Heavy Ion Flows in the Upper Ionosphere of the Venusian North Pole

• Published in: Journal of Geophysical Research: Space Physics
• Main Authors: Persson, M., Futaana, Y., Nilsson, H., Stenberg Wieser, G., Hamrin, M., Fedorov, A., Zhang, T. L., Barabash, S.
• Other Authors: Institut de recherche en astrophysique et planétologie (IRAP), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales Toulouse (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales Toulouse (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France-Centre National de la Recherche Scientifique (CNRS)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2019
• Subjects: Venus ionosphere nightward flow; trans-terminator flow; ion dynamics; dusk-to-dawn flow pattern; Venus North Pole; [SDU]Sciences of the Universe [physics]; North Pole; Venus
• Online Access: https://insu.hal.science/insu-03674435; https://insu.hal.science/insu-03674435/document; https://insu.hal.science/insu-03674435/file/JGR%20Space%20Physics%20-%202019%20-%20Persson%20-%20Heavy%20Ion%20Flows%20in%20the%20Upper%20Ionosphere%20of%20the%20Venusian%20North%20Pole.pdf; https://doi.org/10.1029/2018JA026271

International audience We investigate the heavy ion density and velocity in the Venusian upper ionosphere near the North Pole, using the Ion Mass Analyzer, a part of the Analyzer of Space Plasmas and Energetic Atoms 4, together with the magnetic field instruments on Venus Express. The measurements were made during June-July 2014, covering the aerobraking campaign with lowered altitude measurements ( 130 km). The plasma scale heights are 15 km below 150-km altitude and 200 km at 150-400-km altitude. A clear trend of dusk-to-dawn heavy ion flow across the polar ionosphere was found, with speeds of 2-10 km/s. In addition, the flow has a significant downward radial velocity component. The flow pattern does not depend on the interplanetary magnetic field directions nor the ionospheric magnetization states. Instead, we suggest a thermal pressure gradient between the equatorial and polar terminator regions, induced by the decrease in density between the regions, as the dominant mechanism driving the ion flow.