Can Proton Beam Heating Flare Models Explain Sunquakes?

TL;DR

This study investigates whether proton beam heating in solar flares can explain sunquakes by using simulations that model deep atmospheric heating and compare synthetic observables with actual data.

Contribution

It introduces a novel simulation approach with proton beams to explore their role in sunquake generation, extending beyond traditional electron beam models.

Findings

Proton beam heating can produce observable continuum enhancements.

Models with higher energy protons (≥500 keV) show stronger continuum effects.

Lower energy protons (≤100 keV) produce more significant helioseismic impacts.

Abstract

SDO/HMI observations reveal a class of solar flares with substantial energy and momentum impacts in the photosphere, concurrent with white-light emission and helioseismic responses, known as sunquakes. Previous radiative hydrodynamic modeling has demonstrated the challenges of explaining sunquakes in the framework of the standard flare model of `electron beam' heating. One of the possibilities to explain the sunquakes and other signatures of the photospheric impact is to consider additional heating mechanisms involved in solar flares, for example, via flare-accelerated protons. In this work, we analyze a set of single-loop Fokker-Planck and radiative hydrodynamics RADYN+FP simulations where the atmosphere is heated by non-thermal power-law-distributed proton beams which can penetrate deeper than the electron beams into the low atmospheric layers. Using the output of the RADYN models, we calculate synthetic Fe I 6173 A line Stokes profiles and from those the line-of-sight (LOS) observables of the SDO/HMI instrument, as well as the 3D helioseismic response and compare them with the corresponding observational characteristics. These initial results show that the models with proton beam heating can produce the enhancement of the HMI continuum observable and explain qualitatively generation of sunquakes. The continuum observable enhancement is evident in all models but is more prominent in ones with $E_{c}\geq$500 keV. In contrast, the models with $E_{c}\leq$100 keV provide a stronger sunquake-like helioseismic impact according to the 3D acoustic modeling, suggesting that low-energy (deka- and hecto-keV) protons have an important role in the generation of sunquakes.