Abstract
Abstract In an earlier work, we found that large metallic iron fractions in dust aggregates and strong magnetic fields boost preplanetary growth. This sets an initial bias for the formation of Mercury-like planets in the inner part of protoplanetary disks. We extended these experiments here by adding pure quartz aggregates to the iron-rich aggregates. Magnetic boost still leads to the formation of larger clusters of aggregates. These clusters now include silicate aggregates, which can also be connecting bridges between chains. However, at least a certain fraction of iron-rich aggregates are needed to trigger magnetic boost. Without a magnetic field, the sticking properties of the aggregates and their constituents determine the composition of clusters of a given size. This introduces a new fractionation and sorting mechanism by cluster formation at the bouncing barrier.
Highlights
As in Kruss & Wurm (2018), the motivation behind this work is still the high iron fraction of some rocky planets
While aggregation of magnets in the context of planetesimal formation has been studied before by Nuth et al (1994), Dominik & Nübold (2002), and Nübold et al (2003), the boost reported here and in Paper I is related to magnetization due to magnetic fields in protoplanetary disks
Here, only one species of aggregates is used per experiment and no magnetic field is applied
Summary
As in Kruss & Wurm (2018), the motivation behind this work is still the high iron fraction of some rocky planets. While aggregation of magnets in the context of planetesimal formation has been studied before by Nuth et al (1994), Dominik & Nübold (2002), and Nübold et al (2003), the boost reported here and in Paper I is related to magnetization due to magnetic fields in protoplanetary disks These fields can be up to several mT at the inner disk edge and decrease with radial distance (Donati et al 2005; Wardle 2007; Dudorov & Khaibrakhmanov 2014; Bertrang et al 2017; Brauer et al 2017; Maurel et al 2019). Such clusters can be several times larger than the size of individual aggregates at the bouncing barrier
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