International Research Journal of Engineering and Technology (IRJET)
e-ISSN: 2395 -0056
Volume: 04 Issue: 04 | Apr -2017
p-ISSN: 2395-0072
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Characterization of last four and half solar cycles on the basis of intense geomagnetic storms A. K. Singh1, Apeksha Tonk2and A. Bhargawa*3 1Professor,
Department of Physics, University of Lucknow, Lucknow-226007, India of Physics, University of Lucknow, Lucknow-226007, India 3Department of Physics, University of Lucknow, Lucknow-226007, India --------------------------------------------------------------------------------------------------------------------------------------------2Department
Abstract- In the present study, we have restricted
networks and water pipelines [15]. In fact a geomagnetic storm has three phases namely an initial phase, a main phase and a recovery phase. The initial phase which is also referred as storm sudden commencement (SSC) is characterized by Dst increasing by 20 to 50 nT in few minutes. The main phase is defined by Dst decreasing to less than -50 nT. The minimum Dst value during a storm can reach as low as -500 nT while the duration may vary between 2 and 8 hours. Recovery phase is the period when Dst changes from its minimum value to its quiet time value and its period may vary from few hours to few days [5]. Storms based on minimum Dst index values can be classified into various categories such as: weak (Dst < -30 to -50 nT), moderate (Dst < -50 to -100 nT), intense (Dst < -100 to -200 nT), severe (Dst < -200 to 350 nT) and great (Dst < -350nT).
ourselves to three categories only i.e., intense, severe and great i.e. Dst < -100nT. We have examined the characteristic properties of storms observed during the years 50 years (1964 - 2013) falling into the solar cycles 20 to 24. During the process, we analyzed 579 cases of storms observed during solar cycle 20, 924 cases in solar cycle 21, 1163 cases in solar cycle 22, 1038 cases in solar cycle 23 and only 55 cases of geomagnetic storms observed during the years 2008 – 2013 of solar cycle 24. We have also examined the variation in sunspot numbers during the same period 1964 - 2013 and have correlated their association with storms and other phenomena. The sunspot numbers (yearly mean total sunspot number) observed for solar cycle 20 were 105.8 while for cycles 21, 22 and 23 observed numbers were 155.4, 157.6 and 119.6 respectively. During the half period of solar cycle 24 (2008-2013) the yearly mean sunspot numbers were observed 64.9. Based on above facts, we found that solar cycle 22 was comparatively more active and solar cycle 24 is comparatively less active than other cycles. We have also noticed and analyzed seven cases of great storms that occurred in last fifty years.
Geomagnetic storms are very much connected with the solar activities and sunspot numbers and vary with the well-known 11-year cycle [5,6,18]. Large active sunspots are responsible for severe geomagnetic storms. The intense magnetic field of sunspots leads to sudden release of magnetic energy manifested by flares and coronal mass ejections that ultimately produces geomagnetic storms [14, 18]. Sunspot number provides the most useful data for the prediction of solar cycle and geomagnetic activity [4] In recent past, solar cycle 23 and solar cycle 24 have been the subject of numerous studies that have emphasized various unusual properties [3, 1,12, 11,14, 9, 18].
Key words: Solar cycle; solar activity; sunspot numbers; geomagnetic storms.
In the present paper, we have examined the trend of geomagnetic storm occurrence observed during last fifty years (1964 - 2013) i.e., for solar cycle 20, solar cycle 21, solar cycle 22, solar cycle 23 and till mid of solar cycle 24. We have noticed 3,759 total cases of geomagnetic storms of intense and above (Dst < -100 to 600 nT) categories. We have also studied the variation in sunspot numbers occurred during last fifty years (1964 2013) and have found that sunspot numbers varied from 157.6 to 64.9 in last fifty years.
1. INTRODUCTION Space weather and its impact on technological infrastructures as well as on mankind is most talked topic of research in recent years [15, 17]. One of the most known reasons of space weather is impact of geomagnetic storms. Violent eruptions of plasma and magnetic fields from the Sun are the origin of geomagnetic storms. Geomagnetic storms create disturbances that affects the Earth`s magnetic field and can disrupt the operation of critical infrastructures relying on spacebased assets including satellites’ signal strength and global positioning system (GPS) as well as have terrestrial effects including electricity distribution
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