Direct observations of blob deformation during a substorm
- 1National Institute of Polar Research, Tokyo 190-8518, Japan
- 2Department of Polar Science, SOKENDAI (The Graduate University for Advanced Studies),Tokyo 190-8518, Japan
- 3Department of Communication Engineering and Informatics, University of Electro-Communications,Tokyo 182-8585, Japan
- 4Solar-Terrestrial Environment Laboratory, Nagoya University, Nagoya 464-8601, Japan
Abstract. Ionospheric blobs are localized plasma density enhancements, which are mainly produced by the transportation process of plasma. To understand the deformation process of a blob, observations of plasma parameters with good spatial–temporal resolution are desirable. Thus, we conducted the European Incoherent Scatter radar observations with high-speed meridional scans (60–80 s) during October and December 2013, and observed the temporal evolution of a blob during a substorm on 4 December 2013. This paper is the first report of direct observations of blob deformation during a substorm. The blob deformation arose from an enhanced plasma flow shear during the substorm expansion phase, and then the blob split into two smaller-scale blobs, whose scale sizes were more than ~100 km in latitude. Our analysis indicates that the Kelvin–Helmholtz instability and dissociative recombination could have deformed the blob structure.