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@article{Vecchio:2026:0004-6361/202557868,
author = {Vecchio, A and Maksimovic, M and Galand, MIF and Bonnin, X and Astier, P-L and Edberg, NJT and Pía, D and Boldú, JJ and Matteini, L and Chust, T and Hadid, LZ and Kretzschmar, M and Khotyaintsev, YV and Souek, J and Horbury, T and Bale, SD},
doi = {0004-6361/202557868},
journal = {Astronomy and Astrophysics (A & A)},
title = {Electron temperatures in the ionosphere of Venus from Solar Orbiter/Radio and Plasma Waves instrument},
url = {http://dx.doi.org/10.1051/0004-6361/202557868},
volume = {709},
year = {2026}
}
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TY  - JOUR
AB  - Context. On February 18, 2025, Solar Orbiter (SO) completed its fourth gravity assist maneuver of Venus (VGAM4) and reached an unprecedented proximity coming within 378 km of the planet. This flyby was necessary to steer the spacecraft into an orbit outside the plane of the ecliptic. Near the closest approach, only the Radio and Plasma Wave (RPW) and Magnetometer (MAG) instruments were operational; this enabled high-cadence measurements to be taken to investigate the plasma properties of the Venusian ionosphere.Aims. The main goal of this study is to derive the electron density and temperature in the ionosphere of Venus using electric potential measurements from RPW, and to characterize them.Methods. During approximately five minutes around the closest approach, the High Frequency Receiver of RPW detected radio emissions of a type naturally generated by planetary ionospheres whose frequency can be related to the electron density. Using quasithermal noise spectroscopy, we inferred the electron temperature at discrete altitudes and solar zenith angles.Results. Solar Orbiter measured an average density and electron temperature in the ionosphere of Venus of 12 385 ± 148 cm−3 and 0.43 ± 0.05 eV, respectively. These values are in agreement with in-situ measurements by Pioneer Venus Orbiter (PVO) obtained at the solar maximum. Binned magnetic fields and temperatures are anticorrelated, which suggests that the magnetic flux ropes, observed in the Venus ionosphere, are more likely non-force-free structures.Conclusions. The findings presented in this paper, together with the measurement from the Parker Solar Probe (PSP) during the third gravity assist, support the conclusion that the plasma density in the Venusian ionosphere above 350 km varies with solar activity, whereas the electron temperature shows a much weaker dependence. Notably, the electron temperature remains consistent across the three missions (SO, PSP, and PVO), despite varying levels of sola
AU  - Vecchio,A
AU  - Maksimovic,M
AU  - Galand,MIF
AU  - Bonnin,X
AU  - Astier,P-L
AU  - Edberg,NJT
AU  - Pía,D
AU  - Boldú,JJ
AU  - Matteini,L
AU  - Chust,T
AU  - Hadid,LZ
AU  - Kretzschmar,M
AU  - Khotyaintsev,YV
AU  - Souek,J
AU  - Horbury,T
AU  - Bale,SD
DO  - 0004-6361/202557868
PY  - 2026///
SN  - 0004-6361
TI  - Electron temperatures in the ionosphere of Venus from Solar Orbiter/Radio and Plasma Waves instrument
T2  - Astronomy and Astrophysics (A & A)
UR  - http://dx.doi.org/10.1051/0004-6361/202557868
UR  - https://doi.org/10.1051/0004-6361/202557868
VL  - 709
ER  -
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