Debye screening under non-equilibrium plasma conditions

Abstract

As has been revealed in a number of more recent astrophysical papers, in most of the tenuous space plasmas Maxwellian distribution functions cannot be expected for ions or electrons because of the lack of efficient relaxation processes. Many of the classical characteristics of plasmas, such as plasma frequency or Debye length, are calculated on the basis of the assumption, however, that Maxwellians prevail, which under most of the relevant astrophysical plasma conditions is not the case. We here therefore consider this specific problem of Debye shieldings of single charges in a plasma for the case of prevailing non-equilibrium distribution functions for ions and electrons. As typical non-equilibrium functions, so-called Kappa functions were considered with clear preference, and we therefore study here the Debye shielding in a plasma with Kappa-distributed electrons and ions. We show that the so-called Debye shielding increases with increasing extent of the high-velocity tail of the electron distribution function, or in other words, with lower Kappa index of the underlying Kappa function. In our calculations we demonstrate that the Debye lengths become enlarged by about a factor of 10 with respect to its classically expexted value if highly suprathermal electron distributions prevail with Kappa indices close to 1.5.

Quasi‐thermal noise spectroscopy: The art and the practice

“…In the ideal case of a plasma at equilibrium temperature T, this noise reduces to Nyquist's formula (1) with R = R P , the antenna resistance resulting from the plasma thermal fluctuations. If the plasma is nonthermal, the noise is still fully determined by the particle velocity distributions provided that it is stable [e.g., Sitenko, 1967;Fejer and Kan, 1969]. This result can be generalized to a magnetized plasma and enables one to deduce the plasma properties from the measured voltage spectrum [Meyer-Vernet, 1979].…”

The κ-cookbook: a novel generalizing approach to unify κ-like distributions for plasma particle modelling

“…The Debye length is discussed in Treumann et al (2004), Livadiotis & McComas (2004) and Fahr & Heyl (2016) as well as in Livadiotis et al (2018, and references therein). These authors use the Debye-Hückel theory to determine the Debye length (see Appendix C).…”

“…To calculate the Debye length, we replace the velocity by the kinetic energy E kin and add as a perturbation the potential energy V (or "chemical" potential as in Treumann et al (2004) and Fahr & Heyl (2016)) of the test particle:…”

“…The concept of a non-additive entropy mentioned above is also still controversial (see, e.g., the exchange between Nauenberg (2003); Tsallis (2004); Nauenberg (2004) and the discussion in Fichtner et al (2018)). For the SKD there is also some discrepancy regarding the Debye length: for example, while Mace et al (1998) and Livadiotis & Mc-Comas (2004) derive a vanishing Debye length for κ → 3/2, Treumann et al (2004) find it to diverge in this limit, and Fahr & Heyl (2016) determine it to be ten times that of the associated Maxwellian plasma.…”

Особенности Поведения Моды Дебая В Электронной Плазме При Различных Степенях Вырождения Электронного Газа

“…Впервые показано, что при достаточно высоких степенях вырождения электронного газа область существования моды Дебая имеет существенно нетривиальный характер, при котором области существования и отсутствия этой моды чередуются по мере роста частоты электрического поля. DOI: 10.21883/PJTF.2018.24.47042.17495 В последнее время проявляется растущий интерес к вопросу об экранировании внешнего переменного электромагнитного поля в плазме в зависимости от различных параметров [1][2][3][4].…”