scholarly journals Simultaneous observations of the main trough using GPS imaging and the EISCAT radar

2005 ◽  
Vol 23 (3) ◽  
pp. 753-757 ◽  
Author(s):  
R. W. Meggs ◽  
C. N. Mitchell ◽  
V. S. C. Howells
Keyword(s):  
Magnetic Activity ◽  
The West ◽  
West Side ◽  
Gps Receivers ◽  
Equatorial Ionization Anomaly ◽  
Main Trough ◽  
Spread F ◽  
A Chain ◽  
Eiscat Radar ◽  
June July

Abstract. We use a digisonde at Jicamarca and a chain of GPS receivers on the west side of South America to investigate the effects of the pre-reversal enhancement (PRE) in ExB drift, the asymmetry (Ia) of equatorial ionization anomaly (EIA), and the magnetic activity (Kp) on the generation of equatorial spread F (ESF). Results show that the ESF appears frequently in summer (November, December, January, and February) and equinoctial (March, April, September, and October) months, but rarely in winter (May, June, July, and August) months. The seasonal variation in the ESF is associated with those in the PRE ExB drift and Ia. The larger ExB drift (>20m/s) and smaller |Ia| (<0.3) in summer and equinoctial months provide a preferable condition to development the ESF. Conversely, the smaller ExB drift and larger |Ia| are responsible for the lower ESF occurrence in winter months. Regarding the effects of magnetic activity, the ESF occurrence decreases with increasing Kp in the equinoctial and winter months, but not in the summer months. Furthermore, the larger and smaller ExB drifts are presented under the quiet (Kp<3) and disturbed (Kp≥3) conditions, respectively. These results indicate that the suppression in ESF and the decrease in ExB drifts are mainly caused by the decrease in the eastward electric field.

scholarly journals The effects of the pre-reversal ExB drift, the EIA asymmetry, and magnetic activity on the equatorial spread F during solar maximum

2005 ◽  
Vol 23 (3) ◽  
pp. 745-751 ◽  
Author(s):  
C.-C. Lee ◽  
J.-Y. Liu ◽  
B. W. Reinisch ◽  
W.-S. Chen ◽  
F.-D. Chu
Keyword(s):  
Solar Maximum ◽  
Magnetic Activity ◽  
The West ◽  
West Side ◽  
Gps Receivers ◽  
Equatorial Spread F ◽  
Equatorial Ionization Anomaly ◽  
Spread F ◽  
A Chain ◽  
June July

Abstract. We use a digisonde at Jicamarca and a chain of GPS receivers on the west side of South America to investigate the effects of the pre-reversal enhancement (PRE) in ExB drift, the asymmetry (Ia) of equatorial ionization anomaly (EIA), and the magnetic activity (Kp) on the generation of equatorial spread F (ESF). Results show that the ESF appears frequently in summer (November, December, January, and February) and equinoctial (March, April, September, and October) months, but rarely in winter (May, June, July, and August) months. The seasonal variation in the ESF is associated with those in the PRE ExB drift and Ia. The larger ExB drift (>20m/s) and smaller |Ia| (<0.3) in summer and equinoctial months provide a preferable condition to development the ESF. Conversely, the smaller ExB drift and larger |Ia| are responsible for the lower ESF occurrence in winter months. Regarding the effects of magnetic activity, the ESF occurrence decreases with increasing Kp in the equinoctial and winter months, but not in the summer months. Furthermore, the larger and smaller ExB drifts are presented under the quiet (Kp<3) and disturbed (Kp≥3) conditions, respectively. These results indicate that the suppression in ESF and the decrease in ExB drifts are mainly caused by the decrease in the eastward electric field.

scholarly journals Statistical analysis of low-latitude spread F observed over Puer, China, during 2015–2016

2019 ◽  
Vol 71 (1) ◽  
Author(s):  
Ting Lan ◽  
Chunhua Jiang ◽  
Guobin Yang ◽  
Yuannong Zhang ◽  
Jing Liu ◽  
...  
Keyword(s):  
Statistical Analysis ◽  
Magnetic Activity ◽  
Ionospheric Disturbances ◽  
Low Latitude ◽  
Equatorial Ionization Anomaly ◽  
Spread F ◽  
Latitude Region ◽  
Range Spread ◽  
Activity Dependence ◽  
Maximum Occurrence

