I propose the coefficient, $t_h$, and its modification $N_t$ which in a simple way reflect dynamics of scientific activity of an individual researcher. I determine $t_h$ as a time period (from some moment in the past till the present moment) during which papers responsible for 1/2 of the total citation index were published. Parameter $N_t$ represents average of the citation index over this period: $N_t={ \mathrm{ C.I.}}/2t_h$.
Categories: physics.soc-ph