Solar cycle 23: An unusual solar minimum?

摘要: We are currently observing the minimum phase of Cycle 23. Magnetic activity during years 2006–2009 has been very weak with sunspot numbers reaching lowest values in about 100 years. This long and extended is characterized by polar magnetic fields, small coronal holes, a relatively complex morphology. configuration at Sun remarkably different from one observed previous two solar minima. review observations made wind recent minima discuss implications differences for heliosphere geospace.