AbstractStatistical analysis of spread F (SF), recorded at Puer (PUR, 22.7° N, 101.05° E, Dip Latitude 12.9° N) during 2015–2016, was carried out to reveal its characteristics at the northern equatorial ionization anomaly. In our study, SF was categorized into four types, frequency spread F (FSF), range spread F (RSF), mix spread F (MSF) and strong range spread F (SSF). The statistical results presented that FSF and MSF were dominant over Puer. Most types of SF appeared mostly in summer months, except the maximum occurrence of SSF in equinox months. Moreover, observations of SF events also showed that the solar activity and magnetic activity dependence of SF varied with seasons. Compared with observations at other region, the present results suggest that medium-scale traveling ionospheric disturbances (MSTIDs) may play a key role in generation of SF in low-latitude region.

scholarly journals Effect of equatorial ionization anomaly on the occurrence of spread-F

1997 ◽  
Vol 15 (2) ◽  
pp. 255-262 ◽  
Author(s):  
P. T. Jayachandran ◽  
P. Sri Ram ◽  
V. V. Somayajulu ◽  
P. V. S. Rama Rao
Keyword(s):  
Electric Field ◽  
Geomagnetic Field ◽  
Critical Frequency ◽  
Equatorial Ionosphere ◽  
Equatorial Ionization Anomaly ◽  
Spread F ◽  
Field Lines ◽  
A Chain ◽  
Indian Sector

Abstract. The unique geometry of the geomagnetic field lines over the equatorial ionosphere coupled with the E-W electric field causes the equatorial ionization anomaly (EIA) and equatorial spread-F (ESF). Ionosonde data obtained at a chain of four stations covering equator to anomaly crest region (0.3 to 33 °N dip) in the Indian sector are used to study the role of EIA and the associated processes on the occurrence of ESF. The study period pertains to the equinoctial months (March, April, September and October) of 1991. The ratios of critical frequency of F-layer (ƒ0F2) and electron densities at an altitude of 270 km between Ahmedabad (33 °N dip) and Waltair (20 °N dip) are found to shoot up in the afternoon hours on spread-F days showing strengthening of the EIA in the afternoon hours. The study confirms the earlier conclusions made by Raghava Rao et al. and Alex et al. that a well-developed EIA is one of the conditions conducive for the generation of ESF. This study also shows that the location of the crest is also important in addition to the strength of the anomaly.

scholarly journals La datation du choeur de l’église de Vaucelles reproduit en plan par Villard de Honnecourt

2018 ◽  
Vol 81 (3) ◽  
pp. 411-417
Author(s):  
Laurence Terrier Aliferis
Keyword(s):  
Nineteenth Century ◽  
Historical Sources ◽  
The West ◽  
West Side ◽  
Villard De Honnecourt ◽  
The Church

Abstract The ruined Cistercian church of Vaucelles is known only by a few preserved fragments and a plan of the choir reproduced by Villard of Honnecourt. Historical sources provide three key dates: 1190 (start of construction), 1215 (entry into the new church), 1235 (date of the dedication). From the nineteenth century until now, it was considered that the foundations were laid in 1190 and that the construction started on the west side of the church. In 1216, the nave would have been completed, and the choir would have been built between 1216 and 1235. Consultation of the historical sources and examination of the historiographic record changes this established chronology of the site. In fact, the construction proceeded from east to west. The choir reproduced in 1216 or shortly before by Villard de Honnecourt presents the building as it then appeared, with the eastern part of the building totally completed.

Equatorial Spread-F and Magnetic Activity

Nature ◽  
1958 ◽  
Vol 181 (4625) ◽  
pp. 1724-1725 ◽  
Author(s):  
A. J. LYON ◽  
N. J. SKINNER ◽  
R. W. WRIGHT
Keyword(s):  
Magnetic Activity ◽  
Equatorial Spread F ◽  
Spread F
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