Ionizing the Gas in Protoplanetary Disks by Pebble Collisions

原行星盘中气体的电离是调节化学和磁相互作用的基本过程。电离水平可以设定条件，决定磁盘是否局部湍流。到目前为止，考虑的电离方式仅限于高温和各种高能辐射源，从恒星x射线，宇宙射线到放射性衰变的辐射。一种电离盘内气体的新方法刚刚出现。毫米大小的鹅卵石是目前原行星盘和行星形成的标准成分，在原行星盘的整个生命周期中都会发生弹跳碰撞。最近的研究表明，碰撞充电（摩擦充电）对促进粒子簇的生长是非常有效的。此外，还发现——这是一个新发现——在两个鹅卵石碰撞的过程中，气体也会电离。估计电离速率高达10- 15s -1，这一过程在电离盘物质方面比宇宙射线要有效得多，而且在原行星盘的致密部分效果更好。因此，卵石电离对圆盘电离具有潜在的高影响，但关于这一过程的定量数据很少。通过本项目，我们首次在实验室实验中系统地研究了这种电离。

Ionization of gas in protoplanetary disks is a fundamental process that regulates chemistry and magnetic interactions. The level of ionization can set conditions that decide if the disk is locally turbulent or not. So far, ways of ionization considered are restricted to high temperatures and various high energy radiation sources from stellar X-rays, over cosmic rays to radiation by radioactive decay. A new way of ionizing the disk‘s gas just emerged. With millimeter-sized pebbles being a current standard ingredient in protoplanetary disks and for planet formation, bouncing collisions occur throughout the lifetime of the disk. It was recently shown that collisions charging (tribocharging) is very efficient to promote growth of particle clusters. In addition, it was found - and that is new - that also the gas is ionized during the collision of two pebbles. With an estimated ionization rate of up to 10-15 s-1, the process can be way more efficient than cosmic rays in ionizing disk material and it works better in the dense part of protoplanetary disks. Pebble ionization therefore has a potentially high impact on disk ionization but there are only few quantitative data on the process. With this project, we approach this ionization in laboratory experiments for the first time systematically.