Etienne Parizot
Université Paris Cité, APC (Astroparticle and Cosm), Paris, France
Ultra-High-Energy Cosmic Rays: The Unfinished Quest for Messengers of the Extreme
Cosmic rays were the first non-photonic cosmic messenger to be discovered over a century ago. Despite intense research activity both theoretical and observational their astrophysical origins remain largely elusive particularly for the most energetic subset unimaginatively referred to as ultra-high-energy cosmic rays (UHECRs). In this seminar we will briefly trace the history of cosmic ray discovery and summarize our current understanding of these intriguing particles. We will further highlight the interest of UHECRs review what was recently learned about them and describe the specific efforts of the JEM-EUSO collaboration to bring UHECR studies one step further from ground to space, through the stratosphere.