Estimation of cold plasma outflow during geomagnetic storms

Friday, 18 December 2015: 14:54
2016 (Moscone West)
Stein Haaland1,2, Anders I Eriksson3, Mats Andre3, Lukas Maes4, Lisa J Baddeley5, Abdallah R Barakat6, Charles R Chappell7, Vincent Eccles6, Christine Johnsen8, Bjorn Lybekk9, Kun Li10, Arne Pedersen9, Robert Walter Schunk6 and Daniel T Welling11, (1)Max-Planck Institute, Goettingen, Germany, (2)Birkeland Centre for Space Science, Bergen, Norway, (3)IRF Swedish Institute of Space Physics Uppsala, Uppsala, Sweden, (4)Belgisch Instituut voor Ruimte-Aeronomie, Brussel, Belgium, (5)UNIS, Longyearbyen, Norway, (6)Utah State University, Logan, UT, United States, (7)Vanderbilt University, Nashville, TN, United States, (8)University of Oslo, Department of Geophysics, Oslo, Norway, (9)University of Oslo, Department of Physics, Oslo, Norway, (10)Max Planck Institute for Solar System Research, Katlenburg-Lindau, Germany, (11)University of Michigan Ann Arbor, Ann Arbor, MI, United States
Low energy ions of ionospheric origin provide a significant contributon to the magnetospheric plasmapopulation. Measuring cold ions is difficult though. Observations have to be done at sufficiently high altitudes and typically in regions of space where spacecraft attain a positive charge due to solar illumination. Cold ions are therefore shielded from the satellite particle detectors. Furthermore, spacecraft can only cover key regions of ion outflow during segments of their orbit, so additional complications arise arise if continuous longtime observations such as the during a geomagnetic storms are needed. In this paper we suggest a new approach, based on a combination of synoptic observations and a novel technique to estimate the flux and total outflow during the various phases of geomagnetic storms. Our results indicate large variations in both outflow rates and transport throughout the storm. Prior to the storm main phase, outflow rates are moderate, and the cold ions are mainly emanating from moderately sized polar cap regions. Throughout the main phase of the storm, outflow rates increase and the polar cap source regions expand. Furthermore, faster transport, resulting from enhanced convection, leads to a much larger supply of cold ions to the near Earth region during gemagnetic storms.