Browsing by Subject "MEDIUM REFERENCE FRAME"

Sort by: Order: Results:

Now showing items 1-2 of 2
  • Pulkkinen, T. I.; Dimmock, A. P.; Lakka, A.; Osmane, A.; Kilpua, E.; Myllys, M.; Tanskanen, E. I.; Viljanen, A. (2016)
    We examine the role of the magnetosheath in solar wind-magnetosphere-ionosphere coupling using the Time History of Events and Macroscale Interactions during Substorms plasma and magnetic field observations in the magnetosheath together with OMNI solar wind data and auroral electrojet recordings from the International Monitor for Auroral Geomagnetic Effects (IMAGE) magnetometer chain. We demonstrate that the electric field and Poynting flux reaching the magnetopause are not linear functions of the electric field and Poynting flux observed in the solar wind: the electric field and Poynting flux at the magnetopause during higher driving conditions are lower than those predicted from a linear function. We also show that the Poynting flux normal to the magnetopause is linearly correlated with the directly driven part of the auroral electrojets in the ionosphere. This indicates that the energy entering the magnetosphere in the form of the Poynting flux is directly responsible for driving the electrojets. Furthermore, we argue that the polar cap potential saturation discussed in the literature is associated with the way solar wind plasma gets processed during the bow shock crossing and motion within the magnetosheath.
  • Dimmock, A. P.; Osmane, A.; Pulkkinen, T. I.; Nykyri, K.; Kilpua, E. (2017)
    The magnetosheath contains an array of waves, instabilities, and nonlinear magnetic structures which modify global plasma properties by means of various wave-particle interactions. The present work demonstrates that ion-scale magnetic field structures (similar to 0.2-0.5 Hz) observed in the dayside magnetosheath are statistically correlated to ion temperature changes on orders 10-20% of the background value. In addition, our statistical analysis implies that larger temperature changes are in equipartition to larger amplitude magnetic structures. This effect was more pronounced behind the quasi-parallel bow shock and during faster solar wind speeds. The study of two separate intervals suggests that this effect can result from both local and external drivers. This manuscript presents two separate case studies, one from using THEMIS (Time History of Events and Macroscale Interactions during Substorms) data and another from Magnetospheric Multiscale; these measurements are then supported by extensive THEMIS statistical observations. These results could partly explain the 10-20% dawn-favored asymmetry of the magnetosheath ion temperature seed population and contribute to the dawn-favored asymmetry of cold component ions in the cold dense plasma sheet.