Effects of the vertical plasma drift velocity on the generation and evolution of equatorial spread <i>F</i>

Fejer, Bela G.; Scherliess, L.; Paula, E. R. de

doi:10.1029/1999ja900271

Cited by 644 publications

(827 citation statements)

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“…One of the basic requirements for the development of spread-F is the rapid uplifting of the F-layer to very high altitudes by the pre-reversal enhancement of zonal electric field in the post-sunset hours (Farley et al, 1970;Tsunoda and Ecklund, 2007). The evening vertical drift, or the pre-reversal electric field increases with solar flux (Abdu et al, 1983;Fejer et al, 1999), which could lead to greater rate of occurrence of ESF and EPB during the periods of higher solar activity (Sahai et al, 2000;Sobral et al, 2002). Growth rate for Perkins instability (Perkins, 1973), which is used to explain the generation of MSTID (Kelley and Fukao, 1991), is inversely proportional to ion-neutral collision frequency.…”

Section: Discussionmentioning

confidence: 99%

Airglow observations over the equatorial ionization anomaly zone in Taiwan

et al. 2011

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Abstract. Airglow imaging at mid-latitude stations often show intensity modulations associated with medium scale travelling ionospheric disturbances (MSTID), while those carried out near the equatorial regions reveal depletions caused by equatorial plasma bubbles (EPB). Two all sky cameras are used to observe plasma depletions in the 630.0 nm emission over the equatorial ionization anomaly (EIA) region, Taiwan (23 • N, 121 • E; 13.5 • N Magnetic) during 1998-2002 and 2006-2007. The results show EPB and MSTID depletions in different solar activity conditions. Several new features of the EPB depletions such as bifurcation, secondary structure on the walls, westward tilt, etc., are discussed in this paper. Evidence of tilted depletions with secondary structures developing on the eastern wall that later evolve to appear as bifurcations, are presented for the first time. Moreover, detail investigations are carried out using International Reference Ionosphere (IRI) model as well as the electron density from Ionosonde and Global Positioning System (GPS) Occultation Experiment (GOX) onboard FORMOSAT-3/COSMIC satellite, to understand the conditions that favor the propagation of MSTID to the latitude of Taiwan.

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Section: Discussionmentioning

confidence: 99%

Airglow observations over the equatorial ionization anomaly zone in Taiwan

et al. 2011

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“…Fejer et al [1999] derived a threshold upward plasma drift velocity necessary for the generation of plasma bubbles, and the threshold varies from $10 m s À1 at solar minimum to $40 m s À1 at solar maximum. Our observations are consistent with Fejer et al [1999]. However, the results of Fejer et al [1999] were derived from the measurements at a fixed longitude (Jicamarca).…”

Section: Discussionmentioning

confidence: 99%

“…This prereversal enhancement in the vertical plasma drift moves the F region to higher altitudes and increases the growth rate of the Rayleigh-Taylor instability, causing the occurrence of plasma bubbles. Fejer et al [1999] found that the upward plasma drift velocities necessary for the generation of equatorial spread F vary from $10 m s À1 near solar minimum to $40 m s À1 near solar maximum. Anderson et al [2004] found that equatorial plasma bubbles and resulting ionospheric scintillation occur, in general, when the vertical plasma drift is greater than 20 m s À1 .…”

Section: Introductionmentioning

confidence: 99%

Generation and characteristics of equatorial plasma bubbles detected by the C/NOFS satellite near the sunset terminator

et al. 2012

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We present the observations of equatorial plasma bubbles in the evening sector by the Communication/Navigation Outage Forecasting System (C/NOFS) satellite during 2011. We illustrate with a few examples the overall properties of the equatorial ionosphere as the solar activity approached maximum. C/NOFS was often below the F peak and this allowed us to examine the early phases of irregularity formation. We show examples when C/NOFS detected a continuous generation of plasma bubbles near the sunset terminator over eight successive orbits (∼12 h). A clear prereversal enhancement of upward plasma drift occurred between 18:00 and 19:00 LT when plasma bubbles were detected by C/NOFS, and the peak value of the upward ion drift at or near the magnetic equator was 40–70 m s−1. In some cases, C/NOFS was well below the Fpeak and detected wide regions with very low plasma density over ∼3000 km in longitude in the evening sector, and plasma bubbles were generated within the low‐density region. C/NOFS also detected simultaneous existence of plasma bubbles between 19:00 and 03:00 LT, corresponding to a longitudinal coverage of ∼12,000 km. Significant differences in the characteristics of plasma bubbles between periods of low and high solar activity are identified. Large plasma bubbles occur in the midnight‐dawn sector at low solar activity but in the evening sector at high solar activity. The lifetime of plasma bubbles is long (7 h or longer) at low solar activity but is short (∼3 h) at high solar activity. Broad plasma depletions occur near dawn at low solar activity, but wide low‐density regions with multiple plasma bubbles occur in the evening sector at high solar activity.

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“…Many papers have described a secondary maximum in ESF occurrence in the post-midnight period (Abdu et al, , 1983Fejer et al, 1999;Hysell and Burcham, 2002;MacDougall et al, 1998). During periods of high geomagnetic activity, electric fields can penetrate to low latitudes and cause the equatorial electric field to reverse in the post-midnight period, which is a source of ESF during periods of high geomagnetic activity (Kelley et al, 1979b;Fejer et al, 1999). Hysell and Burcham (2002) divides the pre-sunrise ESF into two categories.…”

Section: Equatorial Spread-fmentioning

confidence: 99%

Observations and modeling of post-midnight uplifts near the magnetic equator

et al. 2006

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Abstract. We report here on post-midnight uplifts near the magnetic equator. We present observational evidence from digital ionosondes in Brazil, a digisonde in Peru, and other measurements at the Jicamarca Radio Observatory that show that these uplifts occur fairly regularly in the post-midnight period, raising the ionosphere by tens of kilometers in the most mild events and by over a hundred kilometers in the most severe events. We show that in general the uplifts are not the result of a zonal electric field reversal, and demonstrate instead that the uplifts occur as the ionospheric response to a decreasing westward electric field in conjunction with sufficient recombination and plasma flux. The decreasing westward electric field may be caused by a change in the wind system related to the midnight pressure bulge, which is associated with the midnight temperature maximum. In order to agree with observations from Jicamarca and Palmas, Brazil, it is shown that there must exist sufficient horizontal plasma flux associated with the pressure bulge. In addition, we show that the uplifts may be correlated with a secondary maximum in the spread-F occurrence rate in the post-midnight period. The uplifts are strongly seasonally dependent, presumably according to the seasonal dependence of the midnight pressure bulge, which leads to the necessary small westward field in the post-midnight period during certain seasons. We also discuss the enhancement of the uplifts associated with increased geomagnetic activity, which may be related to disturbance dynamo winds. Finally, we show that it is possible using simple numerical techniques to estimate the horizontal plasma flux and the vertical drift velocity from electron density measurements in the post-midnight period.

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Effects of the vertical plasma drift velocity on the generation and evolution of equatorial spread F

Cited by 644 publications

References 50 publications

Airglow observations over the equatorial ionization anomaly zone in Taiwan

Airglow observations over the equatorial ionization anomaly zone in Taiwan

Generation and characteristics of equatorial plasma bubbles detected by the C/NOFS satellite near the sunset terminator

Observations and modeling of post-midnight uplifts near the magnetic equator

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