Response of polar cap to solar wind conditions

Abstract:

The ionospheric polar cap is an optically dark area encircled by the luminous auroral oval. It is created by solar wind-magnetospheric coupling, and its size is proportional to the open magnetic flux available for nightside reconnection. One of the difficulties in the study of solar wind-magnetosphere coupling is the large spatial domain it involves. Systematic studies of the polar cap dynamics are still rare. This study addresses this issue by utilizing global auroral images, from which the polar cap area can be extracted, acquired with the Ultraviolet Imager on board the Polar satellite. In particular, we quantify the area of polar cap and correlate it with solar wind parameters. Our preliminary results clearly demonstrate, as expected, a clear relationship between the dayside polar cap area and the north-south component of the interplanetary magnetic field. Other solar wind parameters also affect the polar cap size but with a lesser degree. We will present a detailed analysis and discuss the resulting implications.