On dipolarization and its relation to the substorm current wedge

1991 ◽  
Vol 96 (A11) ◽  
pp. 19417 ◽  
Author(s):  
Michael Hesse ◽  
Joachim Birn
Keyword(s):  
Substorm Current Wedge ◽  
Current Wedge

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 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

scholarly journals Coupling between Mercury and its nightside magnetosphere: Cross-tail current sheet asymmetry and substorm current wedge formation

2017 ◽  
Vol 122 (8) ◽  
pp. 8419-8433 ◽  
Author(s):  
Gangkai Poh ◽  
James A. Slavin ◽  
Xianzhe Jia ◽  
Jim M. Raines ◽  
Suzanne M. Imber ◽  
...  
Keyword(s):  
Current Sheet ◽  
Substorm Current Wedge ◽  
Tail Current ◽  
Current Wedge

scholarly journals Influence of the substorm current wedge on theDstindex

1999 ◽  
Vol 104 (A3) ◽  
pp. 4567-4575 ◽  
Author(s):  
Erena Friedrich ◽  
Gordon Rostoker ◽  
Martin G. Connors ◽  
R. L. McPherron
Keyword(s):  
Substorm Current Wedge ◽  
Current Wedge

scholarly journals THEMIS observations of double-onset substorms and their association with IMF variations

2011 ◽  
Vol 29 (3) ◽  
pp. 591-611 ◽  
Author(s):  
C.-C. Cheng ◽  
C. T. Russell ◽  
V. Angelopoulos ◽  
I. R. Mann ◽  
K.-H. Glassmeier ◽  
...  
Keyword(s):  
Energetic Electron ◽  
Dominant Frequency ◽  
Magnetic Fluctuations ◽  
Substorm Current Wedge ◽  
Early Afternoon ◽  
Magnetic Perturbations ◽  
Magnetotail Reconnection ◽  
Vortex Patterns ◽  
The One ◽  
Current Wedge

Abstract. On 16 July 2008, two pairs of consecutive bursts of Pi2 pulsations were recorded simultaneously across the THEMIS ground-based observatory system. Wavelet transformation reveals that for each high-latitude pair, the dominant frequency of the first burst is higher than that of the second. But at low latitudes, the dominant frequency does not change. It is suggested that both pairs result from fast magnetospheric cavity waves with the second burst also containing shear Alfvén waves. INTERMAGNET magnetograms at auroral latitudes showed magnetic variations affected by two recurrent electrojets for each pair. The ground-based magnetometers and those at geostationary orbit sensed magnetic perturbations consistent with the formation of the substorm current wedge. Four consecutive enhancements of energetic electron and ion fluxes detected by the THEMIS probes in the dayside magnetosphere appeared in the later afternoon and then in the early afternoon. The horizontal magnetic variation vectors had vortex patterns similar to those induced by the upward and downward field-aligned currents during substorm times. The hodogram at mid-L stations had a polarization pattern similar to the one induced by the substorm current wedge for each Pi2 burst. The mapping of ground Pi2 onset timing to the interplanetary magnetic field (IMF) observations shows that they appear under two cycles of north-to-south and then north variation. CLUSTER 4 in the south lobe observed wave-like magnetic fluctuations, probably driven by near-Earth reconnection, similar to those on the ground. These two observations are consistent with the link of double-onset substorms to magnetotail reconnection externally triggered by IMF variations.

scholarly journals Substorm behavior of the auroral electrojet indices

2004 ◽  
Vol 22 (6) ◽  
pp. 2135-2149 ◽  
Author(s):  
J. W. Gjerloev ◽  
R. A. Hoffman ◽  
M. M. Friel ◽  
L. A. Frank ◽  
J. B. Sigwarth
Keyword(s):  
Current System ◽  
Three Dimensional ◽  
Recovery Phase ◽  
Auroral Electrojet ◽  
Spatial Behavior ◽  
Early Recovery ◽  
Substorm Current Wedge ◽  
Expansion Phase ◽  
Systematic Behavior ◽  
Current Wedge

Abstract. The behavior of the auroral electrojet indices AU and AL during classical substorms is investigated by the use of global auroral images. A superposition of the 12 AE stations onto global auroral images and identification of the AL and AU contributing stations enable an understanding of the temporal as well as spatial behavior of the indices with respect to the substorm coordinate system and timeframe. Based on this simple technique it was found that at substorm onset the AL contributing station makes a characteristic jump from a location near the dawn terminator to the onset region, typically bypassing one or more AE stations. During the expansion phase this station typically lies at the poleward edge of the surge region. This is the location of the intense substorm current wedge electrojet in the semiempirical self-consistent substorm model of the three-dimensional current system by Gjerloev and Hoffman (2002). This current wedge is fed primarily pre-midnight by an imbalance of the Region 0 and Region 1 field-aligned currents, not from the dawnside westward electrojet. Then during the early recovery phase the AL contributing station jumps back to the dawn sector. The defining AU station does not show any similar systematic behavior. We also find that the dawn side westward electrojet seems to be unaffected by the introduction of the substorm current wedge. According to our model, much of this current is closed to the magnetosphere as it approaches midnight from dawn. Based on the characteristics of the AL station jumps, the behavior of the dawn-side electrojet, and the understanding of the three-dimensional substorm current system from our model, we provide additional experimental evidence for, and an understanding of, the concept of the two component westward electrojet, as suggested by Kamide and Kokubun (1996).

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