Primary authors : Dr. PAVLOV, Anatoly (Ioffe Institute) Analysis of Superflare “Isotopic Imprints” in Lunar and Terrestrial Samples Primary authors : Dr. PAVLOV, Anatoly (Ioffe Institute) Co-authors : Mr. FROLOV, Dminry (Peter the Great Saint-Petersburg Polytechnic University) ; Prof. OSTRYAKOV, Valery (Peter the Great Saint-Petersburg Polytechnic University) ; Dr. VASILYEV, Gennady (Ioffe Institute) ; Dr. STRUMINSKY, Alexei (Space Research Institute) Presenter : Dr. STRUMINSKY, Alexei (Space Research Institute) 8 September 2016 Torino, ECRS 2016

Mekhaldi et al, 2015 The origin of two large peaks in the atmospheric radiocarbon (14C) concentration at AD 774/5 and 993/4 is still debated. There is consensus that these features can only be explained by an increase in the atmospheric 14C production rate due to an extraterrestrial event. The authors provided evidence that these peaks were most likely produced by extreme solar events, based on several new annually resolved 10Be measurements from both Arctic and Antarctic ice cores. Using ice core 36Cl data in pair with 10Be, they showed that these solar events were characterized by a very hard energy spectrum with high fluxes of solar protons with energy above 100MeV. Experimental results 14C 10Be 36CL Enhancement relative background 4 3.4 6.3

Model for the Earth atmosphere (Pavlov, Ostryakov, Vasiliev, Frolov) In this work 10Be 36Cl Model for the Earth atmosphere (Pavlov, Ostryakov, Vasiliev, Frolov) OUTPUT INPUT 14C Spectra of GCR, solar protons COMPARE 775 AD

METHOD Terrestrial samples We used the standard GEANT4.10.0 code for simulations of atmospheric interactions of high-energy charged particles and gamma-rays. Production rates for 14С, 10Ве and 36Cl were calculated for 0-130 km altitudes with 1 km step with the isotropic particle flux penetrating the Earth's atmosphere. The yield function of a nuclide is defined as its integrated production in all channels induced by the primary interacting particle of a given energy.

775 AD, model calculations 14C 10Be 36Cl F(1956)*75.6 = F(775) 2 1.35 Enhancement relative observations 14C 10Be 36Cl F(1956)*75.6 = F(775) 2 1.35 F(1972)*283= F(775 ) 1.5 9 F(2005)*620= F(775) 2.2

Ultimate spectra of solar protons Strumimsky, 2015 Propagation limits for different values of the IMF strength. (Freier&Webber, 1963). Spectra of non – relativistic (γ=2.5) and relativistic (γ=4) solar protons (Syrovatsky, 1961) . Red - - normalised to j (E=10 MeV, B=100γ) Green -- normalized to GCR intensity at 20 GeV Brown -- normalized to GCR intensity at 100 GeV. Blue line - the spectrum of GCR. 100 nTl soft mean hard J(>30 МэВ) F(>30 МэВ) 934 4.2∙109 4.9∙105 1.8∙1011 J(>200 МэВ) F(>200 МэВ) 244 9.2 ∙107 13981 5.3∙109 1.7∙105 6.4∙1010

775AD, ultimate spectra 14C 10Be 36Cl Soft*149 1.8 7 medium *1.2 2 2.4 Enhancement relative observations 14C 10Be 36Cl Soft*149 1.8 7 medium *1.2 2 2.4 hard* 0.074 1

Lunar samples AJT Jull, S Cloudt, DJ Donahue, JM Sisterson, RC Reedy, and J Masarik. 14 C depth profiles in Apollo 15 and 17 cores and lunar rock 68815. Geochimica et Cosmochimica Acta, 2(17):3025–3036, 1998. K Nishiizumi, JR Arnold, CP Kohl, MW Caffee, J Masarik, and RC Reedy. Solar cosmic ray records in lunar rock 64455. Geochimica et Cosmochimica Acta, 73 (7):2163–2176, 2009

Model for lunar samples (Pavlov, Ostryakov, Vasiliev, Frolov) In this work 14C 26Al Model for lunar samples (Pavlov, Ostryakov, Vasiliev, Frolov) OUTPUT INPUT Spectra of GCR, solar protons Number of possible events

METHOD Lunar Equilibrium densities of long living isotopes 14С, 26Al, (origin by CR interaction = decay) for different models (BIC and BERT) of internal nuclear cascade within GEANT 14С and 36Cl are better described by BIC, but 26Al and 10Be by BERT There is an excess of radionuclei density within first cm’s of lunar kerns in comparison with their production by GCR, it’s of solar origin (SCR) An estimate of event frequency for events similar to the 775AD event. An impact is less than excess. 14С – scale 10-20 thousands years, 26Al – scale 1-2 billion years

Lunar samples, 775AD Like 1956 Like 1972 14С – less than one event per 3000 years on a scale of <20000 years, 26Al - the same but on a scale of 1-2 million years. 14С - less than one event per 10000 years on a scale of <20000 years, 26Al – less than one event per 60000 years on a scale of 1-2 million years. Like 1956 Like 1972 14 C (BIC) at/cm^3 at 1 g/cm*2 26 Al (BERT) at/cm^3 at 1 g/cm*2 observations 8Е7 10Е10 1956 1.4Е5 1.3Е5 1972 8.7Е5 9,5Е5

Lunar samples Ultimate spectra 775AD 14C (BIC) at/cm^3 at 1 g/cm*2 26Al(BERT) at/cm^3 at 1 g/cm*2 observations 1.17Е8 1.8Е10 Model, soft spectrum 7,1Е4 7Е5 Model, medium spectrum 5,9Е6 2.9 Е7 Model, hard spectrum 1.8Е7 4.9Е7 14С - less than one event per 3000 years on a scale of <20000 years, 26Al the same but on a scale of 1-2 million years. 14С - less than one event per 1800 years on a scale of <20000 years, 26Al – less than one event per 10000 years on a scale of 1-2 million years. 14С – less than one event per 330 years on a scale of <20000 years, 26Al - less than one event per 1000 years on a scale 1-2 million years. soft Medium hard

Conclusions The ultimate spectra (Struminsky, 2015) do not contradict to radionuclide production in the Earth atmosphere and Lunar rocks. Modeling of global radionuclide production in the Earth atmosphere during the 775AD event with different spectra of solar protons showed an excess by several times of 10 Be and 36Cl isotopes in comparison with observation for production of 14С equal to observations. An agreement of measured and calculated values is possible under an assumption that majority of 10 Be and 36Cl have been produced in the polar troposphere. Additional investigations are necessary. A comparison of calculated and measured densities of radionuclide in the upper layer of lunar soil gives a frequency of superflares on a scale of 20000 years is 1 event per 330 years for “hard” events and per 10000 years for “soft”. On a scale of 1-2 million years – one “hard” event per 1000 years for events and one ‘soft” event 60000 years.