Swarm in situ observations of <b><i>F</i></b> region polar cap patches created by cusp precipitation

Goodwin, Lindsay; Iserhienrhien, B.; Miles, David M.; Patra, S.; Meeren, Christer van der; Buchert, Stephan; Burchill, J. K.; Clausen, L. B. N.; Knudsen, D. J.; McWilliams, K. A.; Moen, J.

doi:10.1002/2014gl062610

Cited by 71 publications

(80 citation statements)

References 39 publications

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“…Soft particle precipitation in the cusp region where particles precipitate directly from the magnetosheath can produce polar cap patches that can be convected over the polar cap (e.g., Walker et al, 1999;Oksavik et al, 2006;Goodwin et al, 2015). As a result of plasma transport and particle precipitation, the high-latitude F region ionosphere is nonuniform and highly dynamic.…”

Section: Introductionmentioning

confidence: 99%

An evaluation of International Reference Ionosphere electron density in the polar cap and cusp using EISCAT Svalbard radar measurements

et al. 2016

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Abstract. Incoherent scatter radar measurements are an important source for studies of ionospheric plasma parameters. In this paper the EISCAT Svalbard radar (ESR) long-term database is used to evaluate the International Reference Ionosphere (IRI) model. The ESR started operations in 1996, and the accumulated database up to 2012 thus covers 16 years, giving an overview of the ionosphere in the polar cap and cusp during more than one solar cycle. Data from ESR can be used to obtain information about primary plasma parameters: electron density, electron and ion temperature, and line-ofsight plasma velocity from an altitude of about 50 and up to 1600 km. Monthly averages of electron density and temperature and ion temperature and composition are also provided by the IRI model from an altitude of 50 to 2000 km. We have compared electron density data obtained from the ESR with the predicted electron density from the IRI-2016 model. Our results show that the IRI model in general fits the ESR data well around the F2 peak height. However, the model seems to underestimate the electron density at lower altitudes, particularly during winter months. During solar minimum the model is also less accurate at higher altitudes. The purpose of this study is to validate the IRI model at polar latitudes.

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Section: Introductionmentioning

confidence: 99%

An evaluation of International Reference Ionosphere electron density in the polar cap and cusp using EISCAT Svalbard radar measurements

et al. 2016

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“…While such gain variations clearly compromise the accuracy of the EFI measurements, the relative stability of the gain patterns over one orbit provides an opportunity to calibrate the measurements on an orbit-by-orbit basis, based on the assumption of relatively low convection velocity at subauroral latitudes. This approach has been used in preliminary studies of high-latitude flow channels (Goodwin et al 2015;Archer et al 2015).…”

Section: Introductionmentioning

confidence: 99%

Calibration and assessment of Swarm ion drift measurements using a comparison with a statistical convection model

et al. 2016

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The electric field instruments onboard the Swarm satellites make high-resolution measurements of the F-region ion drift. This paper presents an initial investigation of preliminary ion drift data made available by the European Space Agency. Based on data taken during polar cap crossings, we identify large offsets in both the along-track and crosstrack components of the measured ion drift. These offsets are removed by zeroing drift values at the low-latitude boundary of the high-latitude convection pattern. This correction is shown to significantly improve agreement between the Swarm ion drift measurements and velocity inferred from a radar-based statistical convection model for periods of quasi-stability in the solar wind and interplanetary magnetic field. Agreement is most pronounced in the cross-track direction (R = 0.60); it improves slightly (R = 0.63) if data are limited to periods with IMF B z < 0. The corrected Swarm data were shown to properly identify the convection reversal boundary for periods of IMF B z < 0, in full agreement with previous radar and satellite measurements, making Swarm ion drift measurements a valuable input for ionospheric modeling.

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“…Localized enhancements in plasma density (100-1000 km in extent) known as polar patches have received even more attention than their low-density counterparts [Buchau et al, 1983;Weber et al, 1984;Rodger et al, 1994;Milan et al, 2002;Hosokawa et al, 2009;Dahlgren et al, 2012aDahlgren et al, , 2012bZhang et al, 2013;Burston et al, 2014;Goodwin et al, 2015]. A fundamental problem is what causes the plasma to be chopped into islands and what happens with patches after they have been separated from their source region including further structuring processes [Carlson, 2012].…”

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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Swarm in situ observations of F region polar cap patches created by cusp precipitation

Cited by 71 publications

References 39 publications

An evaluation of International Reference Ionosphere electron density in the polar cap and cusp using EISCAT Svalbard radar measurements

An evaluation of International Reference Ionosphere electron density in the polar cap and cusp using EISCAT Svalbard radar measurements

Calibration and assessment of Swarm ion drift measurements using a comparison with a statistical convection model

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

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