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Prikryl P.,Communications Research Center Canada | Spogli L.,Italian National Institute of Geophysics and Volcanology | Jayachandran P.T.,University of New Brunswick | Kinrade J.,University of Bath | And 15 more authors.
Annales Geophysicae | Year: 2011

Arrays of GPS Ionospheric Scintillation and TEC Monitors (GISTMs) are used in a comparative scintillation study focusing on quasi-conjugate pairs of GPS receivers in the Arctic and Antarctic. Intense GPS phase scintillation and rapid variations in ionospheric total electron content (TEC) that can result in cycle slips were observed at high latitudes with dual-frequency GPS receivers during the first significant geomagnetic storm of solar cycle 24 on 5-7 April 2010. The impact of a bipolar magnetic cloud of north-south (NS) type embedded in high speed solar wind from a coronal hole caused a geomagnetic storm with maximum 3-hourly Kp Combining double low line 8-and hourly ring current Dst Combining double low line-73 nT. The interhemispheric comparison of phase scintillation reveals similarities but also asymmetries of the ionospheric response in the northern and southern auroral zones, cusps and polar caps. In the nightside auroral oval and in the cusp/cleft sectors the phase scintillation was observed in both hemispheres at about the same times and was correlated with geomagnetic activity. The scintillation level was very similar in approximately conjugate locations in Qiqiktarjuaq (75.4 N; 23.4 E CGM lat. and lon.) and South Pole (74.1 S; 18.9 E), in Longyearbyen (75.3 N; 111.2 E) and Zhongshan (74.7 S; 96.7 E), while it was significantly higher in Cambridge Bay (77.0 N; 310.1 E) than at Mario Zucchelli (80.0 S; 307.7 E). In the polar cap, when the interplanetary magnetic field (IMF) was strongly northward, the ionization due to energetic particle precipitation was a likely cause of scintillation that was stronger at Concordia (88.8 S; 54.4 E) in the dark ionosphere than in the sunlit ionosphere over Eureka (88.1 N; 333.4 E), due to a difference in ionospheric conductivity. When the IMF tilted southward, weak or no significant scintillation was detected in the northern polar cap, while in the southern polar cap rapidly varying TEC and strong phase scintillation persisted for many hours. This interhemispheric asymmetry is explained by the difference in the location of solar terminator relative to the cusps in the Northern and Southern Hemisphere. Solar terminator was in the immediate proximity of the cusp in the Southern Hemisphere where sunlit ionospheric plasma was readily convected into the central polar cap and a long series of patches was observed. In contrast, solar terminator was far poleward of the northern cusp thus reducing the entry of sunlit plasma and formation of dense patches. This is consistent with the observed and modeled seasonal variation in occurrence of polar cap patches. The GPS scintillation and TEC data analysis is supported by data from ground-based networks of magnetometers, riometers, ionosondes, HF radars and all-sky imagers, as well as particle flux measurements by DMSP satellites. © 2011 Author(s).

Marshall R.A.,IPS Radio and Space Services | Dalzell M.,Transpower | Waters C.L.,University of Newcastle | Goldthorpe P.,University of Newcastle | And 2 more authors.
Space Weather | Year: 2012

Adverse space weather conditions have been shown to be directly responsible for faults within power networks at high latitudes. A number of studies have also shown space weather to impact power networks at lower latitudes, although most of these studies show increases in GIC activity within networks not directly related to hardware faults. This study examines a GIC event that occurred in New Zealand's South Island power network on 6th November 2001. A transformer failure that occurred during this day is shown to be associated with a change in the solar wind dynamic pressure of nearly 20 nPa. Measurements of GICs recorded on the neutral lines of transformers across the Transpower network during this event show good correlation with a GIC-index, a proxy for the geoelectric field that drives GIC. Comparison of this event with GIC activity observed in the Transpower network during large space weather storms such as the "2003 Halloween storm," suggests that solar wind shocks and associated geomagnetic sudden impulse (SI) events may be as hazardous to middle latitude power networks as GIC activity occurring during the main phase of large storms. Further, this study suggests that the latitudinal dependence of the impacts of SI events on power systems differs from that observed during large main phase storms. This study also highlights the importance of operating procedures for large space weather events, even at middle latitude locations. © 2012 by the American Geophysical Union.

