On the spatial relationship between auroral emissions and magnetic signatures of plasma convection in the midday polar cusp and cap ionospheres during negative and positive IMFBz: A case study

1986 ◽  
Vol 91 (A11) ◽  
pp. 12108 ◽  
Author(s):  
P. E. Sandholt ◽  
A. Egeland ◽  
B. Lybekk
Keyword(s):  
Spatial Relationship ◽  
Plasma Convection ◽  
Polar Cusp ◽  
Magnetic Signatures ◽  
Auroral Emissions

scholarly journals Multi-site observations of the association between aurora and plasma convection in the cusp/polar cap during a southeastward(<i>B<sub>y</sub></i> <u>~</u> |<i>B<sub>z</sub></i>|) IMF orientation

2003 ◽  
Vol 21 (2) ◽  
pp. 539-558 ◽  
Author(s):  
P. E. Sandholt ◽  
J. Moen ◽  
C. J. Farrugia ◽  
S. W. H. Cowley ◽  
M. Lester ◽  
...  
Keyword(s):  
Central Feature ◽  
Plasma Convection ◽  
Polar Cap ◽  
Westward Expansion ◽  
Equatorward Boundary ◽  
Dayside Magnetopause ◽  
On Line ◽  
Auroral Emissions ◽  
Auroral Phenomena

Abstract. In a case study we demonstrate the spatiotemporal structure of aurora and plasma convection in the cusp/polar cap when the interplanetary magnetic field (IMF) Bz < 0 and By ~ | Bz | (clock angle in GSM Y - Z plane: ~ 135°). This IMF orientation elicited a response different from that corresponding to strongly northward and southward IMF. Our study of this "intermediate state" is based on a combination of ground observations of optical auroral emissions and ionospheric plasma convection. Utilizing all-sky cameras at NyAlesund, Svalbard and Heiss Island (Russian arctic), we are able to monitor the high-latitude auroral activity within the ~10:00–15:00 MLT sector. Information on plasma convection is obtained from the SuperDARN radars, with emphasis placed on line of sight observations from the radar situated in Hankasalmi, Finland (Cutlass). A central feature of the auroral observations in the cusp/polar cap region is a ~ 30-min long sequence of four brightening events, some of which consists of latitudinally and longitudinally separated forms, which are found to be associated with pulsed ionospheric flows in merging and lobe convection cells. The auroral/convection events may be separated into different forms/cells and phases, reflecting a spatiotem-poral evolution of the reconnection process on the dayside magnetopause. The initial phase consists of a brightening in the postnoon sector (~ 12:00–14:00 MLT) at ~ 73° MLAT, accompanied by a pulse of enhanced westward convection in the postnoon merging cell. Thereafter, the event evolution comprises two phenomena which occur almost simultaneously: (1) westward expansion of the auroral brightening (equatorward boundary intensification) across noon, into the ~ 10:00–12:00 MLT sector, where the plasma convection subsequently turns almost due north, in the convection throat, and where classical poleward moving auroral forms (PMAFs) are observed; and (2) auroral brightening at slightly higher latitudes (~ 75° MLAT) in the postnoon lobe cell, with expansion towards noon, giving rise to a clear cusp bifurcation. The fading phase of PMAFs is accompanied by a "patch" of enhanced (~ 1 km/s) poleward-directed merging cell convection at high latitudes (75–82° MLAT), e.g. more than 500 km poleward of the cusp equatorward boundary. The major aurora/convection events are recurring at ~ 5–10 min intervals. Key words. Magnetospheric physics (auroral phenomena; magnetopause, cusp, and boundary layers; plasma convection)

Electrodynamics of the polar cusp ionosphere; A case study

1989 ◽  
Vol 94 (A6) ◽  
pp. 6713-6722 ◽  
Author(s):  
P. E. Sandholt ◽  
B. Jacobsen ◽  
B. Lybekk ◽  
A. Egeland ◽  
P. F. Bythrow ◽  
...  
Keyword(s):  
Polar Cusp

