Magnetic flaring in the young Sun and implications for solar nebula solids

E. Feigelson, G. Garmire, Y. Tsuboi(Penn State) S. Pravdo (JPL),

Abstract

To address the role of energetic processes in the solar nebula, we provide a detailed characterization of magnetic flaring in stellar analogs of the pre-main sequence Sun based on two 0.5-day observations of analogs of the young Sun in the Orion Nebula Cluster obtained with the Chandra X-ray Observatory. The sample consists of 41 stars with masses 0.7-1.4 M$_\odot$ and ages <1 to $\simeq 10$ Myr. We find the X-ray luminosities are strongly elevated over main sequence levels, and decline during the pre-main sequence phase according to $\log L_x \simeq 29.7 - 0.6(\log t - 6)$, where L_x is in erg s^-1 measured in the 2-8 keV band and t is in years. The X-ray emission is strongly variable in time in most solar analogs; about 20 flares with $29 < \log L_x(peak) < 31$ erg s^-1 on timescales from 0.5 to >12 hours are seen during the Chandra observations. The ubiquity of the strong, hard and variable X-ray emission in this sample is strong evidence that the early Sun exhibited similar enhanced magnetic activity.

Comparison to the contemporary Sun shows that, at an age of 1 Myr, the Sun exhibited long duration events (LDE) with 10² higher peak X-ray luminosities occurring 10² times more frequently than the most powerful LDE flares seen today. MeV proton fluxes are inferred to have been 10^5.5 times greater than current levels. The results support a local flare origin of various properties of pristine meteorites. The particles and shocks produced by the magnetic reconnection flares may have flash melted meteoritic chondrules, produced correlated excess ²²Ne and particle tracks in free-floating meteoritic grains, and generated at least some of the short-lived nuclides found in CAI inclusions by spallogenic nuclear reactions.

CATEGORY: SOLAR SYSTEM AND MISC