A thorough analysis of the atmospheric response to different forcing factors during winter 2004-2005 reveals that the major role in the formation of positive ozone anomaly - found in January over the Atlantic Ocean - is played by precipitating relativistic electrons and lower energetic protons. Unlike the common opinion that precipitating particles deplete the atmospheric O3 through forcing of HOx and NOx destructive cycles, we have shown that mid-latitude middle stratosphere could respond with an ozone enhancement. The abundance of stratospheric O3 is explained with the reduction of O3 optical depth aloft, due to its chemical losses at mesospheric levels - an effect known as ozone self-healing. This conclusion is based on the analysis of O3 data from ERA Interim and MLS (Aura) profiles, confirmed also by modelling estimations. We have shown that the ozone response to particles’ forcing varies not only with latitude but with longitude as well. For the first time we have pointed out that mid-latitude O3 enhancement should be attributed to precipitating relativistic electrons or lower energetic protons from Earth’s radiation belts, and not to a precipitation along the open magnetic field lines. The latter are confined to the polar cap while the former can reach L=2 shells in periods of intense geomagnetic storms. In regard to the longitudinally varying sensitivity of the middle atmosphere to particles’ forcing - it follows naturally from the equatorward meandering of the L shells in the 270E longitudinal sector, which confines the longitudinal drift of trapped particles.