A LOFAR Observation of Ionospheric Scintillation from Two Simultaneous Travelling Ionospheric Disturbances

Research output: Contribution to journalArticle

Authors

  • RA Fallows
  • B Forte
  • I Astin
  • A Arnold
  • Alan Wood
  • M Mevius
  • H Rothkaehl
  • B Matyjasiak
  • A Krankowski
  • J. M. Anderson
  • A Asgekar
  • I. V. Avruch
  • M. J. Bentum
  • M. M. Bisi

Colleges, School and Institutes

External organisations

  • Netherlands Inst Radio Astron ASTRON
  • University of Bath
  • Nottingham Trent University, Nottingham
  • Polish Academy of Sciences
  • University of Warmia and Mazury
  • Technical University of Berlin
  • Shell Technology Centre, Bangalore, India
  • Science and Technology B.V., Delft, the Netherlands
  • RUTHERFORD APPLETON LAB

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 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 10-80MHz.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 20-40m/s with a northwest 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.

Bibliographic note

+42 additional co-authors

Details

Original languageEnglish
JournalJournal of Space Weather and Space Climate
Publication statusAccepted/In press - 13 Feb 2020

Keywords

  • LOFAR, Ionosphere, Scintillation