GEOMAGNETIC-ACTIVITY AND WIND VELOCITY DURING THE MAUNDER MINIMUM

Following a given classification of geomagnetic activity, we obtained aa index values for the Maunder minimum (1645-1715). It is found that the recurrent and fluctuating activities were not appreciable and that the shock activity levels were very low. The aa index level was due a lmost entirely to the quiet days. Calculated average solar-wind veloci ties were 194.3 km s(-1) from 1657 to 1700 and 218.7 km s(-1) from 170 0 onwards. Also, the coronal magnetic held magnitude and southward int erplanetary magnetic field component Bz were lower. It is concluded th at the nearly absent levels of geomagnetic activity during this period were due to lower coronal and Bz magnetic field magnitudes as well as to the continuous impinging on the Earth of a slow wind.