Interplanetary magnetic field: Statistical properties and discrete modes

Thomson, David J.; Lanzerotti, L. J.; Maclennan, C. G.

doi:10.1029/2000ja000113

Cited by 34 publications

(33 citation statements)

References 76 publications

(24 reference statements)

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“…We believe that the fact of their occurrence should not be controversial. While some of the analyses of solar wind data have been open to criticism we consider that the work of Thomson et al (2001Thomson et al ( , 2002; Ghosch et al (2009) shows their existence beyond reasonable doubt. What is controversial is whether such oscillations have any relevance to the generation of Pc5 pulsations in the magnetosphere at the same frequency.…”

Section: Discussionmentioning

confidence: 99%

“…This implies that charged particles are being scattered, and therefore diffused, in the interplanetary medium not only by a continuous spectrum of IMF fluctuations but also by discrete wave frequencies. Other works (Thomson et al, 2001(Thomson et al, , 2002Ghosch et al, 2009) have strengthened the case that p modes excite waves in the solar wind.…”

Section: Introductionmentioning

confidence: 99%

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Coherence between radar observations of magnetospheric field line resonances and discrete oscillations in the solar wind

Stephenson

Walker

2010

Ann. Geophys.

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Abstract.Field line resonances have been observed for decades by ground-based and in situ instruments. The driving mechanism(s) are still unclear, although previous work has provided strong grounds that coherent waves in the solar wind may be a source. Here we present further evidence, with the use of multitaper analysis, a sophisticated spectrum estimation technique. A set of windows (dpss tapers) is chosen with characteristics that best suit the width of the narrowband peaks to be identified. The orthogonality of the windows allows for a confidence level (of say 95%) against a null hypothesis of a noisy spectrum, so that significant peaks can be identified. Employing multitaper analysis we can determine the phase and amplitude coherence at the sampling rate of the data sets and, over their entire duration. These characteristics make this technique superior to single windowing or wavelet analysis. A high degree of phase and amplitude (greater then 95%) coherence is demonstrated between a 2.1 mHz field line resonance observed by the SHARE radar at Sanae, Antarctica and the solar wind oscillation detected by WIND and ACE satellites.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Coherence between radar observations of magnetospheric field line resonances and discrete oscillations in the solar wind

Stephenson

Walker

2010

Ann. Geophys.

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“…[8] Two runs are considered here with frequencies, f w = 0.1 mHz and f w = 1 mHz, chosen to correspond to the g-modes and p-modes of solar oscillations [Thomson et al, 1995]. We do not attempt to explain why those modes could generate Alfven waves of those frequencies at the coronal base.…”

Section: Modelmentioning

confidence: 99%

“…Estimated high Reynolds numbers further support the turbulent scenario. However, recent data analysis [Thomson et al, 1995[Thomson et al, , 2001] points out the persistency of low-frequency discrete modes in the frequency spectra computed from interplanetary magnetic field (IMF) observations. This conclusion has been challenged by Roberts et al [1996], who showed a numerical example in one-dimensional MHD which develops a continuous spectra from an initial configuration with three waves (see also more recent results in Goldstein et al [1999]).…”

Section: Introductionmentioning

confidence: 99%

“…As we will show, this opens up the possibility for both discrete and turbulent signatures to coexist in a system, without an inherent contradiction. We consider here a particular system, one that is inspired by a simplified model of an open coronal region, but is not to be construed as a simulation of the physical system (corona and solar wind) to which the Thomson et al [1995] observations apply. Nonetheless the present results could have implications for observations in space, astrophysical and laboratory plasmas.…”

Section: Introductionmentioning

confidence: 99%

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Discrete modes and turbulence in a wave‐driven strongly magnetized plasma

Dmitruk

Matthaeus

Lanzerotti³

2004

Geophysical Research Letters

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[1] We show the coexistence of discrete modes and t u r b u l e n c e i n n u m e r i c a l e x p e r i m e n t s o f magnetohydrodynamics with a strong background magnetic field. The particular system we consider is a model of an open magnetic region which we have previously used in coronal heating studies. In the simulations shown here, Alfven waves at discrete frequencies with values corresponding to solar g-modes and p-modes are injected at the boundary (although the question of how those modes could generate Alfven waves is not addressed). Numerical probes are used to compute the magnetic field fluctuations at the output. The frequency spectra obtained from those probes are broadband, but with peaks at the driving frequencies. The perpendicular (to the mean magnetic field) wavenumber energy spectrum is of a turbulent Kolmogorov-like type, and formation of small scale structures is observed. This shows, numerically, the possibility of persistence of discrete modes in a turbulent system.

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Unaliasing of aliased line component frequencies

Moghtaderi¹,

Takahara²,

Thomson³

2010

Can J Statistics

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This paper is concerned with undoing aliasing effects, which arise from discretely sampling a continuous‐time stochastic process. Such effects are manifested in the frequency‐domain relationships between the sampled and original processes. The authors describe a general technique to undo aliasing effects, given two processes, one being a time‐delayed version of the other. The technique is based on the observations that certain phase information between the two processes is unaffected by sampling, is completely determined by the (known) time delay, and contains sufficient information to undo aliasing effects. The authors illustrate their technique with a simulation example. The theoretical model is motivated by the helioseismological problem of determining modes of solar pressure waves. The authors apply their technique to solar radio data, and conclude that certain low‐frequency modes known in the helioseismology literature are likely the result of aliasing effects. The Canadian Journal of Statistics 38: 116–135; 2010 © 2010 Statistical Society of Canada

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Interplanetary magnetic field: Statistical properties and discrete modes

Cited by 34 publications

References 76 publications

Coherence between radar observations of magnetospheric field line resonances and discrete oscillations in the solar wind

Coherence between radar observations of magnetospheric field line resonances and discrete oscillations in the solar wind

Discrete modes and turbulence in a wave‐driven strongly magnetized plasma

Unaliasing of aliased line component frequencies

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