http://repository.unn.edu.ng/handle/123456789/208 2026-09-02T18:17:15Z http://repository.unn.edu.ng/handle/123456789/5492 Analysis of Glitch Activity In Rotating Neutron Stars Asogwa, Ejiuwa-Aka Lovina A total of 660 discrete jumps in the rotation frequency () and the spin-down rate () of about 140 pulsars were studied. Out of the 660 discrete jumps, 394 were classical glitches (the so-called macroglitches) and 266 were microglitches. The objects are grouped into normal radio pulsars, anomalous x-ray pulsars and recycled millisecond pulsars. A bimodal distribution was observed in many of the pulsar glitch parameters, namely the discrete absolute fractional jumps in the rotation frequency (), the entire absolute discrete jumps in the spin down rate (|Δ|), cumulative of the absolute jumps in the rotation frequency (), cumulative of the absolute fractional jumps in rotation frequency ) for macroglitches may suggest that glitch events may be triggered by dual glitch mechanism. The distribution of the entire absolute discrete fractional jumps in the rotation frequency (||) cumulative of the absolute jumps in the rotation frequency () and the cumulative of the absolute jumps in spin down rate (∑|Δ|) of microglitches equally suggests that a glitch event is triggered by one mechanism. It was observed that some of the macroglitches have magnitudes in (rotation frequency) which overlapped with the microglitches completely which suggest that some of the rotational jumps that was characterized as macroglitches by previous authors should have been recorded as microglitches since their glitch magnitude . The distribution of the glitches over the spin down parameters shows that pulsars with characteristic age 3 4, rotational frequency of 0.9, spin down rate ) and surface magnetic field strength of 12 13 on logarithmic scales exhibit the highest frequency of macroglitches while those within the characteristic age 5 6 , rotational frequency of 0.4 , spin down rate of and surface magnetic field strength of 11 12 on logarithmic scales exhibit the highest frequency of microglitches. From the regression analysis, it was observed that there was a strong positive linear relationship between () (∑|Δ|)for the macroglitches and microglitches data when analysed separately and jointly. There was no correlation between () data for both samples. On the otherhand, there was a strong ( || correlation for the macroglitches and microglitches data when analysed separately and jointly. 2017-01-01T00:00:00Z http://repository.unn.edu.ng/handle/123456789/5376 Cosmic Rays Variability in the Mid and High Latitudes During Solar Quiet Days Okiyi, Miracle Ugochukwu We have studied the variability of Cosmic rays flux during solar quiet days at mid and high latitudes. By using the five (5) quietest days for each month, the monthly mean diurnal variation of cosmic ray anisotropy have been derived for the period 1981-2007, which covers part of cycles 21, 22 and 23.  These quiet days are days during which the sun is relatively magnetically quiet, leading to less anisotropic behavior in the diurnal flux of cosmic rays measured on the earth’s surface. Four stations (Rome, Oulu, Inuvik and Thule) were used in this study to understand the important features of the high latitude and mid-latitude diurnal wave, and how solar and geomagnetic activity may be influencing the wave characteristics. Cosmic ray wave characteristics were obtained by discrete Fourier transform (DFT).  The mean, diurnal amplitude, phase and dispersion for each month's diurnal wave were calculated and profiled. There was clear indication that the terrestrial effect on the variability of the monthly mean was more associated with geomagnetic activity rather than rigidity of the cosmic rays.  Correlation of the time series of these wave characteristics with solar and geomagnetic activity index showed better association with solar activity.  2017-06-07T00:00:00Z http://repository.unn.edu.ng/handle/123456789/5361 Geophysical Investigation of Abakaliki Area Using Aeromagnetic Method Idike, Julius Igboji Aeromagnetic data over Abakaliki area of the lower Benue trough of Nigeria was interpreted qualitatively and quantitatively using Oasis montaj software (version: 6.4.2 H.J).The interpretation unveiled basic intrusive bodies like dyke, lacolyte and batholyte in the study area. It also showed fault zone which trends North East to south western (NE-SW) part of the study area. Quantitative interpretation of the area was carried out by source parameter imaging and forward and inverse modeling. Source parameter imaging unveiled predominance of deep seated bodies in the south western part of the area, while shallow bodies are predominant in the south eastern part of the study area. Depth obtained by source parameter imaging ranged from 99.50m to 5930.78m. Forward and inverse modeling was carried out using potent Q software which is an extension of the Oasis montaj software used in the work. The magnetic anomalies over the area were modeled by bodies in the form of sphere and ellipsoid by varying the total magnetic intensity parameters such as susceptibility, inclination, declination, depth of burial and by varying the length, width and height of the bodies used in the model. The radius of the spherical bodies are 1457m, 17704m and 4883m for models A, B and D representing Obubra, Abakaliki and Ameka respectively. Lengths of the ellipsoids are 6099m and 5341m.Width of the ellipsoids are 411m and 2203m while Heights of the ellipsoids are 6017m and 275m (for models C and E representing Enyigba and Ameri respectively). Depth obtained by forward and inverse modeling ranged from 477m to 6366m. Depth obtained for model A (Obubra) is 546m with susceptibility of 0.0180SI (signifying limestone). Height obtained for model B (Abakaliki) is 50m (likely the out crop near college of Agricultural sciences-CAS EBSU) with susceptibility of -0.0017SI (signifying calcite). Depth obtained for model C (Enyigba) is 956m with susceptibility of -0.0134SI (signifying Rock salt). Depth obtained for model D (Ameka) is 6366m with susceptibility of -0.009SI (signifying Quartz). Depth obtained for model E (Ameri) is 477m with susceptibility of -0.006SI (signifying Calcite). These values correlate with some of the works done in the study area. The presence of out crop, intrusive and minerals like calcite, pyrite, rock salt and limestone were delineated in the area. 2017-06-07T00:00:00Z http://repository.unn.edu.ng/handle/123456789/4273 Long – Term Rotational Stability of Some Isolated Radio Pulsars Ugwuanyi, Joseph Chinonso We re-examined the phenomenon of rotational instability in radio pulsars on decadal timescales using a sample of 315 radio pulsars whose spin-rates [rotation period and spin-down rate ] have been measured on, at least two different epochs. The first stage of our analysis involves a direct comparison of the measured values of and at two epochs that are years apart in order to estimate the fluctuation in the parameters. The results show that the fluctuation in the objects’ rotational period is significant in 293 pulsars, while it is at the level of measurement uncertainties in the remaining 22 pulsars. For 293 objects, the fractional change in was found to have absolute values in the range of . Similarly, the observed fluctuation in spin-down rate was considered significant in only 178 pulsars in the sample. In this case, the fractional change in the parameter , irrespective of sign, has values in the range of . Further analysis of our sample reveals a moderate correlation with between and . On the other hand, only weak correlations with were found between and the pulsar spindown parameters, which suggests that they are unrelated. For seven radio pulsars, whose spin-rates and have been measured at five different epochs, we found strong evidence for non-stationarity of the objects’ spin-down rates. The braking indices of the 315 radio pulsars were extensively measured using three different methods that involve: (i) integration of the spin-down law , differentiation of the spin-down law and direct measurement of pulsar period second derivative using measurement of at two epochs years apart . The three methods produced braking indices of anomalous values with magnitudes in the range of . Irrespective of methods of measurement, the absolute values of were found to be strongly correlated with with the pulsar spin-down age and anti-correlated with with objects’ spin-down rate and surface magnetic field . 2017-03-27T00:00:00Z