Geomagnetic Quiet Research Articles

On the relationship between the postmidnight thermospheric equatorial mass anomaly and equatorial ionization anomaly under geomagnetic quiet conditions

The equatorial mass anomaly (EMA) in the thermosphere and equatorial ionization anomaly (EIA) in the ionosphere are two interesting phenomena in low-equatorial latitude regions. Previous studies have shown that the EMA appears between 1000 and 2000 local time (LT) and its location of trough is aligned with dip equator, indicating the plausible role of the EIA structure in the development of EMA. In this report, we conducted a statistical study of the occurrence of postmidnight EMA and EIA on the basis of the CHAMP in situ measurements during 2002-2008. Our results revealed that clear EMA and EIA structures are sometimes visible in the postmidnight sector (0100-0600 LT) during geomagnetic quiet periods (Kp < 3). The postmidnight EMA is not necessarily accompanied by the EIA signature in both case study and statistics sense being distinct from the daytime situation. In addition, the occurrence rates of postmidnight EMA and EIA display contrasting behavior with respect to their local time, longitudinal and solar activity dependences. The highest occurrence rate for EMA is 8% at around 0300 LT, while the occurrence rate of the EIA decreases gradually from about 30% at around 2300 LT to similar to 5% at 0600 LT. Longitudinal occurrence of postmidnight EIA presents a wave-like pattern; however, no salient feature appears for the longitudinal occurrence of EMA. Postmidnight EMA is more likely to occur at lower solar activity, whereas an opposite trend presents in the EIA. On the basis of above results, our findings imply that a simple EIA-EMA cause-effect relationship does not hold in the postmidnight sector.

Peculiarities of the nighttime winter foF2 increase over Irkutsk

An analysis of properties and peculiarities of the nighttime winter foF2 increases (NWI) in the East Siberia is made on data of ionospheric station Irkutsk in the periods 1958–1992 and 2002–2009 and the empirical model of the F2 layer critical frequency under the geomagnetic quiet conditions deduced from these data (model Q-F2). It is revealed, that the NWI is the stable regularity of the quiet ionosphere over Irkutsk. The amplitude of the NWI (the difference between maximum and minimum foF2 values at night hours) is the greatest in December–January and nearly the same at low and middle solar activity. It is a peculiarity of the quiet ionosphere in the East Siberia. Maximum in night foF2 under quiet geomagnetic conditions is observed mainly after midnight (02-04 LT) and is shifted to predawn hours as solar activity increases. At low solar activity the quiet ionosphere at ∼02–04 LT shows the following properties: (a) the fluctuations of foF2 and hmF2 are in the reverse correlation but this dependence is weak; (b) very strong fluctuations of foF2 (|δfoF2| > 30%) occur seldom (∼4% of events) and almost all of them are positive; an example of very strong fluctuations of foF2 up to 60% can be an extreme increase in the foF2 on 19.12.2008; (c) the very strong enhancements of foF2 in the NWI maximum can be observed at the low geomagnetic activity, they occur more often during substorms but very seldom during geomagnetic storms. Possible reasons of these properties of NWI are discussed.

Low Latitude Ionospheric Electrodynamics

The low latitude ionosphere is strongly affected by several highly variable electrodynamic processes. Over the last two decades ground-based and satellite measurements and global numerical models have been extensively used to study the longitude-dependent climatology of low latitude electric fields and currents. These electrodynamic processes and their ionospheric effects exhibit large ranges of temporal and spatial variations during both geomagnetic quiet and disturbed conditions. Numerous recent studies have investigated the short term response of equatorial electric fields and currents to lower atmospheric transport processes and solar wind-magnetosphere driving mechanisms. This includes the large electric field and current perturbations associated with arctic sudden stratospheric warming events during geomagnetic quiet times and highly variable storm time prompt penetration and ionospheric disturbance dynamo effects. In this review, we initially describe recent experimental and numerical modeling results of the global climatology and short term variability of quiet time low latitude electrodynamic plasma drifts. Then, we examine the present understanding of equatorial electric field and current perturbation fields during periods of enhanced geomagnetic activity.

