Figure - available from: Geophysical Research Letters
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Top panels: Observed electron density (blue color) by Akatsuki‐RS experiment on 21 November 2021. Red shows the simulated electron density by 1D‐PCM. The difference in both depicts the V0 layer in the top right panel. Bottom Panels: The similar observation as above by Venus Radio Science experiment on 31 January 2007. Vertical lines in black and red color show the mean and standard deviation in electron density above the 400 km altitude.
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Venus is known to have a peak in the plasma density at ∼140 km altitude (V2 layer), and a secondary permanent peak at ∼127 km (V1 layer). A sporadic enhancement in the electron density below 120 km altitude (now known as V0 layer) has also been reported. Earlier believed to be geographically localized, Akatsuki measurements h...
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Inspired by the observations suggesting that at altitudes of about $1000$ km the interaction between solar wind streams and Venus' ionosphere plasma leads to ions acceleration and outflow, the influence of different solar wind physical parameters, such as densities, temperatures and initial streaming velocities, has been studied. The ionosphere pla...
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Previous investigations have suggested that Venus has a much stronger electrical potential in its ionosphere than expected. This electrical potential is important as it helps charged particles escape into space. At Venus, the potential can be strong enough to directly propel all water‐group ions (including oxygen) to escape v...
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... Absorption of X-rays having a wavelength less than 20 Å was also considered to be a possible source (Fox & Sung, 2001). A recent study using Akatsuki measurements discusses various sources of its origin including forcings from the lower atmosphere (Tripathi, Choudhary, Jose, et al., 2023). The origin of V 0 layers, however, still remains an open question. ...
Plain Language Summary
The planetary ionosphere forms by the ionization of available neutrals via various ionization sources, like solar radiations, and solar energetic particles. Depending upon the neutral composition and solar flux, different layers of the ionosphere form at different heights. Based on the ion distribution, the Venusian ionosphere is divided into four layers, namely V3, V2, V1, and V0. The impact of low solar activity conditions on the characteristics of these layers has been studied using the radio science payload onboard the Akatsuki orbiter, which is truly the first near‐equatorial orbiting satellite. Observations show a clear impact of the low solar activity period on its primary (V2) and secondary (V1) peak electron densities which are the minimum reported so far. The heights corresponding to these peaks do not vary with respect to the solar zenith angle, unlike on Earth. A major highlight of observation is the presence of the V0 layer at 110 ± 4 km altitude. Earlier it was observed to be sporadic in nature occurring mostly during morning and evening hours. The nightside ionosphere has been rarely observed despite good coverage, which helps to surmise that no discernible electron density is transported from dayside to nightside during the profound solar minima.
