Ground magnetic signatures of multiple field-aligned current sheets in flux transfer events

1989 ◽  
Vol 94 (A6) ◽  
pp. 6655-6664 ◽  
Author(s):  
L. Zhu ◽  
J. R. Kan
Keyword(s):  
Current Sheets ◽  
Flux Transfer Events ◽  
Magnetic Signatures ◽  
Field Aligned Current ◽  
Flux Transfer ◽  
Ground Magnetic ◽  
Multiple Field

scholarly journals Cluster observations of bounday layer structure and a flux transfer event near the cusp

2005 ◽  
Vol 23 (7) ◽  
pp. 2605-2620 ◽  
Author(s):  
R. C. Fear ◽  
A. N. Fazakerley ◽  
C. J. Owen ◽  
A. D. Lahiff ◽  
E. A. Lucek ◽  
...  
Keyword(s):  
Boundary Layer ◽  
High Latitude ◽  
Layer Structure ◽  
Normal Component ◽  
Transfer Event ◽  
Flux Transfer Events ◽  
Magnetic Signatures ◽  
Northern High Latitude ◽  
Flux Transfer ◽  
The Magnetic Field

Abstract. On the 25th January 2002 between 10:00 and 12:00 UT, the four Cluster spacecraft passed through the northern high-latitude cusp, the dayside magnetosphere and into the magnetosheath in a linear formation. In the magnetosphere the PEACE electron spectrometers on the four spacecraft all observed a series of transient bursts of magnetosheath-like plasma, but without bipolar magnetic signatures in the magnetopause normal component as might be expected if the plasma had been injected by transient reconnection (flux transfer events – FTEs). Reordering the data using the magnetopause transition parameter reveals that these plasma observations, the related variations in the magnetic field and the balance of magnetic and thermal gas pressures are consistent with transient entries into a stable high-latitude boundary layer structure. However, once some of the spacecraft entered the magnetosheath, FTE signatures were observed outside the magnetopause at the same time as some of the boundary layer entries occurred at the other spacecraft inside. Thus, (a) the lack of a bipolar BN signature is inconsistent with the traditional picture of a magnetospheric FTE, and (b) the cause of the observed entry of the spacecraft into the boundary layer (pressure pulse or passing magnetosheath FTE) can only be determined by spacecraft observations in the magnetosheath. Keywords. Magnetospheric physics (Magnetopause, cusp and bondary layers; Solar wind- magnetosphere interactions; Magnetosheath)

scholarly journals The dayside ultraviolet aurora and convection responses to a southward turning of the interplanetary magnetic field

2001 ◽  
Vol 19 (7) ◽  
pp. 707-721 ◽  
Author(s):  
K. A. McWilliams ◽  
T. K. Yeoman ◽  
J. B. Sigwarth ◽  
L. A. Frank ◽  
M. Brittnacher
Keyword(s):  
Large Scale ◽  
Small Region ◽  
Radar Data ◽  
Hf Radar ◽  
Current Response ◽  
Plasma Convection ◽  
Flux Transfer Events ◽  
Field Aligned Current ◽  
Flux Transfer ◽  
The Imf

Abstract. We examine the large-scale ultraviolet aurora and convection responses to a series of flux transfer events that immediately followed a sharp and isolated southward turning of the IMF. During the interval of interest, SuperDARN was monitoring the plasma convection in the dayside northern ionosphere, while the VIS Earth Camera and the Far Ul-traviolet Imager (UVI) were monitoring the northern hemisphere’s ultraviolet aurora. Reconnection signatures were seen in the SuperDARN HF radar data in the postnoon sector following a sharp southward turning of the IMF. The presence of flux transfer events is supported by measurements of a classic dispersed ion signature in the low-altitude cusp from the DMSP spacecraft. Subsequent to the onset of reconnection, the postnoon convection and ultraviolet aurora expanded in concert, reaching 18 MLT in half an hour. The auroral oval was found to move equatorward at the convection speed in the 16–18 MLT sector, implying that it was related directly to an adiaroic magnetospheric boundary. In the present study, we have estimated the field-aligned current response to magnetic reconnection in terms of the vorticity of the ionospheric plasma convection velocity. The convection velocities were obtained using two methods: (a) direct reconstruction of the full vector velocities from bistatic measurements of the convection by the SuperDARN HF radars in a relatively small region of the auroral zone, and (b) from global-scale spherical harmonic fits to the SuperDARN velocities deduced from the map potential model. Regions of high vorticity, which were predicted to be an estimate of a component of the total field-aligned current, agree extremely well with the images of the dayside UV aurora, indicating that, in this case, the plasma vorticity is an excellent estimator of the morphology of dayside field-aligned currents (FACs). The morphology of the aurora and ionospheric electric field in the postnoon sector supports the existence of a dayside current wedge induced in response to dayside reconnection.Key words. Magnetospheric physics (auroral phenomena; magnetosphere-ionosphere interactions; solar wind magne-tosphere interactions)

scholarly journals The UV aurora and ionospheric flows during flux transfer events

