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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Discussion papers
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: regular paper 26 Aug 2019

Submitted as: regular paper | 26 Aug 2019

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This discussion paper is a preprint. It is a manuscript under review for the journal Annales Geophysicae (ANGEO).

Using the Galilean Relativity Principle to Understand the Physical Basis for Magnetosphere-Ionosphere Coupling Processes

Anthony J. Mannucci1, Ryan McGranaghan2, Xing Meng1, Bruce T. Tsurutani1, and Olga P. Verkhoglyadova1 Anthony J. Mannucci et al.
  • 1Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
  • 2Atmospheric and Space Technology Research Associates (ASTRA), Boulder CO, USA

Abstract. We use the Principle of Galilean Relativity (PGR) to gain insight into the physical basis for magnetosphere-ionosphere coupling. The PGR states that the laws of physics are the same in all inertial reference frames, considering relative speeds between such reference frames that are significantly less than the speed of light. The PGR is a limiting case of the principle of Special Relativity, the latter applicable to any relative speeds between two inertial reference frames. Although the PGR has been invoked in past works related to magnetosphere-ionosphere coupling, it has not been fully exploited for the insights it can provide into such topics as large-scale ionospheric convection and high latitude heating. In addition, the difficulties of applying the PGR to electrodynamics has not been covered. The PGR can be used to show that in the high latitude ionosphere there often exists a reference frame where electric fields vanish at lower altitudes where collisions are important (altitudes near ~ 100–120 km). In this reference frame, it is problematic to assert that currents of magnetospheric origin cause horizontal electric fields in the ionosphere, as has been suggested for the causal origin of Subauroral Polarization Stream electric fields. Electric fields have also been invoked as the causal origin of large-scale ionospheric convection, which may be a problematic assertion in certain reference frames. The PGR reinforces the importance of the neutral species and ion-neutral collisions in magnetosphere-ionosphere coupling, which has been noted by several authors using detailed multi-species plasma calculations. A straightforward estimate shows that the momentum carried by electron field aligned currents of magnetospheric origin during disturbed periods is much less than the momentum changes experienced by the neutral species in an Earth-fixed frame. The primary driver of neutral species momentum changes during disturbed periods is the momentum imparted by the solar wind to ionospheric ions resulting from electrodynamic interactions. This is consistent with the idea that electric fields do not lead to large scale ionospheric convection.

Anthony J. Mannucci et al.
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Anthony J. Mannucci et al.
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Publications Copernicus
Short summary
The interaction between the Earth's environment and the electrically charged gas known as the solar wind is highly complex and has been under study for decades. We use a universal principle of physics – the relativity principle – to gain physical insight into this interaction. We apply this principle to physical processes that occur during geomagnetic storms. We clarify how the solar wind ultimately causes currents to flow between the Earth's upper atmosphere and space.
The interaction between the Earth's environment and the electrically charged gas known as the...