Very low frequency waves in the heliosphere: Ulysses observations

Lin, N.; Kellogg, P. J.; MacDowall, R. J.; Scime, Earl; Balogh, A.; Forsyth, R. J.; McComas, D. J.; Phillips, J. L.

doi:10.1029/98ja00764

Cited by 37 publications

(49 citation statements)

References 28 publications

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“…However, it is not the objective of this paper to provide an accurate theory on the physics of wave generation in interplanetary space. The variation of the wave spectrum with distance from the Sun as described by equation (9) is in good agreement with both the model results and Helios data that are presented by Hu et al (1999) and the Ulysses observations of Lin et al (1998), so this model spectrum is appropriate for the kinetic study of electron diffusion in interplanetary space. Equation (9) describes the total wave power B !…”

Section: Sunward-propagating Whistler Wavessupporting

confidence: 74%

Electron Halo and Strahl Formation in the Solar Wind by Resonant Interaction with Whistler Waves

Vocks

Salem

Lin

et al. 2005

ApJ

172

150

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Observations of solar wind electron distribution functions (VDFs) reveal considerable deviations from a simple Maxwellian VDF. A thermal core and a suprathermal halo and antisunward, magnetic field-aligned beam, or ''strahl,'' can be distinguished. At higher energies above 2 keV, a superhalo can even be observed. A kinetic description of electrons in the solar corona and wind, including resonant interaction between electrons and whistler waves, can reproduce an enhancement of suprathermal electron fluxes compared to the core flux. The whistler waves are assumed to be generated below the solar coronal base and propagate through the corona into interplanetary space. However, the resonance condition with these whistlers can only be fulfilled by electrons that move sunward. For antisunwardmoving electrons, such a model lacks an efficient diffusion mechanism. The mirror force due to the opening magnetic field geometry of a solar coronal hole and in the solar wind focuses the electrons into a very narrow beam. This expectation of an extremely narrow beam is contradicted by observations of a ''strahl'' that has a finite width, and of an quasi-isotropic superhalo component. Thus, a diffusion mechanism for antisunward-moving electrons must exist in interplanetary space. In this paper, antisunward-propagating whistler waves are introduced into the kinetic model in order to provide this diffusion. Their wave power is estimated as a small fraction of the total wave power that is measured in interplanetary space. The kinetic results show that the whistler waves are capable of influencing the solar wind electron VDFs significantly, leading to the formation of both the halo and strahl populations and a more isotropic distribution at higher energies, in good agreement with solar wind observations.

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Section: Sunward-propagating Whistler Wavessupporting

confidence: 74%

Electron Halo and Strahl Formation in the Solar Wind by Resonant Interaction with Whistler Waves

Vocks

Salem

Lin

et al. 2005

ApJ

172

150

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“…We do not find any correlation between the electrostatic energy E 2 between 4 and 6 kHz and the electron heat flux or the normalised heat flux: if the heat flux is controlled by wave-particle interactions, then the interacting waves are probably not the ion acoustic waves (Lin et al, 1998;Gary et al, 1999). Similarly, we find no correlation between E 2 and T e /T p , a parameter that controls the damping of the ion acoustic waves in the linear Maxwell-Vlasov theory.…”

Section: Introductioncontrasting

confidence: 60%

Evidence for the interplanetary electric potential? WIND observations of electrostatic fluctuations

et al. 2002

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Abstract. In the solar wind at 1 AU, coherent electrostatic waveforms in the ion acoustic frequency range ( 1 kHz) have been observed by the Time Domain Sampler (TDS) instrument on the Wind spacecraft. Small drops of electrostatic potential ( ≥ 10 −3 V) have been found across some of these waveforms, which can thus be considered as weak double layers . The rate of occurrence of these potential drops, at 1 AU, is estimated by a comparison of the TDS data with simultaneous data of another Wind instrument, the Thermal Noise Receiver (TNR), which measures continuously the thermal and non-thermal electric spectra above 4 kHz. We assume that the potential drops have a constant amplitude and a constant rate of occurrence between the Sun and the Earth. The total potential drop between the Sun and the Earth, which results from a succession of small potential drops during the Sun-Earth travel time, is then found to be about 300 V to 1000 V, of the same order of magnitude as the interplanetary potential implied by a two-fluid or an exospheric model of the solar wind: the interplanetary potential may manifest itself as a succession of weak double layers. We also find that the hourly average of the energy of the non-thermal ion acoustic waves, observed on TNR between 4 and 6 kHz, is correlated to the interplanetary electrostatic field, parallel to the spiral magnetic field, calculated with a two-fluid model: this is another evidence of a relation between the interplanetary electrostatic field and the electrostatic fluctuations in the ion acoustic range. We have yet to discuss the role of the Doppler effect, which is strong for ion acoustic waves in the solar wind, and which can bias the measure of the ion acoustic wave energy in the narrow band 4-6 kHz.

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“…If we do not need the nonlinear calculations required to estimate the maximum values of the Ñuctuating Ðeld energy density which determine an e †ective collision frequency, our calculations are more likely to be correct if we stay with the simpler linear theory. Third, enhanced Ñuctuations in the solar wind which may be due to heat Ñux instabilities are typically observed to be sporadic (Lengyel-Frey et al 1996 ;Lin et al 1998), implying that the associated wave-particle scattering does not take place uniformly. A constraint such as equation (2) is commensurate with scattering that is sporadic and/or inhomogeneous, whereas the derivation which leads to equation (1) requires that the associated scattering process is uniform throughout the plasma.…”

Section: Introductionmentioning

confidence: 99%

Whistler Heat Flux Instability at High Beta

Gary

2000

ApJ

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Enhanced Ñuctuations from electromagnetic heat Ñux instabilities in collisionless plasmas may, through wave-particle scattering, constrain the electron heat Ñux which Ñows parallel to the backq e ground magnetic Ðeld. This manuscript examines the linear Vlasov theory predictions for threshold conditions on the whistler heat Ñux instability at high the electron beta, a situation which may have b e , application to both solar wind and astrophysical plasmas. Theory predicts a threshold heat Ñux which scales approximately as One possible consequence of this instability is that it imposes an upper b ẽ 0.9. bound onWe discuss possible applications of such a heat Ñux limit in the cooling Ñows of clusters of q e . galaxies with b e ? 1.

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Very low frequency waves in the heliosphere: Ulysses observations

Abstract: Abstract. An overall profile of plasma wave activity in a frequency range of 0.2 to 448 Hz in the solar wind is presented using 6 years of Ulysses data which cover a large range ofheliographic latitudes (0 ø to +80 ø) at distances from I to 5 AU from the Sun.

Cited by 37 publications

References 28 publications

Electron Halo and Strahl Formation in the Solar Wind by Resonant Interaction with Whistler Waves

Electron Halo and Strahl Formation in the Solar Wind by Resonant Interaction with Whistler Waves

Evidence for the interplanetary electric potential? WIND observations of electrostatic fluctuations

Whistler Heat Flux Instability at High Beta

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