Defining and resolving current systems in geospace
N. Y. Ganushkina1,2,M. W. Liemohn2,S. Dubyagin1,I. A. Daglis3,I. Dandouras4,D. L. De Zeeuw2,Y. Ebihara5,R. Ilie2,R. Katus2,M. Kubyshkina6,S. E. Milan7,8,S. Ohtani9,N. Ostgaard8,J. P. Reistad8,P. Tenfjord8,F. Toffoletto10,S. Zaharia11,and O. Amariutei1N. Y. Ganushkina et al. N. Y. Ganushkina1,2,M. W. Liemohn2,S. Dubyagin1,I. A. Daglis3,I. Dandouras4,D. L. De Zeeuw2,Y. Ebihara5,R. Ilie2,R. Katus2,M. Kubyshkina6,S. E. Milan7,8,S. Ohtani9,N. Ostgaard8,J. P. Reistad8,P. Tenfjord8,F. Toffoletto10,S. Zaharia11,and O. Amariutei1
1Earth Observations Department, Finnish Meteorological Institute, Helsinki, Finland
2Department of Climate and Space Sciences and Engineering, University of Michigan, Ann Arbor, Michigan, USA
3Department of Physics, University of Athens, Panepistimiopolis Zografou, 15784 Athens, Greece
4Astrophysics and Planetary Science Research Institute, CNRS/University of Toulouse, Toulouse, France
5Research Institute for Sustainable Humanosphere, Kyoto University, Gokasho, Uji, Kyoto, Japan
6Institute of Physics, University of St. Petersburg, St. Petersburg, Russia
7Department of Physics and Astronomy, University of Leicester, Leicester, UK
8Birkeland Centre for Space Science, Department of Physics and Technology, University of Bergen, Bergen, Norway
9Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland, USA
10Physics and Astronomy Department, Rice University, Houston, Texas, USA
11ISR-1 Division, Los Alamos National Laboratory, Los Alamos, New Mexico, USA
1Earth Observations Department, Finnish Meteorological Institute, Helsinki, Finland
2Department of Climate and Space Sciences and Engineering, University of Michigan, Ann Arbor, Michigan, USA
3Department of Physics, University of Athens, Panepistimiopolis Zografou, 15784 Athens, Greece
4Astrophysics and Planetary Science Research Institute, CNRS/University of Toulouse, Toulouse, France
5Research Institute for Sustainable Humanosphere, Kyoto University, Gokasho, Uji, Kyoto, Japan
6Institute of Physics, University of St. Petersburg, St. Petersburg, Russia
7Department of Physics and Astronomy, University of Leicester, Leicester, UK
8Birkeland Centre for Space Science, Department of Physics and Technology, University of Bergen, Bergen, Norway
9Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland, USA
10Physics and Astronomy Department, Rice University, Houston, Texas, USA
11ISR-1 Division, Los Alamos National Laboratory, Los Alamos, New Mexico, USA
Correspondence: N. Y. Ganushkina (natalia.ganushkina@fmi.fi)
Received: 30 Mar 2015 – Revised: 01 Sep 2015 – Accepted: 30 Sep 2015 – Published: 10 Nov 2015
Abstract. Electric currents flowing through near-Earth space (R ≤ 12 RE) can support a highly distorted magnetic field topology, changing particle drift paths and therefore having a nonlinear feedback on the currents themselves. A number of current systems exist in the magnetosphere, most commonly defined as (1) the dayside magnetopause Chapman–Ferraro currents, (2) the Birkeland field-aligned currents with high-latitude "region 1" and lower-latitude "region 2" currents connected to the partial ring current, (3) the magnetotail currents, and (4) the symmetric ring current. In the near-Earth nightside region, however, several of these current systems flow in close proximity to each other. Moreover, the existence of other temporal current systems, such as the substorm current wedge or "banana" current, has been reported. It is very difficult to identify a local measurement as belonging to a specific system. Such identification is important, however, because how the current closes and how these loops change in space and time governs the magnetic topology of the magnetosphere and therefore controls the physical processes of geospace. Furthermore, many methods exist for identifying the regions of near-Earth space carrying each type of current. This study presents a robust collection of these definitions of current systems in geospace, particularly in the near-Earth nightside magnetosphere, as viewed from a variety of observational and computational analysis techniques. The influence of definitional choice on the resulting interpretation of physical processes governing geospace dynamics is presented and discussed.
A number of current systems exist in the Earth's magnetosphere. It is very difficult to identify local measurements as belonging to a specific current system. Therefore, there are different definitions of supposedly the same current, leading to unnecessary controversy. This study presents a robust collection of these definitions of current systems in geospace, particularly in the near-Earth nightside magnetosphere, as viewed from a variety of observational and computational analysis techniques.
A number of current systems exist in the Earth's magnetosphere. It is very difficult to identify...
