Plasma density features associated with strong convection in the winter high‐latitude F region

Sojka, J. J.; Raitt, W. J.; Schunk, R. W.

doi:10.1029/ja086ia08p06908

Cited by 67 publications

(41 citation statements)

References 14 publications

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“…In the Earth's frame, the solar wind's dawn‐dusk electric field ( E SW ) and its speed ( V SW ) relate by the equation E SW = − V SW × B [ Burton et al , 1975]. Accordingly, increase in V SW would enhance the E SW , which could enhance E I by mapping along the magnetic field lines downward into ionosphere, further enhancing the E × B convection and expanding the convection pattern [ Sojka et al , 1981; Khan and Cowley , 1999]. As a result, the stagnation point and the stagnation MIT would shift equatorward.…”

Section: Resultsmentioning

confidence: 99%

A study on the nighttime midlatitude ionospheric trough

Liu

Wan

et al. 2011

J. Geophys. Res.

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[1] Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) electron density profiles are used to investigate the nighttime midlatitude ionospheric trough (MIT). We find that at midnight the longitudinally deepest MIT occurs to the west of the geomagnetic pole in both the Northern and Southern Hemispheres during the equinox seasons and local summer. The deepest MIT could be ascribable to the enhanced depletion caused by horizontal neutral wind. In the early evening, the eastward neutral wind prevails in the midlatitude F region, which blows the plasma downward where the declination is eastward in the Northern Hemisphere but westward in the Southern Hemisphere, both lying to the west of the geomagnetic pole. The downward drift would enhance the plasma depletion for more molecular composition at lower altitude. In addition, we find for the first time that the location of nighttime MIT minimum oscillated with a periodicity of 9 days and an amplitude of about 1°-1.5°geomagnetic latitude during 2007-2008, associated with the recurrent high-speed solar wind. Our results shed new light on the empirical description and numerical simulation of MIT.

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Section: Resultsmentioning

confidence: 99%

A study on the nighttime midlatitude ionospheric trough

Liu

Wan

et al. 2011

J. Geophys. Res.

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“…Sojka et al () reported that under conditions of enhanced magnetospheric convection, TOI is more pronounced. The main characteristics of the TOI occurrence during strong geomagnetic storms have been studied using multi‐instrumental observations and theoretical models (e.g., Foster et al, ; David et al, ; Liu et al, , Liu, Wang, Burns, Solomon, et al, ; Liu, Wang, Burns, Yue, et al, ; Thomas et al, ).…”

Section: Introductionmentioning

confidence: 99%

Simulation and Observations of the Polar Tongue of Ionization at Different Heights During the 2015 St. Patrick's Day Storms

et al. 2019

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We present the observational and modeling study focused on the major factors determining the spatiotemporal structure of the high‐latitude ionospheric plasma density enhancement—the tongue of ionization (TOI) structure—during the 2015 St. Patrick's Day geomagnetic storm. We use the Global Self‐consistent Model of the Thermosphere, Ionosphere, Protonosphere (GSM TIP) to reproduce the plasma density distribution, and the results are compared with the observational data as deduced from the ground‐based global positioning system total electron content and in situ plasma probe measurements at different altitudes. Both the simulation and observation results show that a large‐scale TOI‐like structure of enhanced plasma density extends from the dayside midlatitude region toward the central polar cap along the antisunward cross‐polar convection flow. We reveal an important role of the clockwise convection cell rotation for the modification of TOI structure. According to model results during the storm main phase, the neutral thermospheric composition, particularly the “tongue” in n(N2), modifies the spatial structure of TOI in such a way that (1) the near‐pole region of enhanced plasma density is shifted to the duskside and, (2) at F region heights, the TOI is split into the dusk and dawn branches. The signature of TOI in the topside ionosphere considerably differs from that in the F region because of a lesser influence of the neutral composition changes at higher altitudes. Model results revealed that at plasmaspheric heights, the TOI structure appears in both the dawn and dusk convection cells.

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“…This is because polar holes are assumed to be formed when convection is either very slow [Brinton et al, 1978;Sojka et al, 1981aSojka et al, , 1981b or perhaps strongly enhanced [Sojka et al, 1981c]. In most previous experimental investigations of polar holes, however, the convection context was mainly provided by statistical maps [Brinton et al, 1978;Benson and Grebowsky, 2001] since concurrent measurements were not available.…”

Section: Density Depressions: Characteristics and Relation To Plasma mentioning

confidence: 99%

“…Polar holes and auroral cavities have been identified using different observational techniques, but they are statistically colocated so that a common term of the polar hole-auroral cavity region, or simply the polar hole, has been used more recently [Benson and Grebowsky, 2001]. It is thought that a polar hole can form either due to continuous recombination over a long interval under quiet conditions [Sojka et al, 1981a[Sojka et al, , 1981b or large downward plasma transport driven by strong convection [Sojka et al, 1981c].…”

Section: Introductionmentioning

confidence: 99%

Resolute Bay Incoherent Scatter Radar observations of plasma structures in the vicinity of polar holes

2015

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The Resolute Bay Incoherent Scatter Radar North (RISR‐N) data collected between January 2012 and June 2013 are employed to identify and analyze 14 events with significant plasma density depressions (Ne<4 × 1010 m−3) in the winter polar cap ionosphere. The RISR‐N observations near a magnetic latitude (MLAT) of 85°N refer to the region poleward of the previously identified polar hole‐auroral cavity region 70°–80° MLAT where extremely low densities (down to 2 × 108 m−3 near 300 km in altitude) are found at times. Multipoint observations by RISR‐N are also characterized by multiple series of propagating local density enhancements (plasma structures) both well outside and in the vicinity of polar holes. A superposed epoch analysis of plasma density and convection reveals that the density depressions tend to reach their minimum near the reversal of the meridional convection component. The wavelet analysis of plasma density time series shows that the wave power is enhanced within the depressions and tends to peak near the density minimum. The plasma structures are more elongated at mesoscales (>150 km), with no apparent differences between structure shapes outside and inside low‐density regions. The structure propagation velocity is perpendicular to its elongation direction and consistent with that of the large‐scale plasma convection. The observations indicate that large‐scale density depressions can form under a variety of convection conditions and that plasma structuring processes outside the depressions may be responsible for their partial filling.

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Plasma density features associated with strong convection in the winter high‐latitude F region

Cited by 67 publications

References 14 publications

A study on the nighttime midlatitude ionospheric trough

A study on the nighttime midlatitude ionospheric trough

Simulation and Observations of the Polar Tongue of Ionization at Different Heights During the 2015 St. Patrick's Day Storms

Resolute Bay Incoherent Scatter Radar observations of plasma structures in the vicinity of polar holes

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