Nonlinear low-frequency structures in the auroral plasma in the presence of an oxygen beam including charge separation

Abstract

Observations from the Fast Auroral SnapshoT (FAST) satellite indicate that the parallel and perpendicular (to the Earth’s magnetic field) electric field structures exhibit a spiky appearance. In this study, a magnetized plasma system consisting of protons, electrons, and a cold oxygen ion beam is considered. Both background electrons and protons are treated as hot species with Boltzmann density distributions. The dynamics of the oxygen ion beam is governed by the fluid equations. Effect of charge separation is studied on nonlinear fluctuations arising from a coupling of ion cyclotron and ion-acoustic waves. A scan of parameter space reveals a range of solutions for the parallel electric field from sinusoidal to sawtooth to highly spiky waveforms. The inclusion of charge separation effects tends to in most cases increase the frequency of oscillation of the nonlinear structures. In the case of a weakly magnetized plasma, the amplitude of the oscillations are found to be constant while they are modulated for a strongly magnetized plasma. The findings are compared with satellite observations.

Periodic low-frequency electric field structures in a magnetized non-thermal auroral plasma

“…For the present model, the unnormalized electric field is given as [14], [17], [18]EUNbadbreakafter=EMTeeρi. Note that the ratio of the Mach numbers, M2M1 is equal to the amplitudes of the electric field E1E2, i.e., E1false(E2false) is the electric field corresponding to the Mach number M1false(M2false). In this paper, the electric field structures obtained are for electron temperature Tegoodbreakafter=1goodbreakafter−10 eV [9] and the ion-cyclotron frequency of about normalΩi≈1000 rad/sec.…”

“…Further investigations revealed that BENs consist of non-linear, quasi-static, time-domain parallel or/and perpendicular electric field structures, such as spiky, sawtooth and sinusoidal structures in an electrostatic ion cyclotron (EIC) wave reported by S3-3 [8], Viking [9], FREJA [10], POLAR [11], [12] and FAST [13] satellites. Various theoretical investigations of such electric field structures parallel and perpendicular to the geomagnetic field line have been done by several authors [14], [15], [16], [17], [18] using the fluid theory technique. In order to explain the generating mechanism of the parallel electric field fluctuations which exhibit sawtooth or spiky wave structures observed by FAST satellite mission, Reddy et al [14] presented a magnetized two-component auroral plasma model consisting of a cold ion and Boltzmann electron distribution, which is responsible for the field-aligned current.…”

Modulation instability and dissipative rogue waves in ion-beam plasma: Roles of ionization, recombination, and electron attachment

“…À3l n k 4 a 2 þ 3l b k 4 b 2 À 2c 2 x 4 À 3l b k 4 b þ 3k 2 x 2 c 1 þ 12k 4 x 2 À 3l n k 4 a À Á ; 4 A À3 l b k 4 b 2 À 3 l p k 4 þ 2 c 2 x 4 À 3 k 4 a l b bÀ3 k 4 a l p þ 3 k 2 a x 2 c 1 þ 12 k 4 a x 2 ;…”

“…1,2 The presence of such ion beams can significantly modify the collective behavior in plasmas 3,4 and introduce ion-ion instability. 5 Spacecraft observations indicate that electron and ion beams can drive broadband electrostatic waves in the Earth's plasma sheet boundary layer.…”

Effect of ion beam on the propagation of rarefactive solitons in multicomponent plasma with negative ions

“…18,19 Various satellite observations of solitary wave in space plasma indicate that it generally appears in association with electron or ion beams. 8,9,20,21 In the presence of an ion beam in a plasma, ion-acoustic waves have been widely studied in which the domains of beam velocity for the excitation of various modes and the existence of ion-ion instability have been obtained and experimentally established. [22][23][24] Different modes of wave propagation and beam plasma instability in a nearly electron-free positive ion-negative ion plasma in the presence of a positive ion beam have also been investigated for a wide range of beam velocities.…”