Nitrate abundance in polar ice during the great solar activity minimum Original Research Article

In the present paper we study variations of the nitrate content in Greenland ice core for the last 400 years. These data were obtained by high-precision measurements performed by the University of Kansas. It is shown that approximately 20-year periodicity dominates in the nitrate series during the Maunder minimum (1645-1715) due to similar variations of galactic cosmic ray intensity. During times of normal high solar activity level, the 4–6-year periodicity dominates in the nitrate series. This is probably due to a superposition of fluxes of galactic and solar cosmic rays, and due to the creation of favourable conditions for the nitrate precipitation.