Neutral gas composition changes and E×B vertical plasma drift contribution to the daytime equatorial F2-region storm effects

Mikhailov, Alexey; Förster, M.; Skoblin, M. G.

doi:10.1007/s005850050052

Cited by 7 publications

(8 citation statements)

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“… Strickland et al [2001] showed that the peak F region electron density varies approximately linearly with Σ[O]/[N 2 ] in the region where Σ[O]/[N 2 ] is depressed. An increase in Σ[O]/[N 2 ] in low and middle latitudes during large geomagnetic storms is also a common feature identified by observations [e.g., Mikhailov et al , 1994; Burns et al , 1995a; Meier et al , 2005; Crowley et al , 2006; Grigorenko et al , 2007; Mannucci et al , 2009] and model simulations [e.g., Burns et al , 1995a; Immel et al , 2001; Crowley et al , 2006; Lu et al , 2008]. An increase in Σ[O]/[N 2 ] in low and middle latitudes is understood in the context of global wind circulation induced by the heating of the polar atmosphere during storm periods; divergence and upwelling of the polar upper atmosphere cause the Σ[O]/[N 2 ] decrease in high latitudes and convergence and downwelling of the atmosphere cause the Σ[O]/[N 2 ] increase in low and middle latitudes [ Rishbeth et al , 1987; Rodger et al , 1989; Crowley et al , 1989; Fuller‐Rowell et al , 1994, 1996; Burns et al , 1995a, 1995b].…”

Section: Introductionmentioning

confidence: 70%

“…The disturbance in Σ[O]/[N 2 ] does not provide precise information for the storm‐time behavior of [O] and [N 2 ] in the F region. For example, the increase in Σ[O]/[N 2 ] during storm periods can be explained either by the increase in [O] [e.g., Mikhailov et al , 1994] or by the decrease in [N 2 ] [e.g., Burns et al , 1995a]. Connection of the positive ionospheric storm to the neutral composition change in the region where Σ[O]/[N 2 ] is enhanced can be clarified by examining the disturbances in [O] and [N 2 ] in the F region.…”

Section: Introductionmentioning

confidence: 99%

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O and N₂disturbances in theFregion during the 20 November 2003 storm seen from TIMED/GUVI

et al. 2011

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The ratio of height‐integrated atomic oxygen number density, [O], to molecular nitrogen number density, [N2], defined as Σ[O]/[N2], has been used as an indicator of the thermosphere‐ionosphere coupling during geomagnetic storms. However, the disturbance in [O]/[N2] in the F region can be different from the disturbance in Σ[O]/[N2], and knowledge of the storm‐time behaviors of [O] and [N2] is necessary to precisely describe the thermospheric neutral composition disturbance and its effect on the ionosphere. In this study, we examine the separate roles of [O] and [N2] in modifying the F region [O]/[N2] and Σ[O]/[N2] by analyzing far ultraviolet images made by Thermosphere, Ionosphere, Mesosphere Energetics and Dynamics (TIMED)/Global Ultraviolet Imager (GUVI) during the severe 20 November 2003 geomagnetic storm. The GUVI observation shows that the fractional storm‐time change in [N2] is greater than that in [O] in the F region in areas where Σ[O]/[N2] is both decreased and increased. Therefore the disturbance in [O]/[N2] in the F region is primarily determined by the change in [N2]. The reduction in [O]/[N2] in the F region during the storm period is consistent with the reduction in Σ[O]/[N2]. However, only a minor change of the F region [O]/[N2] is observed in the region where the increase in Σ[O]/[N2] is observed. The TEC increase observed at the locations of the Σ[O]/[N2] increase in the American‐Atlantic sectors is associated with the poleward extension of the equatorial ionization anomaly rather than with the neutral composition change in the F region.

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Section: Introductionmentioning

confidence: 70%

Section: Introductionmentioning

confidence: 99%

O and N₂disturbances in theFregion during the 20 November 2003 storm seen from TIMED/GUVI

et al. 2011

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“…The role of the TCD in low‐latitude ionospheric plasma depletions has been considered by only a few researchers. Mikhailov et al [1994] (see also Mikhailov and Leshchinskaya [1991]) considered both the E × B drift and TCD to explain the suppression of the daytime F peak plasma density near the magnetic equator during magnetic storms. They interpreted their observations as showing that the positive storm effect (increase in plasma density) induced by the increase of O concentration is reduced by the simultaneous increase of N 2 concentration.…”

Section: Discussionmentioning

confidence: 99%

Ionospheric disturbances during the magnetic storm of 15 July 2000: Role of the fountain effect and plasma bubbles for the formation of large equatorial plasma density depletions

