The probability increase at every solar max. We have not seen everything the sun can put out in our modern space age. I have written several papers on this. Please check out my publications.

John, let me note to you a couple of things. The Carrington event was in Aug-Sep 1859 and came from a huge naked-eye sunspot. These type of sunspots only occur every couple of cycles. Please read the special issue of the Advances Space Research on this topic.

There is an interesting paper by Mark Giampapa that is relevant your question. He surveyed magnetic activity in a group of sun-like stars in the similarly aged M67 cluster. There are examples of stars that fall both above and below the current ranges of solar activity. We do not yet understand what controls this range, so as James Green mentions above, it is possible that the Sun could become much more (or less) active in the near future - both of which would have serious consequences for mankind.

Giampapa et al. http://adsabs.harvard.edu/abs/2006ApJ...651..444G

Another paper (i can't remember the reference right now) looked at 10,000 or more G2 stars from the Kepler spacecraft and found significant solar activity from 2/3 of those stars at a level much higher than our sun. The data from our sun was from two solar cycles of soho data in which each day's sun was reduced to ONE intensity near the kepler wavelength. That enabled the appropriate comparison. It is important to note that not all these stars are the same AGE as our sun and it is believed that most are younger so that there is a bias in age. Even that result is great since it may imply that the solar system has survived a much more extensive solar wind over the billions of years then what we have now. Perhaps easily stripping significant atmosphere from Mars for example.

Yes, it was a below average sunspot cycle (ranked 10th in the last 15) and the event occurred BEFORE the max by several months. So what we learn from that is that it is NOT about sunspot number or location in the cycle but sunspot size. The event was actually two CMEs, one right after the other (about 24 hours or so apart). Carrington observed the second one as a white light flare. The WLF means that the reconnection happened right at the photosphere lifting a huge amount of coronal material above it. Since the first CME already cleared the way in the solar wind the second one hit the earth in about 17 hours. moving at about 2400 km/sec. CME are so huge in size that even one moving away from the sun coming from midlatitudes can hit us. Also near equinox a CME is more geo-effective and all that added up to a big one. The SPE's from this event are also enormous. We found that out from looking at nitrate concentrations in the ice cores. They are an order of magnitude greater than anything we have ever seen in the modern space era. This is all in the special issue of ASR by the way.

These probabilities are put on a form footing now by, of all things, observing the stars! No surprise since the Sun is merely a star. But amazingly, the statistics speak very loudly: simply look at the very nice piece of work by the Japanese group headed by Shibata:

"Can Superflares Occur on Our Sun?", Publ. Astron. Soc. Japan 65, 49, 2013 June 25

There is also a letter to nature reporting first results by

Hiroyuki Maehara et al.

I hope these references help. They are wonderful examples of learning about our Sun from the stars, I wish this kind of work were more popular and better supported by funding agencies here in the US.

Thanks guys for answering my query. Interesting answers and a lot of homework for me too!

James Green I've requested you a copy of your publication. Kindly send me that.

Philip and John I will surely check the info. Thanks!

Abhijeet .. the one you requested is in Scientific American and is easily found on the web. Hope that helps.

If one of the forthcoming solar cycles is strong enough,meaning if the sun is active enough, we can surely expect a carrington type event. It will certainly be scientifically interesting. However, what technological impact (if any) will it have is a subject open to speculation.

Well, it might surprise you since it happened so long ago but it can be estimated. See:

1. Odenwald, S., J. L. Green, W. W. L. Taylor, Forecasting the impact of an 1859-calibre superstorm on satellite resources, Adv. Space Res., doi:10.1016/j.asr.2005.10.046, 2006.

2. Odenwald, S. F., and J. L. Green (2007), Forecasting the impact of an 1859-caliber superstorm on geosynchronous Earth-orbiting satellites: Transponder resources, Space Weather, 5, S06002, doi:10.1029/2006SW000262.

The following reference is HIGHLY relevant. Shibayama et al. (2013).

http://adsabs.harvard.edu/abs/2013ApJS..209....5S

This discusses the statistics of "superflares" on sun-like stars as seen by Kepler.

There appear to be a group, consisting of 1% of stars that show (repeated) superflares more than 100 times the size of the Carrington event. These appear a little less likely around stars rotating as slow as the sun, but the bottom line is that, if there is nothing "special" about these stars, then these events occur every 800-5000 years (for events of energy 1e34 - 1e35 ergs) on a slow-rotating G-star. (Though you need to read carefully - it is probably a function of temperature and rotation).

The authors note that superflares may be associated with the formation of very large starspots (or starspot groups).

Well, let me put up another part of the question, if such an event occurs, are we prepared for it ?

A further contribution to this thread is that a recent paper reports observations of two "superflaring" sun-like stars, with sun-like rotation periods. Nogami et al. http://arxiv.org/abs/1402.3772

The authors claim "These results claim that the spectroscopic properties of these superflare stars are very close to those of the Sun, and support the hypothesis that the Sun might cause a superflare."

NASA Science News for May 2, 2014 email:

Carrington Class CME narrowly misses earth:

Two years ago, an intense solar storm narrowly missed Earth. If it had hit, researchers say, we could still be picking up the pieces.

FULL STORY: http://science.nasa.gov/science-news/science-at-nasa/2014/02may_superstorm/

VIDEO: http://www.youtube.com/watch?v=7ukQhycKOFw

I thiink that our paper may be useful for you.

Yermolaev, Y. I., I. G. Lodkina, N. S. Nikolaeva, and M. Y. Yermolaev (2013), Occurrence rate of extreme magnetic storms, J. Geophys. Res. Space Physics, 118, 4760–4765, doi:10.1002/jgra.50467.

Abstract

We investigate the occurrence rate of magnetic storms at the Earth. During the first part of our study, the standard and integral distribution functions of magnetic storm value (minimal Dst index) for the period 1963–2012 are analyzed and results show that the standard and integral distribution functions have power law tails with indexes γ=−4.4 and −3.4, respectively. During the second part, statistical analysis of occurrence rate of magnetic storms induced by different types of interplanetary drivers is made using OMNI data for the period 1976–2000. Using our catalog of large-scale types of solar wind streams, we study storms induced by interplanetary coronal mass ejections (ICMEs) (separately magnetic clouds (MCs) and Ejecta) and both types of compressed regions: corotating interaction regions (CIRs) and Sheaths. For these types of drivers, we calculate the integral probabilities of storms with minimum Dst ≤−50, −70, −100, −150, and −200 nT. The highest probability in this interval of Dst is observed for MCs, with the probabilities for other drivers being 3–10 times lower. Extrapolation of these results to extreme storms shows that a magnetic storm as large as the Carrington storm in 1859 with Dst=−1760 nT is observed on the Earth with frequency not higher than one event during ~500 years.

Thanks to all, this discussion has truly beefed up my current understanding. For a young researcher like me, its a gold mine :)

@yuri great work. if that's the frequency, i hope we should be ready in the next 450yrs for such an event. maybe on Mars?

@gary thanks for the link. I had read that. Interesting to note.