Engwall, E. et al. Earthâs ionospheric outflow dominated by hidden cold plasma. Nat. Geosci. 2, 24â27 (2009).
Haaland, S. et al. Estimating the capture and loss of cold plasma from ionospheric outflow. J. Geophys. Res. Space Phys. 117, A07311 (2012).
André, M., Toledo-Redondo, S. & Yau, A. W. in Space Physics and Aeronomy Collection Vol. 2: Magnetospheres in the Solar System (eds Maggiolo, R. et al.) Geophysical Monograph 259 (American Geophysical Union, Wiley, 2021).
Kistler, L. M. et al. Cusp and nightside auroral sources of O+ in the plasma sheet. J. Geophys. Res. Space Phys. 124, 10036â10047 (2019).
Strangeway, R. J., Ergun, R. E., Su, Y.-J., Carlson, C. W. & Elphic, R. C. Factors controlling ionospheric outflows as observed at intermediate altitudes. J. Geophys. Res. Space Phys. 110, A03221 (2005).
Collinson, G. et al. Ionospheric ambipolar electric fields of Mars and Venus: comparisons between theoretical predictions and direct observations of the electric potential drop. Geophys. Res. Lett. 46, 1168â1176 (2019).
Moore, T. E. & Khazanov, G. V. Mechanisms of ionospheric mass escape. J. Geophys. Res. Space Phys. 115, A00J13 (2010).
Axford, W. I. The polar wind and the terrestrial helium budget. J. Geophys. Res. 73, 6855â6859 (1968).
Banks, P. M. & Holzer, T. E. The Polar Wind. J. Geophys. Res. Space Phys. 73, 6846â6854 (1968).
Li, K. et al. The effects of the polar rain on the polar wind ion outflow from the nightside ionosphere. J. Geophys. Res. Space Phys. 128, e2023JA031496 (2023).
Varney, R. H., Solomon, S. C. & Nicolls, M. J. Heating of the sunlit polar cap ionosphere by reflected photoelectrons. J. Geophys. Res. Space Phys. 119, 8660â8684 (2014).
Khazanov, G. V., Liemohn, M. W. & Moore, T. E. Photoelectron effects on the self-consistent potential in the collisionless polar wind. J. Geophys. Res. Space Phys. 102, 7509â7521 (1997).
Collinson, G. A. et al. The electric wind of Venus: a global and persistent âpolar windâ-like ambipolar electric field sufficient for the direct escape of heavy ionospheric ions. Geophys. Res. Lett. 43, 5926â5934 (2016).
Xu, S. et al. Field-aligned potentials at Mars from MAVEN observations. Geophys. Res. Lett. 45, 10,119â10,127 (2018).
Xu, S., Frahm, R. A., Ma, Y., Luhmann, J. G. & Mitchell, D. L. Magnetic topology at Venus: new insights into the Venus plasma environment. Geophys. Res. Lett. 48, e2021GL095545 (2021).
Collinson, G. A. et al. A survey of strong electric potential drops in the ionosphere of Venus. Geophys. Res. Lett. 50, e2023GL104989 (2023).
Coates, A. J., Jonstone, A. D., Sojka, J. J. & Wrenn, G. L. Ionospheric photoelectrons observed in the magnetosphere at distances up to 7 earth radii. Planet. Space Sci. 33, 1267â1275 (1985).
Fung, S. F. & Hoffman, R. A. A search for parallel electric fields by observing secondary electrons and photoelectrons in the low-altitude auroral zone. J. Geophys. Res. Space Phys. 96, 3533â3548 (1991).
Collinson, G. et al. The Endurance Rocket Mission. Space Sci. Rev. 218, 39 (2022).
Coates, A. J. et al. Ionospheric photoelectrons: comparing Venus, Earth, Mars and Titan. Planet. Space Sci. 59, 1019â1027 (2011).
Collinson, G. A. et al. Rocket measurements of electron energy spectra from Earthâs photoelectron production layer. Geophys. Res. Lett. 49, e2022GL098209 (2022).
Gardner, J. L. & Samson, J. A. R. 304âà photoelectron spectra of CO, N2, O2 and CO2. J. Electron Spectros. Relat. Phenomena 2, 259â266 (1973).
Goembel, L., Doering, J. P., Morrison, D. & Paxton, L. J. Atmospheric O/N2 ratios from photoelectron spectra. J. Geophys. Res. 102, 7411â7419 (1997).
Gombosi, T. I. & Nagy, A. Time-dependent modeling of field-aligned current-generated ion transients in the polar wind. J. Geophys. Res. 94, 359â369 (1989).
Liemohn, M. W., Khazanov, G. V., Moore, T. E. & Guiter, S. M. Self-consistent superthermal electron effects on plasmapheric refilling. J. Geophys. Res. 102, 7523â7536 (1997).
Godbole, N. H. et al. Observations of ion upflow and 630.0 nm emission during pulsating aurora. Front. Phys. 10, 997229 (2022).
Wahlund, J.-E., Opgenoorth, H. J., Häggström, I., Winser, K. J. & Jones, G. O. L. EISCAT observations of topside ionospheric ion outflows during auroral activity: revisited. J. Geophys. Res. 97, 3019â3037 (1992).
Wu, J. et al. Observations of the structure and vertical transport of the polar upper ionosphere with the EISCAT VHF radar. II – first investigations of the topside O(+) and H(+) vertical ion flows. Ann. Geophys. 10, 375â393 (1992).
Collinson, G. et al. Electric Mars: a large trans-terminator electric potential drop on closed magnetic field lines above Utopia Planitia. J. Geophys. Res. Space Phys. 112, 2260â2271 (2017).
Schunk, R. & Nagy, A. Ionospheres (Cambridge Univ. Press, 2009).
Collinson, G., Chornay, D. J., Glocer, A., Paschalidis, N. & Zesta, E. A hybrid electrostatic retarding potential analyzer for the measurement of plasmas at extremely high energy resolution. Rev. Sci. Instrum. 89, 113306 (2018).
Oyama, K. & Takumi, A. Anisotropy of electron temperature in the ionosphere. Geophys. Res. Lett. 14, 1195â1198 (1987).