The role of the vertical &amp;lt;I&amp;gt;&amp;lt;B&amp;gt;E&amp;lt;/B&amp;gt;&amp;lt;/I&amp;gt;×&amp;lt;I&amp;gt;&amp;lt;B&amp;gt;B&amp;lt;/B&amp;gt;&amp;lt;/I&amp;gt; drift for the formation of the longitudinal plasma density structure in the low-latitude F region

Oh, Seungjun; Kil, H.; Kim, W.-T.; Paxton, L. J.; Kim, Y. H.

doi:10.5194/angeo-26-2061-2008

Cited by 31 publications

(27 citation statements)

References 18 publications

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“…The bottom two panels (c) and (f) show the calculated F-region vertical motion at 350 km resulting from a uniform zonal wind of 100 m/s to the west in the morning to the east in the evening local times. The correspondence between O + density enhancements and depletions with the wind induced upward and downward drifts provides a simple illustration of variable background upon which the WN4 variations are also modulated (Hartman and Heelis, 2007;Kil et al, 2008;Ren et al, 2009;Oh et al, 2008).…”

Section: Discussionmentioning

confidence: 99%

WN4 effect on longitudinal distribution of different ion species in the topside ionosphere at low latitudes by means of DEMETER, DMSP-F13 and DMSP-F15 data

et al. 2009

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Abstract. Plasma probe data from DMSP-F13, DMSP-F15 and DEMETER satellites were used to examine longitudinal structures in the topside equatorial ionosphere during fall equinox conditions of 2004 year. Since the launch of DEME-TER satellite on 29 June 2004, all these satellites operate close together in the topside ionosphere. Here, data taken from Special Sensor-Ion, Electron and Scintillations (SSIES) instruments on board DMSP-F13, F15 and Instrument Analyser de Plasma (IAP) on DEMETER, are used. Longitudinal variations in the major ions at two altitudes (∼730 km for DEMETER and ∼840 km for DMSP) are studied to further describe the recently observed "wavenumber-four" (WN4) structures in the equatorial topside ionosphere. Different ion species H + , He + and O + have a rather complex longitudinal behavior. It is shown that WN4 is almost a regular feature in O + the density distribution over all local times covered by these satellites. In the evening local time sector, H + ions follow the O + behavior within WN4 structures up to the premidnight hours. Near sunrise H + and later in the daytime, He + longitudinal variations are out of phase with respect to O + ions and effectively reduce the effect of WN4 on total ion density distribution at altitudes 730-840 km. It is shown that both a WN4 E × B drift driver and local F-region winds must be considered to explain the observed ion composition variations.

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Section: Discussionmentioning

confidence: 99%

WN4 effect on longitudinal distribution of different ion species in the topside ionosphere at low latitudes by means of DEMETER, DMSP-F13 and DMSP-F15 data

et al. 2009

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“…During the equinox it is known that DE3 and SPW4 reach their maxima amplitudes (Pedatella et al, 2012). During this season the effects of the interhemispheric wind are low and the vertical E × B drift is the main factor related to the longitudinal density structure formation (Oh et al, 2008). Using an empirical model from Alken and Maus (2007), Lühr et al (2008) studied the non-migrating tides' influence on EEJ (equatorial electrojet) intensity, and they noticed that the DE3 wave was the main contributor to EEJ longitudinal variation during equinoxes.…”

Section: Observations and Resultsmentioning

confidence: 99%

Wavenumber-4 structures observed in the low-latitude ionosphere during low and high solar activity periods using FORMOSAT/COSMIC observations

Onohara¹,

Batista

2018

Ann. Geophys.

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Abstract. The main purpose of this study is to investigate the four-peak structure observed in the low-latitude equatorial ionosphere by the FORMOSAT/COSMIC satellites. Longitudinal distributions of NmF2 (the density of the F layer peak) and hmF2 (ionospheric F2-layer peak height) averages, obtained around September equinox periods from 2007 to 2015, were submitted to a bi-spectral Fourier analysis in order to obtain the amplitudes and phases of the main waves. The four-peak structure in the equatorial and low-latitude ionosphere was present in both low and high solar activity periods. This kind of structure possibly has tropospheric origins related to the tidal waves propagating from below that modulate the E-region dynamo, mainly the eastward nonmigrating diurnal tide with wavenumber 3 (DE3, "E" for eastward). This wave when combined with the migrating diurnal tide (DW1, "W" for westward) presents a wavenumber-4 (wave-4) structure under a synoptic view. Electron densities observed during 2008 and 2013 September equinoxes revealed that the wave-4 structures became more prominent around or above the F-region altitude peak ( ∼ 300-350 km). The four-peak structure remains up to higher ionosphere altitudes (∼ 800 km). Spectral analysis showed DE3 and SPW4 (stationary planetary wave with wavenumber 4) signatures at these altitudes. We found that a combination of DE3 and SPW4 with migrating tides is able to reproduce the wave-4 pattern in most of the ionospheric parameters. For the first time a study using wave variations in ionospheric observations for different altitude intervals and solar cycle was done. The conclusion is that the wave-4 structure observed at high altitudes in ionosphere is related to effects of the E-region dynamo combined with transport effects in the F region.