Marshall R.A.,IPS Radio and Space Services | Smith E.A.,IPS Radio and Space Services | Smith E.A.,Defence Science and Technology Organisation, Australia | Francis M.J.,IPS Radio and Space Services | And 2 more authors.
Space Weather | Year: 2011

It is well documented that power networks at high latitudes are vulnerable to the effects of space weather. In recent years the eastern Australia state power networks have been connected across state boundaries in order to improve robustness under increasing load demands and deliver power at competitive prices. However, this interconnectivity is likely to increase susceptibility of the network to space weather. Geomagnetically induced currents (GICs) flow in power transmission lines as the result of "geoelectric" fields and their associated geomagnetic field variations according to Faraday's Law. In this paper previously documented occurrences of GIC activity from regions around the world are investigated and categorized by their effects on nearby power networks. A frequency domain filter that produces an index representing GIC activity is applied to geomagnetic field data recorded at locations near the documented GIC activity to determine risk level "GIC index" thresholds. Geomagnetic field data from the Australian region are processed using the "GIC filter" to provide a preliminary risk assessment of space weather related GIC activity to the Australian power network. The analysis suggests lower limit threshold GICy indices of 50, 100, 250, and 600 corresponding to the risk levels of "low," "moderate," "high," and "extreme," respectively. Analysis of GIC y indices derived from Australian magnetometer data shows that only southern Australian regions reached the "moderate" risk levels defined in this study with mainland southern Australia stations reaching this risk level twice over the previous two solar cycles. Southern Australian regions such as Tasmania reached moderate levels approximately 20 times during the previous solar cycle. Furthermore, elevated risk levels are typically only observed in Australia during solar maximum and its decline phase. Copyright © 2011 by the American Geophysical Union.

Carter B.A.,Boston College | Carter B.A.,RMIT University | Retterer J.M.,Boston College | Yizengaw E.,Boston College | And 8 more authors.
Geophysical Research Letters | Year: 2014

Describing the day-to-day variability of Equatorial Plasma Bubble (EPB) occurrence remains a significant challenge. In this study we use the Thermosphere-Ionosphere Electrodynamics General Circulation Model (TIEGCM), driven by solar (F10.7) and geomagnetic (Kp) activity indices, to study daily variations of the linear Rayleigh-Taylor (R-T) instability growth rate in relation to the measured scintillation strength at five longitudinally distributed stations. For locations characterized by generally favorable conditions for EPB growth (i.e., within the scintillation season for that location), we find that the TIEGCM is capable of identifying days when EPB development, determined from the calculated R-T growth rate, is suppressed as a result of geomagnetic activity. Both observed and modeled upward plasma drifts indicate that the prereversal enhancement scales linearly with Kp from several hours prior, from which it is concluded that even small Kp changes cause significant variations in daily EPB growth. Key Points Daily EPB occurrence analyzed from five longitudinally spaced ground stations TIEGCM can identify days of decreased EPB growth during peak EPB periods PRE strength is affected by Kp from hours prior, causing daily EPB variability © 2014. American Geophysical Union. All Rights Reserved.

Marshall R.A.,IPS Radio and Space Services | Waters C.L.,University of Newcastle | Sciffer M.D.,University of Newcastle
Space Weather | Year: 2010

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. Copyright 2010 by the American Geophysical Union.

Kumar V.V.,La Trobe University | Parkinson M.L.,IPS Radio and Space Services | Dyson P.L.,La Trobe University
Journal of Geophysical Research: Space Physics | Year: 2010

Superposed Epoch Analysis (SEA) is used to examine a 5-year (1999 to 2003) database of Digisonde drift measurements made at Bundoora (145.1°E, 37.7°S geographic, 49°S magnetic), Australia, to determine the temporal evolution of midlatitude F region electric fields associated with the magnetospheric (lifetimes of about an hour) and ionospheric disturbance (lifetimes of a few to several hours) dynamos. The magnetospheric effects are qualified using AE "step-up" and "step-down" temporal filters and the SEA results reveal features fairly consistent with under- and over-shielding conditions described by the Rice Convention Model (RCM). The disturbance dynamo effects are qualified using onset times of AE- and Dst-defined storms. These onset times are further subdivided into three categories: short-, medium- and long-duration storms. We find there are no noticeable changes in ionospheric electric fields near Bundoora during short-duration AE-defined storms. In contrast, the SEA responses for medium-duration AE-defined storms and short- and medium-duration Dst-defined storms are in good agreement with the ionospheric disturbance dynamo predictions. The SEA results associated with long-duration AE or Dst-defined storms indicate that the electric field perturbations agree with the effects of the high-latitude two-cell convection pattern expanding to the latitude of the station (49° magnetic) for up to 20 h after t = 0 h. Overall, the perturbation drifts are predominantly westward with largest amplitudes in the dusk to midnight sector and continued for nearly 50 h in storm time. These enhancements are also consistent with the influence of the sub-auroral polarization stream (SAP) extending to the latitude of the station. Copyright 2010 by the American Geophysical Union.

Ptplot is a set of two dimensional signal plotters components written in Java with multiple properties, such as being embeddable in applets or applications, utilizing automatic or manual tick marks, logarithmic axes, infinite zooming, and much more. The World Data Centre of IPS applies Ptplot as a multiple function online data plot tool by converting various text format data files into Ptplot recognizable XML files with the AWK language. At present, Ptplot has allowed eight archived solar-terrestrial science data sets to be easily plotted, viewed, and downloaded from the IPS web site.

