&amp;lt;i&amp;gt;F&amp;lt;/i&amp;gt;-region Pedersen conductivity deduced using the TIMED/GUVI limb retrievals

Kil, H.; Demajistre, M.; Paxton, L. J.; Zhang, Y.

doi:10.5194/angeo-24-1311-2006

Cited by 12 publications

(14 citation statements)

References 15 publications

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“…However, our simplified 3-D bubble reconstruction method is not capable of producing the altitude and latitude plasma distribution in a plasma depletion shell. We have chosen the arch-shaped emission depletion to demonstrate the formation of a plasma depletion shell but there exist different optical bubble morphologies that are variable with local time and longitude [e.g., Kil et al, 2006;Park et al, 2007]. The optical bubble image is a trace of the 3-D bubble structure at the F peak height and therefore the shell structure varies depending on the optical bubble morphology.…”

Section: Discussionmentioning

confidence: 99%

Formation of a plasma depletion shell in the equatorial ionosphere

et al. 2009

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[1] An accurate description of the irregularity region defined by a plasma bubble is critically important in understanding the dynamics of the region and its effects on radio scintillation. Here we describe a plasma depletion region as a ''depletion shell'' and show how two-dimensional optical images from space can be used to define the shape of the depletion shell. Our simple model calculation demonstrates that the space-based optical observation can detect the plasma-depleted magnetic flux tubes only near the F-peak height. The backward C-shape in bubble images from optical observations is the trace of the plasma depletion shell near the F-peak height. The westward tilt of bubbles at the magnetic equator can also be explained by this shell structure. The in situ measurement of the ion velocity at night in the topside shows the decrease of the eastward plasma drift with an increase of latitude. The formation of the plasma depletion shell is consistent with the latitudinal/altitudinal shear in the zonal plasma flow.

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Section: Discussionmentioning

confidence: 99%

Formation of a plasma depletion shell in the equatorial ionosphere

et al. 2009

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“…The daytime plasma distribution at low latitudes shows hemispheric symmetry in all seasons. The occurrence of the hemispheric symmetry even during solstices indicates that the daytime low‐latitude ionospheric morphology at an altitude of 600 km was not significantly affected by interhemispheric winds [e.g., West and Heelis , 1996; Venkatraman and Heelis , 2000; Kil et al , 2006]. The signatures of the daytime wave structure remain at night but the occurrence of the hemispheric asymmetry significantly modifies the wave‐4 structure.…”

Section: Longitudinal Density Structurementioning

confidence: 99%

“…However, the GUVI observation during this period (Figure 3a) shows the occurrence of stronger EIA in the northern hemisphere. The altitudinal difference in the hemispheric asymmetry may be explained by considering the altitudinal variations of the wind and fountain effects [ Kil et al , 2006].…”

Section: Longitudinal Density Structurementioning

confidence: 99%

“…As we can see in Figure 3, the absolute radiance near 0° is comparable to that during equinox. We explain the longitudinal difference of the radiance during November–December by the effects of the magnetic declination and displacement of the magnetic equator from the geographic equator [e.g., Kil et al , 2006]. In the region where the magnetic declination is positive (130°–280°E), the nighttime summer‐to‐winter (south‐to‐north during northern winter) wind parallel to the magnetic field line is enforced by the eastward zonal wind.…”

Section: Longitudinal Density Structurementioning

confidence: 99%

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Wave structures of the plasma density and vertical E × B drift in low‐latitude F region

