Anomalous resistivity and the nonlinear evolution of the ion‐acoustic instability

Petkaki, P.; Freeman, M. P.; Kirk, Toby; Watt, Clare E. J.; Horne, Richard B.

doi:10.1029/2004ja010793

Cited by 44 publications

(68 citation statements)

References 29 publications

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“…In space science, 1D Vlasov simulation has been used to study the ion-acoustic instability of the initial drift Maxwellian or non-Maxwellian distribution in the magnetopause. It has been found that the anomalous resistivity in saturation state depends on reduced mass ratio, and increases with the enhancement of the mean drift velocity (Watt et al 2002;Petkaki et al 2003Petkaki et al , 2006. In 2D PIC simulations, Pritchett (2006) discovered that the most efficient electron acceleration in RCS takes place near the X-line of the externally driven RCS with a guiding magnetic field.…”

Section: Conclusion and Discussionmentioning

confidence: 99%

“…The initial unstable waves originate in a white noise electric field applied at t = 0 (see Eqs. (4) and (5) in Petkaki et al 2003). The simulation parameters are summed in Table 1, where n, T are respectively the plasma density and temperature, v d , v e0 , and v i are respectively the initial bulk drift velocity, electron, and proton thermal velocity (…”

Section: Basic Equation and Simulation Methodsmentioning

confidence: 99%

“…The space, velocity space, and time numbers of grid points are carefully selected to ensure the numeric stability and accuracy of the integration algorithm (Horne & Freeman 2001;Petkaki et al 2003).…”

Section: Basic Equation and Simulation Methodsmentioning

confidence: 99%

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Electron acceleration in the turbulent reconnecting current sheets in solar flares

Huang

2009

A&A

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Context. We investigate the nonlinear evolution of the electron distribution in the presence of the strong inductive electric field in the reconnecting current sheets (RCS) of solar flares. Aims. We aim to study the characteristics of nonthermal electron-beam plasma instability and its influence on electron acceleration in RCS. Methods. Including the external inductive field, the one-dimensional Vlasov simulation is performed with a realistic mass ratio for the first time. Results. Our principal findings are as follows: 1) the Buneman instability can be quickly excited on the timescale of 10 −7 s for the typical parameters of solar flares. After saturation, the beam-plasma instabilities are excited due to the non-Maxwellian electron distribution; 2) the final velocity of the electrons trapped by these waves is of the same order as the phase speed of the waves, while the untrapped electrons continue to be accelerated; 3) the inferred anomalous resistance of the current sheet and the energy conversion rate are basically of the same order as those previously estimated, e.g., "the analysis of Martens". Conclusions. The Buneman instability is excited on the timescale of 10 −7 s and the wave-particle resonant interaction limits the low-energy electrons to be further accelerated in RCS.

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Section: Conclusion and Discussionmentioning

confidence: 99%

Section: Basic Equation and Simulation Methodsmentioning

confidence: 99%

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Electron acceleration in the turbulent reconnecting current sheets in solar flares

Huang

2009

A&A

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“…In the astrophysical and geophysical literature, the effect of the generation of anomalous resistivity in the regions with the high current density has been studied in great detail (see, e.g. Büchner & Elkina 2005;Petkaki et al 2006). We emphasise that the anomalous resistivity is generated before the fast wave pulse forms a shock, because the necessary condition for the onset of the current-driven instabilities is that the current density exceeds some certain (finite) threshold value (e.g., Yokoyama & Shibata 1994;Nakariakov et al 2006, for the discussion of this effect in the solar flare context).…”

