scholarly journals THEMIS two‐point measurements of the cross‐tail current density: A thick bifurcated current sheet in the near‐Earth plasma sheet

2015 ◽  
Vol 120 (8) ◽  
pp. 6258-6275 ◽  
Author(s):  
Miho Saito
Keyword(s):  
Current Sheet ◽  
Current Density ◽  
Plasma Sheet ◽  
Tail Current ◽  
The Cross

scholarly journals Local structure of the magnetotail current sheet: 2001 Cluster observations

2006 ◽  
Vol 24 (1) ◽  
pp. 247-262 ◽  
Author(s):  
A. Runov ◽  
V. A. Sergeev ◽  
R. Nakamura ◽  
W. Baumjohann ◽  
S. Apatenkov ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Current Sheet ◽  
Electric Current ◽  
Current Density ◽  
Plasma Sheet ◽  
Field Measurements ◽  
Theoretical Models ◽  
Type I ◽  
Density Peak ◽  
Magnetotail Current Sheet

Abstract. Thirty rapid crossings of the magnetotail current sheet by the Cluster spacecraft during July-October 2001 at a geocentric distance of 19 RE are examined in detail to address the structure of the current sheet. We use four-point magnetic field measurements to estimate electric current density; the current sheet spatial scale is estimated by integration of the translation velocity calculated from the magnetic field temporal and spatial derivatives. The local normal-related coordinate system for each case is defined by the combining Minimum Variance Analysis (MVA) and the curlometer technique. Numerical parameters characterizing the plasma sheet conditions for these crossings are provided to facilitate future comparisons with theoretical models. Three types of current sheet distributions are distinguished: center-peaked (type I), bifurcated (type II) and asymmetric (type III) sheets. Comparison to plasma parameter distributions show that practically all cases display non-Harris-type behavior, i.e. interior current peaks are embedded into a thicker plasma sheet. The asymmetric sheets with an off-equatorial current density peak most likely have a transient nature. The ion contribution to the electric current rarely agrees with the current computed using the curlometer technique, indicating that either the electron contribution to the current is strong and variable, or the current density is spatially or temporally structured.

scholarly journals Brightening of onset arc precedes the dipolarization onset: THEMIS observations of two events on 1 March 2008

2011 ◽  
Vol 29 (11) ◽  
pp. 2045-2059 ◽  
Author(s):  
J. R. Kan ◽  
H. Li ◽  
C. Wang ◽  
H. U. Frey ◽  
M. V. Kubyshkina ◽  
...  
Keyword(s):  
Time Delay ◽  
Plasma Sheet ◽  
Coupling Model ◽  
Mhd Waves ◽  
Current Loop ◽  
Expansion Phase ◽  
Tail Current ◽  
Electrojet Current ◽  
The Cross ◽  
Poleward Expansion

Abstract. We present a new M-I coupling model of substorm during southward IMF based on the THEMIS observations of two events on 1 March 2008. The first event (E-1) was classified as a pseudo-breakup: brightening of the onset arc preceded the first dipolarization onset by ∼71 ± 3 s, but the breakup arcs faded within ∼5 min without substantial poleward expansion and the dipolarization stopped and reversed to thinning. The second event (E-2) was identified as a substorm: brightening of the second onset arc preceded the second dipolarization onset by ∼80 ± 3 s, leading to a full-scale expanding auroral bulge during the substorm expansion phase for ∼20 min. The Alfvén travel time from the ionosphere to the dipolarization onset region is estimated at ∼69.3 s in E-1; at ∼80.3 s in E-2, which matched well with the observed time delay of the dipolarization onset after the brightening of the onset arc, respectively in E-1 and E-2. Brightening of the onset arc precedes the dipolarization onset suggest that the onset arc brightening is caused by the intense upward field-aligned currents originating from the divergence of the Cowling electrojet in the ionosphere. The Cowling electrojet current loop (CECL) is formed to close the field-aligned currents at all times. The closure current in the Alfvén wavefront is anti-parallel to the cross-tail current. Dipolarization onset occurs when the Alfvén wavefront incident on the near-Earth plasma sheet to disrupt the cross-tail current in the dipolarization region. Slow MHD waves dominate the disruption of the cross-tail current in the dipolarization region.

scholarly journals MMS Observation on the Cross‐Tail Current Sheet Roll‐up at the Dipolarization Front

2021 ◽  
Vol 126 (4) ◽  
Author(s):  
L. Q. Zhang ◽  
C. Wang ◽  
L. Dai ◽  
H. S. Fu ◽  
A. T. Y. Lui ◽  
...  
Keyword(s):  
Current Sheet ◽  
Tail Current ◽  
Dipolarization Front ◽  
The Cross

scholarly journals Asymmetry in the Earth’s magnetotail neutral sheet rotation due to IMF $$B_y$$ sign?

