The worst drought in a century could end this year, according to a scientist who has linked the cycle of sunspots and the "looping" of the sun's magnetic field to Australia's weather patterns.

Associate Professor Robert Baker, University of New England, Armidale, NSW, says the rhythmic pattern in the sun's energy output strongly influences weather patterns.

The rhythms apply especially in the southern Hemisphere and in eastern Australia under the influence of the huge size of the Pacific Ocean.

The two key, related sun rhythms are:

- The sun's poles which switch every 11 years

- The sun's magnetic emissions which peak, every 11 years also, in periods of increased sunspot activity.

On earth, periods of high sun magnetic activity coincide with periods of high rainfall, according to Prof Baker's data, using records of observations made as far back as 1876.

Periods of stable magnetic activity coincide with dry periods.

The fluctuations appear to impact on the earth's upper atmosphere, which, in turn, contributes to changes in the Southern Oscillation Index (SOI) - and a consistently positive SOL is linked to wetter years, a negative SOI indicates dry years.

About half of the variations in the SOI can be attributed to the sun's magnetic rhythms.

Prof Baker said the current stage of the cycle, since the last "flip" in 2001, meant that the eastern half of Australia could look forward to 18 months of heavy rain and then a 10-year "window" of average rainfalls.

"The sun's magnetic field is now in a similar position to what it was in 1924 and 1925, when eastern Australia had particularly good rainfall," Prof Baker said.

"If this tracking continues, we can expect average to heavy rainfall for eastern Australia within six months.

"Then the wet cycle should continue into 2008."

Prof Baker said sunspot activity was currently increasing as it normally did in this part of the sun's magnetic cycle, which has been an historic pointer to above-average rainfall.

While long-range weather prediction, using the sun or any other measure, was problematic, Prof Baker said his own theory pointed to 2009 as the next period of potential drought in Australia.

In the longer term, an even worse drought could await the country in the 2020s.

The most intense droughts tend to occur about a year after the sun flips its magnetic poles, every 22 years.

Prof Baker said his system of analysis simply complemented other methods of weather prediction and did not take into account the effects of carbon emissions on climate change.

"If this coming cycle of predicted rainfall does not occur, it will be undeniable that carbon emissions are impacting on our climate in a very profound way," Prof Baker said.

"In using this system, as opposed to other methods of long-range weather prediction, I'm trying to be as transparent as possible.

"This is a very useful tool - this is the engine that drives the whole climate system."

But Prof Baker said even if his predictions were borne out and Australia received solid rainfall over the next 18 months, government and water consumers should not rest on their laurels.

"We will simply have a 10-year window of opportunity to get our act together," he said.

A paper on this research has been submitted to the journal Solar Terrestrial Physics.