Numerical simulations of the production of extinct short‐lived nuclides by magnetic flaring in the early solar system

Abstract

Abstract-Using the X-ray flare observations of low-mass protostars, we developed numerical simulations of thermal processing and irradiation of protoCAIs in the magnetic reconnection ring within the X-wind formulation. Observed X-ray flare luminosities have been used to model various simulation flare characteristics. Several approximations have been made regarding the thermal evolution that involve condensation, evaporation, and coagulation of protoCAIs. Ensembles of refractory cores with ferromagnesian mantles were evolved for irradiation production of the shortlived nuclides 7 Be, 10 Be, 41 Ca, 36 Cl, 26 Al, and 53 Mn. Three distinct grain-size distributions of protoCAIs with refractory cores in the ranges of 32 μm-20 mm, 125 μm-16 mm, and 500 μm-13 mm were thermally evolved for irradiation. The latter two size distributions were found to result in the accumulation of protoCAIs in the reconnection ring during an X-wind cycle, and hence can account for the total inventory of 26 Al in the early solar system. The canonical value of ~5 × 10 −5 for 26 Al/ 27 Al can be inferred from the impulsive flare simulations by a suitable choice of simulation parameters. However, in most of the remaining simulations, the irradiation of protoCAIs by superflare(s) with Lx > 10 32 ergs s −1 subsequent to their thermal processing in the reconnection ring would be required to explain the experimental abundances of the short-lived nuclides. These superflares have never been reliably observed in young stellar objects. If they are real, they would be extremely rare. The paucity of these superflares could impose stringent constraints on the validity of the X-wind irradiation scenario as the source of the short-lived nuclides.

Short-Lived Radionuclides and Early Solar System Chronology

“…Some short-lived nuclides are likely to have formed by spallation reactions with nuclear particles (protons, a-particles) accelerated by interaction with an active young Sun (e.g., Duprat and Tatischeff, 2007;Gounelle et al, 2001;Lee et al, 1998;Leya et al, 2003;Sahijpal and Soni, 2007). Beryllium-7 certainly requires local production by irradiation in the solar system because of its short half-life, but evidence for its presence in CAIs remains tentative (Chaussidon et al, 2006a,b).…”

Search for extinct 36Cl: Vigarano CAIs, the Pink Angel from Allende, and a Ningqiang chondrule

“…The 36 Cl/ 35 Cl ratio produced by spallation reactions induced by energetic particles emitted from the young Sun, on the other hand, may be as high as 1.3 Â 10 À4 (short irradiation of solar composition matter, with no saturation; Leya et al, 2003). The X-wind model calculations of Sahijpal and Soni (2007) predict a 36 Cl/ 35 Cl ratio up to 3 Â 10 À5 , which is only somewhat lower than the inferred initial 36 Cl/ 35 Cl for the solar system. Thus, spallation reactions induced by energetic particles emitted from the young Sun may be responsible for the inferred initial 36 Cl/ 35 Cl (Hsu et al, 2006).…”

Measurement of the33S(α,p)36Cl cross

“…In this model, SEPs are accelerated from the protoSun during intense x-ray events to energies in excess of 1 MeV/A. Numerous attempts have been made to reproduce the initial Solar System 36 Cl abundance using the x-wind model [13][14][15][16]. However, due to a lack of experimental cross section data the models are forced to rely on theoretical predictions, which is a large source of uncertainty in the results [14,15].…”