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。电离水平可以设置条件，以确定磁盘是否局部动荡。到目前为止，考虑的电离方式仅限于高温和来自恒星X射线的各种高能辐射源，通过宇宙射线辐射到放射性衰变的辐射。一种新的电离光盘气体的方法刚刚出现。由于毫米大小的鹅卵石是原行星盘和行星形成的当前标准成分，在盘的整个生命周期中都会发生反弹碰撞。最近的研究表明，碰撞荷电(摩擦荷电)对促进粒子团簇的生长是非常有效的。此外，还发现了--这是新发现--气体在两块鹅卵石碰撞时也被电离了。据估计，电离率高达10-15 S-1，这一过程在电离盘材料方面比宇宙射线有效得多，而且在原行星盘的致密部分工作得更好。因此，鹅卵石电离对圆盘电离有潜在的很大影响，但关于这一过程的量化数据很少。有了这个项目，我们第一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.