COSMIC/FORMOSAT‐3 observations of equatorial F region irregularities in the SAA longitude sector

The data of ionospheric electron density and S4 scintillation index from COSMIC/FORMOSAT‐3 GPS occultation soundings are used to study the morphology of the equatorial F region irregularity (EFI) in the longitude sector (0°∼75°W) where the South Atlantic magnetic anomaly (SAA) is located. Launched into low Earth orbits on 14 April 2006, the six‐satellite constellation COSMIC provides daily global measurements of the ionosphere at altitudes below ∼800 km. The large data set enables us a statistically correlative study of electron density depletion and GPS L1 scintillation, which allows the global and altitudinal distributions of irregularity to be examined. Under solar minimum and geomagnetic quiet conditions, postsunset EFI/scintillation events are found to concentrate in the SAA longitude sector during northern winter months (D months), but nearly disappeared in the same longitude sector during the opposite season (J months). The D months’ average pattern of EFI reveals that most of irregularities occurred in the bottom side F region (200–350 km altitude) and at low magnetic latitudes adjacent to the locations of the maximum postsunset Nmax and Hmax. This is consistent with the early postsunset irregularities that are generated in the region where plasma upward drifts have been greatly enhanced. By examining the UT snapshots of the global distributions of electron density and scintillation events, strong spatial correlations are found to exist among the sunset terminator, the westward declined geo‐magnetic field, strong scintillation event, and density depletion in the SAA longitude sector only during D months, where the E region sunset terminator is most possibly parallel to the magnetic field direction at equatorial latitudes. Density depletion structures within this longitude sector were bounded by two postsunset ionization enhancement bands (EIA) that extended over central SAA and its conjugated region, respectively. Such features provide further evidence that the enhanced conductivity gradients due to particle induced ionization in the vicinity of SAA contribute additional electric field enhancements in the equatorial F region. At the walls of the depletion region near the sunset lines, prominent horizontal density gradients exist in both westward and southward directions due to sun setting and SAA ionization enhancement, respectively. The combination of horizontal density gradients with antiparallel (north‐eastward) neutral winds during D months can contribute additional growth rate to the EFI generation. These COSMIC observations not only confirm that the sunset equatorial electrodynamics plays a key role in controlling the seasonal and longitudinal occurrences of the quiet time EFI, but also reveal that seasonally dependent ionospheric responses to the energetic particle precipitation in SAA can affect considerably the morphology of EFI in the SAA longitude sector.

A new ionospheric tomographic algorithm — constrained multiplicative algebraic reconstruction technique (CMART)

For the limitation of the conventional multiplicative algebraic reconstruction technique (MART), a constrained MART (CMART) is proposed in this paper. In the new tomographic algorithm, a popular two-dimensional multi-point finite difference approximation of the second order Laplacian operator is used to smooth the electron density field. The feasibility and superiority of the new method are demonstrated by using the numerical simulation experiment. Finally, the CMART is used to reconstruct the regional electron density field by using the actual GNSS data under geomagnetic quiet and disturbed days. The available ionosonde data from Beijing station further validates the superiority of the new method.

Storm time electric fields in the equatorial ionosphere observed near the dusk meridian

We compare the dynamics of plasma drifts (VP) and ionospheric electric fields (EI), measured near the dusk meridian at the magnetic equator by the Defense Meteorological Satellite Program (DMSP) F13 satellite, with those of the dawn‐to‐dusk component of the interplanetary electric field (IEF) Ey during four large magnetic storms. Presented data indicate that during the main phase of the magnetic storms when the interplanetary magnetic field (IMF) had a southward component, VP had upward and westward components that ranged up to 120 and 210 m s−1. The corresponding eastward and upward components of EI were approximately 5% and 10% of Ey. The persistence of eastward EI for many hours indicates that electric field shielding of the inner magnetosphere is ineffective during prolonged periods of southward IMF. During periods of northward IMF (Ey &lt; 0) ionospheric responses depended on prior history. No ionospheric response is apparent after strong northward IMF turnings preceded by geomagnetic quiet. If they occurred after a long southward interval, EI often had westward and downward components. The polarity of the zonal component of EI remained well correlated with that of Ey for up to 21 h during periods of slowly varying IMF. Phenomena associated with southward IMF periods are consistent with models that allow for prolonged penetration electric field from high latitudes superposed on those of the Sq current system. However, it is not understood why the remarkable correspondence between the polarities of the zonal component of EI and the IEF Ey occurs during northward IMF. In some Ey &lt; 0 periods, the vertical component of EI remained upward. DMSP detections of upward EI (westward VP) during periods of Ey &lt; 0 are not predicted by existing models.

