Articles | Volume 30, issue 12
Ann. Geophys., 30, 1693–1701, 2012
Ann. Geophys., 30, 1693–1701, 2012

Regular paper 14 Dec 2012

Regular paper | 14 Dec 2012

Spatial characteristics of wave-like structures in diffuse aurora obtained using optical observations

K. Axelsson1,2, T. Sergienko1, H. Nilsson1, U. Brändström1, Y. Ebihara3, K. Asamura4, and M. Hirahara5 K. Axelsson et al.
  • 1Swedish Institute of Space Physics, Kiruna, Sweden
  • 2Division of Space Technology, Luleå University of Technology, Kiruna, Sweden
  • 3Research Institute for Sustainable Humanosphere, Kyoto University, Kyoto, Japan
  • 4Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Sagamihara, Japan
  • 5Department of Earth and Planetary Science, Graduate School of Science, University of Tokyo, Tokyo, Japan

Abstract. We present the results of a statistical study using optical images from ALIS (Auroral Large Imaging System) to investigate the spatial and temporal variations of structures in diffuse aurora. Analysis of conjugate Reimei data shows that such fine structures are a result of modulation of high-energy precipitating electrons. Pitch angle diffusion into the loss cone due to interaction of whistler mode waves with plasma sheet electrons is the most feasible mechanism leading to high-energy electron precipitation. This suggests that the fine structure is an indication of modulations of the efficiency of the wave–particle interaction. The scale sizes and variations of these structures, mapped to the magnetosphere, can give us information about the characteristics of the modulating wave activity. We found the scale size of the auroral stripes and the spacing between them to be on average 13–14 km, which corresponds to 3–4 ion gyro radii for protons with an energy of 7 keV. The structures move southward with a speed close to zero in the plasma convection frame.