A method for determining the drift velocity of plasma depletions in the equatorial ionosphere using far‐ultraviolet spacecraft observations

Park, S. H.; England, S.; Immel, T. J.; Frey, H. U.; Mende, S. B.

doi:10.1029/2007ja012327

Cited by 23 publications

(30 citation statements)

References 20 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 eastward drift velocity of the F region plasma has a maximum value at ∼20:00 LT, then gradually decreases, and becomes nearly zero near dawn. The zonal drift velocity of plasma bubbles and its variation with local time are similar to those of the average F region plasma drift [ Valladares et al , 1996; Immel et al , 2003; Park et al , 2007]. If a series of plasma bubbles exists and drifts eastward with the pattern of the average F ‐region plasma drift, the drift velocity of a bubble in the western (trailing) side is always faster than that of the bubble in the eastern (leading) side.…”

Section: Observationsmentioning

confidence: 99%

Observations and simulations of formation of broad plasma depletions through merging process

Huang¹,

Retterer²,

Beaujardière³

et al. 2012

J. Geophys. Res.

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[1] Broad plasma depletions in the equatorial ionosphere near dawn are region in which the plasma density is reduced by 1-3 orders of magnitude over thousands of kilometers in longitude. This phenomenon is observed repeatedly by the Communication/Navigation Outage Forecasting System (C/NOFS) satellite during deep solar minimum. The plasma flow inside the depletion region can be strongly upward. The possible causal mechanism for the formation of broad plasma depletions is that the broad depletions result from merging of multiple equatorial plasma bubbles. The purpose of this study is to demonstrate the feasibility of the merging mechanism with new observations and simulations. We present C/NOFS observations for two cases. A series of plasma bubbles is first detected by C/NOFS over a longitudinal range of 3300-3800 km around midnight. Each of the individual bubbles has a typical width of $100 km in longitude, and the upward ion drift velocity inside the bubbles is 200-400 m s À1 . The plasma bubbles rotate with the Earth to the dawn sector and become broad plasma depletions. The observations clearly show the evolution from multiple plasma bubbles to broad depletions. Large upward plasma flow occurs inside the depletion region over 3800 km in longitude and exists for $5 h. We also present the numerical simulations of bubble merging with the physics-based low-latitude ionospheric model. It is found that two separate plasma bubbles join together and form a single, wider bubble. The simulations show that the merging process of plasma bubbles can indeed occur in incompressible ionospheric plasma. The simulation results support the merging mechanism for the formation of broad plasma depletions.

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“…The Jicamarca radar measurements show that the average zonal drift of the equatorial ionospheric F region plasma is eastward at night and becomes westward near dawn [ Fejer et al , 1991, 2005]. The zonal drift velocity of the plasma depletions and its variation with local time are similar to those of the average F region plasma drift [ Abdu et al , 1985, 2003; Valladares et al , 1996; Taylor et al , 1997; Sobral et al , 1999; Immel et al , 2003, 2004; Park et al , 2007]. It was suggested that the depletions are embedded in the surrounding plasma and that the zonal drift velocity of the depletions can be used as an indicator of the ambient plasma drift.…”

Section: Introductionmentioning

confidence: 99%

Zonal drift of plasma particles inside equatorial plasma bubbles and its relation to the zonal drift of the bubble structure

et al. 2010

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[1] It has been observed that the zonal drift velocity of equatorial plasma bubbles is generally eastward. However, it has not been well understood whether the zonal drift of plasma bubbles is the same as the ambient plasma drift and what process causes differences in the drift velocities of the ambient plasma and bubbles. In this study we analyze the ion drift velocities measured by the Defense Meteorological Satellites Program and ROCSAT-1 satellites and the electric fields measured by the Communications/ Navigation Outage Forecasting System (C/NOFS) satellite in the presence of equatorial spread F. We find that the zonal drift velocity of the plasma particles inside plasma bubbles is significantly different from the ambient plasma drift. The relative zonal velocity of the ions inside the depletion region with respect to the ambient plasma is generally westward. In most cases it can be as high as several hundreds of meters per second. The plasma bubbles detected by the C/NOFS satellite in the midnight-dawn sector are still growing, and the polarization electric field inside the postmidnight bubbles is much stronger than the electric field in the ambient plasma. We suggest that the zonal drift velocity of the plasma particles inside the depletion region is driven by polarization electric field. When a plasma bubble is tilted, the E × B drift velocity caused by the polarization electric field has an upward component and a zonal component. Because of the zonal motion of the plasma particles inside the bubble, the eastward drift velocity of the bubble structure is faster than the ambient plasma drift for a west-tilted bubble and slower than the ambient plasma drift for an east-tilted bubble.

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A method for determining the drift velocity of plasma depletions in the equatorial ionosphere using far‐ultraviolet spacecraft observations

Cited by 23 publications

References 20 publications

Formation of a plasma depletion shell in the equatorial ionosphere

Formation of a plasma depletion shell in the equatorial ionosphere

Observations and simulations of formation of broad plasma depletions through merging process

Zonal drift of plasma particles inside equatorial plasma bubbles and its relation to the zonal drift of the bubble structure

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