https://ogma.newcastle.edu.au/vital/access/ /manager/Index en-au 5 https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:31247 Wed 11 Apr 2018 13:18:24 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:10964 2 MeV electron flux observed at geosynchronous orbit, starting at 00 UT on 25 June 2008, is attributed to a rapid (1–4 h) nonadiabatic loss process. ULF waves were observed by the THEMIS-A, -D, and -E probes in the afternoon-to-dusk sector from the magnetopause to geosynchronous altitude. Estimates of the electron resonant energies indicate strong drift resonant interactions occurring between the energetic electrons and the observed waves. The rate of outward radial diffusion was estimated for MeV electrons using the observed ULF wave azimuthal electric field and compressional magnetic field and the diffusion time (~2.5 h) was found to be in good agreement with the observed time for nonadiabatic flux decreases at geosynchronous orbit. The magnetopause was compressed inside of its nominal position because of increased solar wind dynamic pressure. The electron loss is interpreted as a combination of magnetopause shadowing (from the compressed magnetosphere) and enhanced outward diffusion from ULF wave-particle drift resonant interactions. The enhanced day-night asymmetry of the MeV electron drift path from the compression suggests that enhanced losses may have also occurred around local noon as well as in the afternoon-to-dusk sector.]]> Wed 11 Apr 2018 11:48:02 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:6847 Wed 11 Apr 2018 10:21:51 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:54349 20 nT/s) geomagnetic disturbances (GMDs, also denoted as MPEs—magnetic perturbation events)—impulsive nighttime disturbances with time scale ∼5–10 min, have sufficient amplitude to cause bursts of geomagnetically induced currents (GICs) that can damage technical infrastructure. In this study, we present occurrence statistics for extreme GMD events from five stations in the MACCS and AUTUMNX magnetometer arrays in Arctic Canada at magnetic latitudes ranging from 65° to 75°. We report all large (≥6 nT/s) and extreme GMDs from these stations from 2011 through 2022 to analyze variations of GMD activity over a full solar cycle and compare them to those found in three earlier studies. GMD activity between 2011 and 2022 did not closely follow the sunspot cycle, but instead was lowest during its rising phase and maximum (2011–2014) and highest during the early declining phase (2015–2017). Most of these GMDs, especially the most extreme, were associated with high-speed solar wind streams (Vsw >600 km/s) and steady solar wind pressure. All extreme GMDs occurred within 80 min after substorm onsets, but few within 5 min. Multistation data often revealed a poleward progression of GMDs, consistent with a tailward retreat of the magnetotail reconnection region. These observations indicate that extreme GIC hazard conditions can occur for a variety of solar wind drivers and geomagnetic conditions, not only for fast-coronal mass ejection driven storms.]]> Tue 20 Feb 2024 16:19:14 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:10989 300 keV and ~1 MeV trapped electrons, and also consistent with the daily average ULF (ultralow frequency) Pc1–2 power (L = 3.9) from Lucky Lake, Canada, which was elevated during the ~1 MeV electron precipitation period. This suggests that Pc1–2 waves may play a role in outer radiation belt loss processes during this interval. We show that the >300 keV trapped electron flux from POES is a reasonable proxy for electron precipitation during recurrent high-speed solar wind streams, although it did not describe all of the variability that occurred. While energetic electron precipitation can be described through a proxy such as Kp or Dst, careful incorporation of time delays for different electron energies must be included. Dst was found to be the most accurate proxy for electron precipitation during the weak recurrent-activity period studied.]]> Sat 24 Mar 2018 08:07:56 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:10988 Sat 24 Mar 2018 08:07:55 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:29480 E region can reduce the chance of F region and increase the chance of E region backscatter. It was also shown that reduction in backscatter cannot be explained by D region absorption. Using a normalized SYM-H value, percentage time through recovery phase can be estimated during storm progression which allows a prediction of backscatter return in real time that accounts for varying storm recovery phase duration.]]> Sat 24 Mar 2018 07:29:45 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:28303 Sat 24 Mar 2018 07:27:05 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:53436 Mon 27 Nov 2023 11:48:05 AEDT ]]>