Magnetization by core dynamo activity in large asteroids and planetesimals is suggested by the remnant magnetization of many achondritic meteorites. However, the conditions for a sustained dynamo in such small bodies is problematic for several reasons. Such bodies may not have the energy budget or size to achieve a sufficient dynamo. Moreover, given their low internal pressures, planetesimal cores likely freeze from the top down, wherein the gravitationally unstable solid in the freezing front has high viscosity and is not easily destabilized. The solid may delaminate in intermittent pulses, which can lead to ephemeral intervals of vigorous convection sufficient to drive dynamo activity, although they may be too short lived to fully magnetize the planetesimal. However, delaminated diapiric downwellings from the solidification front are likely to be partial melts or mushes and thus porous, two-phase bodies. Percolative flow or seepage through the diapir can potentially induce magnetization in the diapir quickly, possibly allowing rapid triggering of dynamo activity. We build on our recent two-phase magnetohydrodynamic theory to examine the magnetization of a porous metallic diapir sinking through a liquid metal in the presence of an imposed background field. Without seepage of liquid through the diapir (i.e., if it were rigid and impermeable), the background magnetic field is distorted by flow around the diapir, as expected. Some of the field distortion is offset with the addition of seepage through the diapir. However, fast seepage can establish a dipole moment inside the diapir, which points opposite the direction of diapiric descent. Wide-spread delamination and diapirism could therefore rapidly establish a multi-polar poloidal field whose field lines extend outside the core, thereby allowing remanent magnetization of the solid and solidifying material above it.

许多小型线粒体陨石的残余磁化表明，在大型小行星和小行星中，通过核心发电机的活动进行了磁化。然而，由于以下几个原因，在这样小的身体中维持发电机的条件是有问题的。这样的物体可能没有足够的能量预算或大小来实现足够的发电机。而且，由于它们的内部压力低，行星状核很可能自上而下冻结，其中在冻结前沿的重力不稳定固体具有高粘度并且不容易不稳定。固体可能会以间歇性脉冲分层，这可能导致短暂的强对流间隔，足以驱动发电机活动，尽管它们的寿命太短，无法完全磁化行星状星体。然而，从凝固前沿开始的分层双apirings可能是部分融化或糊状，因此是多孔的两相体。通过底盘的渗流或渗漏可能会在底盘中迅速引起磁化，从而可能迅速触发发电机的活动。我们基于最新的两相磁流体动力学理论来研究在施加背景场的情况下通过液态金属下沉的多孔金属diapir的磁化强度。如所预期的那样，在没有液体通过底盘渗漏的情况下（即，如果它是刚性且不可渗透的），背景磁场会由于在底盘周围的流动而失真。某些电场畸变会因通过透水膜的渗漏而被抵消。但是，快速渗漏会在底盘内部建立偶极矩，指向相反的方向。因此，广泛的分层和透散现象可以迅速建立一个多极极化电场，其场线延伸到铁心外部，从而使铁心和上方的固体和凝固材料保持剩余的磁化强度。