Over the past few years, the long-term sustainability of ICT initiatives has increasingly come under question. Despite persistent doubts, governments, international agencies, NGOs, and private companies are pressing ahead to set up more such projects. This paper studies the financial sustainability of India's largest rural ICT initiative known as eChoupal. The eChoupals are distinct from other telecenter projects in that the value added is not in providing ICT infrastructure alone, but rather, in enabling efficiencies in the agricultural sector through greater information exchange and creation of an alternative market structure.An analysis of available data indicates that this project has a potential payback period of 3.9 years. Although several assumptions have been used in these calculations, a sensitivity analysis has been performed to provide a range of possible scenarios that show the profitability of the project. Through this analysis it seems that ICT projects can be financially sustainable when they are viewed not as an end in themselves but as tools to facilitate information exchange whereby, use of the technology enables higher efficiencies in another existing or new business setting, which provides the source of revenue to recover the initial investment. Copyright (c) 2005 Massachusetts Institute of Technology.

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-In this letter we investigate the dynamics of magnetic energy growth in small-scale dynamo by studying energy transfers, mainly energy fluxes and shell-to-shell energy transfers. We perform dynamo simulations for magnetic Prandtl number Pm = 20 on 1024 3 grid using pseudospectral method. We demonstrate that the magnetic energy growth is caused by nonlocal energy transfers from the large-scale or forcing-scale velocity field to small-scale magnetic field. The peak of these energy transfers move towards lower wavenumbers as dynamo evolves, which is the reason why the integral scale of the magnetic field increases with time. The energy transfers U 2U (velocity to velocity) and B2B (magnetic to magnetic) are forward and local.Spontaneous generation of magnetic fields in magnetohydrodynamics (MHD), particularly in stars, planets, and galaxies, is known as "dynamo effect" [1]. A small seed magnetic field is amplified by self-induced currents. It has been argued that the swirling and twisting of the magnetic field lines lead to this growth [2,3]. In this letter we attempt to quantify the energy transfers during the dynamo process.The magnetic energy growth is called "small-scale dynamo" (SSD) or "large-scale dynamo" (LSD) depending on the scale at which magnetic field grows maximally. Following Cattaneo et al. [4], in LSD (SSD), the magnetic field is generated at characteristic lengths larger (smaller) than those of the velocity field. The nature of dynamo generally depends on the magnetic Prandtl number Pm, which is the ratio of the kinematic viscosity (ν) and the magnetic diffusivity (η) of the fluid. Typically, SSD is observed for larger Pm [5], while LSD is for smaller Pm [13]. Yet, there are many exceptions. For example, both SSD and LSD coexist in solar dynamo for which Pm ≪ 1 [4].Scale-dependent energy transfers in MHD have been computed using numerical and analytical tools. Primarily this is done by computing various energy fluxes and (a) E-mail: rohitkr@iitk.ac.in (b) E-mail: mkv@iitk.ac.in (c) E-mail: ravi.samtaney@kaust.edu.sa shell-to-shell energy transfers of MHD. Several simulations [6-8] employed logarithmic-binned shells, while Alexakis et al.[9] used linearly-binned shells. For unit Prandtl number, these diagnostics demonstrate that under steady state, the large-scale magnetic field is fed by the large-scale velocity field. The magnetic energy thus enhanced at large scales cascades forward to small scales. The magnetic energy at large scales is maintained by this mechanism.Moll et al.[10] employed Alexakis et al.'s method [9] to compute energy transfers for small-scale dynamo with high Pm. They showed that during dynamo action, kinetic energy at large scales is transferred to the magnetic energy at smaller scales. In our letter we compute energy transfers using Dar et al.'s method [6] for a small-scale dynamo on a high-resolution grid. We observe that the magnetic energy growth is due to nonlocal energy transfers from large-scale velocity fields to small-scale magnetic fields. The peak of the...

Context. Magnetohydrodynamic interactions between plasma flows and magnetic fields is fundamental to the origin and sustenance of the 11-year sunspot cycle. These processes are intrinsically three-dimensional (3D) in nature. Aims. Our goal is to construct a 3D solar dynamo model that on the one hand captures the buoyant emergence of tilted bipolar sunspot pairs, and on the other hand produces cyclic large-scale field reversals mediated via surface flux-transport processes -that is, the Babcock-Leighton mechanism. Furthermore, we seek to explore the relative roles of flux transport by buoyancy, advection by meridional circulation, and turbulent diffusion in this 3D dynamo model. Methods. We perform kinematic dynamo simulations where the prescribed velocity field is a combination of solar-like differential rotation and meridional circulation, along with a parametrized turbulent diffusivity. We use a novel methodology for modeling magnetic buoyancy through field-strength-dependent 3D helical up-flows that results in the formation of tilted bipolar sunspots. Results. The bipolar spots produced in our simulations participate in the process of poloidal-field generation through the Babcock-Leighton mechanism, resulting in self-sustained and periodic large-scale magnetic field reversal. Our parameter space study varying the amplitude of the meridional flow, the convection zone diffusivity, and parameters governing the efficiency of the magnetic buoyancy mechanism reveal their relative roles in determining properties of the sunspot cycle such as amplitude, period, and dynamical memory relevant to solar cycle prediction. We also derive a new dynamo number for the Babcock-Leighton solar dynamo mechanism which reasonably captures our model dynamics.Conclusions. This study elucidates the relative roles of different flux-transport processes in the Sun's convection zone in determining the properties and physics of the sunspot cycle and could potentially lead to realistic, data-driven 3D dynamo models for solar-activity predictions and exploration of stellar magnetism and starspot formation in other stars.