Mevius, M;
van der Tol, S;
Pandey, VN;
Vedantham, HK;
Brentjens, MA;
de Bruyn, AG;
Abdalla, FB;
... Zaroubi, S; + view all
(2016)
Probing ionospheric structures using the LOFAR radio telescope.
RADIO SCIENCE
, 51
(7)
pp. 927-941.
10.1002/2016RS006028.
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Abstract
LOFAR is the LOw-Frequency Radio interferometer ARray located at midlatitude (52°53′N). Here we present results on ionospheric structures derived from 29 LOFAR nighttime observations during the winters of 2012/2013 and 2013/2014. We show that LOFAR is able to determine differential ionospheric total electron content values with an accuracy better than 0.001 total electron content unit = 1016m−2 over distances ranging between 1 and 100 km. For all observations the power law behavior of the phase structure function is confirmed over a long range of baseline lengths, between 1 and 80 km, with a slope that is, in general, larger than the 5/3 expected for pure Kolmogorov turbulence. The measured average slope is 1.89 with a one standard deviation spread of 0.1. The diffractive scale, i.e., the length scale where the phase variance is 1rad2, is shown to be an easily obtained single number that represents the ionospheric quality of a radio interferometric observation. A small diffractive scale is equivalent to high phase variability over the field of view as well as a short time coherence of the signal, which limits calibration and imaging quality. For the studied observations the diffractive scales at 150 MHz vary between 3.5 and 30 km. A diffractive scale above 5 km, pertinent to about 90% of the observations, is considered sufficient for the high dynamic range imaging needed for the LOFAR epoch of reionization project. For most nights the ionospheric irregularities were anisotropic, with the structures being aligned with the Earth magnetic field in about 60% of the observations.
| Type: | Article |
|---|---|
| Title: | Probing ionospheric structures using the LOFAR radio telescope |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.1002/2016RS006028 |
| Publisher version: | http://dx.doi.org/10.1002/2016RS006028 |
| Additional information: | © 1999 - 2017 John Wiley & Sons, Inc. |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Physics and Astronomy |
| URI: | https://discovery-pp.ucl.ac.uk/id/eprint/1540223 |
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