Thermal effects on Farley–Buneman waves at nonzero aspect and flow angles. II. Behavior near threshold

Kissack, R. S.; Kagan, L. M.; Maurice, Jean

doi:10.1063/1.2834276

Cited by 14 publications

(28 citation statements)

References 16 publications

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“…In our companion paper, 30 we proceed to study threshold behavior of the dispersion relation, focusing on the physical processes that dominate the behavior of Farley-Buneman waves at different altitudes, aspect and flow angles, and wavelengths. In our companion paper, 30 we proceed to study threshold behavior of the dispersion relation, focusing on the physical processes that dominate the behavior of Farley-Buneman waves at different altitudes, aspect and flow angles, and wavelengths.…”

Section: Discussionmentioning

confidence: 99%

Thermal effects on Farley–Buneman waves at nonzero aspect and flow angles. I. Dispersion relation

2008

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With the increasingly accepted notion that E-region electrostatic plasma waves move at their instability threshold speed when they attain their maximum amplitude, it has become more important to determine just what that threshold speed is supposed to be. An accurate determination requires a calculation of the electron temperature fluctuation level, which can sometimes dramatically influence the results. In this paper, the Grad 8-moment transport equations have been employed with the addition of a generalized electron cooling rate to account for cooling via inelastic collisions, and a general electron volume heating rate that includes frictional heating as a special case. The derived generalized dispersion relation is presented in such a way that a variety of other earlier treatments, including the isothermal and adiabatic limits and an instability associated with electron friction, all fall out transparently, allowing us to easily compare our results with earlier ones while tracking down the physical processes involved. The presentation format is also geared to facilitate the computation of the dispersion relation for the purpose of comparing the theoretical results with observations.

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Section: Discussionmentioning

confidence: 99%

Thermal effects on Farley–Buneman waves at nonzero aspect and flow angles. I. Dispersion relation

2008

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“…The other approach, which is based on Grad's set of fluid equations closed at the heat flow level, self‐consistently describes the effects of collisions using Burgers' expressions for collision integrals [ Burgers , 1969]. This approach has been used in work of Kissack et al [1995, 1997, 2008a, 2008b], St.‐Maurice and Kissack [2000], and Kagan and St.‐Maurice [2004].…”

Section: Introductionmentioning

confidence: 99%

Unexpected rapid decrease in phase velocity of submeter Farley‐Buneman waves with altitude

Kagan

Kissack

Kelley

et al. 2008

Geophysical Research Letters

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[1] An unexpected and drastic drop in the phase velocity V ph of Farley-Buneman (FB) waves with increasing altitude was observed in the equatorial electrojet over Jicamarca. The effect was detected with the newly employed 430-MHz radar looking vertically. The decrease in V ph was 67 m/s and 36 m/s over 2.4 km for the FB waves moving towards and away from the radar, respectively. By contrast, the 430-MHz data from 20°west displayed little dependence on altitude. Simultaneous observations with a 50-MHz radar at 23°and 51°west also displayed little change of V ph with altitude. We show that electron inelastic cooling which defines gradual transition from super-adiabatic to isothermal processes at 50 MHz (used in majority of observations), becomes unimportant at higher frequencies. The effect is evinced at radar frequencies !150 MHz and requires altitude resolution <2 km to be observed. Averaging over >7 km at oblique incidence masks the effect.

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“…Many factors conspire to the production of threshold speeds that, however, differ from the isothermal ion-acoustic speed. For one thing, the electrons are neither isothermal nor isotropic (e.g., Sudan, 1995, 1997;Kagan and St.-Maurice, 2004;Kissack et al, 2008). At decameter wavelengths, this conspires to increase the threshold speed of the irregularities, particularly at the lower altitudes (e.g., Kagan and St.-Maurice, 2004).…”

Section: Magnitude Of Saturation Speedmentioning

confidence: 99%

“…For ease of comparison with previous work we continue here to use this parameter even though it has now become clear that a proper calculation of the ion-acoustic speed should include not just electron adiabatic effects mentioned above, but also electron heat flows and thermal diffusion effects. During electron heating events, or in the lower parts of the E-region, these corrections can be substantial (e.g., Sudan, 1995, 1997;Kagan and St.-Maurice, 2004;St.-Maurice and Kissack, 2000;Kissack et al, 1995Kissack et al, , 2008 and we should note that their effects have clearly been observed in the equatorial electrojet (St.-Maurice et al, 2003). An additional problem is that while C S is fairly stable in the equatorial ionosphere, it can vary significantly in the high-latitude region in the presence of electric fields that become so strong that the FB waves themselves will heat the electrons to temperatures well above the ambient atmospheric temperature (e.g., Schlegel and St.-Maurice, 1981;St.-Maurice et al, 1981Wickwar et al, 1981;Jones et al, 1991;Dimant and Milikh, 2003;Milikh and Dimant, 2003;Bahcivan, 2007).…”

Section: Introductionmentioning

confidence: 99%

Velocity of E-region HF echoes under strongly-driven electrojet conditions

et al. 2012

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Abstract. Data collected by the Stokkseyri SuperDARN HF radar simultaneously at short and far ranges are used to investigate the relationship between the velocity of E-region HF echoes, E × B electron drift and the isothermal ionacoustic speed C S . The work targets large E × B drifts of >1000 m s −1 and observations predominantly along the flow. By considering the EISCAT temperature and electric field data, an empirical relationship between the E ×B drift velocity and C S is established for a number of ionospheric heights. For the Stokkseyri HF radar beams oriented roughly along the E × B direction, the observed E-region HF velocities are consistent with the C S values at the bottom of the electrojet but not at its center. For a subset of the data with smooth and consistent velocity variation with the beam azimuth at both short and far radar ranges the velocity varies according to the cosine law. For the E-region echoes, the proportionality coefficient in the cosine law is consistent with the C S values at the bottom of the electrojet. For these events, the E-region velocity maximum is shown to be between the E × B and electric field directions. The statistically average shift is ∼20 • and it increases slightly with the E × B magnitude.

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Thermal effects on Farley–Buneman waves at nonzero aspect and flow angles. II. Behavior near threshold

Cited by 14 publications

References 16 publications

Thermal effects on Farley–Buneman waves at nonzero aspect and flow angles. I. Dispersion relation

Thermal effects on Farley–Buneman waves at nonzero aspect and flow angles. I. Dispersion relation

Unexpected rapid decrease in phase velocity of submeter Farley‐Buneman waves with altitude

Velocity of E-region HF echoes under strongly-driven electrojet conditions

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