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Title:	Geomagnetic storm phenomenon as inferred from the low-latitude geomagnetic field variations and interplanetary parameters
Authors:	Rawat, Rashmi
Keywords:	Geomagnetic field variations Solar atmosphere Geomagnetic storms Solar cycle Geomagnetic activity Solar terrestrial interaction PhD Thesis
Issue Date:	2008
Publisher:	Indian Institute of Geomagnetism, Mumbai
Citation:	PhD Thesis, IIG, p.xv+245, 2008.
Description:	A thesis submitted to the University of Mumbai for the Ph.D. in Physics, under the guidance of Prof. Shobhana Alex. Part of Conclusion : The thesis compiles the extensive analysis work done with large data set from low latitude geomagnetic observatories Alibag (Geog. Lat. 18.63◦N, long. 72.87◦E; Ge omag. Lat. 10.03◦N, Long. 145.97) and Tirunelvelli (Geog. Lat. 8.42◦N, long. 77.48◦E; Geomag. Lat. 0.57◦S, Long. 149.42) along with solar wind and interplane tary parameters, covering the solar cycle-23. Investigations are carried out on diverse modulations exhibited by the meridional (Bz) and zonal (By) components of the in terplanetary magnetic field (IMF) and their significant guiding roles for producing different patterns of geomagnetic field variations and good results are obtained. As sociation of dawn-dusk electric field responsible for magnetospheric convection with low-latitude H and D components of geomagnetic field is examined. From the data set, we have identified various types of storms, which include: Initial phase storms, Sharp and intense main phase storms, Two-step main phase storms, Double-dip (DD) storms and magnetic cloud driven storms. Currently, the differen tiation is primarily explained on the basis of meridional (Bz) and zonal (By) compo nents of IMF and total energy influx into the magnetosphere. However, many more parameters need to be looked into for their distinct contribution for producing varied geomagnetic storm patterns. A study topic to be dealt in is the investigation of the long term variability of solar wind velocity (Vsw) and intensity of interplanetary magnetic field (|B|). The corre spondence between the long term variability of Vsw and |B| and the geomagnetic storm events may also be attempted. My present dissertation deals with solar cycle 23, the work may be extended for more solar cycles for examining the long term variability of certain parameters. The product of Bz and square of solar wind speed (Vsw) correlates well with activity on time scales between hours and years. In order to determine the crossover point where the southward component of the IMF and the square of the solar wind speed correlate equally well with geomagnetic activity, a possible way would be to compare appropriately normalized power spectra of each parameter based on the span of data over the entire solar cycle. At high frequencies (periods of the order of hours) the power is expected to be greater in Bz fluctuations than in Vsw 2 fluctuations; at low frequencies (periods of the order of days) the reverse is expected. Although long term spectra of Vsw 2 and Bz are not available, the crossover point could be estimated from spectra based on yearly data spans and their variation throughout the solar cycle. An in-depth analysis will be carried out with respect to the other solar wind plasma parameters like solar wind dynamic pressure, thermal pressure. Quantitative aspects of energy inputs from the contribution of different current systems in the magnetopause, ring current region, magnetotail is to be explored. Determination of occurrence of electrons and different ions during the storm phenomenon will be in teresting to differentiate between phases of storm. Advanced analysis techniques like modelling and simulations are to be used for understanding finer aspects involved in the storm dynamics. Comprehensive work with larger data set will certainly provide better understanding of the complex coupling between the solar wind-magnetosphere and ionosphere.
URI:	http://localhost:8080/xmlui/handle/123456789/219
Appears in Collections:	PhD_Thesis

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