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“…Liu and Watanabe (2008) from CHAMP satellite data have observed significant seasonal variation of the longitudinal plasma density structure at fixed solar activity levels. It has also been shown (Sagawa et al 2005;Immel et al 2006;Oh et al 2008) that along these four high-density regions, the anomaly crest moves poleward to higher magnetic latitude. Using FORMOSAT-3/COSMIC (F3/C) satellite constellation, Lin et al (2007b) have shown that the four-peaked EIA longitudinal structure evolve with local time and tend to move eastward with velocity of several tens of meters per second.…”

Section: Introductionmentioning

confidence: 99%

“…Lühr et al (2007) have reported a four-peaked longitudinal structure in electron density and zonal wind measured by the CHAMP satellite at 400 km. Kil et al (2007) and Oh et al (2008) reported the existence of a structure of four peaks of enhanced plasma density along the equatorial anomaly even at the topside of F region near 10°E, 100°E, 200°E, and 280°E and showed its relation to the vertical E × B drift. Liu and Watanabe (2008) from CHAMP satellite data have observed significant seasonal variation of the longitudinal plasma density structure at fixed solar activity levels.…”

Section: Introductionmentioning

confidence: 99%

“…The optical observations (Sagawa et al 2005;Henderson et al 2005;Immel et al 2006) provide information of the density near the F region. The measurements by ROCSAT-1 (Kil et al 2007;Kil et al 2008;Oh et al 2008;Fang et al 2009) basically give a picture of the topside density structure. The TEC measurements (Scherliess et al 2008) and the radio occultation measurements (Lin et al 2007a(Lin et al , 2007b are altitude independent.…”

Section: Introductionmentioning

confidence: 99%

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NmF2 and hmF2 measurements at 95° E and 127° E around the EIA northern crest during 2010–2014

2015

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The characteristics of the F2 layer parameters NmF2 and hmF2 over Dibrugarh (27.5°N, 95°E, 17°N geomagnetic, 43°dip) measured by a Canadian Advanced Digital Ionosonde (CADI) for the period of August 2010 to July 2014 are reported for the first time from this low mid-latitude station lying within the daytime peak of the longitudinal wave number 4 structure of equatorial anomaly (EIA) around the northern edge of anomaly crest. Equinoctial asymmetry is clearly observed at all solar activity levels whereas the midday winter anomaly is observed only during high solar activity years and disappears during the temporary dip in solar activity in 2013 but forenoon winter anomaly can be observed even at moderate solar activity. The NmF2/hmF2 variations over Dibrugarh are compared with that of Okinawa (26.5°N, 127°E, 17°N geomagnetic), and the eastward propagation speed of the wave number 4 longitudinal structure from 95°E to 127°E is estimated. The speed is found to be close to the theoretical speed of the wave number 4 (WN4) structure. The correlation of daily NmF2 over Dibrugarh and Okinawa with solar activity exhibits diurnal and seasonal variations. The highest correlation in daytime is observed during the forenoon hours in equinox. The correlation of daily NmF2 (linear or non-linear) with solar activity exhibits diurnal variation. A tendency for amplification with solar activity is observed in the forenoon and late evening period of March equinox and the postsunset period of December solstice. NmF2 saturation effect is observed only in the midday period of equinox. Non-linear variation of neutral composition at higher altitudes and variation of recombination rates with solar activity via temperature dependence may be related to the non-linear trend. The noon time maximum NmF2 over Dibrugarh exhibits better correlation with equatorial electrojet (EEJ) than with solar activity and, therefore, new low-latitude NmF2 index is proposed taking both solar activity and EEJ strength into account.

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The role of the vertical <I><B>E</B></I>×<I><B>B</B></I> drift for the formation of the longitudinal plasma density structure in the low-latitude F region

Cited by 31 publications

References 18 publications

WN4 effect on longitudinal distribution of different ion species in the topside ionosphere at low latitudes by means of DEMETER, DMSP-F13 and DMSP-F15 data

WN4 effect on longitudinal distribution of different ion species in the topside ionosphere at low latitudes by means of DEMETER, DMSP-F13 and DMSP-F15 data

Wavenumber-4 structures observed in the low-latitude ionosphere during low and high solar activity periods using FORMOSAT/COSMIC observations

NmF2 and hmF2 measurements at 95° E and 127° E around the EIA northern crest during 2010–2014

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