LOFAR tied-array imaging of Type III solar radio bursts

D. E. Morosan, P. T. Gallagher, P. Zucca, R. Fallows, E. P. Carley, G. Mann, M. M. Bisi, A. Kerdraon, A. A. Konovalenko, A. L. MacKinnon, H. O. Rucker, B. Thidé, J. Magdalenić, C. Vocks, H. Reid, J. Anderson, A. Asgekar, I. M. Avruch, M. J. Bentum, G. BernardiP. Best, A. Bonafede, J. Bregman, F. Breitling, J. Broderick, M. Brüggen, H. R. Butcher, B. Ciardi, J. E. Conway, F. de Gasperin, E. de Geus, A. Deller, S. Duscha, J. Eislöffel, D. Engels, H. Falcke, C. Ferrari, W. Frieswijk, M. A. Garrett, J. Grießmeier, A. W. Gunst, T. E. Hassall, J. W. T. Hessels, M. Hoeft, J. Hörandel, A. Horneffer, M. Iacobelli, E. Juette, A. Karastergiou, V. I. Kondratiev, M. Kramer, M. Kuniyoshi, G. Kuper, P. Maat, S. Markoff, J. P. McKean, D. D. Mulcahy, H. Munk, A. Nelles, M. J. Norden, E. Orru, H. Paas, M. Pandey-Pommier, V. N. Pandey, G. Pietka, R. Pizzo, A. G. Polatidis, W. Reich, H. Röttgering, A. M. M. Scaife, D. Schwarz, M. Serylak, O. Smirnov, B. W. Stappers, A. Stewart, M. Tagger, Y. Tang, C. Tasse, S. Thoudam, C. Toribio, R. Vermeulen, R. J. van Weeren, O. Wucknitz, S. Yatawatta, P. Zarka

Research output: Contribution to journalArticlepeer-review

Abstract

Context. 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.

Aims. 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.

Methods. The Sun was imaged with 126 simultaneous tied-array beams within

Results. Over a period of 30 min, multiple Type III radio bursts were observed, a number of which were found to be located at high altitudes (similar to 4 R-circle dot 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.

Conclusions. 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.

Original languageEnglish
Article numberA67
Number of pages8
JournalAstronomy & Astrophysics
Volume568
DOIs
Publication statusPublished - Aug 2014

Keywords

  • Sun: corona
  • Sun: radio radiation
  • Sun: particle emission
  • Sun: coronal mass ejections (CMEs)

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