The Sun is an active star that can launch large eruptions of magnetized plasma into the heliosphere, known as coronal mass ejections (CMEs). These can drive shocks that accelerate particles to high energies, often resulting in radio emission at low frequencies (<200 MHz). So far, the relationship between the expansion of CMEs, shocks and particle acceleration is not well understood, partly due to the lack of radio imaging at low frequencies during the onset of shock-producing CMEs. Here, we report multi-instrument radio, white-light and ultraviolet imaging of the second largest flare in solar cycle 24 (2008–present) and its associated fast CME (3,038 ± 288 km s−1). We identify the location of a multitude of radio shock signatures, called herringbones, and find evidence for shock-accelerated electron beams at multiple locations along the expanding CME. These observations support theories of non-uniform, rippled shock fronts driven by an expanding CME in the solar corona.
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The LOFAR dataset used was obtained under the project code DDT8_005 and it is available in the LOFAR Long Term Archive (LTA; https://lta.lofar.eu). The I-LOFAR data can be obtained from http://data.lofar.ie or on request to firstname.lastname@example.org. The AIA and LASCO datasets are both available from the Virtual Solar Observatory project (http://vso.nso.edu). The SUVI data were made available by NOAA’s National Centers for Environmental Information SUVI team as a community service to the solar physics community studying the September 2017 flaring events (https://doi.org/10.7289/V5FT8J93). These datatsets are also available from the authors upon request.
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This paper is based (in part) on data obtained with the International LOFAR Telescope (ILT) under project code DDT8_005. LOFAR30 is the Low Frequency Array designed and constructed by ASTRON. It has observing, data processing, and data storage facilities in several countries, which are owned by various parties (each with their own funding sources), and are collectively operated by the ILT foundation under a joint scientific policy. The ILT resources have benefited from the following recent major funding sources: CNRS-INSU, Observatoire de Paris and Université d’Orléans, France; BMBF, MIWF-NRW, MPG, Germany; Science Foundation Ireland (SFI), Department of Business, Enterprise and Innovation (DBEI), Ireland; NWO, The Netherlands; and The Science and Technology Facilities Council, UK. I-LOFAR received funding from Science Foundation Ireland (SFI) grant no. 15/RI/3204. D.E.M. received external funding from the MET Office, Exeter, UK at Trinity College Dublin. E.P.C. is supported by the H2020 INFRADEV-1-2017 LOFAR4SW project no. 777442. L.A.H. is supported by Enterprise Partnership Scheme studentship from the Irish Research Council (IRC) between Trinity College Dublin and Adnet System Inc. S.A.M. is supported by the Irish Research Council Postdoctoral Fellowship Programme and the Air Force Office of Scientific Research award number FA9550-17-1-039. E.K.J.K. and D.E.M. acknowledge The Finnish Centre of Excellence in Research of Sustainable Space, funded through the Academy of Finland grant no. 1312390 and Academy of Finland Project 1310445. This project has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant no. 4100103, SolMAG). The authors would like to acknowledge NOAA’s National Centers for Environmental Information SUVI team for providing data on the September 2017 flares and M. Grandin for his advice in correcting for ionospheric effects.
The authors declare no competing interests.
Journal peer review information: Nature Astronomy thanks Iver Cairns, Silja Pohjolainen, Zhongwei Yang and the other anonymous reviewer(s) for their contribution to the peer review of this work.
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Morosan, D.E., Carley, E.P., Hayes, L.A. et al. Multiple regions of shock-accelerated particles during a solar coronal mass ejection. Nat Astron 3, 452–461 (2019). https://doi.org/10.1038/s41550-019-0689-z
Nature Astronomy (2020)
Solar Physics (2020)
Solar Physics (2020)