Yardley, Stephanie L;
Green, Lucie M;
James, Alexander W;
Stansby, David;
Mihailescu, Teodora;
(2022)
The Magnetic Field Environment of Active Region 12673 That Produced the Energetic Particle Events of September 2017.
The Astrophysical Journal
, 937
(2)
, Article 57. 10.3847/1538-4357/ac8d69.
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Abstract
Forecasting solar energetic particles (SEPs), and identifying flares/coronal mass ejections (CMEs) from active regions (ARs) that will produce SEP events in advance is extremely challenging. We investigate the magnetic field environment of AR 12673, including the AR's magnetic configuration, the surrounding field configuration in the vicinity of the AR, the decay index profile, and the footpoints of the Earth-connected magnetic field, around the time of four eruptive events. Two of the eruptive events are SEP productive (2017 September 4 at 20:00 UT and September 6 at 11:56 UT), while two are not (September 4 at 18:05 UT and September 7 at 14:33 UT). We analyzed a range of EUV and white-light coronagraph observations along with potential field extrapolations and find that the CMEs associated with the SEP-productive events either trigger null point reconnection that redirects flare-accelerated particles from the flare site to the Earth-connected field and/or have a significant expansion (and shock formation) into the open Earth-connected field. The rate of change of the decay index with height indicates that the region could produce a fast CME (v > 1500 km s−1), which it did during events 2 and 3. The AR's magnetic field environment, including locations of open magnetic field and null points along with the magnetic field connectivity and propagation direction of the CMEs play an important role in the escape and arrival of SEPs at Earth. Other SEP-productive ARs should be investigated to determine whether their magnetic field environment and CME propagation direction are significant in the escape and arrival of SEPs at Earth.
| Type: | Article |
|---|---|
| Title: | The Magnetic Field Environment of Active Region 12673 That Produced the Energetic Particle Events of September 2017 |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.3847/1538-4357/ac8d69 |
| Publisher version: | https://doi.org/10.3847/1538-4357/ac8d69 |
| Language: | English |
| Additional information: | Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence (http://creativecommons.org/licenses/by/4.0/). Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. |
| UCL classification: | UCL 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 Space and Climate Physics UCL > Provost and Vice Provost Offices > UCL BEAMS |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10156842 |
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