scholarly journals Bursty bulk flows without a near-Earth neutral line: Generation of fast intermittent flow in a highly curved magnetic field

2001 ◽  
Vol 106 (A1) ◽  
pp. 289-300 ◽  
Author(s):  
W. William Liu
Keyword(s):  
Magnetic Field ◽  
Neutral Line ◽  
Intermittent Flow ◽  
Line Generation ◽  
Bursty Bulk Flows

scholarly journals Filter Magnetograph Measurements at Meudon Observatory

1993 ◽  
Vol 141 ◽  
pp. 199-202
Author(s):  
Audouin Dollfus ◽  
Jacques Moity
Keyword(s):  
Magnetic Field ◽  
Transverse Magnetic Field ◽  
Observational Studies ◽  
Neutral Line ◽  
Active Regions ◽  
Transverse Magnetic ◽  
Birefringent Filter ◽  
Solar Active Regions

SummaryWe report observational studies of solar active regions n°6150 and n°6850 during cycle 22. Observations were carried out with a tunable monochromatic birefringent filter coupled with a line-shifter and a Stokesmeter as well as with a spectro-magnetograph, both at Meudon Observatory. AR n°6150 is typical of emerging flux regions, while AR n° 6850, with a complex preceding δ-spot, exhibits characteristic configurations of the transverse magnetic field for flaring activity: shear along the neutral line, and curvature coupled with anomalous Evershed mass motions.

Bloch-line generation in cross-tie walls by fast magnetic-field pulses

2006 ◽  
Vol 99 (8) ◽  
pp. 08F302 ◽  
Author(s):  
Andreas Neudert ◽  
Jeffrey McCord ◽  
Rudolf Schäfer ◽  
Rainer Kaltofen ◽  
Ingolf Mönch ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Bloch Line ◽  
Line Generation

scholarly journals On the retreat of near-Earth neutral line during substorm expansion phase: a THEMIS case study during the 9 January 2008 substorm

2012 ◽  
Vol 30 (1) ◽  
pp. 143-151 ◽  
Author(s):  
X. Cao ◽  
Z. Y. Pu ◽  
A. M. Du ◽  
V. M. Mishin ◽  
X. G. Wang ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetic Reconnection ◽  
Hall Current ◽  
Neutral Line ◽  
Tail Region ◽  
Expansion Phase ◽  
Reconnection Site

Abstract. The location of magnetic reconnection in the mid-tail during a substorm was studied in many researches. Here we present multi-point THEMIS observations of a reconnection event in the near-Earth magnetotail during substorm. In this event, THEMIS probes stayed in the near-Earth and mid-tail region aligning along the magnetotail. This allows reconnection evolution to be probed simultaneously from about −10 RE to −23 RE down tail. The Hall current related electron streams were observed at the same time by two probes far away from the reconnection site. Before near-Earth reconnection involved the tail lobe magnetic field, the reconnection site was restricted in earthward −23 RE. When reconnection involved into the tail lobe region, the reconnection site started to retreat gradually.

scholarly journals Evolution of magnetic helicity under kinetic magnetic reconnection: Part II B ≠ 0 reconnection

2002 ◽  
Vol 9 (2) ◽  
pp. 139-147 ◽  
Author(s):  
T. Wiegelmann ◽  
J. Büchner
Keyword(s):  
Magnetic Field ◽  
Magnetic Reconnection ◽  
Hall Current ◽  
Neutral Line ◽  
Magnetic Helicity ◽  
Perpendicular Magnetic Field ◽  
Guide Field ◽  
Magnetic Neutral Line ◽  
Field Lines ◽  
The Magnetic Field

Abstract. We investigate the evolution of magnetic helicity under kinetic magnetic reconnection in thin current sheets. We use Harris sheet equilibria and superimpose an external magnetic guide field. Consequently, the classical 2D magnetic neutral line becomes a field line here, causing a B ≠ 0 reconnection. While without a guide field, the Hall effect leads to a quadrupolar structure in the perpendicular magnetic field and the helicity density, this effect vanishes in the B ≠ 0 reconnection. The reason is that electrons are magnetized in the guide field and the Hall current does not occur. While a B = 0 reconnection leads just to a bending of the field lines in the reconnection area, thus conserving the helicity, the initial helicity is reduced for a B ≠ 0 reconnection. The helicity reduction is, however, slower than the magnetic field dissipation. The simulations have been carried out by the numerical integration of the Vlasov-equation.

scholarly journals Microwave indicator of potential geoeffectiveness and magnetic flux-rope structure of a solar active region

2021 ◽  
Vol 7 (1) ◽  
pp. 3-12
Author(s):  
Anastasiia Kudriavtseva ◽  
Ivan Myshyakov ◽  
Arkadiy Uralov ◽  
Victor Grechnev
Keyword(s):  
Magnetic Field ◽  
Active Region ◽  
Magnetic Flux ◽  
Neutral Line ◽  
Flux Rope ◽  
Coronal Magnetic Field ◽  
Horizontal Magnetic Field ◽  
Magnetic Flux Rope ◽  
Magnetic Flux Ropes ◽  
Class Flare

We analyze the presence of a microwave neutral-line-associated source (NLS) in a super-active region NOAA 12673, which produced a number of geo-effective events in September 2017. To estimate the NLS position, we use data from the Siberian Radioheliograph in a range 4–8 GHz and from the Nobeyama Radioheliograph at 17 GHz. Calculation of the coronal magnetic field in a non-linear force-free approximation has revealed an extended structure consisting of interconnected magnetic flux ropes, located practically along the entire length of the main polarity separation line of the photospheric magnetic field. NLS is projected into the region of the strongest horizontal magnetic field, where the main energy of this structure is concentrated. During each X-class flare, the active region lost magnetic helicity and became a CME source.

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