Tangential component of the YORP effect

TL;DR

This paper investigates the Tangential YORP effect, where surface re-emission causes a recoil force that can alter an asteroid's rotation, potentially comparable to the normal YORP effect.

Contribution

It introduces a simplified model to study the Tangential YORP effect and estimates its magnitude relative to the normal YORP effect.

Findings

The Tangential YORP effect can significantly influence asteroid spin rates.

The effect's magnitude is comparable to the normal YORP effect under certain conditions.

Surface temperature asymmetries drive the tangential recoil forces.

Abstract

This article discusses how re-emission of absorbed solar light by centimeter- to decimeter-sized structures on the surface of an asteroid can create a component of the recoil force parallel to the surface. Under certain conditions the west side of stones appear to be on average slightly warmer than their east sides, thus experiencing a stronger recoil force and increasing the rotation rate of the asteroid. We study this effect, called the Tangential YORP effect, in a toy model, replacing stones with walls and simulating heat conductivity in them. We discuss general trends of the effect, estimate its magnitude, and find it to be comparable to the normal YORP effect determined by gross-scale asymmetry of the asteroid. The existence of this effect would modify the predictions of the YORP acceleration of asteroids.