Imaging riometer and HF radar measurements of driftingFregion electron density structures in the polar cap

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-of-sight 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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A comparison of optical and coherent HF radar backscatter observations of a post-midnight aurora

Annales Geophysicae ◽

10.1007/s00585-997-1388-0 ◽

1997 ◽

Vol 15 (11) ◽

pp. 1388-1398 ◽

Cited By ~ 2

Author(s):

S. E. Milan ◽

M. Lester ◽

J. Moen

Keyword(s):

Flow Velocity ◽

Plasma Flow ◽

Hf Radar ◽

Polar Cap ◽

Common Features ◽

Optical Feature ◽

Radar Measurements ◽

Coherent Backscatter ◽

East West ◽

Poleward Expansion

Abstract. A poleward-progressing 630 nm optical feature is observed between approximately 0100 UT and 0230 UT (0400 MLT to 0530 MLT) by a meridian-scanning photometer (MSP) located at Ny Ålesund, Svalbard. Simultaneous coherent HF radar measurements indicate a region of poleward-expanding backscatter with rapid sunward plasma flow velocity along the MSP meridian. Spatial maps of the backscatter indicate a stationary backscatter feature aligned obliquely with respect to the MSP meridian, which produces an impression of poleward-expansion as the MSP progresses to later MLT. Two interpretations of the observations are possible, depending on whether the arc system is considered to move (time-dependent) or to be stationary in time and apparent motion is produced as the MSP meridian rotates underneath it (time-independent). The first interpretation is as a poleward motion of an east-west aligned auroral arc. In this case the appearance of the region of backscatter is not associated with the optical feature, though the velocities within it are enhanced when the two are co-located. The second interpretation is as a polar arc or theta aurora, common features of the polar cap under the prevailing IMF northwards conditions. In this case the backscatter appears as an approximately 150 km wide region adjacent to the optical arc. In both interpretations the luminosity of the optical feature appears related to the magnitude of the plasma flow velocity. The optical features presented here do not generate appreciable HF coherent backscatter, and are only identifiable in the backscatter data as a modification of the flow by the arc electrodynamics.

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Lagrangian coherent structures deduced from HF radar measurements

OCEANS 2015 - Genova ◽

10.1109/oceans-genova.2015.7271350 ◽

2015 ◽

Author(s):

Francesco Enrile ◽

Giovanni Besio ◽

Marcello G. Magaldi ◽

Carlo Mantovani ◽

Simone Cosoli ◽

...

Keyword(s):

Coherent Structures ◽

Hf Radar ◽

Lagrangian Coherent Structures ◽

Radar Measurements

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Polar patches observed by ESR and their possible origin in the cusp region

Annales Geophysicae ◽

10.1007/s00585-000-1043-5 ◽

2000 ◽

Vol 18 (9) ◽

pp. 1043-1053 ◽

Cited By ~ 12

Author(s):

A. M. Smith ◽

S. E. Pryse ◽

L. Kersley

Keyword(s):

Energy Distribution ◽

Electron Density ◽

Plasma Flow ◽

Plasma Temperature ◽

Soft Particle ◽

Polar Ionosphere ◽

Polar Cap ◽

Particle Precipitation ◽

Cusp Region ◽

Reconnection Site

Abstract. Observations by the EISCAT Svalbard radar in summer have revealed electron density enhancements in the magnetic noon sector under conditions of IMF Bz southward. The features were identified as possible candidates for polar-cap patches drifting anti-Sunward with the plasma flow. Supporting measurements by the EISCAT mainland radar, the CUTLASS radar and DMSP satellites, in a multi-instrument study, suggested that the origin of the structures lay upstream at lower latitudes, with the modulation in density being attributed to variability in soft-particle precipitation in the cusp region. It is proposed that the variations in precipitation may be linked to changes in the location of the reconnection site at the magnetopause, which in turn results in changes in the energy distribution of the precipitating particles.Key words: Ionosphere (ionosphere-magnetosphere interactions; plasma temperature and density; polar ionosphere)

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Atmospheric Ionization Module Osnabrück (AIMOS): 3. Comparison of electron density simulations by AIMOS-HAMMONIA and incoherent scatter radar measurements

Journal of Geophysical Research Atmospheres ◽

10.1029/2010ja016300 ◽

2011 ◽

Vol 116 (A8) ◽

pp. n/a-n/a ◽

Cited By ~ 8

Author(s):

J. M. Wissing ◽

M.-B. Kallenrode ◽

J. Kieser ◽

H. Schmidt ◽

M. T. Rietveld ◽

...

Keyword(s):

Electron Density ◽

Incoherent Scatter Radar ◽

Incoherent Scatter ◽

Scatter Radar ◽

Radar Measurements ◽

Atmospheric Ionization

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HF radar measurements of ocean wave parameters during NURWEC

IEEE Journal of Oceanic Engineering ◽

10.1109/joe.1986.1145184 ◽

1986 ◽

Vol 11 (2) ◽

pp. 219-234 ◽

Cited By ~ 18

Author(s):

L. Wyatt ◽

J. Venn ◽

G. Burrows ◽

A. Ponsford ◽

M. Moorhead ◽

...

Keyword(s):

Hf Radar ◽

Ocean Wave ◽

Wave Parameters ◽

Radar Measurements

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Assimilation of HF radar surface currents to optimize forcing in the northwestern Mediterranean Sea

Nonlinear Processes in Geophysics ◽

10.5194/npg-21-659-2014 ◽

2014 ◽

Vol 21 (3) ◽

pp. 659-675 ◽

Cited By ~ 30

Author(s):

J. Marmain ◽

A. Molcard ◽

P. Forget ◽

A. Barth ◽

Y. Ourmières

Keyword(s):

Surface Wind ◽

Circulation Model ◽

Radar Data ◽

Hf Radar ◽

Open Boundary ◽

Coastal Current ◽

Surface Currents ◽

Data Set ◽

Radar Measurements ◽

Northwestern Mediterranean

Abstract. HF radar measurements are used to optimize surface wind forcing and baroclinic open boundary condition forcing in order to constrain model coastal surface currents. This method is applied to a northwestern Mediterranean (NWM) regional primitive equation model configuration. A new radar data set, provided by two radars deployed in the Toulon area (France), is used. To our knowledge, this is the first time that radar measurements of the NWM Sea are assimilated into a circulation model. Special attention has been paid to the improvement of the model coastal current in terms of speed and position. The data assimilation method uses an ensemble Kalman smoother to optimize forcing in order to improve the model trajectory. Twin experiments are initially performed to evaluate the method skills. Real measurements are then fed into the circulation model and significant improvements to the modeled surface currents, when compared to observations, are obtained.

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