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Secular Changes in Solar Magnetic Flux Amplification Factor and Prediction of Space Weather

We could infer a secular decreasing trend in the poloidal to toroidal solar magnetic flux amplification factor ( Af) using geomagnetic observations ( classic and IHV corrected aa indices) during the sunspot cycles 9-23. A similar decreasing trend is also observed for the solar equatorial rotation (W) which imply possibly a decrease in the efficiency of the solar dynamo during the above period. We could show correlated changes of Af and extreme space weather activity variations near earth since the middle of the 19th century. Indirect solar observations ( solar proton fluence estimates) suggests that the distinct enhancements in extreme space weather activity , Af and W found during sunspot cycles 10 to 15 is probably largest of that kind during the past 400 years. We find that the sunspot activity can reach an upper limit (R<300) when Af becomes unity. If the current sunspot cycle 24 turns out to be weak then very severe space weather conditions is most probable to occur during this cycle. Key words: Flux amplification,solar dynamo, space weather, predictions,cycle 24