The transterminator ion flow at Venus at solar minimum

The transterminator ion flow in the Venusian ionosphere is observed at solar minimum for the first time. Such a flow, which transports ions from the day to the nightside, has been observed previously around solar maximum. At solar minimum this transport process is severely inhibited by the lower alt...

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Bibliographic Details
Published in:Planetary and space science 2012-12, Vol.73 (1), p.341-346
Main Authors: Wood, A.G., Pryse, S.E., Grande, M., Whittaker, I.C., Coates, A.J., Husband, K., Baumjohann, W., Zhang, T.L., Mazelle, C., Kallio, E., Fränz, M., McKenna-Lawlor, S., Wurz, P.
Format: Article
Language:English
Subjects:
Altitude
Antisunward flow
Asymmetry
Counting
Ion flow
Ion transport
Ionosphere
Ionospherics
Onboard
Spacecraft
Transport
Venus
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Summary:The transterminator ion flow in the Venusian ionosphere is observed at solar minimum for the first time. Such a flow, which transports ions from the day to the nightside, has been observed previously around solar maximum. At solar minimum this transport process is severely inhibited by the lower altitude of the ionopause. The observations presented were those made of the Venusian ionospheric plasma by the ASPERA-4 experiment onboard the Venus Express spacecraft, and which constitute the first extensive in-situ measurements of the plasma near solar minimum. Observations near the terminator of the energies of ions of ionospheric origin showed asymmetry between the noon and midnight sectors, which indicated an antisunward ion flow with a velocity of (2.5±1.5)kms−1. It is suggested that this ion flow contributes to maintaining the nightside ionosphere near the terminator region at solar minimum. The interpretation of the result was reinforced by observed asymmetries in the ion number counts. The observed dawn–dusk asymmetry was consistent with a nightward transport of ions while the noon–midnight observations indicated that the flow was highly variable but could contribute to the maintenance of the nightside ionosphere. ► The transterminator ion flow in the Venusian ionosphere is observed at solar minimum. ► This flow has a velocity of (2.5±1.5)kms−1. ► The occurrence of this flow is highly variable, but can be a significant source of the nightside ionosphere.
ISSN:0032-0633
1873-5088
DOI:10.1016/j.pss.2012.08.006