scholarly journals Swarm Satellite and EISCAT Radar Observations of a Plasma Flow Channel in the Auroral Oval Near Magnetic Midnight

2018 ◽  
Vol 123 (6) ◽  
pp. 5140-5158 ◽  
Author(s):  
A. T. Aikio ◽  
H. Vanhamäki ◽  
A. B. Workayehu ◽  
I. I. Virtanen ◽  
K. Kauristie ◽  
...  
Keyword(s):  
Plasma Flow ◽  
Auroral Oval ◽  
Flow Channel ◽  
Radar Observations ◽  
Eiscat Radar ◽  
Swarm Satellite

Sondrestrom and EISCAT radar observations of poleward-moving auroral forms

1990 ◽  
Vol 52 (6-8) ◽  
pp. 411-420 ◽  
Author(s):  
R.M Robinson ◽  
C.R Clauer ◽  
O De La Beaujardiere ◽  
J.D Kelly ◽  
E Friis-christensen ◽  
...  
Keyword(s):  
Radar Observations ◽  
Eiscat Radar

scholarly journals Plasma flow channels with ULF waves observed by Cluster and Double Star

2005 ◽  
Vol 23 (8) ◽  
pp. 2929-2935 ◽  
Author(s):  
M. Volwerk ◽  
T. L. Zhang ◽  
R. Nakamura ◽  
A. Runov ◽  
W. Baumjohann ◽  
...  
Keyword(s):  
Magnetic Structure ◽  
Plasma Flow ◽  
Large Scale ◽  
Double Star ◽  
Flow Channel ◽  
Propagation Direction ◽  
Ulf Waves ◽  
Flow Channels ◽  
Earthward Flow

Abstract. On 14 August 2004 a large-scale magnetic structure was observed by Double Star TC-1 in the southern lobe and by Cluster in the northern lobe of the magnetotail. The structure has the signature of a (localized) dipolarization, decreasing Bx accompanied by an increasing Bz and a strong earthward flow. The propagation direction of this structure, however, seems to be more in the dawnward direction than earthward. The structure is accompanied by ULF waves with a period of ~5 min, which are simultaneously observed by the ground magnetometer station DIK, at the magnetic footpoints of the spacecraft. We interprete these waves as modes driven by the plasma flow and propagating in the flow channel.

scholarly journals On auroral dynamics observed by HF radar: 1. Equatorward edge of the afternoon-evening diffuse luminosity belt

2000 ◽  
Vol 18 (12) ◽  
pp. 1560-1575 ◽  
Author(s):  
M. Uspensky ◽  
P. Eglitis ◽  
H. Opgenoorth ◽  
G. Starkov ◽  
T. Pulkkinen ◽  
...  
Keyword(s):  
Electron Plasma ◽  
Auroral Oval ◽  
Hf Radar ◽  
Phase Development ◽  
Evening Sector ◽  
Density Enhancement ◽  
Late Evening ◽  
Eiscat Radar ◽  
Auroral Phenomena ◽  
Diurnal Rotation

Abstract. Observations and modelling are presented which illustrate the ability of the Finland CUTLASS HF radar to monitor the afternoon-evening equatorward auroral boundary during weak geomagnetic activity. The subsequent substorm growth phase development was also observed in the late evening sector as a natural continuation of the preceding auroral oval dynamics. Over an 8 h period the CUTLASS Finland radar observed a narrow (in range) and persistent region of auroral F- and (later) E-layer echoes which gradually moved equatorward, consistent with the auroral oval diurnal rotation. This echo region corresponds to the subvisual equatorward edge of the diffuse luminosity belt (SEEL) and the ionospheric footprint of the inner boundary of the electron plasma sheet. The capability of the Finland CUTLASS radar to monitor the E-layer SEEL-echoes is a consequence of the nearly zero E-layer rectilinear aspect angles in a region 5–10° poleward of the radar site. The F-layer echoes are probably the boundary blob echoes. The UHF EISCAT radar was in operation and observed a similar subvisual auroral arc and an F-layer electron density enhancement when it appeared in its antenna beam.Key words: Ionsophere (ionospheric irregularities) · Magnetospheric physics (auroral phenomena; magnetosphere–ionosphere interactions)

scholarly journals A plasma flow vortex in the magnetotail and its related ionospheric signatures

2012 ◽  
Vol 30 (3) ◽  
pp. 537-544 ◽  
Author(s):  
C. L. Tang
Keyword(s):  
Plasma Flow ◽  
Plasma Sheet ◽  
Large Scale ◽  
Time History ◽  
High Energy ◽  
Auroral Oval ◽  
Fort Smith ◽  
Flow Speeds ◽  
History Of ◽  
Flow Vortex

Abstract. We presented a large-scale plasma flow vortex event that occurred on 1 March 2009 observed by Time History of Events and Macroscale Interactions during Substorms (THEMIS) satellites. During the interval, THEMIS satellites were located in the premidnight region between 11 and 16 RE downtail. Dawnward-earthward plasma flows were seen initially in the magnetotail, followed by duskward-tailward flows. This suggests that a clockwise plasma flow vortex (seen from above the equatorial plane) was observed on the dawn side of the plasma sheet. Furthermore, high energy (>1 keV) electrons were observed. Auroral images at 427.8 nm and THEMIS white light all-sky imager (ASI) at Fort Smith showed a discrete auroral patch formed at the poleward of the auroral oval, it then intensified. It extended eastward and equatorward first and followed by westward motion to form the clockwise auroral vortex. The auroral feature corresponded to the ionospheric signatures of the plasma flow vortex in the magnetotail when the Alfvén transit time between the magnetotail and the ionosphere was taken into account. We suggest that the large-scale clockwise plasma flow vortex in association with the high energy (>1 keV) electrons on the dawn side of the plasma sheet generated a downward field-aligned current (FAC) that caused the related ionospheric signatures. The plasma flow vortex had rotational flow speeds of up to 300 km s−1. The current density associated with the plasma flow vortex was estimated at 2.0 μA m−2, mapped to the ionosphere.

