Authors: Juan Carlos Martinez Oliveros (SSL/UCB), Amir Caspi (SWRI), Steven Christe (GSFC), Laura Hayes (ESA), Sam Krucker (SSL/UCB), Olivier Limousin (CEA Saclay), Aline Meuris (CEA Saclay), Pascal Saint-Hilaire (SSL/UCB), Juan Camilo Casas (UCB/SSL), Savannah Perez-Piel (UCB/SSL), PADRE Team

The solar PolArization and Directivity X-Ray Experiment (PADRE) is a 12U CubeSat observatory designed to study the Sun in hard X-ray (HXRs) from a low Earth orbit during the maximum of cycle 24. PADRE aims to investigate the angular distribution of accelerated electrons in solar flares using two complementary methods. 1. It will perform spatially-integrated spectro-polarimetric hard X-ray measurements. 2. It will coordinate with Solar Orbiter/STIX to obtain the most reliable two-point measurements of flare hard X-rays fluxes, enabling the determination of the electron directivity.

The acceleration mechanism of solar flare electrons is still not totally constrained. Electron anisotropy and the high-energy cutoff are crucial parameters for understanding electron acceleration in solar flares. However, their precise determination remains challenging. By simultaneously measuring hard X-ray flux and polarization spectra, PADRE will be able to constrain/determine these important parameters. In this presentation, we will highlight the main science outcomes expected from the PADRE mission and how they can be leveraged by using complementary observations from other instruments (e.g., EUV solar imagers to estimate the geometry/inclination of a flaring solar loop) and electron and X-ray transport models. We want to make the high-energy heliophysics community aware PADRE will be joining the cutting-edge instrument fleet as a key asset to improve our understanding of the physics of particle acceleration in solar flares.