tailieunhanh - Geomagnetism during solar cycle 23: Characteristics

On the basis of more than 48 years of morphological analysis of yearly and monthly values of the sunspot number, the aa index, the solar wind speed and interplanetary magnetic field, we point out the particularities of geomagnetic activity during the period 1996–2009. We especially investigate the last cycle 23 and the long minimum which followed it. During this period, the lowest values of the yearly averaged IMF (3 nT) and yearly averaged solar wind speed (364 km/s) are recorded in 1996, and 2009 respectively. The year 2003 shows itself particular by recording the highest value of the averaged solar wind (568 km/s), associated to the highest value of the yearly averaged aa index (37 nT). We also find that observations during the year 2003 seem to be related to several coronal holes which are known to generate high-speed wind stream. From the long time (more than one century) study of solar variability, the present period is similar to the beginning of twentieth century. We especially present the morphological features of solar cycle 23 which is followed by a deep solar minimum. | Journal of Advanced Research 2013 4 265-274 Cairo University Journal of Advanced Research ORIGINAL ARTICLE Geomagnetism during solar cycle 23 Characteristics Jean-Louis Zerbo a b c Christine Amory-Mazaudier b Frederic Ouattara d a Universite Polytechnique de Bobo Dioulasso 01 BP 1091 Bobo-Dioulasso 01 Burkina Faso b LPP - Laboratoire de Physique des PlasmasjUPMCjPolytechniquejCNRS UMR 7648 4 Avenue de Neptune 94 107 Saint-Maur-des-Fosses France c Laboratoire d Energies Thermiques Renouvelables LETRE Universite de Ouagadougou 10 BP 13495 Ouagadougou 10 Burkina Faso d Ecole Normale Superieure de l Universite de Koudougou BP 376 Koudougou Burkina Faso Received 6 April 2012 revised 17 August 2012 accepted 19 August 2012 Available online 8 December 2012 KEYWORDS Geomagnetic activity Solar cycle Solar wind Abstract On the basis of more than 48 years of morphological analysis of yearly and monthly values of the sunspot number the aa index the solar wind speed and interplanetary magnetic field we point out the particularities of geomagnetic activity during the period 1996-2009. We especially investigate the last cycle 23 and the long minimum which followed it. During this period the lowest values of the yearly averaged IMF 3 nT and yearly averaged solar wind speed 364km s are recorded in 1996 and 2009 respectively. The year 2003 shows itself particular by recording the highest value of the averaged solar wind 568 km s associated to the highest value of the yearly averaged aa index 37 nT . We also find that observations during the year 2003 seem to be related to several coronal holes which are known to generate high-speed wind stream. From the long time more than one century study of solar variability the present period is similar to the beginning of twentieth century. We especially present the morphological features of solar cycle 23 which is followed by a deep solar minimum. 2012 Cairo University. Production and hosting by Elsevier . All rights reserved. Introduction .