LOFAR tied-array imaging of Type III solar radio bursts
Abstract
The Sun is an active source of radio emission which is often associated with energetic phenomena such as solar flares and coronal mass ejections (CMEs). At low radio frequencies (<100 MHz), the Sun has not been imaged extensively because of the instrumental limitations of previous radio telescopes. Here, the combined high spatial, spectral and temporal resolution of the Low Frequency Array (LOFAR) was used to study solar Type III radio bursts at 30-90 MHz and their association with CMEs. The Sun was imaged with 126 simultaneous tied-array beams within 5 solar radii of the solar centre. This method offers benefits over standard interferometric imaging since each beam produces high temporal (83 ms) and spectral resolution (12.5 kHz) dynamic spectra at an array of spatial locations centred on the Sun. LOFAR's standard interferometric output is currently limited to one image per second. Over a period of 30 minutes, multiple Type III radio bursts were observed, a number of which were found to be located at high altitudes (4 solar radii from the solar center at 30 MHz) and to have non-radial trajectories. These bursts occurred at altitudes in excess of values predicted by 1D radial electron density models. The non-radial high altitude Type III bursts were found to be associated with the expanding flank of a CME. The CME may have compressed neighbouring streamer plasma producing larger electron densities at high altitudes, while the non-radial burst trajectories can be explained by the deflection of radial magnetic fields as the CME expanded in the low corona.
Keywords
Cite
@article{arxiv.1407.4385,
title = {LOFAR tied-array imaging of Type III solar radio bursts},
author = {D. E. Morosan and P. T. Gallagher and P. Zucca and R. Fallows and E. P. Carley and G. Mann and M. M. Bisi and A. Kerdraon and A. A. Konovalenko and A. L. MacKinnon and H. O. Rucker and B. Thidé and J. Magdalenić and C. Vocks and H. Reid and J. Anderson and A. Asgekar and I. M. Avruch and M. J. Bentum and G. Bernardi and P. Best and A. Bonafede and J. Bregman and F. Breitling and J. Broderick and M. Brüggen and H. R. Butcher and B. Ciardi and J. E. Conway and F. de Gasperin and E. de Geus and A. Deller and S. Duscha and J. Eislöffel and D. Engels and H. Falcke and C. Ferrari and W. Frieswijk and M. A. Garrett and J. Grießmeier and A. W. Gunst and T. E. Hassall and J. W. T. Hessels and M. Hoeft and J. Hörandel and A. Horneffer and M. Iacobelli and E. Juette and A. Karastergiou and V. I. Kondratiev and M. Kramer and M. Kuniyoshi and G. Kuper and P. Maat and S. Markoff and J. P. McKean and D. D. Mulcahy and H. Munk and A. Nelles and M. J. Norden and E. Orru and H. Paas and M. Pandey-Pommier and V. N. Pandey and G. Pietka and R. Pizzo and A. G. Polatidis and W. Reich and H. Röttgering and A. M. M. Scaife and D. Schwarz and M. Serylak and O. Smirnov and B. W. Stappers and A. Stewart and M. Tagger and Y. Tang and C. Tasse and S. Thoudam and C. Toribio and R. Vermeulen and R. J. van Weeren and O. Wucknitz and S. Yatawatta and P. Zarka},
journal= {arXiv preprint arXiv:1407.4385},
year = {2014}
}
Comments
9 pages, 6 figures