Equinoctial Asymmetry of Horizontal Component of Solar Quiet Variation (SqH)

Intermagnetic data was used to obtained hourly values of solar quiet variation of horizontal component of geomagnetic field for 2009. The results obtained from the variability of the amplitude of the solar quiet SqH daily variation was examined. The SqH strength ranges between 90nT and 50nT at Adds Ababa and Guam with low strength values in other stations (Kakioka, Sodankyla, and Guam) around the local noon. The SqH are grouped into two 50nT-70nT and 70nT -90nT at Adds Ababa Kakioka, Sodankyla, Guam and Uppsala. For 50nT -70nT, It  was observed that the SqH occurrence is higher in winter and summer at SqH1 (AAE) than spring and Autumn, while SqH2 (KAK) and SqH3 (SOD) has no values of occurrence of  SqH.  In SqH4 (GUAM), SqH occurrence is higher in Winter and Autumn than Spring and Summer. In SqH5 (UPP), five occurrence of SqH was noticed in winter while other seasons have no occurrence. While 70nT and 90nT, it was noticed that Spring and summer are enhanced in SqH than Autumn and Winter at SqH1 (AAE), with no value of SqH at SqH2, SqH3 and SqH5, while SqH4 with two occurrence of SqH in Autumn while other seasons have no occurrence.  This implies that ionospheric conditions have a direct influence on the occurrence of SqH. Keywords: solar quiet variation (SqH), Season variation and ionospheric conditio

Cubic interpolation based channel estimator for rectangular M-QAM

This paper propose a Pilot Symbol Assisted Modulation (PSAM) channel estimation and compensation technique for rectangular M-QAM based on Cubic interpolation in order to determine the channel state information (CSI) over flat Rayleigh fading channels. The proposed Cubic channel estimator technique is based on sliding window approach and pilot symbol estimates adjustment in order to reduce its computational time complexity. The Cubic estimator is combined with the Koetter and Vardy (KV) Reed-Solomon (RS) decoder to test its performance. The simulation results show that the Cubic interpolation gives the same performance as the Linear, and Sinc interpolators over slow flat Rayleigh fading channel; however, it achieves significant performance improvement of +1.0dB in symbol error rate (SER) over fast flat Rayleigh fading channel.Keywords: CSI, cubic estimator, fading channel, M-QAM, PSA

Storm-time variation of the horizontal and vertical components of the geomagnetic fields and rate of induction at different latitudes

The paper presents the hourly mean variation of horizontal (H) and vertical (Z) components of the geomagnetic field and the rate of induction DH/DZ at different latitudes during magnetic storm of 20 March 2001 and 1 October 2001. The results of the analysis revealed that at high latitude stations greater than 60�, the reduction in DH component was noticed after the noon time while other stations less than 60� experienced reduction of H in the morning time during the geomagnetic storm. Large amplitude of DH and DZ were exhibited during the daytime over the equatorial zone, the amplitude decreases from mid latitudes to the dip equator during the nighttime. The daytime enhancement of DH at AAE, BAN and MBO suggest the presence of a strong eastward directed current which comes under the influence of electrojet. There were strong positive and negative correlations between ring current (DR) and horizontal component of the magnetic field DH. The effect of rate of induction is more significant at high latitudes than lower latitudes, during the geomagnetic storm. More enhancement in rate of induction occurred at nighttime than daytime. This result may be from other sources other than the ionosphere that is magnetospheric process significantly contributes toward the variation of induction. Keywords: Geomagnetic field; Geomagnetic storm; Electromagnetic induction; Ring current; Coronal mass ejectio

Variability changes of some climatology parameters of Nigeria using wavelet analysis

Monthly total rainfall and monthly average temperature data of Nigeria were downloaded from World Bank Data Group site for year 1901 to 2015. Annual total rainfall and annual average temperature were calculated from the data. The decadal average and thirty-year-average of total rainfall and average temperature were also calculated. In order to describe the time-frequency of rainfall and temperature variability, wavelet analysis was employed on time series of the monthly total rainfall, monthly average temperature, annual total rainfall, and annual average temperature using MATLAB software. The constitution of the monthly rainfall and temperature frequency was studied by the global wavelet spectrum. In order to obtain more information, separate bands were modulated. Take for instance, on examining the 8-16-month band by mean of the scales within the range of 8 and 16 months, the periods with low or high variance of the mean monthly and annual temperature were discovered. Variability of the considered climatological parameters was more vivid on thirty-year-average basis than that of annual and decadal basis. Key words: Rainfall data, Temperature data, Wavelet, Climate variability, Climatolog

Geomagnetic field H, Z and electromagnetic induction features of coronal mass ejections in association with geomagnetic storm at African longitudes

The largest geomagnetic disturbance caused by coronal mass ejection (CME) of solar cycle 24 recorded on both 17 March and 22 June 2015 with minimum Dst values of −223 and −195 nT respectively was investigated. This study examine the effect of coronal mass ejection (CME) on Earth geomagnetic field which include the time derivatives of horizontal (H) and vertical (Z) components of the geomagnetic field and the rate of induction ΔZ/ΔH at African longitudes (AAE, MBO, HBK, HER and TAM). The results demonstrated enhancement of dH/dt and dZ/dt at the daytime over the equatorial zone (AAE and MBO) and mid latitudes (TAM, HER and HBK) on 17 March 2015. Nighttime enhancement was observed on 22 June 2015 over the equatorial zones and mid-latitudes. Wavelet spectrum approach is used to investigate ΔZ/ΔH variation observed at AAE, MBO, HBK, HER, and TAM. The CME may have an influence on time derivatives of geomagnetic field H, Z and electromagnetic induction at the African longitudes which might be associated with perturbations in electric fields and currents in the equatorial and low latitude magnetic field linked with the changes in magnetospheric convection.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

