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Intense solar energetic particle (SEP) events data, associated with groundlevel enhancements (GLEs), occurred during 1989 to 2006 have been obtained fromthe spectrometers on board GOES spacecraft in the energy range 10-100 MeV. Theinterplanetary effects of these events and their associated coronal massejections (CMEs) have been provided by the LASCO/SOHO coronagraph images in thefield of view of 2-30 {\rsun} and the interplanetary scintillation images fromthe Ooty Radio Telescope in the heliocentric distance range of $\sim$40-250R$_\odot$. The comparison between the radial evolution of the CME and itsassociated particle spectrum shows that the spectrum is soft at the onset ofthe particle event. A flat spectrum is observed at the peak of the particleevent and the spectrum becomes steeper as the CME moves farther out into theinner heliosphere. However, the magnitude of change in spectral slopes differsfrom one CME to the other, suggesting the difference in energy available withinthe CME to drive the shock. The spectral index evolution as a function ofinitial speed of the CME at different parts of the particle profile has alsobeen compared. The result shows that the change in particle flux with time israther quick for the high-energy portion of the spectrum than that of thelow-energy part, which makes the steepening of the energy spectrum withtime/distance from the Sun. It indicates that the acceleration of particles bya CME-driven shock may be efficient at low energies ($\leq$30 MeV) and theefficiency of the shock decreases gradually towards the high-energy side of thespectrum.

High Energy Solar Particle Events and their Associated Coronal Mass Ejections