No abstract

[1] The polar cap index (PCI) has been shown to be quite useful as an index of the electrodynamic processes within the high-latitude ionosphere. Here we use between 150 and 180 magnetometers to model the high-latitude electrodynamics with the assimilative mapping of ionospheric electrodynamics (AMIE) technique for all of 1997 -2001. We compare AMIE calculations of the cross polar cap potential (CPCP), polar cap electric field, and polar cap area to the Northern PCI and the existing PCIbased relationships for these quantities. We find that the existing PCI estimates underestimate all of the AMIE derived quantities. The PCI is best correlated with the CPCP, while it correlates least with the polar cap electric field. In addition, there is a seasonal effect in the relationship between all AMIE quantities and the PCI. It is most pronounced in the electric field. The polar cap area is shown to have a linear fit in the summer and an asymptotic fit in the winter. These differences indicate that there may be a conductance difference in the techniques. We derive new relationships between the Northern PCI and the AMIE derived polar cap area, CPCP, and polar cap electric field which include the seasonal dependence.

1] Contemporary magnetosphere models now include species-dependent dynamics. Energetic O + has significant consequences for the energy stored in the ring current, the rate of reconnection, and perhaps the timing of substorm injections. The mechanism by which thermal O + escapes from the top of the ionosphere and into the magnetosphere is not fully understood. Previous studies have used dynamic auroral boundary coordinates to describe the outflowing energetic O + ions above the ionosphere. In this study we focus on the vertical flow of O + ions at lower altitudes before they are accelerated to escape velocity. An algorithm has been devised to identify auroral zone boundaries using precipitating electron observations from the Defense Meteorological Satellite Program (DMSP) spacecraft. Vertical ion flows measured by the DMSP special sensor for ions electrons and scintillation ion drift meter and the retarding potential analyzer instruments aboard the F12 (noonmidnight) and F13 (dawn-dusk) spacecraft from 1997 to 1998 were projected into dynamic auroral boundary coordinates and used to investigate the dependence of Southern Hemisphere bulk flows on interplanetary magnetic field (IMF) and geomagnetic conditions. Initial results show that (1) net upward flows occur primarily in the auroral zone and net downward flows occur primarily in the polar cap, (2) there exists a strong upward flow at 9 magnetic local time (MLT) near the polar cap boundary, 3) the downward ion flow orientation is strongly dependent on IMF By, and 4) the auroral boundary does not coincide exactly with the upward/downward boundary for bulk flows.

Time series data from the Defense Meteorological Satellite Program (DMSP) Operational Linescan System (OLS) have been used to derive georeferenced inventories of human settlements for Europe, North and South America, and Asia. The visible band of the OLS is intensified at night, permitting detection of nocturnal visible‐near infrared emissions from cities, towns, and villages. The time series analysis makes it possible to eliminate ephemeral VNIR emission sources such as fire and to normalize for differences in the number of cloud‐free observations. An examination of the area lit (km2) for 52 countries indicates the OLS derived products may be used to perform the spatial apportionment of population and energy related greenhouse gas emissions.

Abstract. Using the hourly mean AE indices for the past 20 years, amounting to a total of 175,296 hours, we examine how the longitudinal station gaps of the present AE network affect the ability to monitor accurately the auroral electrojets. The latitudinal shift of the auroral electrojet location with magnetic activity also affects the reliability of the AE indices. These combined effects would result in pronounced universal time (UT) variations of the AE indices. By counting the number of occurrences recorded during the given ranges of activity, say every 100 and 200 nT for the A U and AL indices, respectively, for each hour of universal time, the UT variations of the two indices are examined separately. The result demonstrates clearly that they are strongly dependent upon UT. Furthermore, it is noted that the equatorward expansion of the auroral electrojets is more responsible for the UT variation than are the longitudinal station gaps. For the range of the magnetic activity levels examined in this study, i.e., 0 to 500 nT and 0 to -1000 nT for the A U and AL indices, the centers of the eastward and westward electrojets seem to be located within the latitudinal ranges of 71ø-65 ø and 680-62 ø , respectively. The seasonal change of ionospheric conductance also contributes to the UT variation, particularly that of the AL index. While maintaining a similar variation pattern, the amplitude of the variation increases during winter and decreases during summer. It indicates that the UT variation of the AL index is more serious during winter than summer. With more AE stations being located within the former range than the latter, it is easily understood why the AL index is more strongly dependent on UT than is the A U index. Considering such a latitudinal distribution, it is highly probable that the present AL indices often underestimate disturbed conditions during specific universal time intervals, particularly 0200-0800 UT.