The Response of Interplanetary Medium to the Geomagnetic Storm of April 2010

Knowledge of the activities within our own solar system is of fundamental importance in our attempts to understand the processes that occur in the upper reaches of our atmosphere; because, space weather is greatly influenced by the speed and density of solar wind and Interplanetary Magnetic Field (IMF) carried by solar wind plasma. For this reason, behaviours of the interplanetary medium during the storm of 5-7 April 2010 were examined using the routinely observed values of southward component of the Interplanetary Magnetic Field, , Disturbance storm time Index, , Solar Wind Speed. Data of H and Z components of the Earth’s magnetic field recorded at some equatorial and polar stations were also considered to investigate ionospheric responses to the storm. Strong solar wind hit the Earth’s magnetosphere about 0800UT on 5 April 2010 and sparked first geomagnetic storm of the new solar cycle. The storm was the largest geomagnetic storm of the Sun caused in the past three years. The commencement, main phase, and recovery phase of the storm were discussed vis-à-vis response of the interplanetary medium. Probable magnetic processes responsible for the storm as well as the ionospheric implications were also highlighted. Keywords: Geomagnetic storm, interplanetary magnetic field, solar speed and disturbance storm time inde

Solar quiet variation of the horizontal and vertical components of geomagnetic field using wavelet analysis.

The solar quiet variations of horizontal and vertical (SqH and SqZ) components of the geomagnetic field obtained from both the Northern Hemisphere and Southern Hemisphere of the International Real-Time Magnetic Observatory Network (INTERMAGNET) during solar maximum years of 2001 were investigated. The results show enlargement of SqH component of the geomagnetic field during the daytime, attributed to equatorial electrojet current closer to the geomagnetic equator at the electrojet stations (BNG and MBO) which are produce from large eastward flow of the current. It was observed that the SqZ is positive at the southward and negative at the northward hemispheres. The SqZ is amplified at HER and HBK around the daytime. Wavelet power spectrum (WPS) based approach was employed to analyse the SqH, SqZ, and rate of induction (SqZ/SqH) time series in a sequence of time scaling from January to December. The higher energy of SqH and SqZ of the wavelet coefficients is noticeable at a high frequency. The monthly variation rate of induction (SqZ/SqH) analyses during the solar quiet (Sq) variations are associated to the influence of equatorwards penetration of electric fields from the field-aligned current, Earth conductivities, the effect of the ocean and ionospheric conductivities.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Investigation of geomagnetic induced current at high latitude during the storm-time variation

During the geomagnetic disturbances, the geomagnetically induced current (GIC) are influenced by the geoelectric field flowing in conductive Earth. In this paper, we studied the variability of GICs, the time derivatives of the geomagnetic field (dB/dt), geomagnetic indices: Symmetric disturbance field in H (SYM-H) index, AU (eastward electrojet) and AL (westward electrojet) indices, Interplanetary parameters such as solar wind speed (v), and interplanetary magnetic field (Bz) during the geomagnetic storms on 31 March 2001, 21 October 2001, 6 November 2001, 29 October 2003, 31 October 2003 and 9 November 2004 with high solar wind speed due to a coronal mass ejection. Wavelet spectrum based approach was employed to analyze the GIC time series in a sequence of time scales of one to twenty four hours. It was observed that there are more concentration of power between the 14–24 h on 31 March 2001, 17–24 h on 21 October 2001, 1–7 h on 6 November 2001, two peaks were observed between 5–8 h and 21–24 h on 29 October 2003, 1–3 h on 31 October 2003 and 18–22 h on 9 November 2004. Bootstrap method was used to obtain regression correlations between the time derivative of the geomagnetic field (dB/dt) and the observed values of the geomagnetic induced current on 31 March 2001, 21 October 2001, 6 November 2001, 29 October 2003, 31 October 2003 and 9 November 2004 which shows a distributed cluster of correlation coefficients at around r = −0.567, −0.717, −0.477, −0.419, −0.210 and r = −0.488 respectively. We observed that high energy wavelet coefficient correlated well with bootstrap correlation, while low energy wavelet coefficient gives low bootstrap correlation. It was noticed that the geomagnetic storm has a influence on GIC and geomagnetic field derivatives (dB/dt). This might be ascribed to the coronal mass ejection with solar wind due to particle acceleration processes in the solar atmosphere

Changes in meteorological parameters in Nigeria by different manifestations of solar activities

The annual mean solar indices of MgII core to core wing ratio, solar flux 10.7 cm and sunspot number over an eleven (11) year period, 2000 – 2010, were correlated with the annual mean rainfall, maximum temperature, relati-ve humidity, cloud cover and wind speed of 8 meteorological stations in Nigeria. Correlation analyses were perfo-rmed to determine relationships between the solar indices and the meteorological parameters at the same temporal scale. In general, weak correlation and significant levels were exhibited between solar indices and meteorological parameters, except Sokoto, Ilorin and Yola, where there were strong negative and positive correlations with high level of significance between solar indices and meteorological parameters. The observations indicated that increa-sed solar activities might have contributed to decrease in rainfall, cloud cover, and relative humidity; but elevated maximum temperature; implying that variability of solar indices affected galactic cosmic radiation reaching the earth’s atmosphere.Keywords: MgII core to core wing ratio, Solar flux, Sunspot number, Solar activities, Meteorological parameters, Correlation coefficien