Variation of Ultra-Low Frequency Waves within Solar Wind and Pc5 Fluctuations on the Ground in High Latitudes during Solar Cycle 23

Abstract:

Ultra-low frequency (ULF) waves in the magnetosphere can be significant for the diffusion of energy and particles in the outer radiation belt. We present a statistical comparison of ULF wave power within the solar wind and in the magnetosphere during years 1998-2008. Data from Advanced Composite Explorer (ACE) spacecraft MAG and SWE experiments is used to examine the solar wind ULF structure and on the ground Kevo magnetometer was used to examine the Pc5 power. We determined the monthly average power in the Pc5 range (2-7 mHz) using Fast Fourier Transforms and study its yearly and monthly variation. We find that ULF power in solar wind is large during the years of declining sunspot phase 2002-2004 in both solar wind and on the ground and that the monthly averages peak at the same times. A close correlation of ULF power in solar wind and on the ground is found in the minimum years 2006-2008. We also report a winter maximum between 2001 and 2006 in the Pc5 power at Kevo.