An assessment of how a combination of shears, field-aligned currents and collisions affect F-region ionospheric instabilities

2007 ◽  
Vol 73 (1) ◽  
pp. 69-88 ◽  
Author(s):  
J.-P. ST.-MAURICE ◽  
J.-M. NOËL ◽  
P. J. PERRON
Keyword(s):  
Magnetic Field ◽  
Low Frequency ◽  
Theoretical Framework ◽  
Fluid Limit ◽  
Ambient Magnetic Field ◽  
Acoustic Instability ◽  
F Region ◽  
Ion Acoustic ◽  
Depth Study ◽  
Zero Frequency

Abstract.We present an in depth study of the fluid limit of a kinetically derived collisional, current-driven instability that includes shears in the field-aligned currents as well as collisions. We show how the theory presented here generalizes other theories, including the collisionless current-driven electrostatic ion acoustic instability and its sheared collisionless version. We offer a low-frequency generalization of the zero frequency ion shear driven instability by minimizing the relative drift magnitude as well as the shears themselves. We discuss the implication of our theoretical framework both for strongly field-aligned modes and modes where the wavevectors have arbitrary angles with respect to the ambient magnetic field. We discuss the results in terms of F-region irregularity observations of coherent echoes by ionospheric radars.

Low-frequency instabilities of a warm plasma in a magnetic field: Part 1. Instabilities driven by field-aligned currents

1977 ◽  
Vol 17 (1) ◽  
pp. 105-122 ◽  
Author(s):  
Dean F. Smith ◽  
Joseph V. Hollweg
Keyword(s):  
Magnetic Field ◽  
Stability Analysis ◽  
Low Frequency ◽  
Marginal Stability ◽  
Numerical Techniques ◽  
Acoustic Instability ◽  
Ion Acoustic ◽  
Warm Plasma ◽  
The Stability ◽  
Thermal Speed

The marginal stability of a plasma carrying current along the static magnetic field with isotropic Maxwellian ions and isotropic Maxwellian electrons drifting relative to the ions is investigated. The complete electromagnetic dispersion relation is studied using numerical techniques; the electron sums are restricted to three terms which limits the analysis to frequencies much less than the electron gyro-frequency, but includes frequencies somewhat above the ion gyro-frequency. A ‘kink-like’ instability and an instability of the Alfvén mode are found to have the lowest threshold drift velocities in most cases. In fact the threshold drift for the kink-like instability can be significantly less than the ion thermal speed. Electrostatic and electromagnetic ion-cyclotron instabilities are also found as well as the electro-static ion-acoustic instability. No instability of the fast magnetosonic mode was found. The stability analysis provides only threshold drift velocities and gives no information about growth rates.

scholarly journals Magnetoreception in laboratory mice: sensitivity to extremely low-frequency fields exceeds 33 nT at 30 Hz

2013 ◽  
Vol 10 (81) ◽  
pp. 20121046 ◽  
Author(s):  
Frank S. Prato ◽  
Dawn Desjardins-Holmes ◽  
Lynn D. Keenliside ◽  
Janice M. DeMoor ◽  
John A. Robertson ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Geomagnetic Field ◽  
Low Frequency ◽  
Good Alternative ◽  
Static Field ◽  
Laboratory Mice ◽  
Extremely Low Frequency ◽  
Ambient Magnetic Field ◽  
Detection Mechanisms ◽  
Biological Endpoint

Magnetoreception in the animal kingdom has focused primarily on behavioural responses to the static geomagnetic field and the slow changes in its magnitude and direction as animals navigate/migrate. There has been relatively little attention given to the possibility that weak extremely low-frequency magnetic fields (wELFMF) may affect animal behaviour. Previously, we showed that changes in nociception under an ambient magnetic field-shielded environment may be a good alternative biological endpoint to orientation measurements for investigations into magnetoreception. Here we show that nociception in mice is altered by a 30 Hz field with a peak amplitude more than 1000 times weaker than the static component of the geomagnetic field. When mice are exposed to an ambient magnetic field-shielded environment 1 h a day for five consecutive days, a strong analgesic (i.e. antinociception) response is induced by day 5. Introduction of a static field with an average magnitude of 44 µT (spatial variability of ±3 µT) marginally affects this response, whereas introduction of a 30 Hz time-varying field as weak as 33 nT has a strong effect, reducing the analgesic effect by 60 per cent. Such sensitivity is surprisingly high. Any purported detection mechanisms being considered will need to explain effects at such wELFMF.

