Current filaments in plasmas

Trubnikov, B. A.

doi:10.1134/1.1469172

Cited by 52 publications

(72 citation statements)

References 9 publications

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“…Trap times are another typical unknown, but collisional pitch angle diffusion has been explored in trap plus precipitation models (e.g., Lin & Johns 1993;Aschwanden 1998). Collisional pitch angle diffusion occurs at a rate of twice the rate of collisional energy loss (Trubnikov 1965). Thus, the trap time is of the order of tens of seconds for typical ambient densities (≈10 11 electrons cm −3 ) and energy of microwave-emitting electrons (≈100 keV or higher).…”

Section: Discussionmentioning

confidence: 99%

Microwave emission from the trapped and precipitated electrons in solar bursts

Costa¹,

Rosal²

2005

A&A

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Abstract.We analyzed the microwave spectra of a sample of 13 solar flares out of 40 events observed by the Nobeyama Radio Polarimeter in the period of August 8, 1998 through November 24, 2001. The solar burst time profiles were filtered to separate the slow component from the fast structures which were associated with the emission from trapped particles and to the emission from the minor precipitating population, respectively. The spectra of both components suggest a trap in a region with a mean magnetic field of about 600 G and a minor emission from the loop legs with a magnetic field of 1100 G, resulting in a mirror ratio of about two. The spectral indices of the optically thin emission from these two regions indicate pitch angle diffusion by Coulomb collisions.

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Section: Discussionmentioning

confidence: 99%

Microwave emission from the trapped and precipitated electrons in solar bursts

Costa¹,

Rosal²

2005

A&A

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“…The equations describing the collisional mean free paths 25 of the interacting streams provide a possible explanation for this change of dynamics. The mean free path scales quadratically with the kinetic energy of the collision and linearly with their particle density.…”

Section: Review Of Aluminium Experimentsmentioning

confidence: 99%

“…In order to further investigate these dynamics, we will require the formulae for the Coulomb collision frequencies. 25,26 The Appendix includes a brief overview to these equations and their scalings. In order to calculate the expected MFPs for collisions between adjacent ablation streams, we must first recast the problem to fit the model.…”

Section: Inter-stream Mean Free Path Calculationsmentioning

confidence: 99%

Shock-less interactions of ablation streams in tungsten wire array z-pinches

et al. 2013

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Shock-less dynamics were observed during the ablation phase in tungsten wire array experiments carried out on the 1.4 MA, 240 ns MAGPIE generator at Imperial College London. This behaviour contrasts with the shock structures which were seen to dominate in previous experiments on aluminium arrays [Swadling et al., Phys. Plasmas 20, 022705 (2013)]. In this paper, we present experimental results and make comparisons both with calculations of the expected mean free paths for collisions between the ablation streams and with previously published Thomson scattering measurements of the plasma parameters in these arrays [Harvey-Thompson et al., Phys. Plasmas 19, 056303 (2012)]. V C 2013 AIP Publishing LLC. [http://dx

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“…This delayed onset of collisional features demonstrates that the plasma flow has undergone a transition of its collisional dynamics. The collisional mechanics of plasmas are discussed in some detail by Trubnikov,29 in which equations are derived for calculating the collisional frequencies corresponding to a range of changes to the velocity distribution function of the plasma. These equations are summarised in the NRL plasma physics formulary.…”

Section: -9mentioning

confidence: 99%

Oblique shock structures formed during the ablation phase of aluminium wire array z-pinches

et al. 2013

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A series of experiments has been conducted in order to investigate the azimuthal structures formed by the interactions of cylindrically converging plasma flows during the ablation phase of aluminium wire array Z pinch implosions. These experiments were carried out using the 1.4 MA, 240 ns MAGPIE generator at Imperial College London. The main diagnostic used in this study was a two-colour, end-on, Mach-Zehnder imaging interferometer, sensitive to the axially integrated electron density of the plasma. The data collected in these experiments reveal the strongly collisional dynamics of the aluminium ablation streams. The structure of the flows is dominated by a dense network of oblique shock fronts, formed by supersonic collisions between adjacent ablation streams. An estimate for the range of the flow Mach number (M ¼ 6.2-9.2) has been made based on an analysis of the observed shock geometry. Combining this measurement with previously published Thomson Scattering measurements of the plasma flow velocity by Harvey-Thompson et al. [Physics of Plasmas 19, 056303 (2012)] allowed us to place limits on the range of the ZT e of the plasma. The detailed and quantitative nature of the dataset lends itself well as a source for model validation and code verification exercises, as the exact shock geometry is sensitive to many of the plasma parameters. Comparison of electron density data produced through numerical modelling with the Gorgon 3D MHD code demonstrates that the code is able to reproduce the collisional dynamics observed in aluminium arrays reasonably well. V C 2013 American Institute of Physics. [http://dx

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Current filaments in plasmas

Cited by 52 publications

References 9 publications

Microwave emission from the trapped and precipitated electrons in solar bursts

Microwave emission from the trapped and precipitated electrons in solar bursts

Shock-less interactions of ablation streams in tungsten wire array z-pinches

Oblique shock structures formed during the ablation phase of aluminium wire array z-pinches

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