Solar wind‐driven thermospheric winds over the Venus North Polar region

Lundin, R.; Barabash, S.; Futaana, Yoshifumi; Holmström, M.; Sauvaud, J. A.; Fedorov, A.

doi:10.1002/2014gl060605

Cited by 5 publications

(11 citation statements)

References 19 publications

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“…The direction of the heavy ion flow in the 130–600‐km altitude range in the terminator region is dusk‐to‐dawn (Figure a). The flow pattern is consistent with those of energetic neutral atom and heavy ions measured above 250 km, previously investigated by Lundin et al (). In addition, Figure b demonstrates that the ions generally have a downward motion.…”

Section: Resultssupporting

confidence: 91%

“…Another possible acceleration mechanism is momentum transfer from the solar wind to the ionosphere (Lundin et al, ). Lundin et al () claim that momentum transfer is significant from their altitude profiles of the fluxes. However, the influence of the solar wind should be small in the lower altitude (<400 km) due to the very low fluxes.…”

Section: Discussionmentioning

confidence: 99%

“…Ion measurements from the Analyzer of Space Plasmas and Energetic Atoms (ASPERA‐4) instrument on board VEx showed that the ions and energetic neutral atoms have a strong dusk‐to‐dawn flow across the pole at altitudes higher than 250 km, in contrast with the measurements of PVO in the equatorial atmosphere. The mass flux of the ionospheric ions was observed to increase below the ionopause, while the solar wind mass flux decreased, which could indicate a transfer of momentum from the solar wind to the ionospheric heavy ions by means of friction between the two plasma populations (Lundin et al, , ). Lundin et al () hypothesized that the dusk‐to‐dawn flow pattern over the pole is a consequence of the 5° aberration angle of the solar wind from the orbital motion of Venus.…”

Section: Introductionmentioning

confidence: 99%

“…The mass flux of the ionospheric ions was observed to increase below the ionopause, while the solar wind mass flux decreased, which could indicate a transfer of momentum from the solar wind to the ionospheric heavy ions by means of friction between the two plasma populations (Lundin et al, , ). Lundin et al () hypothesized that the dusk‐to‐dawn flow pattern over the pole is a consequence of the 5° aberration angle of the solar wind from the orbital motion of Venus. The momentum transfer to the ionosphere would happen through wave‐particle interactions at the induced magnetosphere boundary, and through Coulomb collisions between the ionospheric ions to the lower altitudes (Perez‐de‐Tejada et al, ).…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2019

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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. Plain Language SummaryWe have calculated the ion density and velocities in the Venusian polar ionosphere using measurements from the Ion Mass Analyzer on board the Venus Express spacecraft. During June-July 2014 the periapsis was lowered to~130 km, which allowed for measurements down to low altitudes of the ionosphere near the North Pole. The plasma scale heights are~15 km below 150-km altitude and~200 km at 150-400 km, which is similar to what was found near the equatorial region by the Pioneer Venus mission. In addition, there is a clear trend of dusk-to-dawn flow, along the terminator, for the heavy ions. This is surprising, as a general flow from day-to-night is expected for the Venusian ionosphere due to the long nights and significant heating of the dayside upper atmosphere. The interplanetary magnetic field direction does not appear to affect the ion flow pattern. Instead, we propose a thermal pressure gradient as the dominant accelerating mechanism, induced by the decrease in density from the equator toward the pole.

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Section: Resultssupporting

confidence: 91%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

et al. 2019

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“…In the ionosphere, the plasma velocity is actually dominated by the components along the Y VSO axis (with a contribution of ≈46%) followed by Z VSO (≈39%) and X VSO (≈15%) axes. These results are consistent with Lundin et al(, , ) in which the authors attributed the persistent + Y VSO directed ion flow over the northern polar region to the solar wind aberration.…”

Section: Discussionsupporting

confidence: 93%

A Statistical Study of Ionospheric Boundary Wave Formation at Venus

et al. 2018

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Previous missions to Venus have revealed that encounters with plasma irregularities of atmospheric origin outside the atmosphere are not uncommon. A number of mechanisms have been proposed to discuss their origins as well as their roles in the atmospheric evolution of Venus. One such mechanism involves an ionopause with a wavelike appearance. By utilizing the magnetic field and plasma data from Venus Express, we present the first observational statistical analysis of the ionospheric boundary wave phenomena at Venus using data from 2006 to 2014. Results from the minimum variance analysis of all the photoelectron dropout events in the ionosphere reveal that the ionopause of Venus does not always appear to be smooth but often exhibits a wavelike appearance. In the northern polar region of Venus, the normal directions of the rippled ionospheric boundary crossings lie mainly in the terminator plane with the largest component predominantly along the dawn‐dusk (YVSO) direction. The average estimated wavelength of the boundary wave is 212 ± 12 km, and the average estimated velocity difference across the ionopause is 104 ± 6 km/s. The results suggest that the rippled boundary is a result of Kelvin‐Helmholtz instability. Analysis reveals a correlation between the normal directions and the locations of the boundary wave with respect to Venus. This indicates that the draping of magnetic field lines may play a role in enhancing the plasma flow along the dawn‐dusk direction, which could subsequently set up a velocity shear that favors the excitation of ionospheric boundary wave by the Kelvin‐Helmholtz instability along the dawn‐dusk direction.

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Plasma-neutral gas interactions in various space environments: Assessment beyond simplified approximations as a Voyage 2050 theme

et al. 2022

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In the White Paper, submitted in response to the European Space Agency (ESA) Voyage 2050 Call, we present the importance of advancing our knowledge of plasma-neutral gas interactions, and of deepening our understanding of the partially ionized environments that are ubiquitous in the upper atmospheres of planets and moons, and elsewhere in space. In future space missions, the above task requires addressing the following fundamental questions: (A) How and by how much do plasma-neutral gas interactions influence the re-distribution of externally provided energy to the composing species? (B) How and by how much do plasma-neutral gas interactions contribute toward the growth of heavy complex molecules and biomolecules? Answering these questions is an absolute prerequisite for addressing the long-standing questions of atmospheric escape, the origin of biomolecules, and their role in the evolution of planets, moons, or comets, under the influence of energy sources in the form of electromagnetic and corpuscular radiation, because low-energy ion-neutral cross-sections in space cannot be reproduced quantitatively in laboratories for conditions of satisfying, particularly, (1) low-temperatures, (2) tenuous or strong gradients or layered media, and (3) in low-gravity plasma. Measurements with a minimum core instrument package (< 15 kg) can be used to perform such investigations in many different conditions and should be included in all deep-space missions. These investigations, if specific ranges of background parameters are considered, can also be pursued for Earth, Mars, and Venus.

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Solar wind‐driven thermospheric winds over the Venus North Polar region

Cited by 5 publications

References 19 publications

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

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

A Statistical Study of Ionospheric Boundary Wave Formation at Venus

Plasma-neutral gas interactions in various space environments: Assessment beyond simplified approximations as a Voyage 2050 theme

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