Electrojet-independent ionospheric extremely low frequency/very low frequency wave generation by powerful high frequency waves

Results of extremely low frequency/very low frequency (ELF/VLF) wave generation by intensity-modulated high frequency (HF) heaters of 3.2 MHz in Gakona, Alaska, near local solar noon during a geomagnetic quiet time, are presented to support an electrojet-independent ELF/VLF wave generation mechanism. The modulation was set by splitting the HF transmitter array into two subarrays; one was run at cw full power and the other run alternatively at 50% and 100% power modulation by rectangular waves of 2.02, 5, 8, and 13 kHz. The most effective generation was from the X-mode heater with 100% modulation. While the 8 kHz radiation has the largest wave amplitude, the spectral intensity of the radiation increases with the modulation frequency, i.e., 13 kHz line is the strongest. Ionograms recorded significant virtual height spread of the O-mode sounding echoes. The patterns of the spreads and the changes of the second and third hop virtual height traces caused by the O/X-mode heaters are distinctively different, evidencing that it is due to differently polarized density irregularities generated by the filamentation instability of the O/X-mode HF heaters.

Spectral analysis of pipe-to-soil potentials with variations of the Earth's magnetic field in the Australian region

[1] Long, steel pipelines used to transport essential resources such as gas and oil are potentially vulnerable to space weather. In order to inhibit corrosion, the pipelines are usually coated in an insulating material and maintained at a negative electric potential with respect to Earth using cathodic protection units. During periods of enhanced geomagnetic activity, potential differences between the pipeline and surrounding soil (referred to as pipe-to-soil potentials (PSPs)) may exhibit large voltage swings which place the pipeline outside the recommended “safe range” and at an increased risk of corrosion. The PSP variations result from the “geoelectric” field at the Earth's surface and associated geomagnetic field variations. Previous research investigating the relationship between the surface geoelectric field and geomagnetic source fields has focused on the high-latitude regions where line currents in the ionosphere E region are often the assumed source of the geomagnetic field variations. For the Australian region Sq currents also contribute to the geomagnetic field variations and provide the major contribution during geomagnetic quiet times. This paper presents the results of a spectral analysis of PSP measurements from four pipeline networks from the Australian region with geomagnetic field variations from nearby magnetometers. The pipeline networks extend from Queensland in the north of Australia to Tasmania in the south and provide PSP variations during both active and quiet geomagnetic conditions. The spectral analyses show both consistent phase and amplitude relationships across all pipelines, even for large separations between magnetometer and PSP sites and for small-amplitude signals. Comparison between the observational relationships and model predictions suggests a method for deriving a geoelectric field proxy suitable for indicating PSP-related space weather conditions.

Ionogram inversion F1-layer treatment effect in raytracing

This paper shows the importance of the F1-layer shape in the electron density profiles obtained from ionograms with different inversion techniques when the profiles are used in ray tracing. This layer often controls the propagation on the path with ranges less than about 2000 km, particularly for spring and summer periods. Ionograms from two different stations, Hainan (19.4N, 109E) and El Arenosillo (37.1N, -6.7E), obtained during the month of July 2002 (average sunspot number: 99.6) during geomagnetic quiet conditions (Ap-index between 9 and 15) are analyzed. The profiles obtained with two different inversion techniques with different options are used together with the ray tracing program of the Proplab-Pro software. This program calculates the features of the received signal as angle of arrival, path length, height of reflection and range for each given profile assumed to define a spherically symmetric ionosphere in the region along the path. For each ionospheric condition (location, day, hour) the difference between range values obtained with Proplab-Pro program using profiles from the two techniques and the different options (POLAN no valley, POLAN valley, POLAN1-layer and NHPC) are considered.

Correlation Study of Plasmasheet Ions with Solar Wind and Geomagnetic Conditions

AbstractObservations obtained from CIS/CODIF and RAPID instrument onboard Cluster are used to investigate the temporal behavior of H+ and O+ ions in the storm time plasmasheet and the relationship between plasmasheet ions and solar wind conditions. It is found that: (1) The number density of O+ ions (0~40 keV) is quite low before SSC, and increases slowly as Dst decreases, reaching its peak value at the vicinity of Dst minimum. The density of H+ ions enhances greatly shortly before SSC, and decreases sharply after SSC. It keeps at a relatively low level during the whole main phase and recovery phase. Fluxes of energetic H+ and O+ ions enhance greatly after SSC and reach their maximum values before their low energy counterparts. It is implied that ions injected into ring current at early storm time are mainly H+ ions and only at later times could O+ ions significantly affect the ring current. (2) During geomagnetic active times, solar wind pressure, density and electric field are positively correlated with simultaneous H+ and O+ number density in the plasmasheet. The dependence of H+ number density on solar wind parameters is stronger under northward IMF (Interplanetary Magnetic Field), while O+ number density favors southward IMF. During geomagnetic quiet times, there is no clear evidence for a correlation between solar wind conditions and ions in the plasmasheet.