Staircase ion signature in the polar cusp: A case study

1992 ◽  
Vol 19 (17) ◽  
pp. 1735-1738 ◽  
Author(s):  
C. P. Escoubet ◽  
M. F. Smith ◽  
S. F. Fung ◽  
P. C. Anderson ◽  
R. A. Hoffman ◽  
...  
Keyword(s):  
Polar Cusp

Cao Fei’s nostalgia for the future

2020 ◽  
Vol 7 (2-3) ◽  
pp. 261-279
Author(s):  
Ellen Larson
Keyword(s):  
Spatial Relationship ◽  
Spatial Position ◽  
Full Length ◽  
New Work ◽  
Republic Of China ◽  
Industrial History ◽  
Research Production ◽  
Creative Research ◽  
The Future

Between 2015 and 2020, artist Cao Fei occupied the former Beijing-based Hongxia Theatre, transforming the space into a vehicle for creative research, production and exhibition. This article will examine Cao Fei’s engagement with multiple temporalities as directly shaped by her spatial position within the theatre. Research related to the Hongxia Theatre and surrounding former People’s Republic of China (PRC)-era factory neighbourhood informs her understanding of not only China’s industrial history but also resurging connections to themes that exist across, within and beyond traditional temporal frameworks. The following narrative will employ Asia One (2018), the first full-length film made by Cao Fei since moving into the Hongxia Theatre, as a case study, highlighting strategies in which Hongxia fosters a pivotal spatial relationship between the artist’s new work and intersecting affinities towards time, memory and nostalgia. Drawing on China’s utopian past and dreams of a fully automated future, Asia One demonstrates a temporally nonlinear yearning to record both remembered and imagined emotional attachments, despite both globalizing and domestic conditions, which engender the urge to forget.

Case Study of Crash Severity Spatial Pattern Identification in Hot Spot Analysis

2019 ◽  
Vol 2673 (9) ◽  
pp. 684-695 ◽  
Author(s):  
Myungwoo Lee ◽  
Aemal J. Khattak
Keyword(s):  
Density Estimation ◽  
Motor Vehicle ◽  
Safety Concern ◽  
Hot Spot ◽  
Estimation Method ◽  
Spatial Relationship ◽  
Crash Severity ◽  
Hot Spot Analysis ◽  
Spot Analysis

Traffic crash hot spot analyses allow identification of roadway segments that may be of safety concern. Understanding geographic patterns of existing motor vehicle crashes is one of the primary steps for geostatistical-based hot spot analysis. Much of the current literature, however, has not paid particular attention to differentiating among cluster types based on crash severity levels. This study aims at building a framework for identifying significant spatial clustering patterns characterized by crash severity and analyzing identified clusters quantitatively. A case study using an integrated method of network-based local spatial autocorrelation and the Kernel density estimation method revealed a strong spatial relationship between crash severity clusters and geographic regions. In addition, the total aggregated distance and the density of identified clusters obtained from density estimation allowed a quantitative analysis for each cluster. The contribution of this research is incorporating crash severity into hot spot analysis thereby allowing more informed decision making with respect to highway safety.

scholarly journals Transpolar arc evolution and associated potential patterns

2004 ◽  
Vol 22 (4) ◽  
pp. 1213-1231 ◽  
Author(s):  
J. A. Cumnock ◽  
L. G. Blomberg
Keyword(s):  
Magnetic Field ◽  
Electric Fields ◽  
Polar Region ◽  
Auroral Oval ◽  
Plasma Convection ◽  
Auroral Emission ◽  
Field Aligned Current ◽  
Auroral Emissions ◽  
Institute Of Technology ◽  
Electric Fields And Currents

Abstract. We present two event studies encompassing detailed relationships between plasma convection, field-aligned current, auroral emission, and particle precipitation boundaries. We illustrate the influence of the Interplanetary Magnetic Field By component on theta aurora development by showing two events during which the theta originates on both the dawn and dusk sides of the auroral oval. Both theta then move across the entire polar region and become part of the opposite side of the auroral oval. Electric and magnetic field and precipitating particle data are provided by DMSP, while the Polar UVI instrument provides measurements of auroral emissions. Utilizing satellite data as inputs, the Royal Institute of Technology model provides the high-latitude ionospheric electrostatic potential pattern calculated at different times during the evolution of the theta aurora, resulting from a variety of field-aligned current configurations associated with the changing global aurora. Key words. Ionosphere (auroral ionosphere; electric fields and currents). Magnetospheric physics (magnetosphereionosphere interactions)

scholarly journals <i>Letter to the Editor</i> Simultaneous observations of the ionospheric footprint of flux transfer events and dispersed ion signatures

