Articles | Volume 35, issue 6
Ann. Geophys., 35, 1269–1274, 2017
Ann. Geophys., 35, 1269–1274, 2017

ANGEO Communicates 28 Nov 2017

ANGEO Communicates | 28 Nov 2017

Tail reconnection in the global magnetospheric context: Vlasiator first results

Minna Palmroth1,2, Sanni Hoilijoki1, Liisa Juusola2, Tuija I. Pulkkinen3, Heli Hietala4, Yann Pfau-Kempf1, Urs Ganse1, Sebastian von Alfthan5, Rami Vainio6, and Michael Hesse7 Minna Palmroth et al.
  • 1Department of Physics, University of Helsinki, Helsinki, Finland
  • 2Earth Observation, Finnish Meteorological Institute, Helsinki, Finland
  • 3School of Electrical Engineering, Aalto University, Espoo, Finland
  • 4Institute of Geophysics and planetary physics, University of California, Los Angeles, USA
  • 5CSC – IT Center for Science, Espoo, Finland
  • 6Department of Physics and Astronomy, University of Turku, Turku, Finland
  • 7Department of Physics and Technology, University of Bergen, Bergen, Norway

Abstract. The key dynamics of the magnetotail have been researched for decades and have been associated with either three-dimensional (3-D) plasma instabilities and/or magnetic reconnection. We apply a global hybrid-Vlasov code, Vlasiator, to simulate reconnection self-consistently in the ion kinetic scales in the noon–midnight meridional plane, including both dayside and nightside reconnection regions within the same simulation box. Our simulation represents a numerical experiment, which turns off the 3-D instabilities but models ion-scale reconnection physically accurately in 2-D. We demonstrate that many known tail dynamics are present in the simulation without a full description of 3-D instabilities or without the detailed description of the electrons. While multiple reconnection sites can coexist in the plasma sheet, one reconnection point can start a global reconfiguration process, in which magnetic field lines become detached and a plasmoid is released. As the simulation run features temporally steady solar wind input, this global reconfiguration is not associated with sudden changes in the solar wind. Further, we show that lobe density variations originating from dayside reconnection may play an important role in stabilising tail reconnection.

Short summary
Much like solar flares, substorms occurring within the Earth's magnetic domain are explosive events that cause vivid auroral displays. A decades-long debate exists to explain the substorm onset. We devise a simulation encompassing the entire near-Earth space and demonstrate that detailed modelling of magnetic reconnection explains the central substorm observations. Our results help to understand the unpredictable substorm process, which will significantly improve space weather forecasts.