A comparison of Hα and soft X-ray characteristics of spotless and spot group flares |
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| Authors: | V Ru?djak B Vr?nak A Schroll R Braj?a |
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| Institution: | (1) Hvar Observatory, 58450 Hvar, Yugoslavia;(2) Sonnenobservatorium Kanzelhöhe, Univ. Graz, Austria |
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| Abstract: | A comparative analysis of spotless and spot group flares recorded at Hvar and Kanzelhöhe Observatories during the 21st cycle of solar activity is presented. The rate of occurrence of two-ribbon flares was found to be significantly higher for the spotless flares. In comparison with spot group flares of corresponding H importance, the soft X-ray peak values have been systematically lower for the spotless flares. The highest peak values and the energy released in soft X-rays was found for flares with a H ribbon protruding over a major spot umbra. It was found that the effective plasma temperatures in spotless flares have been considerably lower than the temperatures in spot group flares. |
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