George Howard at http://cosmictusk.com/comet-ison-solar-flares-and-the-775-ad-eichler-event/ … says he has just learnt about the discovery of Comet Ison which has been exciting astronomers over the last couple of months. Ison is as large or larger than Comet Hale-Bopp and is headed for a close encounter with the Sun – promising a dazzling display late in 2013. Howard adds, he is fascinated by the relationship between the orbit of Ison and Newton's Great Comet of 1680 (mentioned in an SIS paper a few years back). Some people have suggested both comets might be fragments of a much larger body while others think it has a periodicity of 333 years, which has extraordinary parallels with Comet Encke's 3.3 year orbit. See also www.universetoday.com/97561/new-sun-skirting-comet-could-provide-dazzlin… and http://ssd.jpl.nasa.gov/sbdb.cgi#top
The most interesting piece on the comet, from a catastrophist and therefore an SIS standpoint, is a paper by David Eichler (link provided by George Howard at http://cosmictusk.com) (see above) where the article or paper can be downloaded complete and without charge. He explores the effects of a huge solar disturbance brought on by such a large comet plunging into the Sun – likening it to the spike at 775AD (see earlier posts on this subject). In that year there was a large jump in the C14 content of the atmosphere which indicates something happened then that was much larger than any known solar flare on record. He points out that a super flare from a large comet of the size of Hale-Bopp could have produced shock accelerated GeV cosmic rays in the solar corona – which were then transported by the solar wind. This might account for the anomaly at 775ad.
In addition, if the coma or tail of a comet were to interact with Earth's magnetosphere the electro-magnetic disturbance would be huge. A big sun grazing comet, or even an asteroid, would due to its energy release near the surfact of the Sun, cause UV exposure and electro-magnetic disturbances on Earth and other planets in the solar system. So, two ways in which a comet might cause such a spike – one due to a comet coming close to the Sun, and another by a comet, rather the coma or a tail of a comet, interacting with the magnetosphere of the Earth. The burst of energy, some of which would be deposited in the oceans, could then super saturate the Earth's atmosphere with water vapour leading to something resembling legendary floods at the same time as it heated other parts of the atmosphere.
Sun grazing comets are a fact of life and Eichler quotes a couple of 2012 papers in support of this assertion. The possibility exists that some of them are potentially quite large. If they actually collide with the Sun, rather than being repelled, we might expect an explosive release of energy (but see the rest of the paper via the link provided). Now, it is clear that the paper was written in an attempt to understand what happened in 775ad, and he has provided an alternative scenario to a simple enormous solar flare (cause unknown). Do we know if there was a lot of rain and flooding around 775ad?
r