TY - JOUR
T1 - A LOFAR observation of ionospheric scintillation from two simultaneous travelling ionospheric disturbances
AU - Fallows, Richard A.
AU - Forte, Biagio
AU - Astin, Ivan
AU - Allbrook, Tom
AU - Arnold, Alex
AU - Wood, Alan
AU - Dorrian, Gareth
AU - Mevius, Maaijke
AU - Rothkaehl, Hanna
AU - Matyjasiak, Barbara
AU - Krankowski, Andrzej
AU - Anderson, James M.
AU - Asgekar, Ashish
AU - Avruch, I. Max
AU - Bentum, Mark
AU - Bisi, Mario M.
AU - Butcher, Harvey R.
AU - Ciardi, Benedetta
AU - Dabrowski, Bartosz
AU - Damstra, Sieds
AU - De Gasperin, Francesco
AU - Duscha, Sven
AU - Eislöffel, Jochen
AU - Franzen, Thomas M.O.
AU - Garrett, Michael A.
AU - Grießmeier, Jean Matthias
AU - Gunst, André W.
AU - Hoeft, Matthias
AU - Hörandel, Jörg R.
AU - Iacobelli, Marco
AU - Intema, Huib T.
AU - Koopmans, Leon V.E.
AU - Maat, Peter
AU - Mann, Gottfried
AU - Nelles, Anna
AU - Paas, Harm
AU - Pandey, Vishambhar N.
AU - Reich, Wolfgang
AU - Rowlinson, Antonia
AU - Ruiter, Mark
AU - Schwarz, Dominik J.
AU - Serylak, MacIej
AU - Shulevski, Aleksander
AU - Smirnov, Oleg M.
AU - Soida, Marian
AU - Steinmetz, Matthias
AU - Thoudam, Satyendra
AU - Toribio, M. Carmen
AU - Van Ardenne, Arnold
AU - Van Bemmel, Ilse M.
AU - Van Der Wiel, Matthijs H.D.
AU - Van Haarlem, Michiel P.
AU - Vermeulen, René C.
AU - Vocks, Christian
AU - Wijers, Ralph A.M.J.
AU - Wucknitz, Olaf
AU - Zarka, Philippe
AU - Zucca, Pietro
N1 - Publisher Copyright:
© R.A Fallows et al., Published by EDP Sciences 2020.
PY - 2020
Y1 - 2020
N2 - 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 Cassiopeia 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 10-80 MHz. 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 ~20-40 ms-1 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 ~110 ms-1 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.
AB - 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 Cassiopeia 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 10-80 MHz. 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 ~20-40 ms-1 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 ~110 ms-1 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.
KW - Instability mechanisms
KW - Ionospheric scintillation
KW - Travelling ionospheric disturbances
UR - http://www.scopus.com/inward/record.url?scp=85088261197&partnerID=8YFLogxK
U2 - 10.1051/swsc/2020010
DO - 10.1051/swsc/2020010
M3 - Article
SN - 2115-7251
VL - 10
JO - Journal of Space Weather and Space Climate
JF - Journal of Space Weather and Space Climate
M1 - 10
ER -