Figure 3. First principal component of IMF  B and solar wind velocity. The component is derived from the data for intervals beginning from 4 days prior to the commencement of a sequence of 4 consecutive days with Ap 4 up to 4 days after the termination of the sequence of quiet intervals. The bottom panels give the coefficients (as percentage) for each row of the data matrix which provides an idea about the magnitude of the contribution of the first component in each case.