Section: Parametric Studies 341 Compression Pulsementioning

confidence: 99%

Magnetoacoustic shock formation near a magnetic null point

Gruszecki

Farahani

Nakariakov

et al. 2011

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Aims. We investigate the interaction of nonlinear fast magnetoacoustic waves with a magnetic null point in connection with the triggering of solar flares. Methods. We model the propagation of fast, initially axisymmetric waves towards a two-dimensional isothermal magnetic null point in terms of ideal magnetohydrodynamic equations. The numerical simulations are carried out with the Lagrangian remap code Lare2D. Results. Dynamics of initially axisymmetric fast pulses of small amplitude is found to be consistent with a linear analytical solution proposed earlier. The increase in the amplitude leads to the nonlinear acceleration of the compression pulse and deceleration of the rarefaction pulse and hence the distortion of the wave front. The pulse experiences nonlinear steepening in the radial direction either on the leading or the back slopes for the compression and rarefaction pulses, respectively. This effect is most pronounced in the directions perpendicular to the field. Hence, the nonlinear evolution of the fast pulse depends on the polar angle. The nonlinear steepening generates the sharp spikes of the electric current density. As in the uniform medium, the position of the shock formation also depends on the initial width of the pulse. Only sufficiently smooth and low-amplitude initial pulses can reach the vicinity of the null point, create there current density spikes, and initiate magnetic reconnection by seeding anomalous electrical resistivity. Steeper and higher amplitude initial pulses overturn at larger distance from the null point, and cannot trigger reconnection.

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“…This has its roots in the Boltzmann-Gibbs statistical mechanics, which is in turn based on the assumption that the collisions in the studied plasma are sufficiently frequent to attain the thermal equilibrium. However, the assumption of the Maxwellian distribution has been challenged in the past decades in a wide variety of astrophysical environments, ranging from laboratory plasmas to planetary magnetospheres, the solar wind, and even galaxies (e.g., Dalla & Ljepojevic 1997;Maksimovic et al 1997a,b;Viñas et al 2000;Petkaki et al 2003;Mauk et al 2004;Leubner 2004aLeubner ,b, 2005Maksimovic et al 2005;Ryu et al 2007Ryu et al , 2009Gaelzer et al 2008;Nieves-Chinchilla & Viñas 2008;Dialynas et al 2009;Prokhorov 2009;Prokhorov et al 2009;Le Chat et al 2009;Pierrard 2009;Pierrard & Lazar 2010;Livadiotis & McComas 2010;Lu et al 2010Lu et al , 2011Leitner et al 2011).…”

Section: Introductionmentioning

confidence: 99%

The non-Maxwellian continuum in the X-ray, UV, and radio range

Dudík

Kašparová

Dzifčáková

et al. 2012

A&A

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Aims. We investigate the X-ray, UV, and also the radio continuum arising from plasmas with a non-Maxwellian distribution of electron energies. The two investigated types of distributions are the κ-and n-distributions. Methods. We derived analytical expressions for the non-Maxwellian bremsstrahlung and free-bound continuum spectra. The spectra were calculated using available cross-sections. Then we compared the bremsstrahlung spectra arising from the different bremsstrahlung cross-sections that are routinely used in solar physics.Results. The behavior of the bremsstrahlung spectra for the non-Maxwellian distributions is highly dependent on the assumed type of the distribution. At flare temperatures and hard X-ray energies, the bremsstrahlung is greatly increased for κ-distributions and exhibits a strong high-energy tail. With decreasing κ, the maximum of the bremsstrahlung spectrum decreases and moves to higher wavelengths. In contrast, the maximum of the spectra for n-distributions increases with increasing n, and the spectrum then falls off very steeply with decreasing wavelength. In the millimeter radio range, the non-Maxwellian bremsstrahlung spectra are almost parallel to the thermal bremsstrahlung. Therefore, the non-Maxwellian distributions cannot be detected by off-limb observations made by the ALMA instrument. The free-bound continua are also highly dependent on the assumed type of the distribution. For n-distributions, the ionization edges disappear and a smooth continuum spectrum is formed for n 5. Opposite behavior occurs for κ-distributions where the ionization edges are in general significantly enhanced, with details depending on κ and T through the ionization equilibrium. We investigated how the non-Maxwellian κ-distributions can be determined from the observations of the continuum and conclude that one can sample the low-energy part of the distribution from the continuum.

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Anomalous resistivity and the nonlinear evolution of the ion‐acoustic instability

Cited by 44 publications

References 29 publications

Electron acceleration in the turbulent reconnecting current sheets in solar flares

Electron acceleration in the turbulent reconnecting current sheets in solar flares

Magnetoacoustic shock formation near a magnetic null point

The non-Maxwellian continuum in the X-ray, UV, and radio range

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