scholarly journals Evolution of the storm magnetic field disturbance around Earth's surface and the associated ring current as deduced from multiple ground observatories

2015 ◽  
Vol 120 (1) ◽  
pp. 564-580 ◽  
Author(s):  
C. Shen ◽  
G. Zeng ◽  
X. Li ◽  
Z. J. Rong
Keyword(s):  
Magnetic Field ◽  
Ring Current ◽  
Field Disturbance

scholarly journals A note on the ring current in Saturn’s magnetosphere: Comparison of magnetic data obtained during the Pioneer-11 and Voyager-1 and -2 fly-bys

2003 ◽  
Vol 21 (3) ◽  
pp. 661-669 ◽  
Author(s):  
E. J. Bunce ◽  
S. W. H. Cowley
Keyword(s):  
Magnetic Field ◽  
Ring Current ◽  
Current System ◽  
Magnetic Data ◽  
Total Current ◽  
Planetary Magnetospheres ◽  
Magnetospheric Configuration And Dynamics ◽  
Magnetospheric Configuration ◽  
First Time ◽  
Current Systems

Abstract. We examine the residual (measured minus internal) magnetic field vectors observed in Saturn’s magnetosphere during the Pioneer-11 fly-by in 1979, and compare them with those observed during the Voyager-1 and -2 fly-bys in 1980 and 1981. We show for the first time that a ring current system was present within the magnetosphere during the Pioneer-11 encounter, which was qualitatively similar to those present during the Voyager fly-bys. The analysis also shows, however, that the ring current was located closer to the planet during the Pioneer-11 encounter than during the comparable Voyager-1 fly-by, reflecting the more com-pressed nature of the magnetosphere at the time. The residual field vectors have been fit using an adaptation of the current system proposed for Jupiter by Connerney et al. (1981a). A model that provides a reasonably good fit to the Pioneer-11 Saturn data extends radially between 6.5 and 12.5 RS (compared with a noon-sector magnetopause distance of 17 RS), has a north-south extent of 4 RS, and carries a total current of 9.6 MA. A corresponding model that provides a qualitatively similar fit to the Voyager data, determined previously by Connerney et al. (1983), extends radially between 8 and 15.5 RS (compared with a noon-sector magnetopause distance for Voyager-1 of 23–24 RS), has a north-south extent of 6 RS, and carries a total current of 11.5 MA.Key words. Magnetospheric physics (current systems, magnetospheric configuration and dynamics, planetary magnetospheres)

scholarly journals The ring current: a short biography

2012 ◽  
Vol 3 (2) ◽  
pp. 131-142 ◽  
Author(s):  
A. Egeland ◽  
W. J. Burke
Keyword(s):  
Magnetic Field ◽  
Ring Current ◽  
Energy Content ◽  
Spectral Characteristics ◽  
Direct Access ◽  
Sufficient Evidence ◽  
Mass Spectrometers ◽  
Before And After ◽  
Magnetic Signatures ◽  
Collective Plasma

Abstract. The "ring current'' grows in the inner magnetosphere during magnetic storms and contributes significantly to characteristic perturbations to the Earth's field observed at low-latitudes. This paper outlines how understanding of the ring current evolved during the half-century intervals before and after humans gained direct access to space. Its existence was first postulated in 1910 by Carl Størmer to explain the locations and equatorward migrations of aurorae under stormtime conditions. In 1917 Adolf Schmidt applied Størmer's ring-current hypothesis to explain the observed negative perturbations in the Earth's magnetic field. More than another decade would pass before Sydney Chapman and Vicenzo Ferraro argued for its necessity to explain magnetic signatures observed during the main phases of storms. Both the Størmer and Chapman–Ferraro models had difficulties explaining how solar particles entered and propagated in the magnetosphere to form the ring current. During the early 1950s Hannes Alfvén correctly argued that the ring current was a collective plasma effect, but failed to explain particle entry. The discovery of a weak but persistent interplanetary magnetic field embedded in a continuous solar wind provided James Dungey with sufficient evidence to devise the magnetic merging-reconnection model now regarded as the basis for understanding magnetospheric and auroral activity. In the mid-1960s Louis Frank showed that ions in the newly discovered plasma sheet had the energy spectral characteristics needed to explain the ring current's origin. The introduction of ion mass spectrometers on space missions during the 1970s revealed that O+ ions from the ionosphere contribute large fractions of the ring current's energy content. Precisely how cold O+ ions in the ionosphere are accelerated to ring-current energies still challenges scientific understanding.

Ring current ion motion in the disturbed magnetosphere with non-equipotential magnetic field lines

2004 ◽  
Vol 33 (5) ◽  
pp. 723-728 ◽  
Author(s):  
G.I Pugacheva ◽  
U.B Jayanthi ◽  
N.G Schuch ◽  
A.A Gusev ◽  
W.N Spjeldvik
Keyword(s):  
Magnetic Field ◽  
Ring Current ◽  
Ion Motion ◽  
Field Lines

Aromaticity of [M3(µ-X)3X6]0/2-(M = Re and Tc, X = Cl, Br, I) Clusters Confirmed by Ring Current Analysis and Induced Magnetic Field

2018 ◽  
Vol 2018 (28) ◽  
pp. 3312-3319 ◽  
Author(s):  
Walter A. Rabanal-León ◽  
Alejandro Vásquez-Espinal ◽  
Osvaldo Yañez ◽  
Ricardo Pino-Rios ◽  
Ramiro Arratia-Pérez ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Ring Current ◽  
Current Analysis ◽  
Induced Magnetic Field

scholarly journals First current density measurements in the ring current region using simultaneous multi-spacecraft CLUSTER-FGM data