Equatorial F-region vertical ion drifts during quiet solar maximum

Median values of ionosonde h′ F data acquired at Ibadan (Geographic:7.4°N, 3.9°E, Magnetic: dip 6°S, and magnetic declination, 3°W), Nigeria, West Africa, have been used to determine vertical ion drift (electric field) characteristics in the postsunset ionosphere in the African region during a time of high solar activity (average F 10.7 −208). The database spans from January and December 1958 during the era of International Geophysical Year (IGY) for geomagnetic quiet conditions. Bimonthly averaged diurnal variations patterns are very similar, but differ significantly in magnitude and in the evening reversal times. Also, monthly variations of F-region vertical ion drift reversal times inferred from the time of h′ F maximum indicates early reversal during equinoxes and December solstice months except for the month of April. Late reversal is observed during the June solstice months. The equatorial evening prereversal enhancement in vertical ion drift ( V zp ) occurs largely near 1900 LT with typical values ∼20–45 m/s. Comparison of Ibadan ionosonde V zp with the values of prereversal peak velocity reported for Jicamarca (South America), Kodaikanal (India), and Scherliess and Fejer global model show considerable disparity. The changes of postsunset peak in virtual height of F-layer ( h′ F P ) with prereversal velocity peak V zp are anti-correlated. Investigation of solar effects on monthly values of V zp and h′ F P revealed that these parameters are independent of monthly averaged solar flux intensity during quiet-time sunspot maximum conditions.

Observations of GW/TID oscillations in the F2 layer at low latitude during high and low solar activity, geomagnetic quiet and disturbed periods

Ionospheric vertical sounding observations, using a digital ionosonde, are being carried out on a routine basis at Sao Jose dos Campos (23.2°S, 45.9°W; dip latitude 17.6°S, hereafter referred to as SJC), Brazil, located under the southern crest of the equatorial ionization anomaly (EIA), since August 2000. In this paper, we present and discuss the seasonal variation of gravity wave (GW) and traveling ionospheric disturbance (TID) oscillations in the ionospheric F2 layer during high solar activity (HSA, September 2000 to August 2001) and low solar activity (LSA, January 2006 to December 2006) observed at SJC during different levels of geomagnetic activity. The GW/TID signatures in the F2 layer can be seen in the isofrequency lines of virtual height daily variations for six fixed frequencies (3, 4, 5, 6, 7, and 8 MHz) which show quasiperiodic oscillations (crests and valleys). The crests and valleys when seen in close frequencies present a phase difference (i.e., first it is observed at higher frequency then at lower frequency), indicating a downward phase velocity. These quasiperiodic oscillations induced in the virtual heights are divided into three groups as small amplitude (lower than 40 km), medium amplitude (between 40 km and 60 km), and large amplitude (greater than 60 km). The observations show that GWs/TIDs are much more pronounced at F layer heights during HSA than LSA and the large‐amplitude GWs/TIDs are present normally only during HSA.

Persistent global proton aurora caused by high solar wind dynamic pressure

Global images of the proton aurora taken with the SI‐12 camera onboard the IMAGE satellite reveal a very direct relationship between the solar wind dynamic pressure and the intensity of the global proton aurora. We show that an increase in dynamic pressure leads to an immediate and persistent increase in proton precipitation, also when the increase is slow. When the dynamic pressure decreases, the proton aurora diminishes. Five events during geomagnetic quiet times, with mostly northward IMF, have been selected in order to characterize the proton aurora caused exclusively by high dynamic pressure and establish important criteria that the dynamic pressure‐induced precipitation mechanism(s) must satisfy. We also present measurements during southward IMF and show that the combined effect of high solar wind dynamic pressure and southward IMF produces intense global proton aurora. Some of the characteristics are: (1) The aurora is global, with peak intensities at midnight and flanks. (2) A dawn/dusk asymmetry shows that the precipitation originates from magnetospheric protons that have undergone gradient/curvature drift. (3) The time delay between ground magnetic signatures of a change in the solar wind dynamic pressure and a change in global proton aurora is short (−2 minutes). Our observations indicate that the precipitation mechanism(s) behind the proton aurora during high dynamic pressure is directly connected to the compression of the magnetosphere, both at the flanks and nightside.

