The Changing Solar Wind
 | The solar wind has long term variations that are correlated with the solar activity cycle. Although the period of these variations is the solar cycle, different solar wind parameters vary with different phases, relative amplitudes and shapes. These variations in the solar wind characteristics are related to the cycle of geomagnetic storm activity at Earth. Recurrent magnetic storms, due to high velocity solar wind streams, are more common three years after sunspot maximum. Storms associated with flare activity are more common near solar maximum.- The strength of the interplanetary magnetic field, entrained in the solar wind, has a double peak one before and one after solar maximum,
- solar wind velocity has a double peak, one at solar max and one several years after solar max, in agreement with the frequency of magnetic storms,
- the Helium abundance peaks during solar max,
- there is little information on the longer-term variations in the solar wind.
Other features, include:- During a solar rotation period, solar wind streams with higher than average velocity occur. A particular stream can persist longer than a year. These streams are responsible for recurrent geomagnetic storms. These types of storms maximize in the declining phase of the solar cycle.
- The structure in the solar wind viewed from Earth is due in part to the structure of the solar wind as it leaves the sun and in part to the interaction between high and low speed solar wind streams as they propagate to the Earth.
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