Abstract
Atmospheric loss and ion outflow play an important role in the magnetospheric dynamics and in the evolution of the atmosphere on geological timescales—an evolution which is also dependent on the solar activity. In this paper, we investigate the total hbox{O}^+ outflow [hbox{s}^{-1}] through the plasma mantle and its dependency on several solar wind parameters. The oxygen ion data come from the CODIF instrument on board the spacecraft Cluster 4 and solar wind data from the OMNIWeb database for a period of 5 years (2001–2005). We study the distribution of the dynamic pressure and the interplanetary magnetic field for time periods with available hbox{O}^+ observations in the plasma mantle. We then divided the data into suitably sized intervals. Additionally, we analyse the extreme ultraviolet radiation (EUV) data from the TIMED mission. We estimate the hbox{O}^+ escape rate [ions/s] as a function of the solar wind dynamic pressure, the interplanetary magnetic field (IMF) and EUV. Our analysis shows that the hbox{O}^+ escape rate in the plasma mantle increases with increased solar wind dynamic pressure. Consistently, it was found that the southward IMF also plays an important role in the hbox{O}^+ escape rate in contrast to the EUV flux which does not have a significant influence for the plasma mantle region. Finally, the relation between the hbox{O}^+ escape rate and the solar wind energy transferred into the magnetosphere shows a nonlinear response. The hbox{O}^+ escape rate starts increasing with an energy input of approximately 10^{11} {hbox{W}}.
Highlights
The Sun plays an important role in terrestrial atmospheric loss
The polar cap represents the mapping of the open field lines to the ionosphere, whereas the cusp is a funnel between the dayside closed magnetic field lines and the open magnetic field lines
Solar wind dynamic pressure and interplanetary magnetic field Based on previous studies of ion escape at Mars by Ramstad et al (2015, 2017), we first looked at the solar wind velocity and density distributions
Summary
The Sun plays an important role in terrestrial atmospheric loss. It is believed that billions of years ago, the Sun was more active than today. The Earth’s atmospheric loss is an important phenomenon which may affect the evolution of the atmosphere on geological timescales This terrestrial phenomenon is driven, at lower altitudes ( ∼ 2 Earth radius [Re]), by atmospheric ions energised to a few eV and photoelectrons called the Schillings et al Earth, Planets and Space (2019) 71:70 field line regions: the polar cap, cusp and plasma mantle. The polar cap represents the mapping of the open field lines to the ionosphere, whereas the cusp is a funnel between the dayside closed magnetic field lines and the open magnetic field lines This funnel provides a direct entry for magnetosheath plasma into the magnetosphere. The plasma mantle located downstream of the cusp has a mixed plasma population of ionospheric and magnetosheath ions It is, dominated by solar wind ions conducted by the mirror force. Several studies have been conducted in different magnetospheric regions to determine how the solar wind affects the O+ outflow (e.g Palmroth et al 2001; Abe et al 1996; Denton and Taylor 2008; Gou et al 2016)
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