Carter B.A.,Boston College | Carter B.A.,RMIT University | Yizengaw E.,Boston College | Retterer J.M.,Boston College | And 5 more authors.
Journal of Geophysical Research: Space Physics | Year: 2014

Presented is an analysis of the occurrence of postsunset Equatorial Plasma Bubbles (EPBs) detected using a Global Positioning System (GPS) receiver at Vanimo. The three year data set shows that the EPB occurrence maximizes (minimizes) during the equinoxes (solstices), in good agreement with previous findings. The Vanimo ionosonde station is used with the GPS receiver in an analysis of the day-to-day EPB occurrence variability during the 2000 equinox period. A superposed epoch analysis (SEA) reveals that the altitude, and the change in altitude, of the F layer height is ∼1 standard deviation (1σ) larger on the days for which EPBs were detected, compared to non-EPB days. These results are then compared to results from the Thermosphere Ionosphere Electrodynamics General Circulation Model (TIEGCM), which show strong similarities with the observations. The TIEGCM is used to calculate the flux-tube integrated Rayleigh-Taylor (R-T) instability linear growth rate. A SEA reveals that the modeled R-T growth rate is 1σ higher on average for EPB days compared to non-EPB days, and that the upward plasma drift is the most dominant contributor. It is further demonstrated that the TIEGCM's success in describing the observed daily EPB variability during the scintillation season resides in the variations caused by geomagnetic activity (as parameterized by Kp) rather than solar EUV flux (as parameterized by F10.7). Geomagnetic activity varies the modeled high-latitude plasma convection and the associated Joule heating that affects the low-latitude F region dynamo, and consequently the equatorial upward plasma drift. Key Points Day-to-day EPB occurrence in Southeast Asia investigated using ground-based GPS TIEGCM exhibits similiar daily variability to the EPB observations Small changes in Kp strongly influence daily EPB occurrence variability. © 2014 American Geophysical Union. All Rights Reserved.

Yamazaki Y.,Kyushu University | Yumoto K.,Kyushu University | Uozumi T.,Kyushu University | Abe S.,Kyushu University | And 5 more authors.
Journal of Geophysical Research: Space Physics | Year: 2010

We reexamined the daily Sq-equatorial electrojet (EEJ) relationship based on these extended magnetometer networks in the east Asian region: (1) the Circum-pan Pacific Magnetometer Network (CPMN), (2) the International Real-time Magnetic Observatory Network (INTERMAGNET), and (3) the World Data Center for Geomagnetism, Kyoto (WDC). Daily variations of the geomagnetic field for geomagnetically quiet days (Kp ≤ 2+) from 1996 to 2005 were analyzed. Noontime eastward Sq current intensities were estimated by latitudinally integrating the north-south component of the S q field. The corresponding EEJ intensities were estimated from the daily geomagnetic field variations observed at Davao station (dip latitude of -0.84°deg). We discovered that these intensities of daily Sq and EEJ are well correlated on a long-term basis (r = 0.80). The dependences on the solar activity (as indicated by F10.7) and season (the day number) of S q and EEJ variations were examined. It was demonstrated that both daily Sq and EEJ intensities are correlated to F10.7 with similar sensitivities. F10.7 is known to show similar variations with solar EUV radiation which causes ionization and heating of the ionosphere. For seasonal dependence, both daily Sq and EEJ intensities show predominant semiannual variations with similar spring-fall asymmetry. The effect of seasonal changes of the EUV flux into the low-latitude ionosphere is considered. Our results indicate that the daily values of Sq and EEJ react, in the same manner, to temporal changes of solar ionization and heating of the ionosphere. Copyright 2010 by the American Geophysical Union.

Takla E.M.,Kyushu University | Yumoto K.,Kyushu University | Sutcliffe P.R.,Hermanus Mag Observatory | Nikiforov V.M.,Russian Academy of Sciences | Marshall R.,IPS Radio and Space Services
Physics of the Earth and Planetary Interiors | Year: 2011

The Molise region, on 31 October and 1 November 2002, was struck by two earthquakes of moderate magnitudes (Mw = 5.7) at depth between 12 and 24. km. Geomagnetic data from the Circum-pan Pacific Magnetometer Network (CPMN) were analyzed in order to detect any anomalous geomagnetic variations in association with the Molise earthquakes. Our results indicate the presence of long-term anomalous variations in the geomagnetic components at L'Aquila (LAQ) station (near the epicenter), which started about four months before the occurrence of the Molise earthquakes. Moreover, the geomagnetic components recorded at LAQ are found to show no correlation with those at other conjugate stations in the period between June and October 2002. In addition, anomalous ULF signal (Pc 3:10-45. s) started few weeks before the Molise earthquakes and lasted for about one week after the onset of the seismic activity. The observed anomalous variations may be explained as a result of the crustal stress variations and the enhancement of the lithospheric conductivity in the Molise region during the preparation period of the Molise earthquakes. © 2010 Elsevier B.V.

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