High-speed flows in the inner central plasma sheet (first reported by Baumjohann et al. (1990)) are studied, together with the concurrent behavior of the plasma and magnetic field, by using AMPTE/IRM data from • 9 to 19 R•r in the Earth's magnetotail. The conclusions drawn from the detailed analysis of a representative event are reinforced by a superposed epoch analysis applied on 2 years of data. The high-speed flows organize themselves in 10-min time scale flow enhancements which we call bursty bulk flow (BBF) events. Both temporal and spatial effects are responsible for their bursty nature. The flow velocity exhibits peaks of very large amplitude with a characteristic time scale of the order of a minute, which are usually associated with magnetic field dipolarizations and ion temperature increases. The BBFs represent intervals of enhanced earthward convection and energy transport per unit area in the y-z GSM direction of the order of 5 x 10 •9 ergs/R•r 2. 17 R•r and were argued to have an (inferred) scale size of 15 R•r in the Yas• direction and fast shock properties. 1DeparUnent Statistical studies have also been used to characterize plasma sheet flows. Prior to 1986 only a few of these studies addressed plasma sheet flows irrespective of substorm phase [Caan et al., 1979; Hayakawa et al., 1982; Slavin et al. 1985, 1987]. For example, Hayakawa et al. [1982] using IMP 6 data from distances of-15 R•r < XOSM < -33 R•r showed that high-speed flows (V,, > 300 km/s) can occur in the plasma sheet within 1 Re from the expected neutral sheet position defined by the Russell and Brody [1967] model, so one might infer that these flows occurred in the CPS. However, the above statistical studies either did not distinguish between the CPS and its boundary or they concentrated in the distant-tail regions [Slavin et al., 1985, 1987]. The first statistical assessment of the significance of the near-Earth CPS for magnetotail transport was made by Huang and Frank [1986]. They constructed a data base using 128-512 s resolution plasma data from the ISEE 1 satellite. They applied the criterion that high-speed flows (Vi > 150 km/s) occurring 1.5 R•r or more away from the GSM equatorial plane are in the PSBL. They found that the average speed in the CPS was low (around 50 km/s) regardless of geomagnetic activity (based on the AE index). They showed (see also Figure 2 of Huang and Frank [ 1987]) that even if high-speed flows existed in their data set, these were not representative of the average properties of the CPS. They therefore argued that even if high-speed flows of short time or spatial scales may occur in the CPS, they are statistically insignificant compared to the vast majority of the (low flow velocity) data. The above study did not attempt to assess the relative contributions of the CPS and the plasma sheet boundary to magnetotail transport. A new statistical selection criterion to distinguish between the central plasma sheet and its boundary was proposed by Baumjohann et al. [1988] (subsequently referred to as BJeta188): ...

Using 8 months of tail data obtained with the AMPTE/IRM satellite, more than 270,000 ion moments and magnetic field measurements were analyzed with respect to the occurrence rates and typical characteristics of high-speed ion flows with velocities in excess of 400 km/s. The occurrence rates in the plasma sheet boundary layer, the outer central plasma sheet and the neutral sheet neighborhood have a 4:1:2 ratio for flows of 400-600 km/s. For flows in excess of 800 km/s, there is only a minimal chance to detect them in the outer central plasma sheet but equal chances in the two other regions. For high AE the chances to detect high-speed flows in the inner central plasma sheet are greater than to find them in the plasma sheet boundary layer. In the outer central plasma sheet the high-speed flow occurrence rate is small and independent of AE. In all three regions the largest occurrence rates are found near the midnight meridian at the largest radial distances accessible to IRM. High-speed flow occurrence rates and ion densities are anticorrelated. The high-speed flows are bursty with the majority of the flows lasting less than 10 s. The occurrence of the high-speed flows is strongly peaked in the sunward direction. Virtually no tailward high-speed ion flow could be detected. About 60-70% of all high-speed flows near the neutral sheet have a dominant component perpendicular to the magnetic field and are associated with comparatively large northward and duskward magnetic field directions. At times, also appreciable duskward flow components appear. Overall, our results indicate that both the plasma sheet boundary layer and the inner central plasma sheet are important regions for the dynamics of the Earth's plasma sheet. 1.

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International audienceThe eleventh generation of the International Geomagnetic Reference Field (IGRF) was adopted in December 2009 by the International Association of Geomagnetism and Aeronomy Working Group V-MOD. It updates the previous IGRF generation with a definitive main field model for epoch 2005.0, a main field model for epoch 2010.0, and a linear predictive secular variation model for 2010.0–2015.0. In this note the equations defining the IGRF model are provided along with the spherical harmonic coefficients for the eleventh generation. Maps of the magnetic declination, inclination and total intensity for epoch 2010.0 and their predicted rates of change for 2010.0–2015.0 are presented. The recent evolution of the South Atlantic Anomaly and magnetic pole positions are also examined

