Evolution of solar indices during the maximum of solar cycle 24

Abstract

Abstract: Solar cycle 24 started in 2008-2009 and the peak ~67 in sunspot number (12-month running means) occurred in February 2012. Several other solar indices (2800 MHz solar radio flux, Lyman-a, Mg II 280 index, TSI Total Solar Irradiance, all of origin in chromosphere or lower corona) also show peaks at February 2012; but coronal indices, X-rays and Coronal Mass Ejection (CME) frequency, show a broad plateau around February 2012. In interplanetary parameters, solar wind speed V shows a broad peak earlier than February 2012 (during September 2010-October 2011) and a decline thereafter. Number density N does not seem to have any relationship with solar indices; but magnetic field B peaked near February 2012. Geomagnetic index Ap shows the same pattern as B. Cosmic ray intensity maximum (peak) decreases at middle and high latitudes shows a delay with respect  to  peak of solar indices by several (more than ten) months.