资源环境科技发展态势分析平台

Cold ion outflow is one of the candidate processes to cause significant atmospheric escape from Mars. We here report on the cold dense heavy ion outflow event observed in Martian-induced magnetotail by Mars Atmosphere and Volatile EvolutioN (MAVEN) on 4 December 2014. In the outflow event, the cold dense heavy ion outflow was observed only in south dusk downward convection electric field (E) lobe. During the event, the strong crustal magnetic field was located on dayside of Mars. It suggests that combination of minimagnetosphere and downward E facilitates the cold dense heavy ion outflow. In order to estimate the CO2+ density, we adopted a fitting method of log-normal distribution to the O-2(+) time of flight distributions to eliminate O-2(+) contamination in the CO2+ time of flight data. Contribution of O-2(+), O+, and CO2+ to the total heavy ions (similar to 134 cm(-3)) is about 71%, 26%, and 3%, respectively. Average heavy ion flux was similar to 5.4 x 10(7) cm(-2) s(-1), assuming the escape velocity at 2,000-km altitude.