Evolution of the current wedge and the generator current circuit by fast reconnection

2009 ◽  
Vol 16 (1) ◽  
pp. 012901 ◽  
Author(s):  
M. Ugai
Keyword(s):  
Fast Reconnection ◽  
Current Wedge

scholarly journals Conditions for substorm onset by the fast reconnection mechanism

2008 ◽  
Vol 26 (12) ◽  
pp. 3875-3883 ◽  
Author(s):  
M. Ugai
Keyword(s):  
Large Scale ◽  
Magnetic Energy ◽  
Magnetic Loop ◽  
Substorm Onset ◽  
Plasma Jets ◽  
Thin Layers ◽  
Closed Field ◽  
Mhd Generator ◽  
Fast Reconnection ◽  
Current Wedge

Abstract. The fast reconnection mechanism, involving slow shocks and Alfvénic fast plasma jets, is most responsible for the explosive conversion of magnetic energy associated with geomagnetic substorms and solar flares. In this paper, the spontaneous fast reconnection model is applied to well-known phenomena of substorms. When the east-west width of the tail current sheet becomes 3–4 times larger than its north-south thickness, the fast reconnection mechanism can fully be established, which may lead to substorm onset. The resulting Alfvénic jet can exactly explain, both qualitatively and quantitatively, the in-situ satellite observations of the traveling compression regions (TCRs) associated with large-scale plasmoids propagating down the tail. Also, the earthward fast reconnection jet causes drastic magnetic field dipolarization, so that the sheet current ahead of the magnetic loop of closed field lines suddenly turns its direction toward the loop footpoint and a large-scale current wedge is formed according to the growth of field-aligned currents. It is demonstrated that an MHD generator arises ahead of the magnetic loop and drives the current wedge to distinctly enhance the current density in a pair of thin layers of the loop footpoint, giving rise to drastic heating in the form of two ribbons.

Conditions for the fast reconnection mechanism in three dimensions

2005 ◽  
Vol 12 (9) ◽  
pp. 092312 ◽  
Author(s):  
M. Ugai ◽  
L. Zheng
Keyword(s):  
Three Dimensions ◽  
Fast Reconnection

scholarly journals Network community structure of substorms using SuperMAG magnetometers

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
L. Orr ◽  
S. C. Chapman ◽  
J. W. Gjerloev ◽  
W. Guo
Keyword(s):  
Large Scale ◽  
Three Dimensional ◽  
Easy Access ◽  
Directed Network ◽  
Coherent System ◽  
Dimensional System ◽  
Ionospheric Currents ◽  
Substorm Current Wedge ◽  
Spatially Extended ◽  
Current Wedge

AbstractGeomagnetic substorms are a global magnetospheric reconfiguration, during which energy is abruptly transported to the ionosphere. Central to this are the auroral electrojets, large-scale ionospheric currents that are part of a larger three-dimensional system, the substorm current wedge. Many, often conflicting, magnetospheric reconfiguration scenarios have been proposed to describe the substorm current wedge evolution and structure. SuperMAG is a worldwide collaboration providing easy access to ground based magnetometer data. Here we show application of techniques from network science to analyze data from 137 SuperMAG ground-based magnetometers. We calculate a time-varying directed network and perform community detection on the network, identifying locally dense groups of connections. Analysis of 41 substorms exhibit robust structural change from many small, uncorrelated current systems before substorm onset, to a large spatially-extended coherent system, approximately 10 minutes after onset. We interpret this as strong indication that the auroral electrojet system during substorm expansions is inherently a large-scale phenomenon and is not solely due to many meso-scale wedgelets.

scholarly journals Effect of interchange instability on magnetic reconnection

2013 ◽  
Vol 20 (3) ◽  
pp. 365-377 ◽  
Author(s):  
W. Lyatsky ◽  
M. L. Goldstein
Keyword(s):  
Magnetic Fields ◽  
Electric Field ◽  
Magnetic Reconnection ◽  
Plasma Flow ◽  
Buoyancy Force ◽  
Strong Turbulence ◽  
Polarization Electric Field ◽  
Interchange Instability ◽  
Reconnection Layer ◽  
Fast Reconnection

Abstract. We present here the results of a study of interacting magnetic fields that involves a force normal to the reconnection layer. In the presence of such force, the reconnection layer becomes unstable to interchange disturbances. The interchange instability results in formation of tongues of heated plasma that leaves the reconnection layer through its wide surface rather than through its narrow ends, as is the case in traditional magnetic reconnection models. This plasma flow out of the reconnection layer facilitates the removal of plasma from the layer and leads to fast reconnection. The proposed mechanism provides fast reconnection of interacting magnetic fields and does not depend on the thickness of the reconnection layer. This instability explains the strong turbulence and bidirectional streaming of plasma that is directed toward and away from the reconnection layer that is observed frequently above reconnection layers. The force normal to the reconnection layer also accelerates the removal of plasma islands appearing in the reconnection layer during turbulent reconnection. In the presence of this force normal to the reconnection layer, these islands are removed from the reconnection layer by the "buoyancy force", as happens in the case of interchange instability that arises due to the polarization electric field generated at the boundaries of the islands.

scholarly journals Relative contributions of large-scale and wedgelet currents in the substorm current wedge

2020 ◽  
Vol 72 (1) ◽  
Author(s):  
Y. Nishimura ◽  
L. R. Lyons ◽  
C. Gabrielse ◽  
J. M. Weygand ◽  
E. F. Donovan ◽  
...  
Keyword(s):  
Large Scale ◽  
Substorm Current Wedge ◽  
Current Wedge

Fast Reconnection in Nonrelativistic 2D Electron-Positron Plasmas

2008 ◽  
Vol 101 (2) ◽  
Author(s):  
L. Chacón ◽  
Andrei N. Simakov ◽  
V. S. Lukin ◽  
A. Zocco
Keyword(s):  
Electron Positron ◽  
Fast Reconnection
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