Prediction for 4 November 2003

On 4 November 2003 at 19:29UT the active region designated 10486 produced the largest soft X-ray flare of the modern era. For details, see e.g. here. This flare was classified as an X28 event by the NOAA, i.e. the flare had a peak soft X-ray 0.0028 Watts per square metre in the 1-8 Angstrom band of the GOES satellites, although this was an estimate because the flare saturated the detectors on the satellites. Based on the effect of the flare on the Earth's ionosphere, Thomson, Rodger and Dowden (2004, Geophysical Research Letters 31, L06803) estimate that the event was actually X45!

It is of interest to try the prediction method for that day (after the fact). The prediction, based on one year of data prior to 4 November 2003, is as follows.

Prediction made at: 2003-11-04T00:00:00.000
for events within 1.00 days based on 365.25 days of data
THRESH = 4.0e-06
Number of flares in year of data = 480
Maximum likelihood GAMMA = 2.069+/-0.049
Total number of events=         480
Segmentation procedure complete - calculating rates...
Check on moments for prior = 1.2e-08
Number of blocks = 13
Number of events in last block = 104
Duration of last block (days) = 15.30
Prob. of at least one flare of size M to X = 0.725+/-0.027
Prob. of at least one flare of X size or greater = 0.192+/-0.017

So the method identifies a 73 percent chance of at least one event of size M to X, and a 19 percent chance of at least one X class event. These are relatively high predictions for the method, so in some sense it has "succeeded". However, this example also highlights the limitations of probabilistic forecasting: the forecast for an X class flare is only 19%, yet the biggest flare of the modern era is imminent.

More details on the prediction are provided by the following three figures. (For explanations of these figures, see this page, with the corresponding figures for today's prediction.)

Figure 1: Top panel: Year of flaring used in prediction. Bottom: Bayesian blocks decomposition.

Figure 2: Top panel: Differential distribution of year of events in peak flux. Bottom: Cumulative distribution in peak flux.

Figure 3: Top panel: Posterior distribution for M-X events. Bottom: Posterior distribution for X events.

Additional information:

Main flare prediction page
More detail on how today's predictions were made
Summary of all predictions made to date
Automatic check of the reliability of the predictions
A test of the method on historical data
Links to other pages related to flare prediction
Mike Wheatland's home page

Acknowledgement: The predictions given here are based on information from the Space Environment Center, Boulder, CO, National Oceanic and Atmospheric Administration (NOAA), US Dept. of Commerce.

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