The origin of chondrules and refractory inclusions in chondritic meteorites

Examples of calcium-aluminum-rich inclusions (CAIs) surrounded by thick cho ndrule mantles have been found in chondritic meteorites and cast doubt on t he conventional belief that CAIs and chondrules possessed different spaceti me origins in the primitive solar nebula. We study specific processes by wh ich such objects, and the more common ordinary CAIs and chondrules, might h ave formed by flare heating of primitive rocks interior to the inner edge o f a gaseous accretion disk that has been truncated by magnetized funnel flo w onto the central proto-Sun. Motivated by the appearance of the chains of Herbig-Haro knots that define collimated optical jets from many young stell ar objects (YSOs), we adopt the model of a fluctuating X-wind, where the in ner edge of the solar nebula undergoes periodic radial excursions on a time scale of similar to 30 yr, perhaps in response to protosolar magnetic cycle s. Flares induced by the stressing of magnetic fields threading both the st ar and the inner edge of the fluctuating disk melt or partially melt solids in the transition zone between the base of the funnel flow and the reconne ction ring, and in the reconnection ring itself. The rock melts stick when they collide at low velocities. Surface tension pulls the melt aggregate in to a quasi-spherical core/mantle structure, where the core consists mainly of refractories and the mantle mainly of moderate volatiles. Orbital drift of rocks past the inner edge of the disk or infall of large objects from th e funnel flow replaces the steady loss of material by the plasma drag of th e coronal gas that corotates with the stellar magnetosphere. In quasi-stead y state, agglomeration of molten or heat-softened rocks leads to a differen tial size-distribution in radius R proportional to R(-3)e(-Lt)/(tLR), where t(L) similar to yr is the drift time of an object of fiducial radius L = 1 cm and t is the time since the last inward excursion of the base of the fu nnel flow and X-wind. Thus, during the similar to 30 yr interval between su ccessive flushing of the reconnection ring, flash-heated and irradiated roc ks have a chance to grow to millimeter and centimeter sizes. The evaporatio n of the moderately volatile mantles above large refractory cores, or the d issolving of small refractory cores inside thick ferromagnesian mantles bef ore launch, plus extended heating in the X-wind produce the CAIs or chondru les that end up at planetary distances in the parent bodies of chondritic m eteorites.