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 GICy 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.

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 (1 ) 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 1 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 F 10.7 ). 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.

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.

We present the first study of early dark energy cosmologies using N‐body simulations to investigate the formation of a non‐linear structure. In contrast to expectations from semi‐analytic approaches, we find that early dark energy does not imprint a unique signature on the statistics of non‐linear structures. Investigating the non‐linear power spectra and halo mass functions, we show that universal mass functions hold for early dark energy, making its presence difficult to distinguish from Λ cold dark matter. Since early dark energy biases the baryon acoustic oscillation scale, the lack of discriminating power is problematic.

For dynamical dark energy cosmologies we carry out a series of N‐body gravitational simulations, achieving per cent level accuracy in the relative mass power spectra within 0.1 < k < 3 at any redshift for values of the dark energy equation of state consistent with current observations. Such accuracy in the power spectrum is necessary for next generation cosmological mass probes. Our matching procedure reproduces the cosmic microwave background distance to last scattering and delivers sub‐per cent level accuracy in the matter power spectra at z= 0 and ≈3. We discuss the physical implications for probing dark energy with surveys of large‐scale structure.