The transterminator ion flow at Venus at solar minimum

Wood, AG ORCID: 0000-0002-7527-4757, Pryse, SE, Grande, M, Whittaker, IC, Coates, AJ, Husband, K, Baumjohann, W, Zhang, T, Mazelle, C, Kallio, E, Fränz, M, McKenna-Lawlor, S and Wurz, P, 2012. The transterminator ion flow at Venus at solar minimum. Planetary and Space Science, 73 (1), pp. 341-346. ISSN 0032-0633

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The transterminator ion flow in the Venusian ionosphere is observed at solar minimum for the first time. This antisunward flow, which transports ions from the day to the nightside, is primarily driven by a pressure gradient caused by photoionisation. Although such a flow was been observed previously around solar maximum, at solar minimum the transport process is severely inhibited by the lower altitude of the ionopause. Observations of ionospheric plasma at solar minimum are routinely made by ASPERA-4 onboard the Venus Express spacecraft and constitute the first extensive in-situ measurements of this plasma under these solar conditions. Observations of ions of ionospheric origin showed asymmetries in both the dawn-dusk and noon-midnight planes for ions of ionospheric origin. Larger numbers of ions are observed on the dusk side than on the dawn side and on the dayside than the nightside, although significant numbers of ions are present nightward of the terminator. Collectively these observations suggest a nightward ion flow with the dawn-dusk asymmetry resulting from variations in the plasma density in the dayside ionosphere. Observations of the ion energies suggest that this flow has a velocity of (2.5 ± 1.5) km s-1. It is suggested that this flow is a significant source of ions for the nightside ionosphere in the terminator region at solar minimum.

Item Type: Journal article
Publication Title: Planetary and Space Science
Creators: Wood, A.G., Pryse, S.E., Grande, M., Whittaker, I.C., Coates, A.J., Husband, K., Baumjohann, W., Zhang, T., Mazelle, C., Kallio, E., Fränz, M., McKenna-Lawlor, S. and Wurz, P.
Publisher: Elsevier
Date: December 2012
Volume: 73
Number: 1
ISSN: 0032-0633
Divisions: Schools > School of Science and Technology
Depositing User: EPrints Services
Date Added: 09 Oct 2015 09:46
Last Modified: 09 Jun 2017 13:10

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