The relationships between disappearing solar filaments,coronal mass ejections,and geomagnetic activity |
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| Authors: | C S Wright L F McNamara |
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| Institution: | (1) Ionospheric Prediction Service, P.O. Box 702, 2010 Darlinghurst, N.S.W., Australia |
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| Abstract: | The relationships between disappearing solar filaments and geomagnetic activity are examined using data obtained between 1974 and 1980. The average level of geomagnetic activity is found to increase after the disappearance of large filaments. The magnitudes of the geomagnetic disturbances depend upon the sizes and, to a lesser extent, upon the darkness of the filaments. The delays between filament disappearances and resulting geomagnetic disturbances are typically 3–6 days, corresponding to Sun-Earth velocities 580–290 km s–1. These are consistent with the observed velocities of those coronal mass ejections that are associated with disappearing filaments.The average delay is: (a) shorter for large and dark filaments than for small and faint filaments respectively; (b) shorter during solar maximum than during solar minimum; (c) dependent in a complex way upon the longitudes of the filaments. Disturbances associated with filaments with longitudes  50 ° have delays  10 days.Quieter than average geomagnetic conditions sometimes occur for several days prior to the geomagnetic disturbances that follow disappearing filaments. |
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