Articles | Volume 35, issue 3
https://doi.org/10.5194/angeo-35-493-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
the Creative Commons Attribution 3.0 License.
https://doi.org/10.5194/angeo-35-493-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
the Creative Commons Attribution 3.0 License.
Variations in energy, flux, and brightness of pulsating aurora measured at high time resolution
School of Electrical Engineering, Royal Institute of Technology KTH, Stockholm, Sweden
School of Physics and Astronomy, University of Southampton, Southampton, UK
Betty S. Lanchester
School of Physics and Astronomy, University of Southampton, Southampton, UK
Nickolay Ivchenko
School of Electrical Engineering, Royal Institute of Technology KTH, Stockholm, Sweden
Daniel K. Whiter
School of Physics and Astronomy, University of Southampton, Southampton, UK
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Photo-electrons and secondary electrons from particle precipitation enhance the incoherent scatter plasma line to levels sufficient for detection. A plasma line gives an accurate measure of the electron density and can be used to estimate electron temperature. The occurrence of plasma line enhancements in the EISCAT Svalbard Radar data was investigated. During summer daytime hours the plasma line is detectable in up to 90 % of the data. In winter time the occurrence is a few percent.
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Anomalous strong echoes with three frequency peaks are occasionally seen with incoherent scatter radars in the ionosphere near 200 km altitude at high latitudes. We investigate how they relate to electron precipitation, by finding the resulting peak electron density and the height of the peak, respectively. We find that occurrence rate increases with density and decreases with height, indicating a correlation between the echoes and precipitating electrons with high energy and energy flux.
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Photo-electrons and secondary electrons from particle precipitation enhance the incoherent scatter plasma line to levels sufficient for detection. A plasma line gives an accurate measure of the electron density and can be used to estimate electron temperature. The occurrence of plasma line enhancements in the EISCAT Svalbard Radar data was investigated. During summer daytime hours the plasma line is detectable in up to 90 % of the data. In winter time the occurrence is a few percent.
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Joshua M. Chadney, Daniel K. Whiter, and Betty S. Lanchester
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A layer of excited OH molecules in the upper atmosphere produces strong airglow emission from which it is possible to obtain the temperature of the layer. To obtain accurate temperatures values, one must take into account the absorption of OH emission by water vapour in the lower atmosphere before this emission is measured by instruments on the ground. This paper provides the amount of absorption suffered by each OH line due to water vapour and presents a method to estimate water concentrations.
Hanna Dahlgren, Nicola M. Schlatter, Nickolay Ivchenko, Lorenz Roth, and Alexander Karlsson
Ann. Geophys., 35, 475–479, https://doi.org/10.5194/angeo-35-475-2017, https://doi.org/10.5194/angeo-35-475-2017, 2017
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Anomalous strong echoes with three frequency peaks are occasionally seen with incoherent scatter radars in the ionosphere near 200 km altitude at high latitudes. We investigate how they relate to electron precipitation, by finding the resulting peak electron density and the height of the peak, respectively. We find that occurrence rate increases with density and decreases with height, indicating a correlation between the echoes and precipitating electrons with high energy and energy flux.
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In this paper we describe a new method for recognition of digits in seven-segment displays. The method is used for adding date and time information to a dataset consisting of about 7 million auroral all-sky images taken during the time period of 1973–1997 at camera stations centred around Sodankylä observatory in Northern Finland. In each image there is a clock display for the date and time together with the reflection of the whole night sky through a spherical mirror.
N. M. Schlatter, V. Belyey, B. Gustavsson, N. Ivchenko, D. Whiter, H. Dahlgren, S. Tuttle, and T. Grydeland
Ann. Geophys., 33, 837–844, https://doi.org/10.5194/angeo-33-837-2015, https://doi.org/10.5194/angeo-33-837-2015, 2015
Short summary
Short summary
The high-latitude ionosphere is a dynamic region where particle precipitation leads to various phenomena including wave instability and turbulence. Anomalous echoes related to aurora are observed in ground-based radar observations of the ionosphere. These echoes indicate enhanced ion acoustic fluctuations. In this article, we show that the origin of the echo is located in or close to the region of particle precipitation and that the echo region itself is limited to hundreds of meters.
N. M. Schlatter, N. Ivchenko, T. Sergienko, B. Gustavsson, and B. U. E. Brändström
Ann. Geophys., 31, 1681–1687, https://doi.org/10.5194/angeo-31-1681-2013, https://doi.org/10.5194/angeo-31-1681-2013, 2013
N. M. Schlatter, N. Ivchenko, B. Gustavsson, T. Leyser, and M. Rietveld
Ann. Geophys., 31, 1103–1108, https://doi.org/10.5194/angeo-31-1103-2013, https://doi.org/10.5194/angeo-31-1103-2013, 2013
W. Reid, P. Achtert, N. Ivchenko, P. Magnusson, T. Kuremyr, V. Shepenkov, and G. Tibert
Atmos. Meas. Tech., 6, 777–785, https://doi.org/10.5194/amt-6-777-2013, https://doi.org/10.5194/amt-6-777-2013, 2013
D. K. Whiter, B. Gustavsson, N. Partamies, and L. Sangalli
Geosci. Instrum. Method. Data Syst., 2, 131–144, https://doi.org/10.5194/gi-2-131-2013, https://doi.org/10.5194/gi-2-131-2013, 2013
Short summary
Pulsating aurora are ubiquitous events that constitute a large amount of energy transfer to the ionosphere. Still there are unsolved issues regarding their formation. Using high-resolution optical and radar data, we find that it is the flux of high-energy electrons that get reduced during the OFF period of the pulsations. We also report on dips in brightness at the transition between ON and OFF, and asymmetric rise and fall times, which may have implications for understanding the pulsations.
Pulsating aurora are ubiquitous events that constitute a large amount of energy transfer to the...