Obliquely Propagating Nonlinear Electrostatic Waves With (r,q) Distributed Electrons in Space Plasmas

Electron velocity distributions (EVDs) in space plasmas, such as solar wind, magnetosheath and Earth’s magnetosphere, are frequently observed with flat tops at the low energies and/or enhanced tails at high energies. Such observed distributions can only be fitted with the two spectral indices generalized (r,q) distribution function and neither Maxwellian nor kappa distributions fit the observed EVDs at low energies as well at high energy part simultaneously. In the limiting cases, r >0, q→∞, r =0, (κ+1) and r =0, q→∞ the (r,q) distribution reduces to Druyvesteyn-Davydov, kappa and Maxwellian distributions, respectively. Thus by employing the (r,q) distribution function for electrons and adopting fully nonlinear Sagdeev potential technique, we derive the Sagdeev potential for electrostatic waves. Then by using the values of the spectral indices r and q which fit the observed distributions, we numerically studied the propagation characteristics of nonlinear structures. We found that propagation characteristics of such nonlinear waves alter significantly from the Maxwellian or kappa distributed plasmas.