Solar–geomagnetic activity and Aa indices toward a standard classification

Legrand and Simon [1989. Solar cycle and geomagnetic activity: a review for geophysicists. Part I. The contributions to geomagnetic activity of shock waves and of the solar wind. Annales Geophysicae 7(6), 565–578] classified one century (1868–1978) of geomagnetic activity, using the Mayaud's Aa index, in four classes related to solar activity: (1) the magnetic quiet activity due to slow solar wind flowing around the magnetosphere, (2) the recurrent activity related to high wind speed solar wind, (3) the fluctuating activity related to fluctuating solar wind and (4) the shock activity due to shock events (CME). In this paper, we use this classification to analyse the solar–geomagnetic activity from 1978 to 2005. We found that during the last three decades the level of geomagnetic quiet activity estimated by Aa indices is decreasing: 2003 is the year of the smallest level of quiet geomagnetic activity since 1868. We compare Legrand and Simon's classification with new in situ solar wind data [Richardson, I.G., Cliver, E.W., Cane, H.V., 2000. Sources of geomagnetic activity over the solar cycle: relative importance of coronal mass ejections, high-speed streams, and slow solar wind. Journal of Geophysical research 105(A8), 18,200–18,213; Richardson, I.G., Cane, H.V., 2002. Sources of geomagnetic activity during nearly three solar cycles (1972–2000). Journal of Geophysical Research 107(A8), 1187] and find a rather good agreement. The differences are only due to minor definitions of the extent of the classes. An attempt is made at defining a more precise standard classification of solar phenomena and at defining time scales of these to understand more precisely the geomagnetic signatures of solar activity.

The F-Region Equatorial Ionospheric Electrodynamics Drifts

The ionospheric plasma drift is one of the most essential parameters for understanding the dynamics of ionospheric F-region. F-region electromagnetic drifts are calculated for three seasonal conditions from ionosonde observations acquired during quiet period of a typical year of high and low solar activity at Ibadan (7.4oN, 3.9oE, dip 6oS), Nigeria. The vertical plasma drifts derived from h' (f) ionosonde data are compared with vertical drifts obtained by incoherent scatter radar and AE-E satellite measurements during nighttime periods under similar solar and geomagnetic conditions. We find comparable variability among the ionosonde drifts at Ibadan, Jicamarca VHF radar drifts, and AE-E satellite drifts during high solar flux and geomagnetic quiet conditions at equinox and solstices periods. The equinoctial average evening upward drifts enhancements by the three methods are roughly similar and occur at the same local time (19 LT) for all the seasons. Additionally, the evening reversal time from upward daytime to downward nighttime does not vary much except during the winter months; and occurs earliest in summer and equinox, but least during winter period. Also the data indicate asymmetry of evening reversal times about the dip-equator between the Peruvian, Indian, and the African equatorial regions. Our observations are in conformity with some results obtained at other equatorial ionospheric stations Journal of the Nigerian Association of Mathematical Physics Vol. 10 2006: pp. 27-34

Parameters of the near-earth interplanetary medium under quiet and disturbed geomagnetic conditions

The distributions of the parameters of the solar wind, IMF, and physical fields (Ey component of the SW electric field, compression field DCF) and the rms errors (σ) of measurements, depending on the daily characteristic of geomagnetic disturbance (Cp), are considered. The scatter of parameters in the interplanetary medium (IM) is actually considerable even during a long interval of geomagnetic quiet. It has been indicated that an unambiguous correspondence between the IM parameters and the characteristic of geomagnetic activity on the Earth is absent, and we have only tendencies toward an increase (decrease) in the parameter of the near-Earth medium (physical quantity) with increasing geomagnetic activity. These tendencies are transformed into linear relationships only after the three-fold averaging of values (hourly, daily, annual), which corresponds to numerous equations of relation between IM parameters and different geomagnetic indices, obtained by many researchers based on statistical analyses.

