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Aims. We seek to estimate the average level of MHD turbulence near coronal mass ejection (CME) fronts as they propagate from the Sun to the Earth. Methods. We examined the cosmic ray data from the GRAPES-3 tracking muon telescope at Ooty, together with the data from other sources for three closely observed Forbush decrease events. Each of these event is associated with frontside halo coronal mass ejections (CMEs) and near-Earth magnetic clouds. The associated Forbush decreases are therefore expected to have significant contributions from the cosmic-ray depressions inside the CMEs/ejecta. In each case, we estimate the magnitude of the Forbush decrease using a simple model for the diffusion of high-energy protons through the largely closed field lines enclosing the CME as it expands and propagates from the Sun to the Earth. The diffusion of high-energy protons is inhibited by the smooth, large-scale magnetic field enclosing the CME and aided by the turbulent fluctuations near the CME front. We use estimates of the cross-field diffusion coefficient D ⊥ derived from the published results of extensive Monte Carlo simulations of cosmic rays propagating through turbulent magnetic fields. We then compare our estimates with the magnitudes of the observed Forbush decreases. Results. Our method helps constrain the ratio of energy density in the turbulent magnetic fields to that in the mean magnetic fields near the CME fronts. This ratio is found to be ∼2% for the 2001 April 11 Forbush decrease event, ∼6% for the 2003 November 20 Forbush decrease event and ∼249% for the much more energetic event of 2003 October 29.

We have observed underground cosmic-ray muons, corresponding to a secondary flux of ~7xlO-11 cm-2 s" 1 , at a depth of 1800 m water equivalent, which appear to be initiated by Cygnus X-3. This identification is based on both direction and phase coherence. The existence of such secondary muons conflicts with the current understanding of photon cascades and/or the nature and location of Cygnus X-3.

The performance of the EAS array at Kolar Gold Fields (working since 1984 and upgraded by 1987) is described. The army has been designed lo seamh for sources of ulba high energy (UHE) photons. The array, the data recording and estimation of shower parameters are briefly described. The angular resolution of the array is discussed in derail. We demonsbate, using our data, that the shower front is not a plane and derive an expression for the correcrion lo be applied lo the observed time delays in each ms before fitting a plane front. We suggest using an accepmce cone, dependent on the number of timing detectors used to estimate lhe anival direction of ms, for pint source searches.