Assessing Doppler velocities of Rankin Inlet F-region echoes

Multiyear (1995–2013) velocity data collected by the Super Dual Auroral Network (SuperDARN) HF radars are considered to investigate the diurnal, seasonal, and solar cycle variation of the polar cap plasma flow speed. By considering monthly data sets, we show that the flows are systematically faster in the dawn/prenoon sector. The effect is particularly strong for interplanetary magnetic field (IMF) Bz < 0, By > 0 and in summer months. For Bz < 0, the flow speed increases with intensification of the IMF transverse component Bt at a rate of 20–30 m/s/nT during near noon summer hours. The dependence is weaker for other seasons and away from noon. For IMF Bz > 0, the flow speed response to the increase in Bt is weak. Despite the general sensitivity of the flow speed to Bt intensity and season, the speed for specific IMF bins and seasons or the speed averaged over a year does not change much over the solar cycle. Overall, the velocity is reduced during years of lowest solar activity, but a progression of the effect throughout the solar cycle was not observed. Inferred diurnal and seasonal trends of the polar cap flow speed are generally consistent with variations in the occurrence of VHF echoes whose onset depends on the strength of the ionospheric electric field or equivalently the magnitude of the plasma flow speed.

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Long‐term variations in the intensity of polar cap plasma flows inferred from SuperDARN

Koustov

Fiori

Zadeh

2015

JGR Space Physics

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Seasonal effect for polar cap sunward plasma flows at strongly northward IMF B_z

2017

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We use Super Dual Auroral Radar Network data to study polar cap ionospheric flow under strongly dominant positive interplanetary magnetic field Bz component. We show that the near‐noon flow along the magnetic meridian is predominantly sunward in summer. The sunward velocity increase with intensification of the external driver (the reverse convection electric field) is also faster in summer, and the rate of the increase is slightly larger for the Southern Hemisphere. The sunward flows simultaneously detected in both hemispheres are faster in the summer hemisphere. In addition, while sunward flows are aligned with the midnight‐noon line in a winter hemisphere, they are oriented toward earlier magnetic local hours in a summer hemisphere.

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On the consistency of the SuperDARN radar velocity and E × B plasma drift

2016

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Joint observations of the Rankin Inlet (RKN) and Inuvik Super Dual Auroral Radar Network (SuperDARN) HF radars and Resolute Bay incoherent scatter radar (RISR) are used to assess consistency in their plasma flow velocity measurements. The analysis covers more than 500 h of successful concurrent measurements. We demonstrate that, overall, the radars show close velocities, although there were minor differences including SuperDARN velocity underestimation, in line with previous publications, and the persistent occurrence of measurements with a SuperDARN velocity magnitude above the RISR velocity magnitude. We argue that, for one event, the velocity overestimation occurs owing to echo detection from a laterally refracted RKN beam while, generally, the effect should be fairly wide‐spread in SuperDARN data because of microstructures with enhanced electron density in the scattering volume that might have either weak irregularities or increased local electric fields. We estimate that the correction of RKN velocity data by considering the effect of the index of refraction improves RKN‐RISR velocity agreement but only for 63% of points. This implies that care should be exercised when attempting to correct raw SuperDARN velocity data by the index of refraction.

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Assessing Doppler velocities of Rankin Inlet F-region echoes

Cited by 3 publications

References 14 publications

Long‐term variations in the intensity of polar cap plasma flows inferred from SuperDARN

Long‐term variations in the intensity of polar cap plasma flows inferred from SuperDARN

Seasonal effect for polar cap sunward plasma flows at strongly northward IMF B_z

On the consistency of the SuperDARN radar velocity and E × B plasma drift

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Assessing Doppler velocities of Rankin Inlet F-region echoes

Cited by 3 publications

References 14 publications

Long‐term variations in the intensity of polar cap plasma flows inferred from SuperDARN

Long‐term variations in the intensity of polar cap plasma flows inferred from SuperDARN

Seasonal effect for polar cap sunward plasma flows at strongly northward IMF Bz

On the consistency of the SuperDARN radar velocity and E × B plasma drift

Contact Info

Product

Resources

About

Seasonal effect for polar cap sunward plasma flows at strongly northward IMF B_z