Kil¹,

Paxton²

2006

J. Geophys. Res.

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[1] We investigate the role of the fountain effect and plasma bubbles for the formation of the large equatorial plasma depletions during the geomagnetic storm of 15 July 2000. The large equatorial plasma depletions are detected in the Atlantic sector on the night of the 15th by the Defense Meteorological Satellite Program (DMSP) F15 and the first Republic of China Satellite (ROCSAT-1). The observations show discontinuous drop of the plasma density at the walls of the depletions, flat plasma density inside the depletions, and persistence or growth of the depletions over night. These properties are not consistent with the trough morphology induced by the fountain effect. The coincident ionospheric observations of DMSP F15 and ROCSAT-1 demonstrate that the large depletions are created in the longitude regions where plasma bubbles are present. The occurrence of the large depletions after sunset, elongation in the north-south direction, formation of steep walls, and colocation with plasma bubbles at lower altitudes or earlier times suggest that the large depletions are closely associated with plasma bubbles.

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“… Adeniyi [1986] found that increases in NmF 2 over the equator during the main and first recovery phases of storms seem to be more common than decreases; the increases in NmF 2 were interpreted as the consequence of a downward motion of the F 2 layer and reduced fountain effect caused by an enhanced westward electric field. Mikhailov et al [1994, 1995] showed that atomic oxygen concentration increases in the equatorial thermosphere may be the main reason for a positive NmF 2 storm effect. On the other hand, an enhanced eastward electric field can cause negative storm effect over the equator and positive storm effect at the anomaly latitudes.…”

Section: Introductionmentioning

confidence: 99%

A strong positive phase of ionospheric storms observed by the Millstone Hill incoherent scatter radar and global GPS network

et al. 2005

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[1] During geomagnetic storms, the ionospheric F region electron density may be greatly increased or decreased, which are termed positive storms or negative storms. It is generally accepted that negative storm phases are caused by neutral composition changes. In contrast, different mechanisms have been proposed to explain the generation of positive storm phases. In this paper, we present observations of a strong positive storm at middle latitudes. The Millstone Hill incoherent scatter radar detected significant increases of the midlatitude ionospheric F region electron density during a magnetic storm on 3 April 2004. The positive phase of the ionospheric storm started to occur in the morning sector (0912 LT at Millstone Hill) and lasted for more than 10 hours. Compared with the quiettime ionosphere, the daytime F peak altitude over Millstone Hill during the storm was $80 km higher, the F region electron density was increased by a factor of 2-4, and the F region electron temperature was decreased by $1000 K (or $40%). The radar also measured an enhanced eastward electric field and a slightly more equatorward neutral wind. Global GPS measurements show that total electron content (TEC) was increased at middle latitudes and decreased at lower latitudes, and the large TEC enhancements occurred primarily in the Atlantic sector. We suggest that electric fields may play an important role in the generation of the observed positive storm phase. The eastward electric field will cause increases in the midlatitude ionospheric electron density by moving the plasma particles upward and decreases in the equatorial ionospheric electron density by strengthening the fountain effect. The daytime poleward wind was reduced or even reversed during the storm, which may also contribute to the occurrence of the positive storm.Citation: Huang, C.-S., J. C. Foster, L. P. Goncharenko, P. J. Erickson, W. Rideout, and A. J. Coster (2005), A strong positive phase of ionospheric storms observed by the Millstone Hill incoherent scatter radar and global GPS network,

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Neutral gas composition changes and E×B vertical plasma drift contribution to the daytime equatorial F2-region storm effects

Cited by 7 publications

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O and N₂disturbances in theFregion during the 20 November 2003 storm seen from TIMED/GUVI

O and N₂disturbances in theFregion during the 20 November 2003 storm seen from TIMED/GUVI

Ionospheric disturbances during the magnetic storm of 15 July 2000: Role of the fountain effect and plasma bubbles for the formation of large equatorial plasma density depletions

A strong positive phase of ionospheric storms observed by the Millstone Hill incoherent scatter radar and global GPS network

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Neutral gas composition changes and E×B vertical plasma drift contribution to the daytime equatorial F2-region storm effects

Cited by 7 publications

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O and N2disturbances in theFregion during the 20 November 2003 storm seen from TIMED/GUVI

O and N2disturbances in theFregion during the 20 November 2003 storm seen from TIMED/GUVI

Ionospheric disturbances during the magnetic storm of 15 July 2000: Role of the fountain effect and plasma bubbles for the formation of large equatorial plasma density depletions

A strong positive phase of ionospheric storms observed by the Millstone Hill incoherent scatter radar and global GPS network

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O and N₂disturbances in theFregion during the 20 November 2003 storm seen from TIMED/GUVI

O and N₂disturbances in theFregion during the 20 November 2003 storm seen from TIMED/GUVI