A LOFAR Observation of Ionospheric Scintillation from Two Simultaneous Travelling Ionospheric Disturbances
Abstract
This paper presents the results from one of the first observations of ionospheric scintillation taken using the Low-Frequency Array (LOFAR). The observation was of the strong natural radio source Cas A, taken overnight on 18-19 August 2013, and exhibited moderately strong scattering effects in dynamic spectra of intensity received across an observing bandwidth of 10-80MHz. Delay-Doppler spectra (the 2-D FFT of the dynamic spectrum) from the first hour of observation showed two discrete parabolic arcs, one with a steep curvature and the other shallow, which can be used to provide estimates of the distance to, and velocity of, the scattering plasma. A cross-correlation analysis of data received by the dense array of stations in the LOFAR "core" reveals two different velocities in the scintillation pattern: a primary velocity of ~30m/s with a north-west to south-east direction, associated with the steep parabolic arc and a scattering altitude in the F-region or higher, and a secondary velocity of ~110m/s with a north-east to south-west direction, associated with the shallow arc and a scattering altitude in the D-region. Geomagnetic activity was low in the mid-latitudes at the time, but a weak sub-storm at high latitudes reached its peak at the start of the observation. An analysis of Global Navigation Satellite Systems (GNSS) and ionosonde data from the time reveals a larger-scale travelling ionospheric disturbance (TID), possibly the result of the high-latitude activity, travelling in the north-west to south-east direction, and, simultaneously, a smaller--scale TID travelling in a north-east to south-west direction, which could be associated with atmospheric gravity wave activity. The LOFAR observation shows scattering from both TIDs, at different altitudes and propagating in different directions. To the best of our knowledge this is the first time that such a phenomenon has been reported.
Keywords
Cite
@article{arxiv.2003.04013,
title = {A LOFAR Observation of Ionospheric Scintillation from Two Simultaneous Travelling Ionospheric Disturbances},
author = {Richard A. Fallows and Biagio Forte and Ivan Astin and Tom Allbrook and Alex Arnold and Alan Wood and Gareth Dorrian and Maaijke Mevius and Hanna Rothkaehl and Barbara Matyjasiak and Andrzej Krankowski and James M. Anderson and Ashish Asgekar and I. Max Avruch and Mark Bentum and Mario M. Bisi and Harvey R. Butcher and Benedetta Ciardi and Bartosz Dabrowski and Sieds Damstra and Francesco de Gasperin and Sven Duscha and Jochen Eislöffel and Thomas M. O. Franzen and Michael A. Garrett and Jean-Matthias Grie\b{eta}meier and André W. Gunst and Matthias Hoeft and Jörg R. Hörandel and Marco Iacobelli and Huib T. Intema and Leon V. E. Koopmans and Peter Maat and Gottfried Mann and Anna Nelles and Harm Paas and Vishambhar N. Pandey and Wolfgang Reich and Antonia Rowlinson and Mark Ruiter and Dominik J. Schwarz and Maciej Serylak and Aleksander Shulevski and Oleg M. Smirnov and Marian Soida and Matthias Steinmetz and Satyendra Thoudam and M. Carmen Toribio and Arnold van Ardenne and Ilse M. van Bemmel and Matthijs H. D. van der Wiel and Michiel P. van Haarlem and René C. Vermeulen and Christian Vocks and Ralph A. M. J. Wijers and Olaf Wucknitz and Philippe Zarka and Pietro Zucca},
journal= {arXiv preprint arXiv:2003.04013},
year = {2020}
}
Comments
24 pages, 16 figures. Accepted for open-access publication in the Journal of Space Weather and Space Climate. For associated movie file, see https://www.swsc-journal.org/10.1051/swsc/2020010/olm