STARE and EISCAT measurements: Evidence for the limitation of STARE Doppler velocity observations by the ion acoustic velocity

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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Short term characteristics of ion-acoustic type radio auroral echoes

Canadian Journal of Physics ◽

10.1139/p78-036 ◽

1978 ◽

Vol 56 (2) ◽

pp. 292-301 ◽

Cited By ~ 10

Author(s):

Christos Haldoupis ◽

George Sofko

Keyword(s):

Signal Amplitude ◽

Acoustic Velocity ◽

Velocity Range ◽

Short Term ◽

Backscatter Signal ◽

Ion Acoustic ◽

Longitudinal Plasma ◽

Digital Demodulation ◽

Signal Fading ◽

Time Sequences

Digital demodulation techniques and spectral analysis are used to study the short term (<1 s) characteristics of the ion-acoustic radio auroral echoes. Examination of 0.4 s time sequences indicates that the signal amplitude undergoes a deep and quasi-periodic fading with strongly marked periodicities in the 2–10 Hz range. Evidence shows that the fading is not due to interference but to the appearance and disappearance of independent scatterers, causing a sequence of backscatter signal bursts. If the assumption is made that these scatterers are longitudinal plasma density waves, the observed signal fading can be interpreted in terms of the growth and decay of individual regions of plasma instability rather than as interference between signals from separated coexisting scattering regions. Investigation of a large number of records suggests the following features for the irregularities associated with the ion-acoustic echoes: (1) their lifetime is in the 0.05–0.25 s range. (2) their growth (or decay) rate is in the 10–60 s−1 range, (3) their velocity remains fairly constant, even during growth and decay, and is always within the ion-acoustic velocity range in the medium.

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Langmuir probe and ion acoustic velocity measurement of the concentration of two species in a multi-dipole plasma

ICOPS 2000. IEEE Conference Record - Abstracts. 27th IEEE International Conference on Plasma Science (Cat. No.00CH37087) ◽

10.1109/plasma.2000.855057 ◽

2002 ◽

Author(s):

A.M. Hala ◽

N. Hershkowitz

Keyword(s):

Langmuir Probe ◽

Velocity Measurement ◽

Acoustic Velocity ◽

Ion Acoustic

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Shielding of moving test particles in warm, isotropic plasma

Journal of Plasma Physics ◽

10.1017/s0022377800007522 ◽

1973 ◽

Vol 9 (3) ◽

pp. 311-324 ◽

Cited By ~ 46

Author(s):

Liu Chen ◽

A. Bruce Landon ◽

M. A. Lieberman

Keyword(s):

Logarithmic Singularity ◽

Field Potential ◽

Acoustic Velocity ◽

Ion Distribution ◽

Potential Wells ◽

Test Particles ◽

Ion Acoustic ◽

Cone Surface ◽

Cone Potential ◽

A Charge

Shielding of test charges in warm, isotropic electron and electron–ion (Te ≫ Ti) plasmas is studied analytically and numerically. For a plasma with hot Maxwellian electrons and cold mobile ions, the potential due to a charge moving faster than the ion acoustic velocity has an ion acoustic Cerenkov cone. Ahead of the particle, the shielding is the usual electron Debye type with a modified longer shielding length. Potential wells with γ−1 dependence exists inside the cone. The potential falls off as along the cone surface. Outside the cone, the potential decays exponentially. A charge moving slower than the ion acoustic velocity also creates a cone, with potential decay as γ−3 outside the cone, potential wells decaying as γ−1 inside the cone, and potential wells falling off as along the cone surface. In both cases a radial logarithmic singularity exists along the trailing axis. Using a mono-energetic ion distribution, the singularity is removed and an ion thermal Cerenkov cone appears. For a monoenergetic electron plasma, assuming immobile ions, a test charge moving faster than the electron thermal velocity excites a thermal Cerenkov cone. Outside the cone, the far-field potential falls off in quadrupole form as γ−3. Inside the cone, potential wells decay as γ−1.

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The electron drift velocity, ion acoustic speed and irregularity drifts in high-latitude E-region

Annales Geophysicae ◽

10.5194/angeo-26-3395-2008 ◽

2008 ◽

Vol 26 (11) ◽

pp. 3395-3409 ◽

Cited By ~ 2

Author(s):

M. V. Uspensky ◽

R. J. Pellinen ◽

P. Janhunen

Keyword(s):

Drift Velocity ◽

Equatorial Electrojet ◽

Electron Drift Velocity ◽

Doppler Velocity ◽

Electron Drift ◽

Velocity Dependence ◽

Flow Angle ◽

Aspect Angle ◽

Ion Acoustic ◽

Acoustic Speed

Abstract. The purpose of this study is to examine the STARE irregularity drift velocity dependence on the EISCAT line-of-sight (los or l-o-s) electron drift velocity magnitude, VE×Blos, and the flow angle ΘN,F (superscript N and/or F refer to the STARE Norway and Finland radar). In the noon-evening sector the flow angle dependence of Doppler velocities, VirrN,F, inside and outside the Farley-Buneman (FB) instability cone (|VE×Blos|>Cs and |VE×Blos|<Cs, respectively, where Cs is the ion acoustic speed), is found to be similar and much weaker than suggested earlier. In a band of flow angles 45°<ΘN,F<85° it can be reasonably described by |VirrN,F|∝AN,FCscosnΘN,F, where AN,F≈1.2–1.3 are monotonically increasing functions of VE×B and the index n is ~0.2 or even smaller. This study (a) does not support the conclusion by Nielsen and Schlegel (1985), Nielsen et al. (2002, their #[18]) that at flow angles larger than ~60° (or |VirrN,F|≤300 m/s) the STARE Doppler velocities are equal to the component of the electron drift velocity. We found (b) that if the data points are averages over 100 m/s intervals (bins) of l-o-s electron velocities and 10 deg intervals (bins) of flow angles, then the largest STARE Doppler velocities always reside inside the bin with the largest flow angle. In the flow angle bin 80° the STARE Doppler velocity is larger than its driver term, i.e. the EISCAT l-o-s electron drift velocity component, |VirrN,F|>|VE×Blos|. Both features (a and b) as well as the weak flow angle velocity dependence indicate that the l-o-s electron drift velocity cannot be the sole factor which controls the motion of the backscatter ~1-m irregularities at large flow angles. Importantly, the backscatter was collected at aspect angle ~1° and flow angle Θ>60°, where linear fluid and kinetic theories invariably predict negative growth rates. At least qualitatively, all the facts can be reasonably explained by nonlinear wave-wave coupling found and described by Kudeki and Farley (1989), Lu et al. (2008) for the equatorial electrojet and studied in numerical simulation by Otani and Oppenheim (1998, 2006).

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