In the present paper, it is argued that non-Maxwellian distribution functions are better suited to model space plasmas. A new model distribution function called the generalized (r,q) distribution function which is the generalized form of the generalized Lorentzian (kappa) distribution function has been employed to carry out theoretical investigation for parallel propagating waves in general and for Alfvén waves in particular. New plasma dispersion functions have been derived and their properties investigated. The new linear dispersion relation for Alfvén waves is investigated in detail.
The purpose of this work is to investigate the linear and nonlinear properties of the ion-acoustic waves (IAW), propagating obliquely to an external magnetic field in a weakly relativistic, rotating, and magnetized electron-positron-ion plasma. The Zakharov–Kuznetsov equation is derived by employing the reductive perturbation technique for this wave in the nonlinear regime. This equation admits the solitary wave solution. The amplitude and width of this solitary wave have been discussed with the effects of obliqueness, relativity, ion temperature, positron concentration, magnetic field, and rotation of the plasma and it is observed that for IAW these parameters affect the propagation properties of solitary waves and these plasmas behave differently from the simple electron-ion plasmas. Likewise, the current density and electric field of these waves are investigated for their dependence on the above-mentioned parameters.
Key Points:• Lion roar emission is explained by (r, q) distribution• Bi-Maxwellian model cannot always explain observation• The (r, q) model satisfactorily resolves observational uncertainties (2006) investigated the underlying cause of the lion roar generation. However, the analysis based upon the bi-Maxwellian distribution function did not adequately explain the observations qualitatively as well as quantitatively. This outstanding problem is revisited in the present paper, and a resolution is put forth in which, the flat-top non-Maxwellian distribution function with a velocity power law energetic tail, known as the (r, q) distribution, or the generalized kappa distribution is employed. Upon carrying out the linear stability analysis of the (r, q) distribution against the whistler wave perturbation, and upon comparison with the Cluster data, good qualitative and quantitative agreements are found between theory and data.
We observed intense emission of the atomic hydrogen Lyman- (121.6 nm) and Lyman- (102.5 nm) lines from microhollow cathode discharges in high-pressure Ne (740 Torr) with a small admixture of H2 (up to 3 Torr). The atomic emission lines are spectrally clean with essentially no background of molecular emissions from the H2 Lyman and Werner bands. We attribute these atomic emissions to near-resonant energy transfer processes in the high-pressure discharge. In one case, near-resonant energy transfer between the Ne2* excimer and H2 leads to the formation of H(n = 2) atoms, a process similar to what was observed recently by Wieser et al (1998 J. Phys. B: At. Mol. Opt. Phys. 31 4589) in a high-pressure Ne/H2 mixture excited by energetic ion and electron impact. In the other case, near-resonant energy transfer between excited N* atoms (or vibrationally excited neon excimer molecules) and H2 leads to the formation of H(n = 3) atoms. The ratio of Lyman- to Lyman- emission intensity depends on the operating parameters of the discharge (gas pressure, gas mixture, discharge current) which supports the notion that different processes are involved in the formation of the H(n = 2) and H(n = 3) atoms, respectively.
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