Whistler radiation in plasmas with cylindrical magnetic field irregularities

2009 ◽  
Vol 76 (2) ◽  
pp. 193-207 ◽  
Author(s):  
C. KRAFFT ◽  
T. M. ZABORONKOVA
Keyword(s):  
Magnetic Field ◽  
Laboratory Experiments ◽  
Low Frequency ◽  
Wave Radiation ◽  
Whistler Waves ◽  
Frequency Wave ◽  
Ambient Magnetic Field ◽  
Physical Conditions ◽  
Local Perturbations ◽  
Dipole Sources

AbstractThe radiation of whistler waves by linear dipole sources immersed in magnetoplasmas with cylindrical magnetic field inhomogeneities are studied. Two types of irregularities are investigated: magnetic field enhancements and depletions. A theoretical analysis is developed for comparatively weak local perturbations of the ambient magnetic field. Results are provided by numerical calculations performed for physical conditions typical of laboratory experiments involving artificially created magnetic field irregularities. It is shown that plasma regions with locally enhanced (depleted) magnetic field intensities can increase (decrease) the amplitudes of whistler waves radiated by dipole sources, regardless of their orientation with respect to the ambient magnetic field. Results are relevant to space and laboratory experiments on very low-frequency wave radiation.

Measurements of the Dispersion Relation of the Low-Frequency Ion Acoustic Instability in the Turbulently Heated TRIAM-1 Tokamak Plasma

1981 ◽  
Vol 20 (1) ◽  
pp. L41-L44
Author(s):  
Osamu Mitarai ◽  
Takechiyo Watanabe ◽  
Yukio Nakamura ◽  
Kazuo Nakamura ◽  
Naoji Hiraki ◽  
...  
Keyword(s):  
Dispersion Relation ◽  
Low Frequency ◽  
Tokamak Plasma ◽  
Acoustic Instability ◽  
Ion Acoustic

Anisotropic-ion-beam-plasma interaction: drift parallel to magnetic field

1990 ◽  
Vol 44 (1) ◽  
pp. 77-90 ◽  
Author(s):  
P. Singh ◽  
R. Bharuthram
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Ion Beam ◽  
Low Frequency ◽  
Plasma Interaction ◽  
Beam Plasma ◽  
Ion Acoustic

In a plasma in which both the ions and electrons are magnetized we investigate low-frequency electrostatic instabilities driven by an anisotropic ion beam drifting parallel to the external magnetic field. The instability spectrum is found to be dominated by the ion-acoustic and ion-ion two-stream instabilities. Detailed comparisons are made with the isotropie case.

scholarly journals Studies of Spectral Broadening of the Lower Hybrid Wave Line in the Current-Drive Regimes and Ion Heating at the FT-2 Tokamak

2021 ◽  
Vol 47 (4) ◽  
pp. 329-336
Author(s):  
V. V. Dyachenko ◽  
A. B. Altukhov ◽  
E. Z. Gusakov ◽  
L. A. Esipov ◽  
A. N. Konovalov ◽  
...  
Keyword(s):  
Electromagnetic Waves ◽  
Low Frequency ◽  
Current Drive ◽  
Lower Hybrid ◽  
Ion Heating ◽  
Lower Hybrid Wave ◽  
Acoustic Instability ◽  
Ion Acoustic ◽  
Lower Hybrid Current Drive ◽  
High Frequency Waves

Abstract The experiments at the FT-2 tokamak are described that were focused on clearing up the role of the parametric decay instabilities in decreasing the generation efficiency of the non-inductive current excited by the electromagnetic waves in the lower hybrid frequency range. The most discussed instability of such kind is the decay of the pump wave into the daughter high-frequency waves and the low-frequency ion–acoustic quasi-modes. The studies performed have shown that, under conditions of the FT-2 experiment, the ion–acoustic instability has no decisive effect on the decrease in the efficiency of the lower hybrid current drive.

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