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Timo Pitkänen ◽  
Anita Kullen ◽  
Lei Cai ◽  
Jong-Sun Park ◽  
Heikki Vanhamäki ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Interplanetary Magnetic Field ◽  
Current Sheet ◽  
The Sun ◽  
Neutral Sheet ◽  
Tail Current ◽  
Cluster Data ◽  
The Asymmetry ◽  
The Cross ◽  
Possible Cause

AbstractEvidence suggests that a non-zero dawn–dusk interplanetary magnetic field (IMF $$B_y$$ B y ) can cause a rotation of the cross-tail current sheet/neutral sheet around its axis aligned with the Sun–Earth line in Earth’s magnetotail. We use Geotail, THEMIS and Cluster data to statistically investigate how the rotation of the neutral sheet depends on the sign and magnitude of IMF $$B_y$$ B y . In our dataset, we find that in the tail range of $$-30<$$ - 30 < XGSM $$<-15$$ < - 15 $$R_{\mathrm{E}}$$ R E , the degree of the neutral sheet rotation is clearly smaller, there appears no significant rotation or even, the rotation is clearly to an unexpected direction for negative IMF $$B_y$$ B y , compared to positive IMF $$B_y$$ B y . Comparison to a model by Tsyganenko et al. (2015, doi:10.5194/angeo-33-1-2015) suggests that this asymmetry in the neutral sheet rotation between positive and negative IMF $$B_y$$ B y conditions is too large to be explained only by the currently known factors. The possible cause of the asymmetry remains unclear.

scholarly journals Properties of a bifurcated current sheet observed on 29 August 2001

2004 ◽  
Vol 22 (7) ◽  
pp. 2535-2540 ◽  
Author(s):  
A. Runov ◽  
V. Sergeev ◽  
R. Nakamura ◽  
W. Baumjohann ◽  
Z. Vörös ◽  
...  
Keyword(s):  
Magnetic Reconnection ◽  
Current Sheet ◽  
Current Density ◽  
Plasma Sheet ◽  
Bulk Velocity ◽  
Ion Density ◽  
Alternative Models ◽  
Magnetic Turbulence

Abstract. Ion density, velocity and temperature, measured by Cluster spacecraft in the plasma sheet during an isolated substorm at 10:20-11:15 UT, 29 August 2001 are discussed. The Custer/CODIF data for subinterval 10:55-11:03 UT, during which a bifurcation of the current sheet was detected, are studied in particular. It is shown that ion density and temperature have a plateau-like profile in the central part of the bifurcated current sheet. An enhanced proton flow directed in positive YGSM was detected during the selected subinterval. Other components of proton bulk velocity are found to be negligibly small, i.e. the structure is likely not directly associated with magnetic reconnection. Alternative models, including ion anisotropy and localized magnetic turbulence, which result in a two-peak profile of the current density, are discussed briefly.

scholarly journals Bifurcation of the tail current sheet and ion temperature anisotropy

2008 ◽  
Vol 26 (7) ◽  
pp. 1759-1765 ◽  
Author(s):  
P. L. Israelevich ◽  
A. I. Ershkovich
Keyword(s):  
Density Distribution ◽  
Current Sheet ◽  
Current Density ◽  
Current Density Distribution ◽  
Plasma Pressure ◽  
Ion Temperature ◽  
Temperature Anisotropy ◽  
Tail Current ◽  
Geomagnetic Tail ◽  
Sheet Current

Abstract. We investigated the relation between the geotail current sheet structure and the anisotropy of the ion temperature in the plasma sheet. Current density distribution in the geomagnetic tail is shown not to depend on the ratio between the parallel and perpendicular ion temperature. The tail current sheet bifurcation is controlled by non-gyrotropicity of plasma pressure: double peaked current density distribution is observed when the ion perpendicular temperature exhibits anisotropy, and the electric current density is stronger for larger ratio · (T⊥max−T⊥min)/T⊥. The current sheet thinning is accompanied by the perpendicular temperature anisotropy, and, generally, double-peaked current sheets are thinner than single-peaked sheets.

The near-Earth cross-tail current sheet: Detailed ISEE 1 and 2 case studies

1986 ◽  
Vol 91 (A4) ◽  
pp. 4287 ◽  
Author(s):  
D. J. McComas ◽  
C. T. Russell ◽  
R. C. Elphic ◽  
S. J. Bame
Keyword(s):  
Current Sheet ◽  
Case Studies ◽  
Tail Current
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