# Controlling crackling dynamics by triggering low intensity avalanches

Jonathan Barés
Daniel Bonamy

When submitted to a slow driving, many physical systems respond with a jerky dynamics also called \textit{crackling}. These systems encompass a large diversity of phenomena going from fracture or damage to imbhibition and even plasticity to mention a few. These crackling dynamics come with rare extreme events that can have devastating effects as for the case of earthquakes or avalanches. Since these large events are, so far, impossible to predict it is paramount to be able to control their occurrence and reduce their intensity.

In the case of seismicity, it is now well documented that local gentle excitations can induce earthquakes even far away from the excitation point. On another side, to deal with snow hazard in mountains, different devices have been set up which permit to inject locally strong pulses of energy that trigger avalanches. Pushing forward these ideas, is it possible to modify and control the full statistics of a crackling system injecting periodically and locally small amounts of energy at the right place in this system? Is it possible to kill extreme avalanches inducing more smaller avalanches just by sacrificing a small amount of energy?

We present how excitation, more precisely amplitude and frequency can decrease the intensity of extreme events in crackling systems. We use long-range elastic depinning interface as a paradigm to model such a crackling system and add excitations of different natures, intensities and periods. Based on extensive simulations, we unravel that excitation on randomly chosen points along the interface have the same effect as excitation on strongly pinned points. We find that, despite the diversity of control parameters the injected power per unit of front length ($\mathcal{Q}$) is the unique parameter that rule the efficiency of excitation. This efficiency, in terms of extreme event killing, has a maximum for a certain value $\mathcal{Q}_c$ for which the rate of event is maximum. Also, surprisingly, excitations below the Larkin length can even have an effect. This work sheds light on a way to control crackling dynamics appearing in systems as diverse as crack front propagation, moving magnetic walls in amorphous ferromagnets or even neural activity.