Nonlinear kinetic Alfvén waves with non‐Maxwellian electron population in space plasmas

Abstract

The present work discusses the effects of non-Maxwellian electron distributions on kinetic Alfvén waves in low-beta plasmas. Making use of the two-potential theory and employing the Sagdeev potential approach, the existence of solitary kinetic Alfvén waves having arbitrary amplitude is investigated. It is found that the use of non-Maxwellian population of electrons in the study of kinetic Alfvén waves leads to solutions corresponding to solitary structures that do not exist for Maxwellian electrons. The present investigation solves the riddle of plasma density fluctuations associated with strong electromagnetic perturbations observed by the Freja satellite. The present findings can also be applied to regions of space where various satellite missions have observed the presence of suprathermal populations of plasma species and where the low assumption is valid.

An alternative explanation for the density depletions observed by Freja and Viking satellites

“…(4) and (5) become a 1 = 1 and a 2 = 1/2 and when r = 0 and q → (κ + 1), we get a 1 = κ−1/2 κ−3/2 and a 2 = (κ−1/2)(κ+1/2) 2(κ−3/2) 2 . 15 The model equations that describe the propagation of ion acoustic waves in one dimension are given here as under:…”

“…However, the data from satellites have shown time and again that the particle distributions in different regions of space exhibit a significant departure from Maxwellian distributions. [11][12][13][14][15][16][17] These deviations imply that Maxwellian distribution function in many instances is not sufficient to understand or predict different waves and instabilities. Qureshi et al 18 in their pioneering work, about a decade ago, gave a new generalized non-Maxwellian electron distribution to incorporate the observed flat-topped behavior at lower energies and modified tails at higher energies in space plasmas.…”

Investigation of cubic non‐linearity‐driven electrostatic structures in the presence of double spectral index distribution function

“…[19] Later, the mKdV equation was derived to study ion acoustic waves in cylindrical and spherical coordinate systems assuming cold ions and isothermal electrons and their numerical solitary solutions were compared. [24,25] In space plasmas, particle distribution functions often deviate from the Maxwellian distribution function either due to the presence of plenty of superthermal particles or the presence of flat top at low energies. [22,23] It has been found that shape of the particle distribution functions changes the characteristics of the non-linear wave structures and play an important role in the wave dynamics.…”

Ion‐acoustic solitary waves in e‐p‐i plasmas with (r, q)‐distributed electrons and kappa‐distributed positrons

“…Several studies on non‐Maxwellian plasmas have shown that wave characteristics change significantly due to the presence of non‐thermal distributions and provided a better insight into the underlying physical processes. [ 22–26 ]…”

“…[ 33 ] Studies on IA waves in arbitrary amplitude limit have shown that the solitary wave characteristics are modified due to the presence of non‐thermal particles. [ 23–24,34–36 ]…”