scholarly journals Dust Ion Acoustic Solitary Structures at the Acoustic Speed in the Presence of Nonthermal Electrons and Isothermal Positrons

2019 ◽  
Vol 45 (5) ◽  
pp. 466-480 ◽  
Author(s):  
A. Paul ◽  
A. Bandyopadhyay ◽  
K. P. Das
Keyword(s):  
Nonthermal Electrons ◽  
Solitary Structures ◽  
Ion Acoustic ◽  
Acoustic Speed

Ion-acoustic solitary structures at the acoustic speed in a collisionless magnetized nonthermal dusty plasma

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Debdatta Debnath ◽  
Anup Bandyopadhyay
Keyword(s):  
Double Layer ◽  
Negative Polarity ◽  
Critical Value ◽  
Magnetized Plasma ◽  
Double Layers ◽  
Nonthermal Electrons ◽  
Solitary Structures ◽  
Ion Acoustic ◽  
Density Of Electrons ◽  
Acoustic Speed

Abstract At the acoustic speed, we have investigated the existence of ion-acoustic solitary structures including double layers and supersolitons in a collisionless magnetized plasma consisting of negatively charged static dust grains, adiabatic warm ions, and nonthermal electrons. At the acoustic speed, for negative polarity, the system supports solitons, double layers, supersoliton structures after the formation of double layer, supersoliton structures without the formation of double layer, solitons after the formation of double layer whereas the system supports solitons and supersolitons without the formation of double layer for the case of positive polarity. But it is not possible to get the coexistence of solitary structures (including double layers and supersolitons) of opposite polarities. For negative polarity, we have observed an important transformation viz., soliton before the formation of double layer → double layer → supersoliton → soliton after the formation of double layer whereas for both positive and negative polarities, we have observed the transformation from solitons to supersolitons without the formation of double layer. There does not exist any negative (positive) potential solitary structures within 0 < μ < μ c (μ c < μ < 1) and the amplitude of the positive (negative) potential solitary structure decreases for increasing (decreasing) μ and the solitary structures of both polarities collapse at μ = μ c, where μ c is a critical value of μ, the ratio of the unperturbed number density of electrons to that of ions. Similarly there exists a critical value β e2 of the nonthermal parameter β e such that the solitons of both polarities collapse at β e = β e2.

scholarly journals Simultaneous observations at different altitudes of ionospheric backscatter in the eastward electrojet

1998 ◽  
Vol 16 (1) ◽  
pp. 55-68 ◽  
Author(s):  
S. E. Milan ◽  
M. Lester
Keyword(s):  
Spectral Characteristics ◽  
Temporal Variations ◽  
Approximate Determination ◽  
Spectral Signature ◽  
Plasma Convection ◽  
Flow Angle ◽  
F Region ◽  
Ion Acoustic ◽  
E Region ◽  
Acoustic Speed

Abstract. A common feature of evening near-range ionospheric backscatter in the CUTLASS Iceland radar field of view is two parallel, approximately L-shell-aligned regions of westward flow which are attributed to irregularities in the auroral eastward electrojet region of the ionosphere. These backscatter channels are separated by approximately 100–200 km in range. The orientation of the CUTLASS Iceland radar beams and the zonally aligned nature of the flow allows an approximate determination of flow angle to be made without the necessity of bistatic measurements. The two flow channels have different azimuthal variations in flow velocity and spectral width. The nearer of the two regions has two distinct spectral signatures. The eastern beams detect spectra with velocities which saturate at or near the ion-acoustic speed, and have low spectral widths (less than 100 m s–1), while the western beams detect lower velocities and higher spectral widths (above 200 m s–1). The more distant of the two channels has only one spectral signature with velocities above the ion-acoustic speed and high spectral widths. The spectral characteristics of the backscatter are consistent with E-region scatter in the nearer channel and upper-E-region or F-region scatter in the further channel. Temporal variations in the characteristics of both channels support current theories of E-region turbulent heating and previous observations of velocity-dependent backscatter cross-section. In future, observations of this nature will provide a powerful tool for the investigation of simultaneous E- and F-region irregularity generation under similar (nearly co-located or magnetically conjugate) electric field conditions.Key words. Auroral ionosphere · Ionospheric irregularities · Plasma convection

scholarly journals Imaging radar observations of Farley Buneman waves during the JOULE II experiment

2008 ◽  
Vol 26 (7) ◽  
pp. 1837-1850 ◽  
Author(s):  
D. L. Hysell ◽  
G. Michhue ◽  
M. F. Larsen ◽  
R. Pfaff ◽  
M. Nicolls ◽  
...  
Keyword(s):  
Electric Fields ◽  
Spectral Width ◽  
Auroral Zone ◽  
Convection Flow ◽  
Coherent Scatter ◽  
Flow Angle ◽  
Doppler Shifts ◽  
Ion Acoustic ◽  
The Waves ◽  
Acoustic Speed

Abstract. Vector electric fields and associated E×B drifts measured by a sounding rocket in the auroral zone during the NASA JOULE II experiment in January 2007, are compared with coherent scatter spectra measured by a 30 MHz radar imager in a common volume. Radar imaging permits precise collocation of the spectra with the background electric field. The Doppler shifts and spectral widths appear to be governed by the cosine and sine of the convection flow angle, respectively, and also proportional to the presumptive ion acoustic speed. The neutral wind also contributes to the Doppler shifts. These findings are consistent with those from the JOULE I experiment and also with recent numerical simulations of Farley Buneman waves and instabilities carried out by Oppenheim et al. (2008). Simple linear analysis of the waves offers some insights into the spectral moments. A formula relating the spectral width to the flow angle, ion acoustic speed, and other ionospheric parameters is derived.

scholarly journals STARE velocity at large flow angles: is it related to the ion acoustic speed?

2006 ◽  
Vol 24 (3) ◽  
pp. 873-885 ◽  
Author(s):  
M. V. Uspensky ◽  
A. V. Koustov ◽  
S. Nozawa
Keyword(s):  
Electron Flow ◽  
Line Of Sight ◽  
Velocity Data ◽  
Ion Acoustic ◽  
E Region ◽  
Linear Fit ◽  
Radar Velocity ◽  
Large Flow ◽  
Eiscat Measurements ◽  
Acoustic Speed

Abstract. The electron drift and ion-acoustic speed in the E region inferred from EISCAT measurements are compared with concurrent STARE radar velocity data to investigate a recent hypothesis by Bahcivan et al. (2005), that the electrojet irregularity velocity at large flow angles is simply the product of the ion-acoustic speed and the cosine of an angle between the electron flow and the irregularity propagation direction. About 3000 measurements for flow angles of 50°–70° and electron drifts of 400–1500 m/s are considered. It is shown that the correlation coefficient and the slope of the best linear fit line between the predicted STARE velocity (based solely on EISCAT data and the hypothesis of Bahcivan et al. (2005)) and the measured one are both of the order of ~0.4. Velocity predictions are somewhat better if one assumes that the irregularity phase velocity is the line-of-sight component of the E×B drift scaled down by a factor ~0.6 due to off-orthogonality of irregularity propagation (nonzero effective aspect angles of STARE observations).

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