The Physical Problem of Sungrazing and Sundiving Comets

In this talk we discuss what is known about the physics of close comet - Sun interactions, based on 16 years of study of cometary x-ray emission, observations of small body impacts on Jupiter, and SOHO long term trending observations of sungrazing comets. Our goal is to put the phenomenon of the SOHO sun-grazing (more than 1800 now detected, coming as close as ~0.01 AU) and the SDO sun-diving comets (2 now found, flying at ~650 km/sec at ~0.0004 AU (100,000 km) above the "surface" of the Sun, in its thin coronal "atmosphere") in physical context. We will do this by discussing the levels of input heating, estimated cometary ablation and vaporization rates, and the observed gross cometary behavior during perihelion passage.; Comet 2001 V1 (NEAT), moving through a close perihelion passage. As observed by the SOHO C3 camera (after Jones et al. 2013). ; Comet 2011 N3 (SOHO) traversing the Sun's corona, as observed by SDO in July 2011. After Schrivjer et al. (2012).