Superposed epoch analysis of pressure and magnetic field configuration changes in the plasma sheet

1993 ◽  
Vol 98 (A6) ◽  
pp. 9249 ◽  
Author(s):  
L. M. Kistler ◽  
W. Baumjohann ◽  
T. Nagai ◽  
E. Möbius
Keyword(s):  
Magnetic Field ◽  
Plasma Sheet ◽  
Field Configuration ◽  
Magnetic Field Configuration ◽  
Superposed Epoch Analysis ◽  
Epoch Analysis ◽  
Configuration Changes

scholarly journals Statistical visualization of the Earth's magnetotail and the implied mechanism of substorm triggering based on superposed-epoch analysis of THEMIS data

2014 ◽  
Vol 32 (2) ◽  
pp. 99-111 ◽  
Author(s):  
S. Machida ◽  
Y. Miyashita ◽  
A. Ieda ◽  
M. Nosé ◽  
V. Angelopoulos ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Plasma Sheet ◽  
Time Lag ◽  
Elevation Angle ◽  
Substorm Onset ◽  
Boundary Layer Flows ◽  
Superposed Epoch Analysis ◽  
Current Disruption ◽  
Central Plasma ◽  
Epoch Analysis

Abstract. To investigate the physical mechanism responsible for substorm triggering, we performed a superposed-epoch analysis using plasma and magnetic-field data from THEMIS probes. Substorm onset timing was determined based on auroral breakups detected by all-sky imagers at the THEMIS ground-based observatories. We found earthward flows associated with north–south auroral streamers during the substorm growth phase. At around X = −12 Earth radii (RE), the northward magnetic field and its elevation angle decreased markedly approximately 4 min before substorm onset. Moreover, a northward magnetic-field increase associated with pre-onset earthward flows was found at around X = −17 RE. This variation indicates that local dipolarization occurs. Interestingly, in the region earthwards of X = −18 RE, earthward flows in the central plasma sheet (CPS) reduced significantly approximately 3 min before substorm onset, which was followed by a weakening of dawn-/duskward plasma-sheet boundary-layer flows (subject to a 1 min time lag). Subsequently, approximately 1 min before substorm onset, earthward flows in the CPS were enhanced again and at the onset, tailward flows started at around X = −20 RE. Following substorm onset, an increase in the northward magnetic field caused by dipolarization was found in the near-Earth region. Synthesizing these results, we confirm our previous results based on GEOTAIL data, which implied that significant variations start earlier than both current disruption and magnetic reconnection, at approximately 4 min before substorm onset roughly halfway between the two regions of interest; i.e. in the catapult current sheet.

Experimental study of force-free, collinear plasma structures

1973 ◽  
Vol 9 (1) ◽  
pp. 1-15 ◽  
Author(s):  
E. E. Nolting ◽  
P. E. Jindra ◽  
D. R. Wells
Keyword(s):  
Magnetic Field ◽  
Experimental Study ◽  
Magnetic Fields ◽  
Flow Fields ◽  
Diagnostic Techniques ◽  
Field Configuration ◽  
Magnetic Mirror ◽  
Magnetic Field Configuration ◽  
Magnetic Barrier ◽  
Magnetic Well

Detailed measurements of the trapped magnetic fields and currents in plasma structures generated by conical theta-pinches are reported. Studies of these structures interacting with a magnetic barrier, and with each other in a collision at the centre of a magnetic mirror, are reported. The magnetic well formed by the collision has been studied by simultaneous use of several diagnostic techniques. The measurements are in agreement with a force-free, collinear magnetic field configuration (Wells 1972). Arguments relating superposability and collinearity of flow fields to these observations are given.

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