A simple model of low‐latitude electric fields

Eccles, J. V.

doi:10.1029/98ja02657

Cited by 106 publications

(165 citation statements)

References 23 publications

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“…Our results are in moderate solar flux conditions, which is very good consist with the results reported by Fejer et al [3] and Sobral et al [16]. The daytime westward and night-time eastward zonal drifts are due to the upward vertical electric fields during the day and the downward fields during the night-time period, respectively [17,18,19].…”

Section: Resultssupporting

confidence: 81%

Equatorial ionospheric plasma drifts velocities using radar observations

Chapagain

2016

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This study presents the experimental results of the equatorial ionospheric plasma drift zonal velocity obtained from Incoherent Scatter Radar (ISR) observations for 6 selective days in 2011 from Jicamarca, Peru. Our results indicate that the daytime drifts are westward with peak values mostly below ~50 m/s, while the night time drifts velocities are eastward, with a maximum value up to 120 m/s at around local midnight hours. The drift velocity decreases during post-midnight hours and starts to reverse westward in early morning hours. Our plasma drifts results are in good agreement with results from previous radar studies and other measurement techniques.

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Section: Resultssupporting

confidence: 81%

Equatorial ionospheric plasma drifts velocities using radar observations

Chapagain

2016

BIBECHANA

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“…Assuming that the last term of Eq. (1) is small for most local times, except near the solar terminator below the F-region ledge (Eccles, 1998), it is assumed to be null and consequently, the zonal plasma drift velocity will depend essentially on the intensity of the zonal wind velocity U P ϕ (Haerendel et al, 1992;Eccles, 1998). So, since during the solar maximum activity the pressure gradients produced by the solar heating are greater and the wind becomes more intense, the zonal plasma drift velocities are expected to be larger in this period as observed in Table 2, where one can also seen that shows that the deceleration is consistently higher in spring (October to December) than in summer (January to March) and that the velocities tend to decrease faster with local time during solar minimum than during solar maximum.…”

Section: Resultsmentioning

confidence: 99%

Plasma bubble zonal velocity variations with solar activity in the Brazilian region

et al. 2004

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Abstract.A statistical study of the zonal drift velocities of the ionospheric plasma bubbles using experimental airglow data acquired at the low-latitude station Cachoeira Paulista (Geogr. 22.5 • S, 45 • W, dip angle 28 • S) during the period of October to March, between 1980 and 1994, is presented here. This study is based on 109 nights of zonal plasma bubble velocity estimations as determined from bubbles signatures on the OI 630 nm scanning photometer airglow data. The zonal velocity magnitudes of the plasma bubbles are investigated with respect to solar activity and local time. It is verified that these velocities tend to increase with the solar EUV flux, using the solar 10.7-cm radio flux as a proxy (F10.7). These velocities are seen to be larger during the solar maximum activity period than in the solar minimum period. As to the local time variation, they are seen to peak before midnight, in the 20:30-22:30 LT time frame, depending on the season. The all-data plot based on the 109 nights of airglow experiments shows that the plasma bubble mean zonal drift velocities tend to decrease with local time, but they peak at 22:25 LT, where the velocity magnitude reaches 127.4 ms −1 . The zonal drift variations with local time and solar flux are shown in Figs. 1 and 2, respectively.

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“…Under these circumstances ionization profiles produced by solar illuminations should be similar. With similar conductance gradients, polarization electric fields required for Sq current continuity should also be similar (Eccles, 1998). The surprising eastward gradient in % max on the western side of the minimum in B eq indicates that the assumption is flawed.…”

Section: Discussionmentioning

confidence: 99%

“…First, any increase in E P decreases γ RT (Stephan et al, 2002). Second, longitudinal gradients in P at sunset should be less severe in the western Pacific than elsewhere and require weaker polarization electric fields to maintain current continuity across the dusk terminator (Eccles, 1998). Weaker electric fields compensate for the effect on γ RT of decreasing B eq .…”

Section: Discussionmentioning

confidence: 99%

“…Basu (1997) studied the temporal dependencies of the unstable equilibria as plasma flux tubes in the evening sector respond to altitude variations of the various force fields. Eastward electric fields in the dusk sector have two sources, leakage of the solar quiet (Sq) current system into the nightside ionosphere (Eccles, 1998) and penetration of high-latitude electric fields into the low-latitude ionosphere (Nopper and Carovillano, 1978). The Sq source acts systematically while penetration occurs during episodes of enhanced polar cap potential prior to the development of shielding (Harel et al, 1981;Burke et al, 1998).…”

Section: Introductionmentioning

confidence: 99%

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Seasonal-longitudinal variability of equatorial plasma bubbles

et al. 2004

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Abstract. We compare seasonal and longitudinal distributions of more than 8300 equatorial plasma bubbles (EPBs) observed during a full solar cycle from 1989-2000 with predictions of two simple models. Both models are based on considerations of parameters that influence the linear growth rate, γ RT , of the generalized Rayleigh-Taylor instability in the context of finite windows of opportunity available during the prereversal enhancement near sunset. These parameters are the strength of the equatorial magnetic field, B eq , and the angle, α, it makes with the dusk terminator line. The independence of α and B eq from the solar cycle phase justifies our comparisons.We have sorted data acquired during more than 75 000 equatorial evening-sector passes of polar-orbiting Defense Meteorological Satellite Program (DMSP) satellites into 24 longitude and 12 one-month bins, each containing ∼250 samples. We show that: (1) in 44 out of 48 month-longitude bins EPB rates are largest within 30 days of when α=0 • ; (2) unpredicted phase shifts and asymmetries appear in occurrence rates at the two times per year when α≈0 • ; (3) While EPB occurrence rates vary inversely with B eq , the relationships are very different in regions where B eq is increasing and decreasing with longitude. Results (2) and (3) indicate that systematic forces not considered by the two models can become important. Damping by interhemispheric winds appears to be responsible for phase shifts in maximum rates of EPB occurrence from days when α=0 • . Low EPB occurrence rates found at eastern Pacific longitudes suggest that radiation belt electrons in the drift loss cone reduce γ RT by enhancing E-layer Pedersen conductances. Finally, we analyze an EPB event observed during a magnetic storm at a time and place where α≈ −27 • , to illustrate how electric-field penetration from high latitudes can overwhelm the damping effects of weak gradients in Pedersen conductance near dusk.

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A simple model of low‐latitude electric fields

Cited by 106 publications

References 23 publications

Equatorial ionospheric plasma drifts velocities using radar observations

Equatorial ionospheric plasma drifts velocities using radar observations

Plasma bubble zonal velocity variations with solar activity in the Brazilian region

Seasonal-longitudinal variability of equatorial plasma bubbles

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