et al. 2008

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[1] We investigate the seasonal, longitudinal, local time (LT), and altitudinal variations of the F region morphology at low latitudes using data from the first Republic of China satellite (ROCSAT-1), Global Ultraviolet Imager (GUVI), on board the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) satellite, and the Defense Meteorological Satellite Program (DMSP) F13 and F15 satellites. Signatures of the longitudinally periodic plasma density structure emerge before 0900 LT. The wave structure is established before noon and further amplified in the afternoon. The amplitudes of the wave structure start to diminish in the evening. The wave-4 structure is clearly distinguishable during equinox and northern hemisphere summer. During northern hemisphere winter, the density structure can be characterized to either wave-4 or wave-3 structure owing to marginal separation of the two peaks in 180°-300°E. Observations of similar density structures from ROCSAT-1 (600 km) and DMSP (840 km) at 0930 and 1800 LT indicate the extension of the wave structure to altitudes greater than 840 km. The daytime wave structure persists into the night during the equinoxes but is significantly modified during the solstices. The modification is more significant at higher altitudes and is attributed to the effects of interhemispheric winds and the prereversal enhancement. The formation of the wavelike density structure in the morning and its temporal evolution in the afternoon show a close association with the vertical E Â B drift. We conclude that the E Â B drift during 0900-1200 LT determines the formation of the wavelike density structure.

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“…In their upward propagation, (waves of longer vertical wavelengths attaining higher altitude) these waves nonlinearly interact with ; b The corresponding Digisonde ionograms; c TIMED/GUVI 135.6 nm images extending in the entire longitude span showing the global distribution of the EIA brightness and the patches of brightness depletions indicating plasma bubbles symmetric on either side of the dip equator (Kil et al 2006) tidal modes whereby electric fields are generated in the dynamo region with consequent modulation of the electrodynamical coupling processes. Oscillations in varying degrees have been observed due to 2, 3-5, 10, and 16-days periods in the key ionospheric parameters: the EEJ intensity, post-sunset/night-time F layer heights, evening prereversal enhancement in the F region vertical drift/zonal electric field (PRE), equatorial bubble/ spread F irregularities, etc.…”

Section: The Variabilities Defining Ionospheric Weathermentioning

confidence: 99%

Electrodynamics of ionospheric weather over low latitudes

Abdu

2016

Geosci. Lett.

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The dynamic state of the ionosphere at low latitudes is largely controlled by electric fields originating from dynamo actions by atmospheric waves propagating from below and the solar wind-magnetosphere interaction from above. These electric fields cause structuring of the ionosphere in wide ranging spatial and temporal scales that impact on space-based communication and navigation systems constituting an important segment of our technology-based day-to-day lives. The largest of the ionosphere structures, the equatorial ionization anomaly, with global maximum of plasma densities can cause propagation delays on the GNSS signals. The sunset electrodynamics is responsible for the generation of plasma bubble wide spectrum irregularities that can cause scintillation or even disruptions of satellite communication/navigation signals. Driven basically by upward propagating tides, these electric fields can suffer significant modulations from perturbation winds due to gravity waves, planetary/Kelvin waves, and non-migrating tides, as recent observational and modeling results have demonstrated. The changing state of the plasma distribution arising from these highly variable electric fields constitutes an important component of the ionospheric weather disturbances. Another, often dominating, component arises from solar disturbances when coronal mass ejection (CME) interaction with the earth's magnetosphere results in energy transport to low latitudes in the form of storm time prompt penetration electric fields and thermospheric disturbance winds. As a result, drastic modifications can occur in the form of layer restructuring (Es-, F3 layers etc.), large total electron content (TEC) enhancements, equatorial ionization anomaly (EIA) latitudinal expansion/contraction, anomalous polarization electric fields/vertical drifts, enhanced growth/suppression of plasma structuring, etc. A brief review of our current understanding of the ionospheric weather variations and the electrodynamic processes underlying them and some outstanding questions will be presented in this paper.

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<i>F</i>-region Pedersen conductivity deduced using the TIMED/GUVI limb retrievals

Abstract: Abstract. As a proxy of the Rayleigh-Taylor instability growth rate for equatorial plasma bubbles,

Cited by 12 publications

References 15 publications

Formation of a plasma depletion shell in the equatorial ionosphere

Formation of a plasma depletion shell in the equatorial ionosphere

Wave structures of the plasma density and vertical E × B drift in low‐latitude F region

Electrodynamics of ionospheric weather over low latitudes

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