Sentence:  Further , the <WSD>corpuscular</WSD> radiation , i.e. , the solar wind protons , must sputter away the surface atoms of the dust and cause a slow diminution in size , with a resultant increase in both the Poynting-Robertson effect and the ratio of the repulsive force to the gravitational force . 
Meaning of the word marked with <WSD> tags:  a stream of atomic or subatomic particles that may be charged positively (e.g. alpha particles) or negatively (e.g. beta particles) or not at all (e.g. neutrons)