Solar and geomagnetic activity effects on nocturnal zonal velocities of ionospheric plasma depletions

Sobral, J. H. A.; Abdu, M. A.; Takahashi, H.; Sawant, H. S.; Zamlutti, C. J.; Borba, Gilvan Luiz

doi:10.1016/s0273-1177(99)00716-4

Cited by 34 publications

(25 citation statements)

References 5 publications

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“…On several occasions, we observed zonal velocities larger than 200 m s −1 . The present result, in general, agrees well with the results from previous studies based on data from scanning photometers and imagers (Sobral and Sobral et al, 1999) and an all-sky imager (Pimenta et al, 2003;Martinis et al, 2003), except with the latitudinal gradient, which will be discussed in the next section. Figure 7 presents the inter-bubble distances with different latitudes.…”

Section: Zonal Drift Velocities Of the Epbssupporting

confidence: 92%

Characteristics of equatorial plasma bubbles observed by TEC map based on ground-based GNSS receivers over South America

et al. 2018

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Abstract. A ground-based network of GNSS receivers has been used to monitor equatorial plasma bubbles (EPBs) by mapping the total electron content (TEC map). The large coverage of the TEC map allowed us to monitor several EPBs simultaneously and get characteristics of the dynamics, extension and longitudinal distributions of the EPBs from the onset time until their disappearance. These characteristics were obtained by using TEC map analysis and the keogram technique. TEC map databases analyzed were for the period between November 2012 and January 2016. The zonal drift velocities of the EPBs showed a clear latitudinal gradient varying from 123 m s −1 at the Equator to 65 m s −1 for 35• S latitude. Consequently, observed EPBs are inclined against the geomagnetic field lines. Both zonal drift velocity and the inclination of the EPBs were compared to the thermospheric neutral wind, which showed good agreement. Moreover, the large two-dimensional coverage of TEC maps allowed us to study periodic EPBs with a wide longitudinal distance. The averaged values observed for the inter-bubble distances also presented a clear latitudinal gradient varying from 920 km at the Equator to 640 km at 30 • S. The latitudinal gradient in the inter-bubble distances seems to be related to the difference in the zonal drift velocity of the EPB from the Equator to middle latitudes and to the difference in the westward movement of the terminator. On several occasions, the distances reached more than 2000 km. Inter-bubble distances greater than 1000 km have not been reported in the literature.

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Section: Zonal Drift Velocities Of the Epbssupporting

confidence: 92%

Characteristics of equatorial plasma bubbles observed by TEC map based on ground-based GNSS receivers over South America

et al. 2018

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“…During their evolution EPBs rise upward and increase in latitudinal extend (Whalen, 2000). The global distribution of EPBs has been studied for decades, and a typical seasonal/longitudinal (S/L) distribution was deduced from both ground observation and satellite measurements (Sobral et al, 1999;Makela and Kelley, 2003;Burke et al, 2004). Their studies have shown that the EPB occurrence shows a seasonal and longitudinal dependence.…”

Section: Introductionmentioning

confidence: 99%

Features of highly structured equatorial plasma irregularities deduced from CHAMP observations

Xiong

Lühr

et al. 2012

Ann. Geophys.

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Abstract. In this study five years of CHAMP (Challenging Mini-satellite Payload) fluxgate magnetometer (FGM) data is used to investigate the characteristics of Equatorial Plasma Bubbles (EPBs). We filtered the FGM data by using bandpasses with four different cut-off periods to get the EPBs with different maximum spatial scale sizes in the meridional plane ranging from 76-608 km. Associated with the EPB observations at about 400 km, the typical altitude of CHAMP during the year 2000-2005, we also investigate the postsunset equatorial vertical plasma drift data from ROCSAT-1 (Republic of China Satellite 1). Since the height of the F-layer is highly correlated with the vertical plasma drift and solar flux, we sorted the ROCSAT-1 data into different groups by F10.7. From the integrated vertical drift we have estimated the post-sunset uplift of the ionosphere. By comparing the properties of EPB occurrence for different scale sizes with the global distribution of plasma vertical uplift, we have found that EPBs reaching higher altitudes are more structured than those which are sampled by CHAMP near the top side of the depleted fluxtube. Such a result is in accord with 3-D model simulations (Aveiro and Hysell, 2010). Small-scale EPB structures are observed by CHAMP when the irregularities reach apex heights of 800 km and more. Such events are encountered primarily in the Brazilian sector during the months around November, when the post-sunset vertical plasma drift is high.

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“…They drift predominantly eastward with velocities of more than 100 m s −1 and are often tilted westward (see e.g. Sobral et al, 1999;Pimenta et al, 2003;Lin et al, 2005;Park et al, 2007;Yao and Makela, 2007;Makela and Kelley, 2003). Many climatological features of the ESF occurrence rates at specific locations in different longitude sectors have been revealed from the analyses of ground-based observations (see for example Fejer et al, 1999;Abdu et al, 2000;Sahai et al, 2004;Wiens et al, 2006).…”

Section: Introductionmentioning

confidence: 99%

Relation between the occurrence rate of ESF and the equatorial vertical plasma drift velocity at sunset derived from global observations

2008

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Abstract. In this study, we investigate two global climatological data sets; the occurrence rate of Equatorial Spread-F (ESF), associated with equatorial plasma irregularities, at ∼400 km altitude obtained from CHAMP observations, and the evening equatorial vertical plasma drift, v z , from ROCSAT-1 measurements. First, as retrieved for a solar flux level of F10.7=150, the longitudinal variation of the two independently derived quantities correlates between 84% and 93% in the seasons December solstice, equinox and June solstice. The highest correlation is found for the solstice seasons when v z is integrated over local time around the prereversal enhancement (PRE) and displaced 6 • towards east. The integrated v z is a suitable estimate of the ionospheric height at the time just after the PRE and the 6 • displacement is consistent with ESF eastward drift during 2 h which is assumed between creation and detection at satellite altitudes. Second, our analyses reveal a global threshold v z which is required to observe ESF at satellite altitudes. This threshold depends linearly on solar flux with correlations of 97%. Both results bring global evidence on the linear relations between ESF and the vertical plasma drift which have been proven only by local observations so far. This paper includes the first global map of the seasonal/longitudinal variation of the ESF occurrence rate over local time being valid for high solar flux years [2001][2002][2003][2004]. The map reveals, e.g. a longitudinal dependence of the persistence of the plasma irregularities indicating that longitude dependent mechanisms other than the PRE determine the ESF lifetime.

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Solar and geomagnetic activity effects on nocturnal zonal velocities of ionospheric plasma depletions

Cited by 34 publications

References 5 publications

Characteristics of equatorial plasma bubbles observed by TEC map based on ground-based GNSS receivers over South America

Characteristics of equatorial plasma bubbles observed by TEC map based on ground-based GNSS receivers over South America

Features of highly structured equatorial plasma irregularities deduced from CHAMP observations

Relation between the occurrence rate of ESF and the equatorial vertical plasma drift velocity at sunset derived from global observations

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