Browsing by Author "Stoneback, R. A."
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Item Open Access Daytime ionospheric equatorial vertical drifts during the 2008–2009 extreme solar minimum(American Geophysical Union, 2015-01-13) Rodrigues, F. S.; Smith, J. M.; Milla, Marco; Stoneback, R. A.One of the most interesting observations made by the Communication/Navigation Outage Forecasting System (C/NOFS) satellite mission was the detection of average equatorial ionospheric vertical drifts that largely differed from model predictions. C/NOFS measurements showed, in particular, downward drifts in the afternoon sector, and upward drifts around local midnight hours during the 2008 and 2009 extreme solar minimum. The unexpected behavior of the drifts has important implications for ionospheric modeling and suggests the necessity for a better understanding of the low‐latitude electrodynamics. We used ground‐based radar measurements to quantify the seasonal and solar flux variability of daytime equatorial drifts at lower altitudes (∼150 km) than those probed by C/NOFS (above ∼400 km). We found that average vertical drifts at 150 km altitude are in good agreement with model predictions of F region drifts and did not show the signatures of an enhanced semidiurnal pattern, as seen by C/NOFS. Comparison of the 150 km echo drifts with model predictions also shows that the increase (decrease) with height of the vertical drifts in the morning (afternoon) hours is a regular feature of the equatorial ionosphere. It occurred in all seasons and solar flux conditions between 2001 and 2011.Item Restricted Daytime zonal drifts in the ionospheric 150 km and E regions estimated using EAR observations(American Geophysical Union, 2017-08-16) Pavan Chaitanya, P.; Patra, A. K.; Otsuka, Y.; Yokoyama, T.; Yamamoto, M.; Stoneback, R. A.; Heelis, R. A.Multibeam observations of the 150 km echoes made using the Equatorial Atmosphere Radar (EAR), located at Kototabang, Indonesia, provide unique opportunity to study both vertical and zonal E × B plasma drifts in the equatorial ionosphere. In this paper, we focus on estimating daytime zonal drifts at the 150 km (140–160 km) and E (100–110 km) regions using multibeam observations of 150 km and E region echoes made using the EAR and study the daytime zonal drifts covering all seasons not studied before from Kototabang. Zonal drifts in the 150 km and E regions are found to be westward and mostly below −80 m s−1 and −60 m s−1, respectively. While the zonal drifts in the 150 km and E regions do not go hand in hand on a case‐by‐case basis, the seasonal mean drifts in the two height regions are found to be in good agreement with each other. Zonal drifts at the 150 km region show seasonal variations with three maxima peaking around May, September, and January. The zonal drifts at the 150 km region are found to be smaller than the F region drifts obtained from Coupled Ion Neutral Dynamics Investigation (CINDI) onboard Communication and Navigation Outage Forecasting System (C/NOFS) by about 25 m s−1 consistent with the height variations of F region zonal drifts observed by the Jicamarca radar. These results constitute the first comprehensive study of zonal drifts at the 150 km and E regions from Kototabang, Indonesia, and the results are discussed in the light of current understanding on the low‐latitude electrodynamics and coupling.