scholarly journals Intensity asymmetries in the dusk sector of the poleward auroral oval due to IMF B x

2014 ◽  
Vol 119 (12) ◽  
pp. 9497-9507 ◽  
Author(s):  
J. P. Reistad ◽  
N. Østgaard ◽  
K. M. Laundal ◽  
S. Haaland ◽  
P. Tenfjord ◽  
...  
Keyword(s):  
Auroral Oval ◽  
Dusk Sector

scholarly journals Ground-based and satellite observations of high-latitude auroral activity in the dusk sector of the auroral oval

2001 ◽  
Vol 19 (10/12) ◽  
pp. 1683-1696 ◽  
Author(s):  
K. Kauristie ◽  
T. I. Pulkkinen ◽  
O. Amm ◽  
A. Viljanen ◽  
M. Syrjäsuo ◽  
...  
Keyword(s):  
Solar Wind ◽  
High Latitude ◽  
Auroral Oval ◽  
Outer Edge ◽  
Satellite Observations ◽  
Mhd Waves ◽  
Clear Correlation ◽  
Close Relationship ◽  
Magnetic Pulsations ◽  
Dusk Sector

Abstract. On 7 December 2000, during 13:30–15:30 UT the MIRACLE all-sky camera at Ny Ålesund observed auroras at high-latitudes (MLAT ~ 76) simultaneously when the Cluster spacecraft were skimming the magnetopause in the same MLT sector (at ~ 16:00–18:00 MLT). The location of the auroras (near the ionospheric convection reversal boundary) and the clear correlation between their dynamics and IMF variations suggests their close relationship with R1 currents. Consequently, we can assume that the Cluster spacecraft were making observations in the magnetospheric region associated with the auroras, although exact magnetic conjugacy between the ground-based and satellite observations did not exist. The solar wind variations appeared to control both the behaviour of the auroras and the magnetopause dynamics. Auroral structures were observed at Ny Ålesund especially during periods of negative IMF BZ. In addition, the Cluster spacecraft experienced periodic (T ~ 4 - 6 min) encounters between magnetospheric and magnetosheath plasmas. These undulations of the boundary can be interpreted as a consequence of tailward propagating magnetopause surface waves. Simultaneous dusk sector ground-based observations show weak, but discernible magnetic pulsations (Pc 5) and occasionally periodic variations (T ~ 2 - 3 min) in the high-latitude auroras. In the dusk sector, Pc 5 activity was stronger and had characteristics that were consistent with a field line resonance type of activity. When IMF BZ stayed positive for a longer period, the auroras were dimmer and the spacecraft stayed at the outer edge of the magnetopause where they observed electromagnetic pulsations with T ~ 1 min. We find these observations interesting especially from the viewpoint of previously presented studies relating poleward-moving high-latitude auroras with pulsation activity and MHD waves propagating at the magnetospheric boundary layers.Key words. Ionosphere (ionosphere-magnetosphere interaction) – Magnetospheric physics (auroral phenomena; solar wind – magnetosphere interactions)

scholarly journals Auroral electrojets and boundaries of plasma domains in the magnetosphere during magnetically disturbed intervals

2006 ◽  
Vol 24 (8) ◽  
pp. 2243-2276 ◽  
Author(s):  
Y. I. Feldstein ◽  
V. A. Popov ◽  
J. A. Cumnock ◽  
A. Prigancova ◽  
L. G. Blomberg ◽  
...  
Keyword(s):  
Magnetic Storm ◽  
Plasma Sheet ◽  
High Speed ◽  
Auroral Oval ◽  
Main Phase ◽  
Particle Precipitation ◽  
Evening Sector ◽  
Central Plasma ◽  
Central Plasma Sheet ◽  
Dusk Sector

Abstract. We investigate variations in the location and intensity of the auroral electrojets during magnetic storms and substorms using a numerical method for estimating the equivalent ionospheric currents based on data from meridian chains of magnetic observatories. Special attention was paid to the complex structure of the electrojets and their interrelationship with diffuse and discrete particle precipitation and field-aligned currents in the dusk sector. During magnetospheric substorms the eastward electrojet (EE) location in the evening sector changes with local time from cusp latitudes (Φ~77°) during early afternoon to latitudes of diffuse auroral precipitation (Φ~65°) equatorward of the auroral oval before midnight. During the main phase of an intense magnetic storm the eastward currents in the noon-early evening sector adjoin to the cusp at Φ~65° and in the pre-midnight sector are located at subauroral latitude Φ~57°. The westward electrojet (WE) is located along the auroral oval from evening through night to the morning sector and adjoins to the polar electrojet (PE) located at cusp latitudes in the dayside sector. The integrated values of the eastward (westward) equivalent ionospheric current during the intense substorm are ~0.5 MA (~1.5 MA), whereas they are 0.7 MA (3.0 MA) during the storm main phase maximum. The latitudes of auroral particle precipitation in the dusk sector are identical with those of both electrojets. The EE in the evening sector is accompanied by particle precipitation mainly from the Alfvén layer but also from the near-Earth part of the central plasma sheet. In the lower-latitude part of the EE the field-aligned currents (FACs) flow into the ionosphere (Region 2 FAC), and at its higher-latitude part the FACs flow out of the ionosphere (Region 1 FAC). During intense disturbances, in addition to the Region 2 FAC and the Region 1 FAC, a Region 3 FAC with the downward current was identified. This FAC is accompanied by diffuse electron precipitation from the plasma sheet boundary layer. Actually, the triple system of FAC is observed in the evening sector and, as a consequence, the WE and the EE overlap. The WE in the evening sector comprises only the high-latitude periphery of the plasma precipitation region and corresponds to the Hall current between the Region 1 FAC and Region 3 FAC. During the September 1998 magnetic storm, two velocity bursts (~2–4 km/s) in the magnetospheric convection were observed at the latitudes of particle precipitation from the central plasma sheet and at subauroral latitudes near the ionospheric trough. These kind of bursts are known as subauroral polarization streams (SAPS). In the evening sector the Alfvén layer equatorial boundary for precipitating ions is located more equatorward than that for electrons. This may favour northward electric field generation between these boundaries and may cause high speed westward ions drift visualized as SAPS. Meanwhile, high speed ion drifts cover a wider range of latitudes than the distance between the equatorward boundaries of ions and electrons precipitation. To summarize the results obtained a new scheme of 3-D currents in the magnetosphere-ionosphere system and a clarified view of interrelated 3-D currents and magnetospheric plasma domains are proposed.

