Determination of the solar minimum period between cycles 22 and 23 from the coronal index of solar activity

Abstract

We present the coronal index of solar activity (CI) for 1997 and use the 1996 and 1997 data to examine the properties of the solar minimum between cycles 22 and 23. To compute CI, we used only the intensities of the green corona from Lomnický Stit and Sacramento Peak coronal stations. Values of CI were low in the first half of 1997 with an increase from September toward the end of 1997. We determined the minimum in the green corona to be May 1996, which is in coincidence with the results from 2800 MHz radio flux, the Mg II index and the Wolf number.