Observations of ULF Waves at the Cusp Latitude in the two Hemispheres

Abstract:

ULF waves are highly associated with the structure of the magnetosphere and the plasma composition in space for both their generation and propagation, and they can act as an indicator of kinds of the physical processes occurring in the outer magnetosphere particularly near the high latitude boundary and magnetopause, which usually map to the cusp region. Three fluxgate magnetometers have been respectively deployed at the cusp latitudes in the both hemispheres, Zhongshan Station (69°S 76°E in GEO, same hereafter) in Antarctica, Yellow River Station (79°N 12°E) and KHO (78°N 16°E) in the Arctic. Another fluxgate magnetometer has been set at Karholl Base (66°N 17°W) in the Iceland, which is located under the radiation belt or near the auroral zone. These magnetometer record data in three orthogonal components with sample frequency at 25 Hz. Observational data have been accumulated since February 2013. Preliminary analysis show that two types of ULF wave activities appears frequency on the observation regions, one is the broadband wave, which can occur over a frequency range 0.5-10 Hz and above, and in three components or only in the transversal components, and the other is the narrowband waves, which are generally limited within a frequency range below 0.5 Hz, and usually associated with harmonic components, in 8, 9 and 10 Hz, and basically occur on the transversal x and y components. Detailed wave properties and conjugated characteristics are under investigated and on progress.