scholarly journals Equatorward propagating auroral arcs driven by ULF wave activity: Multipoint ground- and space-based observations in the dusk sector auroral oval

2017 ◽  
Vol 122 (5) ◽  
pp. 5591-5605 ◽  
Author(s):  
L. J. Baddeley ◽  
D. A. Lorentzen ◽  
N. Partamies ◽  
M. Denig ◽  
V. A. Pilipenko ◽  
...  
Keyword(s):  
Auroral Oval ◽  
Wave Activity ◽  
Ulf Wave ◽  
Auroral Arcs ◽  
Dusk Sector

scholarly journals Observations of high-velocity SAPS-like flows with the King Salmon SuperDARN radar

2006 ◽  
Vol 24 (6) ◽  
pp. 1591-1608 ◽  
Author(s):  
A. V. Koustov ◽  
R. A. Drayton ◽  
R. A. Makarevich ◽  
K. A. McWilliams ◽  
J.-P. St-Maurice ◽  
...  
Keyword(s):  
High Velocity ◽  
Average Velocity ◽  
Recovery Phase ◽  
Auroral Oval ◽  
Hf Radar ◽  
Line Of Sight ◽  
Inner Magnetosphere ◽  
Dusk Sector

Abstract. In this study, a focused investigation of the potential for the King Salmon (KS) SuperDARN HF radar to monitor high-velocity flows near the equatorial edge of the auroral oval is undertaken. Events are presented with line-of-sight velocities as high as 2km/s, observed roughly along the L-shell. Statistically, the enhanced flows are shown to be typical for the dusk sector (16:00–23:00 MLT), and the average velocity in this sector is larger (smaller) for winter (summer) conditions. It is also demonstrated that the high-velocity flows can be very dynamical with more localized enhancements existing for just several minutes. These short-lived enhancements occur when the luminosity at the equatorial edge of the auroral oval suddenly decreases during the substorm recovery phase. The short-lived velocity enhancements can be established because of proton and ion injections into the inner magnetosphere and low conductance of the ionosphere and not because of enhanced tail reconnection. This implies that some KS velocity enhancements have the same origin as subauroral polarization streams (SAPS).

A.E. Nordenski and the auroral oval

Eos ◽  
1982 ◽  
Vol 63 (26) ◽  
pp. 553 ◽  
Author(s):  
Tuomo Nygrén ◽  
Johan Silén
Keyword(s):  
Auroral Oval

Field-aligned currents associated with spatially periodic X ray structures in the morningside auroral oval

1995 ◽  
Vol 100 (A12) ◽  
pp. 23945 ◽  
Author(s):  
R. M. Robinson ◽  
D. L. Chenette ◽  
D. W. Datlowe ◽  
T. L. Schumaker ◽  
R. R. Vondrak ◽  
...  
Keyword(s):  
Auroral Oval ◽  
X Ray ◽  
Spatially Periodic

The continuity of the auroral oval in the afternoon sector

1975 ◽  
Vol 23 (1) ◽  
pp. 225-227 ◽  
Author(s):  
A.L. Snyder ◽  
S.-I. Akasofu ◽  
D.S. Kimball
Keyword(s):  
Auroral Oval

Statistics of pulsating auroras on the basis of all-sky TV data from five stations. I. Occurrence frequency

1981 ◽  
Vol 59 (8) ◽  
pp. 1150-1157 ◽  
Author(s):  
T. Oguti ◽  
S. Kokubun ◽  
K. Hayashi ◽  
K. Tsuruda ◽  
S. Machida ◽  
...  
Keyword(s):  
Local Time ◽  
Cold Plasma ◽  
Geomagnetic Latitude ◽  
Auroral Oval ◽  
Magnetic Activity ◽  
Occurrence Frequency ◽  
Frequency Of Occurrence ◽  
Occurrence Probability ◽  
Energetic Electrons ◽  
Plasma Irregularities

The frequency of occurrence of pulsating auroras is statistically examined on the basis of all-sky TV data for 34 nights from five stations, in a range from 61.5 to 74.3° in geomagnetic latitude. The results are that: (1) occurrence probability of a pulsating aurora is 100% after 4 h in geomagnetic local time, (2) pulsating auroras occur in the morning hours along the auroral oval even when magnetic activity is as small as 0o ≤ Kp ≤ 1, (3) pulsating auroras occur even in the evening when Kp increases to greater than 3−, (4) drift of pulsating auroras is westward in the evening while it is eastward in the morning hours, (5) the region of pulsating auroras splits into two zones, 64 to 68° and 61 to 63° in geomagnetic latitude, after 4 h geomagnetic local time for Kp from 2o to 3−, and the splitting also appears to exist for greater Kp as evidenced by observation other than our auroral data. These results are discussed in relation to distributions of cold plasma irregularities and energetic electrons in the magnetosphere.

Sign in / Sign up

Export Citation Format

Share Document