NOPR Collection:

A new relationship between geomagnetic H and Y fields during disturbed conditions

2016-10-13T07:26:43Z

Title: A new relationship between geomagnetic H and Y fields during disturbed conditions Authors: Rastogi, R G Abstract: The effect of geomagnetic disturbance activity on both the northward (H) and the eastward (Y) components of the geomagnetic field at stations within 0° to 60° dip latitudes along a narrow longitude sector along India and former USSR states is described for the first time. The difference between monthly mean values of both H and Y fields averages on five International Quiet days and on five International Disturbed days varied very sympathetically with the corresponding variation of the monthly mean equatorial D_st index, which is considered to depict the strength of equatorial ring current in the magnetosphere. Averaged over all the stations, a decrease of H field by 70 nT corresponded to an increase of Y field by about 14 nT. At any of the stations, the daily mean value of the H field shows linear decrease with increasing daily sum of A_p index while the daily mean value of Y field shows linear increase with daily sum of A_p index during any of the seasons of the year. The latitudinal variation of the slope of the regression line for H field decreases as the cosine of the geomagnetic latitude while the same for Y field increases as the secant of the geomagnetic latitude. Thus, a systematic increase of the eastward magnetic field is shown, associated with the increasing equatorial ring current for any of the stations in the Indo-Russian longitude sector. Page(s): 300-307

Zonal and meridional ionospheric currents in the Central Asian sector

2016-10-13T07:09:25Z

Title: Zonal and meridional ionospheric currents in the Central Asian sector Authors: Rastogi, R G Abstract: The daily and seasonal variations of all the three components H, Y and Z of the geomagnetic field have been described on the basis of the data from a unique network of observations within a narrow longitude belt extending from the magnetic equator to 60° dip latitude. The daily variations of the westward field (Y) shows remarkable changes between the summer and winter months. The amplitude of the daily variation is reduced to an insignificantly small value during the local winter months. The horizontal field (H) also does not show clear variation at observations north of the latitude of S_q focus during the local winter months. These features lead to the absence of vortex-type S_q current system during local winter months. The latitudinal variations of the diurnal and semi-diurnal components are discussed in detail. Seasonal variations in solar and lunar tides have been discussed and attributed to rather independent sources in the zonal and meridional currents. The tidal modes of ionospheric winds in the Central Asian sector need to the probed for explaining the drastic changes of the observed effects with season. Page(s): 291-299

On the red line emission in nighttime observed from ISIS-II spacecraft and implied thermospheric winds

2016-10-13T07:07:12Z

Title: On the red line emission in nighttime observed from ISIS-II spacecraft and implied thermospheric winds Authors: Bhatnagar, V P; Rochon, Y Abstract: Downward looking vertical observations at 6300 Å and the F-layer critical frequency from the ISIS-II spacecraft at equatorial, middle and high latitudes in the American zone are use to derive F-layer peak height (h_mF2). The observations refer to nighttime periods (2315 to 0250 hrs LT) in September 1972 for geomagnetically quite and disturbed conditions during low solar activity. The h_mF2 values are entered into vector spherical harmonic model of the thermospheric dynamics to find winds in F-region. The equatorial ionospheric anomaly (EIA) in the emission are observed to move closer to the magnetic equator with time, and sometimes are not collocated with EIA in peak electron density (n_mF2) during disturbed conditions. Also the observed intensities do not always indicate the presence of gravity waves or oscillations during disturbed periods as expected. Page(s): 281-290

Some investigations on multilayer microstrip stacked antenna

2016-10-13T07:04:16Z

Title: Some investigations on multilayer microstrip stacked antenna Authors: Vasistha, Prashant; Singh, S; Vishvakarma, Babau R Abstract: The results of investigation on an electromagnetically coupled stacked microstrip antenna have been reported. Experimental work is carried out to study the effect of coupling on various parameters such as pattern, bandwidth, beamwidth, VSWR and input-impedance. The radiated power is found to be maximum for the microstrip stacked antenna with one and two parasitic elements. However, radiated power decreases significantly when the number of parasitic elements in microstrip stacked antenna is more than two. The beamwidth of the main lobe improves with the parasitic elements. The bandwidth of the microstrip antenna is found to depend directly on the number of the parasitic elements. It has been observed that the radiated power depends on inter element spacing with air dielectric in between the elements. An air gap spacing of 2.8 mm is found to provide maximum radiated power from microstrip stacked antenna with single parasitic element. This hints that there is an optimum inter-element spacing that provides maximum coupling and hence maximum radiation. Page(s): 277-280