scholarly journals Current-eddy interaction in the Agulhas Return Current region from the seismic oceanography perspective

2013 ◽  
Author(s):  
Ana E. Rice ◽  
Jeffrey W. Book ◽  
Warren T. Wood ◽  
Tim Fischer
Keyword(s):  
Return Current ◽  
Seismic Oceanography ◽  
Current Region

scholarly journals Current-eddy interaction in the Agulhas Return Current region from the seismic oceanography perspective

2013 ◽  
Vol 133 (5) ◽  
pp. 3314-3314 ◽  
Author(s):  
Ana E. Rice ◽  
Jeffrey W. Book ◽  
Warren T. Wood ◽  
Tim Fischer
Keyword(s):  
Return Current ◽  
Seismic Oceanography ◽  
Current Region

scholarly journals Temporal evolution of two auroral arcs as measured by the Cluster satellite and coordinated ground-based instruments

2004 ◽  
Vol 22 (12) ◽  
pp. 4089-4101 ◽  
Author(s):  
A. T. Aikio ◽  
K. Mursula ◽  
S. Buchert ◽  
F. Forme ◽  
O. Amm ◽  
...  
Keyword(s):  
Electric Fields ◽  
Time Scale ◽  
Large Scale ◽  
Temporal Evolution ◽  
Broad Band ◽  
Radial Distance ◽  
Return Current ◽  
North West ◽  
Current Region ◽  
Auroral Arcs

Abstract. The four Cluster s/c passed over Northern Scandinavia on 6 February 2001 from south-east to north-west at a radial distance of about 4.4 RE in the post-midnight sector. When mapped along geomagnetic field lines, the separation of the spacecraft in the ionosphere was confined to within 110km in latitude and 50km in longitude. This constellation allowed us to study the temporal evolution of plasma with a time scale of a few minutes. Ground-based instrumentation used involved two all-sky cameras, magnetometers and the EISCAT radar. The main findings were as follows. Two auroral arcs were located close to the equatorward and poleward edge of a large-scale density cavity, respectively. These arcs showed a different kind of a temporal evolution. (1) As a response to a pseudo-breakup onset, both the up- and downward field-aligned current (FAC) sheets associated with the equatorward arc widened and the total amount of FAC doubled in a time scale of 1–2min. (2) In the poleward arc, a density cavity formed in the ionosphere in the return (downward) current region. As a result of ionospheric feedback, a strongly enhanced ionospheric southward electric field developed in the region of decreased Pedersen conductance. Furthermore, the acceleration potential of ionospheric electrons, carrying the return current, increased from 200 to 1000eV in 70s, and the return current region widened in order to supply a constant amount of return current to the arc current circuit. Evidence of local acceleration of the electron population by dispersive Alfvén waves was obtained in the upward FAC region of the poleward arc. However, the downward accelerated suprathermal electrons must be further energised below Cluster in order to be able to produce the observed visible aurora. Both of the auroral arcs were associated with broad-band ULF/ELF (BBELF) waves, but they were highly localised in space and time. The most intense BBELF waves were confined typically to the return current regions adjacent to the visual arc, but in one case also to a weak upward FAC region. BBELF waves could appear/disappear between s/c crossings of the same arc separated by about 1min. Key words. Ionosphere (electric fields and currents) – Magnetospheric physics (auroral phenomena; magnetosphereionosphere interactions)

scholarly journals Low-Altitude Ion Heating, Downflowing Ions, and BBELF Waves in the Return Current Region

2018 ◽  
Vol 123 (4) ◽  
pp. 3087-3110 ◽  
Author(s):  
Yangyang Shen ◽  
David J. Knudsen ◽  
Johnathan K. Burchill ◽  
Andrew D. Howarth ◽  
Andrew W. Yau ◽  
...  
Keyword(s):  
Ion Heating ◽  
Return Current ◽  
Current Region ◽  
Low Altitude

scholarly journals Characteristics of quasi-static potential structures observed in the auroral return current region by Cluster

2004 ◽  
Vol 11 (5/6) ◽  
pp. 709-720 ◽  
Author(s):  
G. T. Marklund ◽  
T. Karlsson ◽  
S. Figueiredo ◽  
T. Johansson ◽  
P.-A. Lindqvist ◽  
...  
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Observation Time ◽  
Polar Cap ◽  
Return Current ◽  
Central Plasma ◽  
Potential Structure ◽  
Current Region ◽  
Total Observation ◽  
Temporal And Spatial Characteristics

Abstract. Temporal and spatial characteristics of intense quasi-static electric fields and associated electric potential structures in the return current region are discussed using Cluster observations at geocentric distances of about 5 Earth radii. Results are presented from four Cluster encounters with such acceleration structures to illustrate common as well as different features of such structures. The electric field structures are characterized by (all values are projected to 100 km altitude) peak amplitudes of ≈1V/m, bipolar or unipolar profiles, perpendicular scale sizes of ≈10km, occurrence at auroral plasma boundaries associated with plasma density gradients, downward field-aligned currents of ≈10µA/m2, and upward electron beams with characteristic energies of a few hundred eV to a fewkeV. Two events illustrate the temporal evolution of bipolar, diverging electric field structures, indicative of positive U-shaped potentials increasing in magnitude from less than 1kV to a few kV on a few 100s time scale. This is also the typical formation time for ionospheric plasma cavities, which are connected to the potential structure and suggested to evolve hand-in-hand with these. In one of these events an energy decay of inverted-V ions was observed in the upward field-aligned current region prior to the acceleration potential increase in the adjacent downward current region, possibly suggesting that a potential redistribution took place between the two current branches. The other two events were characterized by intense unipolar electric fields, indicative of S-shaped potential contours and were encountered at the polar cap boundary. The total observation time for these events was typically 10-20s, too short for monitoring the evolution of the structure, but yet of interest for revealing their short term stability. The locations of the two bipolar events at the poleward boundary of the central plasma sheet and of the two unipolar events at the polar cap boundary, suggest that the special profile shape depends on whether plasma populations, dense enough to support upward field-aligned currents and closure of the return current, exist on both sides, or on one side only, of the boundary.

Dynamics and characteristics of electric-field structures in the auroral return current region observed by Cluster

2006 ◽  
Vol T122 ◽  
pp. 34-43 ◽  
Author(s):  
G T Marklund ◽  
T Karlsson ◽  
S Figueiredo ◽  
T Johansson ◽  
P-A Lindqvist ◽  
...  
Keyword(s):  
Electric Field ◽  
Return Current ◽  
Current Region

Plasma transport in the auroral return current region

1987 ◽  
Vol 92 (A8) ◽  
pp. 8673 ◽  
Author(s):  
Supriya B. Ganguli ◽  
Peter J. Palmadesso
Keyword(s):  
Plasma Transport ◽  
Return Current ◽  
Current Region
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