Impulsive event probability in the radiocarbon record in VIII - XI centuries

[摘要] The abundance of cosmogenic isotopes in natural samples is the main source of information about past variations of cosmic ray intensity, in the solar activity and in the strength of the geomagnetic field. Sharp increases could originate from powerful impulsive events such as solar flares, gamma-rays from supernova explosions and gamma-ray bursts. A significant increase in the radiocarbon record has been detected recently in tree rings around AD 775 [1]. Both large solar proton event (SPE) [2] and gamma-ray burst (GRB) in our Galaxy [3] are favored as a source. However, either of the explanations faces difficulties of low event rate because of detection of a similar peak around AD993 [4], [5]. What is more, we know other similar result [6]. We carried out a statistical analysis of these three data sets. It is shown that AD 775 event differs fundamentally from AD 993 and AD 1006 events, because the last two can be explained without the assumption of the impulsive event.

[发布机构] St. Petersburg State Polytechnical University, 29 Polytekhnicheskaya St., St. Petersburg, Russia^1

[效力级别] 天文学 [学科分类] 天文学(综合)

[关键词] Cosmic ray intensity;Cosmogenic isotopes;Gamma ray bursts;Geomagnetic fields;Impulsive Events;Solar activity;Solar proton events;Supernova explosion