Topside Equatorial Zonal Ion Velocities Measured by C/NOFS During Rising Solar Activity

dc.contributor.ISNI0000 0000 3175 0999 (Heelis, RA)
dc.contributor.LCNA88021080‏ (Heelis, RA)
dc.contributor.authorColey, W. R.en_US
dc.contributor.authorStoneback, Russell A.en_US
dc.contributor.authorHeelis, Rodney A.en_US
dc.contributor.authorHairston, M. R.en_US
dc.contributor.utdAuthorColey, W. R.en_US
dc.contributor.utdAuthorStoneback, Russell A.en_US
dc.contributor.utdAuthorHeelis, Rodney A.en_US
dc.contributor.utdAuthorHairston, M. R.en_US
dc.description.abstractThe Ion Velocity Meter (IVM), a part of the Coupled Ion Neutral Dynamic Investigation (CINDI) instrument package on the Communication/Navigation Outage Forecast System (C/NOFS) spacecraft, has made over 5 yr of in situ measurements of plasma temperatures, composition, densities, and velocities in the 400-850 km altitude range of the equatorial ionosphere. These measured ion velocities are then transformed into a coordinate system with components parallel and perpendicular to the geomagnetic field allowing us to examine the zonal (horizontal and perpendicular to the geomagnetic field) component of plasma motion over the 2009-2012 interval. The general pattern of local time variation of the equatorial zonal ion velocity is well established as westward during the day and eastward during the night, with the larger nighttime velocities leading to a net ionospheric superrotation. Since the C/NOFS launch in April 2008, F10.7 cm radio fluxes have gradually increased from around 70 sfu to levels in the 130-150 sfu range. The comprehensive coverage of C/NOFS over the low-latitude ionosphere allows us to examine variations of the topside zonal ion velocity over a wide level of solar activity as well as the dependence of the zonal velocity on apex altitude (magnetic latitude), longitude, and solar local time. It was found that the zonal ion drifts show longitude dependence with the largest net eastward values in the American sector. The pre-mid-night zonal drifts show definite solar activity (F10.7) dependence. The daytime drifts have a lower dependence on F10.7. The apex altitude (magnetic latitude) variations indicate a more westerly flow at higher altitudes. There is often a net topside subrotation at low F10.7 levels, perhaps indicative of a suppressed F region dynamo due to low field line-integrated conductivity and a low F region altitude at solar minimum.en_US
dc.identifier.bibliographicCitationColey, W. R., R. A. Stoneback, R. A. Heelis, and M. R. Hairston. 2014. "Topside equatorial zonal ion velocities measured by C/NOFS during rising solar activity." Annales Geophysicae 32(2), doi:10.5194/angeo-32-69-2014en_US
dc.publisherCopernicus Gesellschaft Mbhen_US
dc.rightsCC BY 3.0 (Attribution)en_US
dc.rights©2014 The Authorsen_US
dc.sourceAnnales Geophysicae
dc.subjectEquatorial ionosphereen_US
dc.subjectIonosphere-atmosphere interactionsen_US
dc.subjectPlasma convectionen_US
dc.subjectPlasma driftsen_US
dc.titleTopside Equatorial Zonal Ion Velocities Measured by C/NOFS During Rising Solar Activityen_US


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