Response of the magnetic field in the geosynchronous orbit to solar wind dynamic pressure pulses

We do a statistical survey of solar wind dynamic pressure (Pd) pulses and geosynchronous magnetic fields observed between 1998 and 2005. In geomagnetic quiet times with Dst &gt; −50 nT, we find 111 solar wind dynamic pressure pulses which produce geosynchronous magnetic field responses. These responses are often observed by two or three GOES spacecraft at different local times in geosynchronous orbit. The magnitudes of the geosynchronous magnetic field changes (dBz) have a peak near the noon meridian, similar to the results obtained in the study of the response of the geosynchronous field to the large and sharp solar wind dynamic pressure variations. However, the relative change of the geosynchronous magnetic field dBz/AV‐Bz (where AV‐Bz is the average of the geosynchronous magnetic field Bz observed during the response to the pressure pulse) depends weakly on the local time; thus the change of Bz(dBz) is proportional to the average field (AV‐Bz). As the magnitude of the relative change of solar wind dynamic pressure (dPd/Pd) increases, the rate of geosynchronous magnetic field variation increases correspondingly. These results imply that the magnitude of the geosynchronous magnetic field response could be determined by AV‐Bz. In addition, the interplanetary field orientation does not affect the response significantly. Using an MHD code which models the global behavior of the solar wind‐magnetosphere‐ionosphere system, we reproduce the main characteristics of the observations.

Continuous quasiperiodic thermospheric waves over Arecibo

Incoherent scatter radar (ISR) power profile observations at Arecibo Observatory (AO) have revealed long vertical wavelength (&gt;100 km) quasi‐coherent waves with periods of ∼1 hour that are observed to be nearly continuously present over two ∼35‐hour geomagnetically quiet observation periods. When properly filtered, results from both 22–23 March 2004 and 5–6 June 2005 provide unambiguous views of these waves. The waves are strong throughout the F region, often spanning 160 to above 500 km in altitude and are present day and night in the F2 layer. Filtering techniques that were used to better reveal the waves are extensively discussed. Barometric pressure and imager data, both of which were taken on site at Arecibo, are used to provide further insight into the nature of these waves. These waves may be linked to high‐latitude medium‐scale traveling ionospheric disturbances (MSTIDs) observed with the superDARN radar network and associated with E region auroral electrojet source(s) that are quasi‐coherent under geomagnetic quiet conditions. As auroral‐zone MSTIDs are believed to dissipate before reaching Arecibo latitudes (Vadas, 2007), various alternative sources including weather patterns are explored.

Use of total electron content data to analyze ionosphere electron density gradients

In the presence of electron density gradients the thin shell approximation for the ionosphere, used together with a simple mapping function to convert slant total electron content (TEC) to vertical TEC, could lead to TEC conversion errors. These “mapping function errors” can therefore be used to detect the electron density gradients in the ionosphere. In the present work GPS derived slant TEC data have been used to investigate the effects of the electron density gradients in the middle and low latitude ionosphere under geomagnetic quiet and disturbed conditions. In particular the data corresponding to the geographic area of the American Sector for the days 5–7 April 2000 have been used to perform a complete analysis of mapping function errors based on the “coinciding pierce point technique”. The results clearly illustrate the electron density gradient effects according to the locations considered and to the actual levels of disturbance of the ionosphere. In addition, the possibility to assess an ionospheric shell height able to minimize the mapping function errors has been verified.

Using global magnetospheric models for simulation and interpretation of Swarm external field measurements

Abstract We have used a global model of the solar wind magnetosphere interaction to model the high latitude part of the external contributions to the geomagnetic field near the Earth. The model also provides corresponding values for the electric field. Geomagnetic quiet conditions were modeled to provide simulated external contributions relevant for internal field modeling. These have proven very valuable for the design and planning of the upcoming multi-satellite Swarm mission. In addition, a real event simulation was carried out for a moderately active time interval when observations from the Ørsted and CHAMP sattelites were available. Comparisons between the simulation results and the satellite observations for this event demonstrate the current level of validity of the global model. We find that the model reproduces quite well the region 1 current system and nightside region 2 currents whereas it consistently underestimates the dayside region 2 currents and overestimates the horizontal ionospheric closure currents in the dayside polar cap. Furthermore, with this example we illustrate the great benefit of utilizing the global model for the interpretation of Swarm external field observations and, likewise, the potential of using Swarm measuremnets to test and improve the global model.