http://nopr.niscair.res.in/handle/123456789/13614 Search the Channel search http://nopr.niscair.res.in/simple-search http://nopr.niscair.res.in/handle/123456789/15634 Title: Response of the mid-latitude ionospheric F2 to the total solar eclipses of solar cycle 23 <br/> <br/>Authors: Adekoya, B J; Chukwuma, V U <br/> <br/>Abstract: A study of the response of the mid-latitude ionospheric F2 to the total eclipses of solar cycle 23 is presented using five-minute resolution ionospheric foF2 data obtained from 14 mid-latitude ionosonde stations located in the path of totality of eclipse. The changes in foF2 are analysed using D(foF2), the normalised deviation of critical frequency F2 from the quite days reference. The D(foF2) variation of the ionosphere in the path of totality, as recorded by the ionosonde stations in this path, is characterized by simultaneous decrease in electron density at elapsed time of totality. The present analysis revealed that sudden Sun radiation removal by the Moon reduces the electron production processes in the ionospheric F2-layer. The impact of total solar eclipse is clearly evident simultaneously with the time of maximum occultation as decrease in the electron density in all ionospheric stations. The results, further, suggest that the maximum electron density of F2-layer redistribution processes were observed not at the time of totality of eclipse but shortly before and after the elapsed time (i.e. about 4 min to few hours). It is noteworthy that mainly response of electron density in ionospheric F2 region varies with the sun intensity. Also, an increase in maximum obscuration of eclipse causes reduction in electron density production processes and the transport processes in the F-layer are affected due to the presence of the westward electric field which may in turn lead to the decrease in <span style="mso-bidi-font-style:italic">foF2 of ionospheric F2 region. This result obtained was reasonably in good agreement with the earlier study of ionospheric response to total solar eclipse using different measurement and methods. </span> <br/> <br/>Page(s): 594-605 http://nopr.niscair.res.in/handle/123456789/15633 Title: An estimate of kinetic energy maxima of cyclotron-resonant electrons interacting with whistler mode waves <br/> <br/>Authors: Ikeda, M <br/> <br/>Abstract: Active experiments to probe hot plasma in the magnetosphere were conducted at Siple Station, Antarctica. The multi-stations measurements of VLF Siple signals on the ground were also conducted in Canada. The results from the Siple active experiments at L=5.1, the relativistic treatments, and the results obtained from the multi-stations measurements at L=4.1 showed almost similar results. The relativistic treatment of separatrix at L=5.1 theoretically indicates the total energy of trapped electron, which was estimated to be 0.315 to 16 keV (at maximum of <i>V</i>_{<img src='http://www.niscair.res.in/jinfo/line.gif' border=0>}) by estimates of parallel resonance velocity and wave magnetic field amplitude of 11 PT, and the effective instability depending on the weak relativistic electrons with kinetic energy 10.9 keV in the perfect resonance condition. The kinetic energy 10.9 keV is almost coincident with some results of Sonwalkar <i style="mso-bidi-font-style:normal">et al. </i>[Properties of the magnetospheric hot plasma distribution deduced from whistler mode wave injection at 2400 Hz: Ground-based detection of azimuthal structure in magnetospheric hot plasmas, <i style="mso-bidi-font-style:normal">J Geophys Res (USA)</i>, 102 (1997) 14363]. <br/> <br/>Page(s): 579-593 http://nopr.niscair.res.in/handle/123456789/15632 Title: Effects of geomagnetic storm on middle latitude ionospheric F2 during storm of 2-6 April 2004 <br/> <br/>Authors: Adekoya, B J; Chukwuma, V U; Bakare, N O; David, T W <br/> <br/>Abstract: A study of the intense geomagnetic storm on 2-6 April 2004 has been carried out using ionospheric data obtained from ionosonde station in the mid-latitude stations with emphasis on the F2 region. Ionospheric storms represent an extreme form of space weather with important effects on ground and space-based technological systems. These phenomena are driven by highly variable solar and magnetospheric energy inputs to the Earth's upper atmosphere. The mid-latitude ionospheric stations are classified into two, depending on their geographic coordinates and ionospheric storm variation (i.e. positive and negative phases of ionospheric storm). The low-mid latitude are characterized with geographic latitude between 20°N< low-mid ≤ 36°N, while high-mid latitude are >36°N. The ionospheric storms are classified as positive storms (P-storm) or negative storms (N-storm) depending on whether maximum electron density variation is positive or negative following the onset of geomagnetic storms (small fluctuations of less than ±20% are neglected). The ionospheric storm produced at low-mid latitude was observed to be negative (N) ionospheric storm at the main phase, and also the declining phase of Dst was simultaneously depleted. The recovery phase is more pronounced with positive (P) ionospheric storm with noticeable effect than the initial and main phase. The D(foF2) response of high-mid latitude was observed with positive storm in the main phase. The initial phase responded with severe negative ionospheric storm compared to low-mid latitude with positive ionospheric storm. During the main phase of the geomagnetic storm, positive and negative phases of ionospheric storm prevailed in the daytime and at night. <br/> <br/>Page(s): 606-616 http://nopr.niscair.res.in/handle/123456789/15631 Title: Comparison between CODG TEC and GPS based TEC observations at Koudougou station in Burkina Faso <br/> <br/>Authors: Ouattara, Frédéric; Zoundi, Christian; Fleury, Rolland <br/> <br/>Abstract: The paper presents the comparison between total electron content (TEC) map given by CODG model and Rinex TEC obtained from Koudougou GPS station, which started its operations in December 2008. The TEC observations were carried out at Koudougou station during 5-10 December 2008 by ionosphere single layer model (SLM). The observation of TEC profiles showed noon bite out profile with predominance of morning or afternoon peak and night time peak. CODG TEC profiles highlighted dome and reverse profiles. There is no night time peak in TEC map profiles. The comparison between GPS based TEC observation at Koudougou station and TEC map shows that CODG model does not estimate Rinex TEC at Koudougou station. <br/> <br/>Page(s): 617-623