  Upcoming missions, including the James Webb Space Telescope, will soon
characterize the atmospheres of terrestrial-type exoplanets in habitable zones
around cool K- and M-type stars searching for atmospheric biosignatures. Recent
observations suggest that the ionizing radiation and particle environment from
active cool planet hosts may be detrimental for exoplanetary habitability.
Since no direct information on the radiation field is available, empirical
relations between signatures of stellar activity, including the sizes and
magnetic fields of starspots, are often used. Here, we revisit the empirical
relation between the starspot size and the effective stellar temperature and
evaluate its impact on estimates of stellar flare energies, coronal mass
ejections, and fluxes of the associated stellar energetic particle events.
