Two New Sub-GLEs Found in Data of Neutron Monitors at South Pole and Vostok: On 09 June 1968 and 27 February 1969
Poluianov, Stepan; Batalla, Oscar; Mishev, Alexander; Koldobskiy, Sergey; Usoskin, Ilya (2024-01-19)
Springer
19.01.2024
Poluianov, S., Batalla, O., Mishev, A. et al. Two New Sub-GLEs Found in Data of Neutron Monitors at South Pole and Vostok: On 09 June 1968 and 27 February 1969. Sol Phys 299, 6 (2024). https://doi.org/10.1007/s11207-023-02245-z
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https://creativecommons.org/licenses/by/4.0/
© The Author(s) 2024. This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.
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Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:oulu-202402021547
https://urn.fi/URN:NBN:fi:oulu-202402021547
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Abstract
Intense solar energetic particle (SEP) events can be observed by neutron monitors (NMs) as so-called ground-level enhancements (GLEs). High-altitude polar NMs have high sensitivity for SEP due to the reduced atmospheric energy cutoff and very low geomagnetic rigidity cutoff compared to other NMs. There is a special class of sub-GLE events, viz. events that are weaker than standard GLEs and can only be observed by high-altitude polar NMs. So far, only one sub-GLE and three candidates are known, all in the period 2012 – 2015. In this work, we inspected the period from March 1964 to December 1969 in the data of the South Pole and Vostok high-altitude polar NMs on the Antarctic Plateau in search of possible sub-GLEs. We found two previously unknown events from 09 June 1968 and 27 February 1969 that formally match the definition of sub-GLE. They were associated with significant enhancements in the integral SEP intensity J (> 60 MeV) measured by space-borne particle detectors, as well as with strong X-class solar flares from the western part of the solar disk. The identified sub-GLEs were analyzed and the corresponding SEP characteristics were estimated.
Intense solar energetic particle (SEP) events can be observed by neutron monitors (NMs) as so-called ground-level enhancements (GLEs). High-altitude polar NMs have high sensitivity for SEP due to the reduced atmospheric energy cutoff and very low geomagnetic rigidity cutoff compared to other NMs. There is a special class of sub-GLE events, viz. events that are weaker than standard GLEs and can only be observed by high-altitude polar NMs. So far, only one sub-GLE and three candidates are known, all in the period 2012 – 2015. In this work, we inspected the period from March 1964 to December 1969 in the data of the South Pole and Vostok high-altitude polar NMs on the Antarctic Plateau in search of possible sub-GLEs. We found two previously unknown events from 09 June 1968 and 27 February 1969 that formally match the definition of sub-GLE. They were associated with significant enhancements in the integral SEP intensity J (> 60 MeV) measured by space-borne particle detectors, as well as with strong X-class solar flares from the western part of the solar disk. The identified sub-GLEs were analyzed and the corresponding SEP characteristics were estimated.
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