Instabilities of a protoplanetary disk : Effects of dust particle growth and settling

Abstract

We have studied the effects of dust size growth and settling on instabilities of a protoplanetary disk. As a result, we have found that although the magnetrotationally unstable region at the disk surface spreads as the total dust surface area, namely, the neutralization rate decreases due to the dust size growth and settling, the disk midplane keeps stable owing to the settling even after 10⁵ yr. Meanwhile, the whole disk becomes convectively stable after 3x10⁴ yr due to the irradiation from the central star and the decrease of the dust opacity.