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Title: Evolution of solar indices during the maximum of solar cycle 24
Authors: Kane, R P
Keywords: Solar cycle 24;Solar indices;Sunspot number;Coronal indices;Interplanetary parameters
Issue Date: Apr-2014
Publisher: NISCAIR-CSIR, India
PACS No.: 96.60.qd;; 96.60.Ub; 96.50.Bh
Abstract: Solar cycle 24 started in 2008-2009 and a first peak (~67) in sunspot number (12-month running means) occurred in February 2012. Recently, sunspot activity seems to have increased. The latest 12-month running mean attained a value 74.5 centered at September 2013 and is larger than the previous maximum 67. Thus, cycle 24 peak could be as high as ~75 but further increase is not ruled out. Several other solar indices (2800 MHz solar radio flux, Lyman-a, Mg II 280 index, total solar irradiance, all of origin in chromosphere or lower corona) also showed peaks at February 2012. But coronal indices, X-rays and coronal mass ejection (CME) frequency showed broad plateaus around February 2012. In interplanetary parameters, solar wind speed (V) showed a broad peak earlier than February 2012 (during September 2010 - October 2011) and a decline thereafter. The number density (N) did not seem to have any relationship with solar indices, but magnetic field (B) peaked near February 2012. The geomagnetic index (Ap) showed the same pattern as B. The decrease in maximum (peak) cosmic ray intensity at middle and high latitudes showed a delay with respect to peak of solar indices by several (more than ten) months. The main conclusion of the present communication is that during the maximum of cycle 24, the finer dynamic characteristics of the solar surface (photosphere) phenomena extend faithfully to the chromosphere and lower corona, but local dynamical effects occur higher up in the corona diluting the effects of the photospheric phenomena.
Page(s): 151-155
ISSN: 0975-105X (Online); 0367-8393 (Print)
Appears in Collections:IJRSP Vol.43(2) [April 2014]

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