observed excessive outflow speed of over 200 km s −1 in the lower corona, and the corresponding intermediate-speed solar wind stream in interplanetary space are all linked in our case study. These phenomena from the low solar atmosphere to the heliosphere near Earth in combination shed new light on the solar wind formation process. These observational results will constrain future modeling of the solar winds originating close to an AR.

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Measurement of the Electric Fluctuation Spectrum of Magnetohydrodynamic Turbulence

Cited by 506 publications

References 19 publications

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

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

Turbulent spectra and spectral kinks in the transition range from MHD to kinetic Alfvén turbulence

Intermittent outflows at the edge of an active region – a possible source of the solar wind?

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