Plasma Instability Growth Rates in the F-Region Cusp Ionosphere

Wednesday, 17 December 2014
Joran Idar Moen1, Y Daabakk1, Kjellmar Oksavik2, Lasse Clausen1, T. A. Bekkeng1, T. Abe3, Yoshifumi Saito3, Lisa J Baddeley4, Dag A Lorentzen4, F. Sigernes4 and Timothy K Yeoman5, (1)University of Oslo, Oslo, Norway, (2)University of Bergen, Bergen, Norway, (3)Inst Space & Astronautical Sci, Kanagawa, Japan, (4)UNIS, Longyearbyen, Norway, (5)University of Leicester, Leicester, United Kingdom
There are at least two different micro-instability processes that applies to the F-region cusp/polar cap ionosphere. These are the Gradient Drift Instability (GDI) and the Kelvin Helmholtz Instability (KHI). Due to space weather effects on radio communication and satellite signals it is of practical interest to assess the relative importance of these two instability modes and to quantify their growth rates. The Investigation of Cusp Irregularities (ICI) rocket program has been developed to investigate these plasma instabilities and formation scintillation irregularities. High resolution measurements are critical to get realistic quantities on the growth rates. The results achieved so far demonstrates that cusp ionosphere precipitation can give rise to km scale plasma structures on which grow rates are down to a few tens of seconds compared to earlier measures of ten minutes based on ground observations. This has to do with the spatial resolution required for these measurements. Growth rates for the KHI instability is found to be of the same order, which is consistent with growth rates calculated from the EISCAT Svalbard Radar. I.e. both instability modes can be highly efficient in the cusp ionosphere.