scholarly journals An auroral westward flow channel (AWFC) and its relationship to field-aligned current, ring current, and plasmapause location determined using multiple spacecraft observations

2007 ◽  
Vol 25 (1) ◽  
pp. 59-76 ◽  
Author(s):  
M. L. Parkinson ◽  
J. A. Wild ◽  
C. L. Waters ◽  
M. Lester ◽  
E. A. Lucek ◽  
...  
Keyword(s):  
Plasma Sheet ◽  
Large Scale ◽  
Ring Current ◽  
Narrow Channel ◽  
Recovery Phase ◽  
Global Scale ◽  
Auroral Oval ◽  
Flow Channel ◽  
Expansion Phase ◽  
Field Aligned Current

Abstract. An auroral westward flow channel (AWFC) is a latitudinally narrow channel of unstable F-region plasma with intense westward drift in the dusk-to-midnight sector ionosphere. AWFCs tend to overlap the equatorward edge of the auroral oval, and their life cycle is often synchronised to that of substorms: they commence close to substorm expansion phase onset, intensify during the expansion phase, and then decay during the recovery phase. Here we define for the first time the relationship between an AWFC, large-scale field-aligned current (FAC), the ring current, and plasmapause location. The Tasman International Geospace Environment Radar (TIGER), a Southern Hemisphere HF SuperDARN radar, observed a jet-like AWFC during ~08:35 to 13:28 UT on 7 April 2001. The initiation of the AWFC was preceded by a band of equatorward expanding ionospheric scatter (BEES) which conveyed an intense poleward electric field through the inner plasma sheet. Unlike previous AWFCs, this event was not associated with a distinct substorm surge; rather it occurred during an interval of persistent, moderate magnetic activity characterised by AL~−200 nT. The four Cluster spacecraft had perigees within the dusk sector plasmasphere, and their trajectories were magnetically conjugate to the radar observations. The Waves of High frequency and Sounder for Probing Electron density by Relaxation (WHISPER) instruments on board Cluster were used to identify the plasmapause location. The Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) EUV experiment also provided global-scale observations of the plasmapause. The Cluster fluxgate magnetometers (FGM) provided successive measurements specifying the relative location of the ring current and filamentary plasma sheet current. An analysis of Iridium spacecraft magnetometer measurements provided estimates of large-scale ionospheric FAC in relation to the AWFC evolution. Peak flows in the AWFC were located close to the peak of a Region 2 downward FAC, located just poleward of the plasmapause. DMSP satellite observations confirmed the AWFC was located equatorward of the nightside plasmasheet, sometimes associated with ~10 keV ion precipitation.

Eiscat radar observations of enhanced incoherent scatter spectra; Their relation to red aurora and field-aligned currents

1991 ◽  
Vol 18 (6) ◽  
pp. 1031-1034 ◽  
Author(s):  
P. N. Collis ◽  
L. Häggström ◽  
K. Kaila ◽  
M. T. Rietveld
Keyword(s):  
Radar Observations ◽  
Incoherent Scatter ◽  
Eiscat Radar

scholarly journals Observations of an auroral streamer in a double oval configuration

2011 ◽  
Vol 29 (4) ◽  
pp. 701-716 ◽  
Author(s):  
O. Amm ◽  
R. Nakamura ◽  
T. Takada ◽  
K. Kauristie ◽  
H. U. Frey ◽  
...  
Keyword(s):  
Southern Hemisphere ◽  
Recovery Phase ◽  
Auroral Oval ◽  
Expansion Phase ◽  
Optical Instruments ◽  
Image Satellite ◽  
Bursty Bulk Flow ◽  
Polarization Electric Field ◽  
Late Evening ◽  
Eiscat Radar

Abstract. During the late evening and night of 14 September 2004, the nightside auroral oval shows a distinct double oval configuration for several hours after a substorm onset at ~18:45 UT. This structure is observed both by the IMAGE satellite optical instruments focusing on the Southern Hemisphere, and by the MIRACLE ground-based instrument network in Scandinavia. At ~21:17 UT during the recovery phase of the substorm, an auroral streamer is detected by these instruments and the EISCAT radar, while simultaneously the Cluster satellites observe a bursty bulk flow in the conjugate portion of the plasma sheet in the magnetotail. Our combined data analysis reveals significant differences between the ionospheric equivalent current signature of this streamer within a double oval configuration, as compared to previously studied streamer events without such a configuration. We attribute these differences to the presence of an additional poleward polarization electric field between the poleward and the equatorward portions of the double oval, and show with a simple model that such an assumption can conceptually explain the observations. Further, we estimate the total current transferred in meridional direction by this recovery phase streamer to ~80 kA, significantly less than for previously analysed expansion phase streamer events. Both results indicate that the development of auroral streamers is dependent on the ambient background conditions in the magnetosphere-ionosphere system. The auroral streamer event studied was simultaneously observed in the conjugate Northern and Southern Hemisphere ionosphere.

scholarly journals Oscillations of the equatorward boundary of the ion auroral oval - radar observations

2008 ◽  
Vol 113 (A8) ◽  
pp. n/a-n/a ◽  
Author(s):  
P. T. Jayachandran ◽  
N. Sato ◽  
Y. Ebihara ◽  
A. S. Yukimatu ◽  
A. Kadokura ◽  
...  
Keyword(s):  
Auroral Oval ◽  
Radar Observations ◽  
Equatorward Boundary
Sign in / Sign up

Export Citation Format

Share Document