Evryscope flares as probes of the space weather environments of Proxima b and the nearest rocky exoplanets

In March 2016, the Evryscope observed the first superflare from Proxima Centauri. The Evryscope array of small optical telescopes recorded the superflare as part of an ongoing survey of all bright southern stars, monitored simultaneously at 2 minute cadence since 2015. Evryscope flares act as probes of the space weather environment of nearby exoplanets in three ways: by constraining their UV surface environments, by looking for planetary magnetic fields via star-planet interaction and flares that phase up with planet orbits, and by monitoring optical counterparts to radio flare observations. We illustrate each of these probes for Proxima Centauri and discuss future work for other nearby planets. By modeling the photochemical effects of particle events accompanying large flares in a recently accepted letter, we find repeated flaring is sufficient to reduce the ozone column of an Earth-like atmosphere at the orbit of Proxima b by 90% within five years. Surface UV-C levels during the Evryscope superflare reach ~100X the intensity required to kill simple UV-hardy microorganisms without ozone, suggesting that life would struggle to survive in the areas of Proxima b exposed to these flares. Next, we discuss a possible correlation between the times of energetic flaring and Proxima b's orbit. Finally, an approved program (PI: M. MacGregor) for 40 hours of simultaneous Evryscope and ALMA observations of large sub-mm flares on Proxima will be undertaken. We discuss constraints on blackbody emission supplied by optical counterparts to observed sub-mm flares. Flares seen by Evryscope give insight into the unknown emission mechanism and habitability impacts of large sub-mm events. With the launch of TESS, providing 27-day ultra-high-precision coverage for most bright stars, multi-year Evryscope monitoring of the TESS field constrains the occurrence of superflares impacting nearby planets. From TESS-discovered planets such as LHS 3844 to previous discoveries TRAPPIST-1, YZ Ceti, Ross 128, and others, we discuss how Evryscope flares probe each planet's space weather environment.