Effect of dust storm and GCR impact on the production rate of O₃+ in MY 28 and MY 29: modeling and SPICAM observation

Abstract

We have developed a seasonally dependent energy loss model to calculate the zonally averaged production rates of O₃+ due to impact of galactic cosmic rays in the day side troposphere of Mars between solar longitudes (L_s) ~0° and 360° at low latitudes (2°N, 2°S, 25°N, and 25°S), midlatitudes (45°N and 45°S), and high latitudes (70°N and 70°S) in the Martian Year (MY) 28 and MY 29. We also represent the seasonal variability of zonally averaged ozone column density obtained from Mars Climate Database during the daytime. These results are compared with the daytime observations of column ozone made by Spectroscopy for the Investigation of the Characteristics of the Atmosphere of Mars onboard Mars Express (MEX). At mid‐to‐high latitudes ozone column density is maximum in northern winter and minimum in southern summer. At low‐to‐middle latitudes (2°N-S, 25°N–S, and 45°N–S), the production rates of O₃+ represent a broad peak between altitudes 26 and 45 km in both hemispheres. The peak production rates are increasing up to L_s = 47.5° and then stabilized at about 2.5 × 10^-8 cm^-3/s. At L_s ≥ 47.5° the peak production rate of O₃+ starts decreasing until it disappeared after L_s = 127.5°. A major dust storm occurred in MY 28 at L_s~280° in southern latitudes (~25°–35°S). During the dust storm period, dust opacity, ozone column density, and O₃+ production rate on the surface of Mars were increased by a factor of ~3.