2001 ◽  
Vol 19 (2) ◽  
pp. 179-188 ◽  
Author(s):  
D. A. Neudegg ◽  
S. W. H. Cowley ◽  
K. A. McWilliams ◽  
M. Lester ◽  
T. K. Yeoman ◽  
...  
Keyword(s):  
Ultra Violet ◽  
Spectral Width ◽  
Hf Radar ◽  
Electron Precipitation ◽  
Flux Transfer Events ◽  
Optical Feature ◽  
Geomagnetic Fields ◽  
Field Aligned Current ◽  
Flux Transfer ◽  
Current Systems

Abstract. Far Ultra Violet (FUV) signatures in the polar ionosphere during a period of magnetopause reconnection are compared with ionospheric flows measured in the cusp ‘throat’ and dusk cell by the CUTLASS Hankasalmi HF radar. Regions of peak FUV emission in the 130.4 nm and 135.6 nm range, observed by the Polar spacecraft’s VIS Earth Camera, consistently lie at the turning point of the flows from the dusk cell, poleward into the throat, and at the equatorward edge of the region of high and varied radar spectral-width associated with the cusp. The Equator-S spacecraft was near the magnetopause at the time of the ionospheric observations and geomagnetically conjugate with the region of ionosphere observed by the radar. Flux transfer events (FTEs), suggestive of bursty reconnection between the IMF and geomagnetic fields, were observed by Equator-S prior to and during the periods of high FUV emission. Enhanced poleward ionospheric flow velocities in the polar cusp region, previously shown to be associated with bursty reconnection, consistently lie poleward of the enhanced FUV optical feature. The enhanced optical feature is consistent with the expected position of the largest upward region 1 field-aligned current, associated with electron precipitation, on the dusk edge of the merging gap. The optical feature moves duskward and equatorward during the course of the reconnection sequence, consistent with expansion of the merging line and the polar cap with newly added open magnetic flux by the FTEs. The DMSP F14 spacecraft passed through the enhanced FUV region and measured strong, structured electron precipitation far greater than in the adjacent regions.Key words. Magnetospheric physics (current systems; magnetopause, cusp and boundary layers; magnetosphere-ionosphere interactions)

The Effect of Solar Wind Mach Numbers on the Occurrence Rate of Flux Transfer Events at the Dayside Magnetopause

2019 ◽  
Vol 46 (8) ◽  
pp. 4106-4113 ◽  
Author(s):  
C. Chen ◽  
T. R. Sun ◽  
C. Wang ◽  
Z. H. Huang ◽  
B. B. Tang ◽  
...  
Keyword(s):  
Solar Wind ◽  
Occurrence Rate ◽  
Flux Transfer Events ◽  
Dayside Magnetopause ◽  
Mach Numbers ◽  
Flux Transfer

scholarly journals Flux transfer events: Scale size and interior structure

1984 ◽  
Vol 11 (2) ◽  
pp. 131-134 ◽  
Author(s):  
M. A. Saunders ◽  
C. T. Russell ◽  
N. Sckopke
Keyword(s):  
Interior Structure ◽  
Flux Transfer Events ◽  
Scale Size ◽  
Flux Transfer

Observations of a possible ground signature of flux transfer events

1985 ◽  
Vol 90 (A5) ◽  
pp. 4069 ◽  
Author(s):  
C. K. Goertz ◽  
E. Nielsen ◽  
A. Korth ◽  
K. H. Glassmeier ◽  
C. Haldoupis ◽  
...  
Keyword(s):  
Flux Transfer Events ◽  
Flux Transfer

Resolving Optimum Magnetic Signatures for Drill-Hole Targeting in Gold Exploration – A Case Study for Mbudzane in Gwanda, Zimbabwe

2013 ◽  
Vol 3 (1) ◽  
pp. 9-29
Author(s):  
Dumisani John Hlatywayo ◽  
Emmanuel Sakala
Keyword(s):  
Drill Hole ◽  
Magnetic Survey ◽  
Gold Exploration ◽  
Rock Formations ◽  
Induced Polarisation ◽  
Line Spacing ◽  
Magnetic Signatures ◽  
Ground Magnetic ◽  
Tilt Derivative ◽  
Resistivity Image

Optimum magnetic signatures for drill-hole targeting in gold exploration in Mbudzane were resolved from induced polarisation-resistivity and magnetic anomalies. Total magnetic field and a gold-in-soil map showed the area is magnetically quiet with high anomalous values along old gold workings. Induced polarisation was carried out along a grid for lines of 500m length, 50m separation and a baseline oriented at 330˚. The survey comprised a gradient array and three real sections. The magnetic survey was conducted over the same grid as the induced polarisation. Stations were set at 5m intervals for a line spacing of 50m. The results show intense anomalies that suggest different degrees of magnetic alteration and a set of conjugate lineaments and faults that possibly control the mineralisation in Mbudzane. The tilt derivative of the reduced-to-pole image resolves the separation between anomalies, giving information on the faulting. High chargeability is confined to the sheared and silicified mafic schist. The gradient resistivity image revealed contact between rock formations. Real section IP shows coincident low chargeability – low resistivity anomalies close to the surface. Chargeability intensity increases with depth, suggesting incipient development of disseminated sulphide replacement zones. A strong correlation between ground magnetic inferred contacts and apparent resistivity-chargeability anomalies forms the basis for suggesting a new drill-hole targeting. They dictate both the depth and angle at which drilling should be carried out. These results should be applicable to any region where drill-hole targeting in gold exploration may be required.

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