Antarctic ionospheric research

Dudeney, J. R.; Piggott, W. R.

doi:10.1029/ar029p0200

Cited by 59 publications

(44 citation statements)

References 67 publications

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“…The ionosonde results in the southern hemisphere in Figures 3a, 5a, and 5d reveal that the nighttime electron density enhancements prefer to appear during summer months than winter months, which are consistent with the previous studies [ Bellchambers and Piggott , 1958; Penndorf , 1965; Dudeney and Piggott , 1978; Burns et al , 2008; Lin et al , 2009; Liu et al , 2010]. Liu et al [2010] and Chen et al [2011] reported that the neutral wind is an important driver for the MSNA formation.…”

Section: Discussionsupporting

confidence: 90%

“… Burns et al , 2008, and references therein], recent renewed observations give wider extended coverage of the anomaly and prompt us to investigate the physical mechanism based on these new observations. According to the previous studies, the possible physical mechanisms of MSNA are photoionization of solar ultraviolet radiation [ Sojka et al , 1985; Horvath and Essex , 2003], equatorward neutral winds [ Park , 1971; Dudeney and Piggott , 1978; Su et al , 1994; Horvath and Essex , 2003; He et al , 2009; Thampi et al , 2009; Liu et al , 2010; Lin et al , 2010; Chen et al , 2011], the magnetic field configuration and offset effect [ Kohl and King , 1967; Dudeney and Piggott , 1978; Horvath , 2006; Lin et al , 2009, 2010; Liu et al , 2010; Chen et al , 2011], and the downward diffusion of the plasmaspheric plasma [ Park , 1971; Bailey et al , 1991; Burns et al , 2008; Liu et al , 2010; Chen et al , 2011]. Recently, Chen et al [2011] used a theoretical model, SAMI2 model [ Huba et al , 2000], to reproduce the integrated three‐dimensional WSA electron density structure and examine the causal mechanisms of WSA formation.…”

Section: Discussionmentioning

confidence: 99%

“…The Weddell Sea Anomaly (WSA) of the Earth's ionosphere is characterized by the greater electron density in the nighttime than that in the daytime near the Weddell Sea region during the summer period. This nighttime electron density enhancement feature was first discovered by an ionosonde located nearby the region in 1950s [ Bellchambers and Piggott , 1958; Penndorf , 1965; Dudeney and Piggott , 1978]. Recently, this feature was further observed by TOPEX/Poseidon [ Horvath and Essex , 2003; Horvath , 2006; Jee et al , 2009], FORMOSAT‐3/COSMIC [ Burns et al , 2008; He et al , 2009; Lin et al , 2009, 2010], and CHAMP [ Liu et al , 2010] satellites, indicating that the WSA extends over a much larger region between the South America and Antarctica.…”

Section: Introductionmentioning

confidence: 89%

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Long‐term variations of the nighttime electron density enhancement during the ionospheric midlatitude summer

et al. 2012

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[1] This study, for the first time, presented the long-term variations of Midlatitude Summer Nighttime Anomaly (MSNA) in the two hemispheres by using 66 ground-based ionosonde observations from 1957 to 2010. MSNA is characterized by the feature of higher nighttime electron density than daytime density in the midlatitude region during local summer months. Observations from 66 ionosonde stations were used to calculate the MSNA index which is defined by the difference between nighttime and noontime NmF2 values. The

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Section: Discussionsupporting

confidence: 90%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 89%

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Long‐term variations of the nighttime electron density enhancement during the ionospheric midlatitude summer

et al. 2012

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“…Thus the strength of plasma drift becomes strongest at 45° dip angle (I) [ Khol and King , 1967; Dudeney and Piggott , 1978], and remains large at dip angles between 20°–70° corresponding to dip latitudes of 10°–54° [ Titheridge , 1995]. During the night, upward ionospheric drifts are produced by the equatorward neutral winds that move the ionization to higher altitudes along the magnetic field lines where the loss rates are lower and thus increase the electron density and TEC.…”

Section: Tec Space Weather Observations and Discussionmentioning

confidence: 99%

“… Horvath and Essex [2003] detected just about the complete image of both phenomena during the 1998/1999 high‐sunspot summer period by utilizing the TOPEX/Poseidon technique. They pointed out first that the real size of the Weddell Sea Anomaly is much larger than was thought previously by other researchers based upon their land‐based ionosonde observations at Faraday, the name of the ionosonde station at Argentine Islands (295.7°E; −65.3°N, geographic) that is now called Vernadsky, in Antarctica providing only a limited data coverage [ Bellchambers and Piggott , 1958; Penndorft , 1965; Dudeney and Piggott , 1978; Clilverd et al , 1991]. With a series of TOPEX TEC maps, Horvath and Essex [2003] demonstrated that larger part of the Weddell Sea Anomaly is situated west of Argentine Islands over the Bellingshausen Sea, not over the Weddell Sea that is east of Argentine Islands, and concluded that it should be called the Bellingshausen Sea Anomaly.…”

Section: Introductionmentioning

confidence: 99%

A total electron content space weather study of the nighttime Weddell Sea Anomaly of 1996/1997 southern summer with TOPEX/Poseidon radar altimetry

