NOPR Collection:

High resolution fast response rain gauge

2016-10-04T09:39:33Z

Title: High resolution fast response rain gauge Authors: Sharma, Sanjay; Barbara, A K; Devi, M Abstract: The technical details of a fast response rain gauge, developed with the basic aim to measure simultaneously total rainfall and fast changes of rain rate, are described. The merits of the system are described by making a comparative assessment of its performance vis-à-vis the conventional rain gauge. Page(s): 301-305

Ray tracking explanation of whistler precursor observed at low latitude ground station Gulmarg

2016-10-04T09:37:49Z

Title: Ray tracking explanation of whistler precursor observed at low latitude ground station Gulmarg Authors: Singh, Rajesh; Singh, R P Abstract: Employing the Hadelgrove ray tracing equations and a diffusive equilibrium model of the ionosphere, the propagation characteristics of whistler precursors recorded on 8 March 1096 during a strong magnetic storm at low latitude ground station Gulmarg (geom. lat., 24°26´N; geom. long., 147°09´E) are discussed. It is shown that the precursors may be associated with transverse propagation in some regions of the magnetosphere and with the consequent reflection at the lower hybrid resonance (LHR) frequency of the medium. The validity of this suggestion has been tested by performing actual ray tracing computations. Page(s): 293-300

Oblique electrostatic ion-cyclotron instability in auroral magnetosphere in the presence of electric field

2016-10-04T09:35:42Z

Title: Oblique electrostatic ion-cyclotron instability in auroral magnetosphere in the presence of electric field Authors: Misra, K D; Pandey, R S Abstract: Current-driven oblique electrostatic ion-cyclotron instability in an anisotropic Maxwellian magnetospheric plasma in the presence of perpendicular d.c. electric field has been studied. The dispersion relation has been obtained using the method of characteristics incorporating the details of particle trajectories. The perpendicular electric field provides E x B drift for both electrons and ion, while the parallel electric field gives rise to field aligned drift velocity. The present expression reduced to the well known results under suitable approximations. Growth rate and real frequency have been evaluated for various plasma parameters or auroral magnetosphere having different electron-ion temperature ratios, temperature anisotropics and electric fields. The growth rate is strongly influenced by the field aligned electron drift, ratio of T_e/T_i and anisotropy in electron and ion temperatures. This approach is useful for computer simulation experiments. Various applications of these results have been discussed. Page(s): 286-292

Surface signatures of meridional currents in the equatorial electrojet

2016-10-04T09:00:34Z

Title: Surface signatures of meridional currents in the equatorial electrojet Authors: Patil, A R; Rajaram, R Abstract: The requirement that the surface magnetic field linked with the equatorial electrojet (EEJ) should be curl free is used to demonstrate that the electrojet has to have variations in the declination (D) component with well defined diurnal and latitudinal structures and an amplitude of around 5-10% of the electrrojet strength. Data from the standard magnetic observatories in the Indian sector are used to identify the predicted signature of the electrojet-associated D variations. The pattern of time variations deduced from the data shows enhancement with respect to the theoretically predicted values in the afternoon sector, but the signatures appear to be suppressed in the forenoon sector. Since even a small displacement or meandering of the main eastward electroject flow can produce changes in declination, various scenarios for the current flow are also considered, and temporal and latitudinal dependence of the D variation evaluated in a bid to identify the source of this forenoon-afternoon asymmetry. It has been shown that, in principle, the field due to deviation of the flow from pure eastward direction can be responsible for, at least, a part of the observed asymmetry. There may also be contributions from the channeling of the induced currents round the southern peninsula in the lower crust and upper mantle. Page(s): 274-285