2002 ◽  
Vol 20 (2) ◽  
pp. 281-287 ◽  
Author(s):  
G. Provan ◽  
S. E. Milan ◽  
M. Lester ◽  
T. K. Yeoman ◽  
H. Khan
Keyword(s):  
Boundary Layers ◽  
High Latitude ◽  
Spectral Width ◽  
Field Of View ◽  
Magnetospheric Physics ◽  
Plasma Convection ◽  
Coherent Scatter ◽  
Flux Transfer Events ◽  
Letter To The Editor

Abstract. We perform a case study of a favourable conjunction of overpasses of the DMSP F11 and F13 spacecraft with the field of view of the Hankasalmi HF coherent scatter. At the time, pulsed ionospheric flows (PIFs) were clearly observed at a high-latitude in the radar field of view. The PIFs were associated with medium spectral width values and were identified as the fossilized signatures of pulsed dayside reconnection. Simultaneously, DMSP spectrograms from the two spacecraft showed dispersed ion signatures, observed equatorwards of the PIF signatures. We identified dayside high-latitude magnetosphere boundaries; these boundaries agreed well with those defined using the algorithm on the JHU/APL auroral particle website (Haerendel et al., 1978; Newell and Meng, 1988, 1995; Newell et al., 1991a, 1991b, 1991c; Traver et al., 1991). We conclude that in this case study the dispersed ion signatures map to regions of very newly-opened flux. It is only when this flux has convected polewards that the signatures of the PIFs with medium spectral widths are observed by the HF radars. These particular PIF signatures map to regions of mantle precipitation, i.e. recently reconnected flux.Key words. Ionosphere (ionosphere-magnetosphere interaction) – Magnetospheric physics (magnetopause, cusp and boundary layers; plasma convection)

scholarly journals UNDERWATER PHOTOGRAMMETRY METHODS FOR A PECULIAR CASE-STUDY: SAN DOMENICO (PRATO-ITALY)

2015 ◽  
Vol XL-5/W5 ◽  
pp. 171-176
Author(s):  
E. Pruno ◽  
C. Marcotulli ◽  
G. Vannini ◽  
P. Drap
Keyword(s):  
Shallow Water ◽  
Spatial Relationship ◽  
Digital Camera ◽  
Underwater Archaeology ◽  
Layer By Layer ◽  
Relevant Model ◽  
Good Opportunity ◽  
Surface Survey ◽  
Peculiar Case

San Domenico Church (Prato, Tuscan, Italy) is a very peculiar case of terrestrial archaeology surveyed with underwater archaeological photogrammetric approach. The vault of the choir was completely filled by a very important numbers of potteries, which is very interesting building technique. To document this technique a complete photogrammetric survey was realized, layer by layer, following underwater archaeology system. It is interesting to note that in underwater archaeology such a case is quite rare, in fact or the wreck is in shallow water and the digging can be made (but this case is now unrealistic because in shallow water all the wreck have been stolen – or already excavated by archaeologist &ndash; !) or we are in deep water, with well conserved wreck but the depth doesn’t allow the excavation. In the last case only a surface survey is possible. Also for these reasons this particular case- study is very interesting in order to test underwater methods on real case. This experimentation is a good opportunity to develop and check methods, algorithm and software to obtain a relevant model of the site merging 3D measure and knowledge about the artefact as typology, theoretical model, spatial relationship between them. Even if this work started in 2006, with now obsolete digital camera and with a photographic campaign which not respect always the current constraints for building a dense cloud of point in photogrammetry,it is now used as a case-study for developing a relevant approach for underwater archaeology survey.

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