2005 ◽  
Vol 23 (5) ◽  
pp. 1849-1865 ◽  
Author(s):  
C. Vallat ◽  
I. Dandouras ◽  
M. Dunlop ◽  
A. Balogh ◽  
E. Lucek ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Current Density ◽  
Ring Current ◽  
Magnetic Activity ◽  
Activity Level ◽  
Local Current Density ◽  
Magnetospheric Configuration And Dynamics ◽  
Local Current ◽  
Current Region ◽  
First Time

Abstract. The inner magnetosphere's current mapping is one of the key elements for current loop closure inside the entire magnetosphere. A method for directly computing the current is the multi-spacecraft curlometer technique, which is based on the application of Maxwell-Ampère's law. This requires the use of four-point magnetic field high resolution measurements. The FGM experiment on board the four Cluster spacecraft allows, for the first time, an instantaneous calculation of the magnetic field gradients and thus a measurement of the local current density. This technique requires, however, a careful study concerning all the factors that can affect the accuracy of the J estimate, such as the tetrahedral geometry of the four spacecraft, or the size and orientation of the current structure sampled. The first part of this paper is thus providing a detailed analysis of the method accuracy, and points out the limitations of this technique in the region of interest. The second part is an analysis of the ring current region, which reveals, for the first time, the large latitudinal extent of the ring current, for all magnetic activity levels, as well as the latitudinal evolution of the perpendicular (and parallel) components of the current along the diffuse auroral zone. Our analysis also points out the sharp transition between two distinct plasma regions, with the existence of high diamagnetic currents at the interface, as well as the filamentation of the current inside the inner plasma sheet. A statistical study over multiple perigee passes of Cluster (at about 4 RE from the Earth) reveals the azimuthal extent of the partial ring current. It also reveals that, at these distances and all along the evening sector, there isn't necessarily a strong dependence of the local current density value on the magnetic activity level. This is a direct consequence of the ring current morphology evolution, as well as the relative positioning of the spacecraft with respect to the bulk of the ring current. It also proves the existence of a substantial ring current at these distances, all over the evening and the post-midnight sector. Keywords. Magnetospheric physics (Current systems; Energetic particles, trapped; Magnetospheric configuration and dynamics)

scholarly journals Strong Southward and Northward Currents Observed in the Inner Plasma Sheet

2019 ◽  
Author(s):  
Yanyan Yang ◽  
Chao Shen ◽  
Yong Ji
Keyword(s):  
Magnetic Field ◽  
Plasma Sheet ◽  
Ring Current ◽  
Generation Mechanism ◽  
Storm Events ◽  
Current Generation ◽  
Inner Magnetosphere ◽  
Latitude Region ◽  
Field Lines ◽  
The Magnetic Field

Abstract. It is generally believed that field aligned currents (FACs) and the ring current (RC) are two dominant parts of the inner magnetosphere. However, using the Cluster spacecraft crossing of the pre-midnight inner plasma sheet in the latitude region between 10° N and 30° N, it is found that, during large storm events, in addition to FACs and the RC, there also exist strong southward and northward currents, which cannot be FACs, because the magnetic field in these regions is mainly along the XY plane. Detailed investigation shows that both magnetic field lines (MFLs) and currents in these regions highly fluctuate. When the curvature of MFLs changes direction in the XY plane, the current also alternatively switches between southward and northward. Further analysis of the current generation mechanism indicates that the most reasonable candidate for the origin of these southward and northward currents is the curvature drift of energetic particles.

scholarly journals Study of the applicability of the curlometer technique with the four Cluster spacecraft in regions close to Earth

2012 ◽  
Vol 30 (3) ◽  
pp. 597-611 ◽  
Author(s):  
S. Grimald ◽  
I. Dandouras ◽  
P. Robert ◽  
E. Lucek
Keyword(s):  
Magnetic Field ◽  
Current Density ◽  
Ring Current ◽  
Current System ◽  
Sufficient Conditions ◽  
Magnetic Activity ◽  
Inner Magnetosphere ◽  
Good Proxy ◽  
The Magnetic Field ◽  
Magnetospheric Current System

Abstract. Knowledge of the inner magnetospheric current system (intensity, boundaries, evolution) is one of the key elements for the understanding of the whole magnetospheric current system. In particular, the calculation of the current density and the study of the changes in the ring current is an active field of research as it is a good proxy for the magnetic activity. The curlometer technique allows the current density to be calculated from the magnetic field measured at four different positions inside a given current sheet using the Maxwell-Ampere's law. In 2009, the CLUSTER perigee pass was located at about 2 RE allowing a study of the ring current deep inside the inner magnetosphere, where the pressure gradient is expected to invert direction. In this paper, we use the curlometer in such an orbit. As the method has never been used so deep inside the inner magnetosphere, this study is a test of the curlometer in a part of the magnetosphere where the magnetic field is very high (about 4000 nT) and changes over small distances (ΔB = 1nT in 1000 km). To do so, the curlometer has been applied to calculate the current density from measured and modelled magnetic fields and for different sizes of the tetrahedron. The results show that the current density cannot be calculated using the curlometer technique at low altitude perigee passes, but that the method may be accurate in a [3 RE; 5 RE] or a [6 RE; 8.3 RE] L-shell range. It also demonstrates that the parameters used to estimate the accuracy of the method are necessary, but not sufficient conditions.

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