Horvath

2006

J. Geophys. Res.

121

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[1] This paper reports on a total electron content space weather study of the nighttime Weddell Sea Anomaly, overlooked by previously published TOPEX/Poseidon climate studies, and of the nighttime ionosphere during the 1996/1997 southern summer. To ascertain the morphology of spatial TEC distribution over the oceans in terms of hourly, geomagnetic, longitudinal and summer-winter variations, the TOPEX TEC, magnetic, and published neutral wind velocity data are utilized. To understand the underlying physical processes, the TEC results are combined with inclination and declination data plus global magnetic field-line maps. To investigate spatial and temporal TEC variations, geographic/magnetic latitudes and local times are computed. As results show, the nighttime Weddell Sea Anomaly is a large ($1,600(°) 2 ; $22 million km 2 estimated for a steady ionosphere) space weather feature. Extending between 200°E and 300°E (geographic), it is an ionization enhancement peaking at 50°S-60°S/250°E-270°E and continuing beyond 66°S. It develops where the spacing between the magnetic field lines is wide/medium, easterly declination is large-medium (20°-50°), and inclination is optimum ($55°S). Its development and hourly variations are closely correlated with wind speed variations. There is a noticeable ($43%) reduction in its average area during the high magnetic activity period investigated. Southern summer nighttime TECs follow closely the variations of declination and field-line configuration and therefore introduce a longitudinal division of four (Indian, western/eastern Pacific, Atlantic). Northern winter nighttime TECs measured over a limited area are rather uniform longitudinally because of the small declination variation. TOPEX maps depict the expected strong asymmetry in TEC distribution about the magnetic dip equator.

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The Midlatitude Summer Night Anomaly as observed by CHAMP and GRACE: Interpreted as tidal features

Xiong

Lühr

2014

JGR Space Physics

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This paper presents a description of the Midlatitude Summer Night Anomaly (MSNA) in terms of solar tidal signatures, based on in situ observations from CHAMP (CHAllenging Minisatellite Payload) and GRACE (Gravity Recovery and Climate Experiment) during the solar minimum years 2008 and 2009. Our analysis is focusing on 40• to 60• magnetic latitude ranges in both hemispheres, where the reversed diurnal variations of the electron density are strongest. The results revealed that in the Southern Hemisphere the longitudinally symmetric tide D0 is particularly strong during December solstice. The well-known Weddell Sea Anomaly is caused by a simultaneous constructive interference of three components D0, DW2, and SPW1. During June solstice the eastward propagating tide DE1 is the strongest in the Northern Hemisphere, which causes a wave-2 longitudinal pattern. The two crests of the wave-2 pattern at nighttime correspond well with the MSNA feature in the Northern Hemisphere. The MSNA feature over the USA continent is particularly strong, which can be explained by the combined contributions of the components DE1, D0, and DW2. The diurnally varying difference in electron density between the USA East and West Coast can also be explained by the phase propagation of the DE1. A similar effect has also been observed in the Asian region.The peak electron densities of the tidal component D0 appear around 0700 LT and 2000 LT in the Southern and Northern Hemispheres, respectively. The time shift suggests that the two hemispheres move in antiphase up and down. The planetary wave SPW1 exhibits an electron density crest near longitude sectors where the dip equator reaches far into the summer hemisphere. IntroductionIn recent years, more and more studies are focusing on the longitudinal modulation of the ionosphere by tidal effects originating from the lower atmosphere. These tides are often excited by latent heat release in tropospheric deep convective tropical clouds and propagate vertically upward. Therefore, tidal effects in the ionosphere have attained more attention in the equatorial and low-latitude regions, where prominent longitudinal wave patterns have been found in ionospheric quantities such as the equatorial ionization anomaly (EIA), Equatorial Electrojet, vertical plasma drift, and total electron content (TEC) Lühr et al., 2008;Kil et al., 2007;Scherliess et al., 2008;Lühr et al., 2012]. The magnitudes of these tidal components vary differently with season, causing the ionospheric quantities to show longitudinal patterns with varying wave numbers over the course of a year. Best known are the wave number-4 (WN4) patterns during the months around August and wave number-3 (WN3) pattern around solstice seasons, corresponding to the diurnal DE3 and DE2 nonmigrating tides, respectively Wan et al., 2010;Lühr et al., 2008Lühr et al., , 2012. For the labeling of the tidal components we use the common convention. The first letter D, S, or T stands for diurnal, semidiurnal or terdiurnal; the second letter E or W for eastwar...

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Antarctic ionospheric research

Cited by 59 publications

References 67 publications

Long‐term variations of the nighttime electron density enhancement during the ionospheric midlatitude summer

Long‐term variations of the nighttime electron density enhancement during the ionospheric midlatitude summer

A total electron content space weather study of the nighttime Weddell Sea Anomaly of 1996/1997 southern summer with TOPEX/Poseidon radar altimetry

The Midlatitude Summer Night Anomaly as observed by CHAMP and GRACE: Interpreted as tidal features

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