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GEOPHYSICAL RESEARCH LETTERS, VOL. 33, L15111, doi:10.1029/2006GL026916, 2006

Estimating drift velocity of polar cap patches with all-sky airglow imager at Resolute Bay, Canada

K. Hosokawa

Department of Information and Communication Engineering, The University of Electro-Communications, Chofu, Japan


K. Shiokawa

Solar-Terrestrial Environment Laboratory, Nagoya University, Toyokawa, Japan


Y. Otsuka

Solar-Terrestrial Environment Laboratory, Nagoya University, Toyokawa, Japan


A. Nakajima

Solar-Terrestrial Environment Laboratory, Nagoya University, Toyokawa, Japan


T. Ogawa

Solar-Terrestrial Environment Laboratory, Nagoya University, Toyokawa, Japan


J. D. Kelly

SRI International, Menlo Park, California, USA


Abstract

Highly sensitive all-sky airglow imager has been operative at Resolute Bay, Canada (74.73°N, 265.07°E; AACGM latitude 82.9°) since January 2005. We present, as a first result from the imager, an event of polar cap patches drifting anti-sunward during the southward IMF conditions. Magnitude and direction of patch drift velocities are computed with a temporal resolution of 2 min by using the newly developed patch-tracking algorithm based on 2D cross correlation analysis. It is well visualized that the patches change their moving speed and direction drastically in a short time scale (a few minutes). Speed of the patch is primally controlled by the IMF Bz. Dawn-dusk component of the patch drift velocities is well correlated with the IMF By in agreement with published By dependence of the nightside polar cap convection. However, response of the patch drift direction to the IMF By is found to be much slower (≈20 min) than that of the drift speed to the IMF Bz (almost instantaneous).

Received 16 May 2006; accepted 10 July 2006; published 15 August 2006.

Index Terms: 2475 Ionosphere: Polar cap ionosphere; 2463 Ionosphere: Plasma convection (2760); 2431 Ionosphere: Ionosphere/magnetosphere interactions (2736); 2439 Ionosphere: Ionospheric irregularities; 2494 Ionosphere: Instruments and techniques.

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Citation: Hosokawa, K., K. Shiokawa, Y. Otsuka, A. Nakajima, T. Ogawa, and J. D. Kelly (2006), Estimating drift velocity of polar cap patches with all-sky airglow imager at Resolute Bay, Canada, Geophys. Res. Lett., 33, L15111, doi:10.1029/2006GL026916.