Asymmetric Ionospheric Outflow Observed at the Dayside Magnetopause

Wednesday, 17 December 2014
Sun-Hee Lee1, Hui Zhang1, Qiugang Zong2, David G Sibeck3, Yongfu Wang4, Karl-Heinz Glassmeier5 and Henri Reme6, (1)University of Alaska, Fairbanks, Fairbanks, AK, United States, (2)Peking University, School of Earth and Space Sciences, Beijing, China, (3)NASA GSFC, Greenbelt, MD, United States, (4)Peking University, Beijing, China, (5)TU Braunschweig, Braunschweig, Germany, (6)CNRS, Paris Cedex 16, France
An important source of the terrestrial magnetospheric plasma is cold plasma from the polar ionosphere. The ionospheric ion outflows have been rarely observed at the dayside magnetopause. We investigate the source and the behaviors of the cold ions observed by the Cluster spacecraft measurements. The pitch angle distributions (0°-75°) of the cold ions observed by both C1 and C3 at the dayside magnetopause indicate that these cold ions are ionospheric outflows coming from the southern hemisphere. The cold ions (< 200 eV) fluxes are modulated by the ULF wave electric field. The cold ions move perpendicular to the magnetic field due to the enhanced convection electric field when they are close to the magnetic reconnection region. Two different populations (possibly H+ and He+) were observed in the magnetosphere. Our results suggest that the ionospheric outflows can be transported to the dayside magnetopause and may play an important role in the dynamics of this region.