A Highway for Atmospheric Ion Escape from Earth during the Impact of an Interplanetary Coronal Mass Ejection

A single satellite hardly measures the overall ion escape rate from a planet. Therefore, the question concerning the long-term atmospheric evolution of whether a planetary magnetic field protects its atmosphere or aggravates atmospheric loss remains unresolved. Here, combined data from multiple platforms including Cluster, DMSP, IMAGE, and Polar satellites and ground stations show that, when an interplanetary coronal mass ejection (ICME) arrived, an ion transport "highway" formed in the inner magnetosphere on the strongly magnetized Earth, along which the magnetospheric processes promoted quick and significant atmospheric ion escape. The escape rate merely through this highway probably reached 10(27) s(-1), far exceeding the current overall rates on those nonmagnetized planets, e.g., Mars and Venus. The relevant interplanetary conditions induced by the ICME were extreme by today's standards but may have been quite common in the ancient solar system. These present-day observations thus allow us to depict a fast but common ion escape scenario on the strongly magnetized planets in ancient times when the Sun was extremely active.