October 8, 2010, 12:00 pm - 1:00 pm

October 8, 2010, 12:00 pm - 1:00 pm

Solar Cycle Effect in Strong Turbulence in IMF Bz

Sonya Lyatskaya (Alabama A&M University, Huntsville, AL)

We found that strong turbulence in IMF Bz near 1 AU during four solar minima shows a good correlation with the absolute value of IMF Bx which varies periodically for even and odd solar cycles. The hourly mean amplitudes of turbulent IMF Bz are about �1 nT that is comparable with the average value of IMF Bz during solar minima. Observations from ACE spacecraft show that this turbulence in IMF Bz strongly decreases with increasing IMF By but increases with both solar wind speed and Helium/proton number ratio which show that this turbulence occurs not within the heliospheric plasma sheet (where both plasma velocity and Helium/proton ratio are low) but probably at the plasma sheet boundaries. A probable cause of this turbulence may be the Kelvin-Helmholtz instability (possibly in combination with interchange instability) developing on the plasma sheet boundaries. This mechanism may be one of main factors responsible for strong turbulence in IMF Bz, which are responsible for geomagnetic activity, during relatively quiet solar wind conditions.