Magnetic Fields and Accreting Giant Planets around PDS 70}

The recent high spatial/spectral resolution observations have enabled constraining formation mechanismsof giant planets, especially at the final stages. The current interpretation of such observations isthat these planets undergo magnetospheric accretion, suggesting the importance of planetary magneticfields. We explore the properties of accreting, magnetized giant planets surrounded by their circumplanetarydisks, using the physical parameters inferred for PDS 70 b/c. We compute the magnetic fieldstrength and the resulting spin rate of giant planets, and find that these planets may possess dipolemagnetic fields of either a few 10 G or a few 100 G; the former is the natural outcome of planetarygrowth and radius evolution, while the resulting spin rate cannot reproduce the observations. Forthe latter, a consistent picture can be drawn, where strong magnetic fields induced by hot planetaryinteriors lead both to magnetospheric accretion and to spin-down due to disk locking. We also computethe properties of circumplanetary disks in the vicinity of these planets, taking into account planetarymagnetic fields. The resulting surface density becomes very low, compared with the canonical models,implying the importance of radial movement of satellite-forming materials. Our model predicts a positivegradient of the surface density, which invokes the traps for both satellite migration and radiallydrifting dust particles. This work thus concludes that the final formation stages of giant planets aresimilar to those of low-mass stars such as brown dwarfs, as suggested by recent studies.