SA33A-04
On which timescales are By induced in the closed magnetosphere?
Wednesday, 16 December 2015: 14:25
2016 (Moscone West)
Paul Tenfjord1, Nikolai Ostgaard1, Robert J Strangeway2, Kristian Snekvik1, Karl Laundal1, Jone Peter Reistad1, Steve E. Milan3 and Stein Haaland4, (1)University of Bergen, Birkeland Centre for Space Science, Bergen, Norway, (2)University of California Los Angeles, IGPP/EPSS, Los Angeles, CA, United States, (3)University of Leicester, Leicester, United Kingdom, (4)University of Bergen, Bergen, Norway
Abstract:
The IMF $B_y$ induces a $B_y$ component in the closed magnetosphere through asymmetric loading of flux from the dayside reconnection process. In the presence of IMF $B_y$, oppositely y-directed stresses exerted on the newly reconnected open flux tubes forces the flux to be added to opposite regions of the lobe between the two hemispheres. For example, a postive IMF $B_y$ results in enhanced flux in the northern dawn and southern dusk lobe. In this paper we study the evolution of these asymmetric stresses. When these stresses are communicated to the different regions of the closed magnetosphere we observe an induced $B_y$ component. The estimates of the timescales on which this process occurs are highly divergent in the literature. We perform a multi-spacecraft and MHD analysis to study the response in different regions of the magnetosphere (on closed field lines) for single events with IMF $B_z<0$ and varying $B_y$ conditions. Using MHD model results and spacecraft data we show how $B_y$ is induced and that this occurs on timescales in the order of tens of minutes. We also use data from AMPERE to investigate the high-latitude ionospheric response to IMF $B_y$.