[1] We have used plasma drift and magnetic field measurements during the [2001][2002][2003][2004][2005][2006][2007][2008][2009] December solstices to study, for the first time, the longitudinal dependence of equatorial ionospheric electrodynamic perturbations during sudden stratospheric warmings. Jicamarca radar measurements during these events show large dayside downward drift (westward electric field) perturbations followed by large morning upward and afternoon downward drifts that systematically shift to later local times. Ground-based magnetometer measurements in the American, Indian, and Pacific equatorial regions show strongly enhanced electrojet currents in the morning sector and large reversed currents (i.e., counterelectrojets) in the afternoon sector with onsets near new and full moons during northern winter warming periods. CHAMP satellite and ground-based magnetic field observations indicate that the onset of these equatorial afternoon counterelectrojets is longitude dependent. Our results indicate that these large electrodynamic perturbations during stratospheric warming periods are due to strongly enhanced semidiurnal lunar wave effects. The results of our study can be used for forecasting the occurrence and evolution of these electrodynamic perturbations during arctic winter warmings.Citation: Fejer, B. G., M. E. Olson, J. L. Chau, C. Stolle, H. Lühr, L. P. Goncharenko, K. Yumoto, and T. Nagatsuma (2010), Lunar-dependent equatorial ionospheric electrodynamic effects during sudden stratospheric warmings,

[1] A global Earth Magnetic Anomaly Grid (EMAG2) has been compiled from satellite, ship, and airborne magnetic measurements. EMAG2 is a significant update of our previous candidate grid for the World Digital Magnetic Anomaly Map. The resolution has been improved from 3 arc min to 2 arc min, and the altitude has been reduced from 5 km to 4 km above the geoid. Additional grid and track line data have been included, both over land and the oceans. Wherever available, the original shipborne and airborne data were used instead of precompiled oceanic magnetic grids. Interpolation between sparse track lines in the oceans was improved by directional gridding and extrapolation, based on an oceanic crustal age model. The longest wavelengths (>330 km) were replaced with the latest CHAMP satellite magnetic field model MF6. EMAG2 is available at http://geomag.org/models/EMAG2 and for permanent archive at http://earthref.org/ cgi-bin/er.cgi?s=erda.cgi?n=970.

The Swarm mission was selected as the 5th mission in ESA's Earth Explorer Programme in 2004. The mission will provide the best ever survey of the geomagnetic field and its temporal evolution that will lead to new insights into the Earth system by improving our understanding of the Earth's interior and its effect on Geospace, the vast region around the Earth where electrodynamic processes are influenced by the Earth's magnetic field. Scheduled for launch in 2010, the mission will comprise a constellation of three satellites, with two spacecraft flying sideby-side at lower altitude (450 km initial altitude), thereby measuring the East-West gradient of the magnetic field, and the third one flying at higher altitude (530 km). High-precision and high-resolution measurements of the strength, direction and variation of the magnetic field, complemented by precise navigation, accelerometer and electric field measurements, will provide the necessary observations that are required to separate and model the various sources of the geomagnetic field. This results in a unique "view" inside the Earth from space to study the composition and processes of its interior. It also allows analysing the Sun's influence within the Earth system. In addition practical applications in many different areas, such as space weather, radiation hazards, navigation and resource management, will benefit from the Swarm concept.

The quasi‐periodic DP 2 magnetic fluctuations (period of 30–40 min) appearing coherently at the auroral and equatorial latitudes during the day are analyzed based on the high time resolution magnetometer data recorded at the International Monitor for Auroral Geomagnetic Effects (IMAGE) stations in Scandinavia and at the Brazilian and African equatorial stations. It is shown that the correlation between the DP 2 magnetic fluctuations at both latitudes is excellent (correlation coefficient of 0.9). No discernible time shift has been found within the resolution of 25 s. The European incoherent scatter (EISCAT) radar observations in Scandinavia show that the DP 2 fluctuations at auroral latitudes are caused by an ionospheric Hall current which is controled by the convection electric field. The DP 2 fluctuations exhibit a strong decrease in magnitude with decreasing latitude, however, it is enhanced considerably at the dip equator with an amplitude comparable to that at the subauroral latitude. The considerable equatorial enhancement of the magnitude of the DP 2 fluctuations with an enhancement ratio of 4 is due to the concentration of the electric current along the highly conductive dayside equatorial ionosphere. These observational facts can be explained in terms of an ionospheric current which is generated by the magnetospheric electric field at the high latitude and extends to the equatorial ionosphere almost instantaneously. From the viewpoint of the electric field penetration, we conclude that the magnetospheric electric field penetrates to the equatorial ionosphere through the polar ionosphere almost instantaneously within the time resolution of 25 s. The nearly instantaneous propagation of the electric field to the equator can be explained primarily by a parallel plane transmission line model composed of the conductive Earth and ionosphere. In addition to our finding of the fast propagation of the DP 2 electric field, it is found that an impulsive magnetic change with a timescale of 100 s appears at the dayside dip equator with a time delay of about 10 s, which requires to include the effect of the high conductivity of the dayside equatorial ionosphere in future studies of the propagation model.