The transmission of upstream waves at polar latitudes through magnetotail lobes

We conducted a statistical analysis of the upstream wave transmission from the foreshock region to the magnetosphere and at polar latitudes, during 2005-2010. We analyzed geomagnetic measurements at Dome C, in Antarctica, close to the geomagnetic pole (λ ~ 88.84° S), and magnetospheric data from Cluster satellites. The analysis was restricted to time intervals when Cluster was located in the southern magnetotail lobe, on a field line whose footprint was close to Dome C. The coherence between the geomagnetic field components and the magnetospheric field components shows highest values in the 20-35 mHz frequency range (i.e. at typical frequencies of the upstream wave), mainly in the early morning and premidnight hours, when DMC was not affected by cusp phenomena. For a case study (27 September 2009), we found a time delay between magnetospheric and ground fluctuations at f~25-30 mHz, consistent with the propagation time of Alfven waves along the geomagnetic field line connected with satellite position.