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ISSN  2096-3955

CN  10-1502/P

Citation: Han, Q. Q., Fraenz, M., Wei, Y., Dubinin, E., Cui, J. Chai, L. H., Rong, Z. J., Wan, W. X., and Futaana, Y. (2020). EUV-dependence of Venusian dayside ionopause altitude: VEX and PVO observations. Earth Planet. Phys., 4(1), 73–81.doi: 10.26464/epp2020011

2020, 4(1): 73-81. doi: 10.26464/epp2020011


EUV-dependence of Venusian dayside ionopause altitude: VEX and PVO observations


Key Laboratory of Earth and Planetary Physics, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China


Beijing National Observatory of Space Environment, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100049, China


College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing 100049, China


Max-Planck-Institute for Solar System Research, Goettingen, DE 37077, Germany


Institutions of Earth Science, Chinese Academy of Sciences, Beijing 100029, China


School of Atmospheric Sciences, Sun Yat-Sen University, Zhuhai Guangdong 519082, China


Key Laboratory of Lunar and Deep Space Exploration, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, China


Swedish Institute of Space Physics, Kiruna, SE 98128, Sweden

Corresponding author: Yong Wei,

Received Date: 2019-09-20
Web Publishing Date: 2020-01-01

The Venusian dayside ionosphere, similar to other planetary ionospheres, is produced primarily by ionization of its neutral upper atmosphere due to solar extreme ultraviolet (EUV) radiation. It has become clear that the expansion of the ionosphere may be strongly controlled by the EUV level, as exhibited in data collected by the Pioneer Venus Orbiter (PVO) during one solar cycle (1978–1992). However, the EUV-dependence of the Venusian dayside ionopause altitude, which defines the outer boundary of the ionosphere, remains obscure because the PVO crossed the dayside ionopause only during the solar maximum; its periapsis lifted too high during the solar minimum. Recently, during the period 2006–2014, which included the longest and quietest solar minimum of the past several decades, Venus Express (VEX) provided measurements of the photoelectron boundary (PEB) over the northern high-latitude region. Since the photoelectron boundary is closely related to the ionopause, we have an opportunity to analyze the EUV effect on the dayside ionopause by combining PVO and VEX observations. We have evaluated and then reduced the orbit bias effect in data from both PVO and VEX, and then used the results to derive a relationship between solar EUV level and the dayside ionopause altitude. We find that the dayside ionopause altitude increases as the solar EUV level increases, which is consistent with theoretical expectations.

Key words: Venus, ionopause, ionosphere, solar activity

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EUV-dependence of Venusian dayside ionopause altitude: VEX and PVO observations

QianQian Han, Markus Fraenz, Yong Wei, Eduard Dubinin, Jun Cui, LiHui Chai, ZhaoJin Rong, WeiXing Wan, Yoshifumi Futaana