scholarly journals Relation of anomalous F region radar echoes in the high-latitude ionosphere to auroral precipitation

2017 ◽  
Vol 35 (3) ◽  
pp. 475-479
Author(s):  
Hanna Dahlgren ◽  
Nicola M. Schlatter ◽  
Nickolay Ivchenko ◽  
Lorenz Roth ◽  
Alexander Karlsson
Keyword(s):  
High Latitude ◽  
Spatial Scales ◽  
Doppler Frequency ◽  
High Energy ◽  
Occurrence Rate ◽  
Characteristic Energy ◽  
Observation Volume ◽  
Radar Echoes ◽  
High Latitude Ionosphere ◽  
E Region

Abstract. Non-thermal echoes in incoherent scatter radar observations are occasionally seen in the high-latitude ionosphere. Such anomalous echoes are a manifestation of plasma instabilities on spatial scales matching the radar wavelength. Here we investigate the occurrence of a class of spatially localized anomalous echoes with an enhanced zero Doppler frequency feature and their relation to auroral particle precipitation. The ionization profile of the E region is used to parametrize the precipitation, with nmE and hmE being the E region peak electron density and the altitude of the peak, respectively. We find the occurrence rate of the echoes to generally increase with nmE and decrease with hmE, thereby indicating a correlation between the echoes and high-energy flux precipitation of particles with a high characteristic energy. The highest occurrence rate of > 20 % is found for hmE  =  109 km and nmE  =  1011. 9 m−3, averaged over the radar observation volume.

scholarly journals ULF wave occurrence statistics in a high-latitude HF Doppler sounder

1999 ◽  
Vol 17 (6) ◽  
pp. 749-758 ◽  
Author(s):  
D. M. Wright ◽  
T. K. Yeoman ◽  
T. B. Jones
Keyword(s):  
Solar Cycle ◽  
Geomagnetic Activity ◽  
High Latitude ◽  
Statistical Study ◽  
Low Frequency ◽  
Occurrence Rate ◽  
Mhd Waves ◽  
Ulf Wave ◽  
High Latitude Ionosphere ◽  
Mhd Waves And Instabilities

Abstract. Ultra low frequency (ULF) wave activity in the high-latitude ionosphere has been observed by a high frequency (HF) Doppler sounder located at Tromsø, Norway (69.7°N, 19.2°E geographic coordinates). A statistical study of the occurrence of these waves has been undertaken from data collected between 1979 and 1984. The diurnal, seasonal, solar cycle and geomagnetic activity variations in occurrence have been investigated. The findings demonstrate that the ability of the sounder to detect ULF wave signatures maximises at the equinoxes and that there is a peak in occurrence in the morning sector. The occurrence rate is fairly insensitive to changes associated with the solar cycle but increases with the level of geomagnetic activity. As a result, it has been possible to characterise the way in which prevailing ionospheric and magnetospheric conditions affect such observations of ULF waves.Key words. Ionosphere (auroral ionosphere; ionosphere -magnetosphere interactions) · Magnetospheric physics (MHD waves and instabilities)

The structure of the mid- and high-latitude ionosphere during the November 2004 storm event obtained from GPS observations

2007 ◽  
Vol 55 (4) ◽  
pp. 490-508 ◽  
Author(s):  
Andrzej Krankowski ◽  
Irk I. Shagimuratov ◽  
Lubomir W. Baran ◽  
Galina Yakimova
Keyword(s):  
High Latitude ◽  
Storm Event ◽  
High Latitude Ionosphere ◽  
Gps Observations

scholarly journals A Statistical study of the Doppler spectral width of high-latitude ionospheric F-region echoes recorded with SuperDARN coherent HF radars

2002 ◽  
Vol 20 (11) ◽  
pp. 1769-1781 ◽  
Author(s):  
J.-P. Villain ◽  
R. André ◽  
M. Pinnock ◽  
R. A. Greenwald ◽  
C. Hanuise
Keyword(s):  
High Latitude ◽  
Statistical Study ◽  
Spectral Width ◽  
Auroral Oval ◽  
F Region ◽  
Radar Network ◽  
Period 2 ◽  
Time Period ◽  
High Latitude Ionosphere ◽  
Data Points

Abstract. The HF radars of the Super Dual Auroral Radar Network (SuperDARN) provide measurements of the E × B drift of ionospheric plasma over extended regions of the high-latitude ionosphere. We have conducted a statistical study of the associated Doppler spectral width of ionospheric F-region echoes. The study has been conducted with all available radars from the Northern Hemisphere for 2 specific periods of time. Period 1 corresponds to the winter months of 1994, while period 2 covers October 1996 to March 1997. The distributions of data points and average spectral width are presented as a function of Magnetic Latitude and Magnetic Local Time. The databases are very consistent and exhibit the same features. The most stringent features are: a region of very high spectral width, collocated with the ionospheric LLBL/cusp/mantle region; an oval shaped region of high spectral width, whose equator-ward boundary matches the poleward limit of the Holzworth and Meng auroral oval. A simulation has been conducted to evaluate the geometrical and instrumental effects on the spectral width. It shows that these effects cannot account for the observed spectral features. It is then concluded that these specific spectral width characteristics are the signature of ionospheric/magnetospheric coupling phenomena.Key words. Ionosphere (auroral ionosphere; ionosphere-magnetosphere interactions; ionospheric irregularities)

scholarly journals IMPACT OF UNCERTAINTIES IN MODEL FREE PARAMETERS AND SEA LEVEL RISE ON SHORELINE CHANGES: A 20-YEAR HINDCAST AT TRUC VERT BEACH, SW FRANCE

2020 ◽  
pp. 10
Author(s):  
Maurizio D'Anna ◽  
Deborah Idier ◽  
Bruno Castelle ◽  
Goneri Le Cozannet ◽  
Jeremy Rohmer ◽  
...  
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Spatial Scales ◽  
High Energy ◽  
Potential Threat ◽  
Shoreline Evolution ◽  
Complex Processes ◽  
Model Free ◽  
Long Time ◽  
Sw France

Chronic erosion of sandy coasts is a continuous potential threat for the growing coastal communities worldwide. The prediction of shoreline evolution is therefore key issue for robust decision making worldwide, especially in the context of climate change. Shorelines respond to various complex processes interacting at several temporal and spatial scales, making shoreline reconstructions and predictions challenging and uncertain, especially on long time scales (e.g. decades or century). Despite the increasing progresses in addressing uncertainties related to the physics of Sea Level Rise, very little effort is made towards understanding and reducing the uncertainties related to wave driven coastal response. To fill this gap, we analyse the uncertainties associated with long-term (2 decades) modelling of the cross-shore transport dominated high-energy sandy coast around Truc Vert beach, SW France, which has been surveyed semi-monthly over the last 12 years.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/_NBJ2v-koMs

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