MIST

Magnetosphere, Ionosphere and Solar-Terrestrial

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About MIST

MIST is the community of Magnetosphere, Ionosphere and Solar-Terrestrial researchers working in the United Kingdom. We represent the interests of MIST scientists and hold meetings to showcase MIST science twice a year.

  • News: News relevant to members of the MIST community.
  • Science: MIST science nuggets, as well as briefing papers designed to introduce policymakers to our research.
  • Meetings: Details of upcoming MIST meetings and summer schools, as well as the list of past MIST meetings.
  • Community: Find out about MIST researchers through the UK, MIST Council, MIST's mailing list, as well as the MIST Charter and history of the organisation.
  • Awards: The awards that MIST researchers are eligible for, alongside a list of those who have been honoured.

Formation and Motion of Horse Collar Aurora Events

By Gemma Bower (University of Leicester)

Horse collar aurora (HCA) are an auroral phenomena that occurs under northward IMF where the polar cap becomes teardrop shaped due to the poleward motion of the dusk and dawn sectors of the auroral oval. Their formation has been linked to prolonged periods of dual-lobe reconnection (DLR). This occurs when the same IMF magnetic field line reconnects in both the northern and southern hemisphere lobes when the IMF clock angle is small. This leads to the closure of magnetic flux at the dayside magnetopause. In order to further study the motion of HCA a list of HCA events previously identified in UV images captured by the Special Sensor Ultraviolet Spectrographic Imager (SSUSI) instrument on-board the Defense Meteorological Satellite Program (DMSP) spacecraft F16, F17 and F18 has been used. Events that have concurrent 630.0 nm all-sky camera (ASC) data from the Redline Geospace Observatory (REGO) Resolute Bay site are studied in more detail, making use of the higher cadence of the ASC images compared to DMSP/SSUSI. 11 HCA events are classified based on the IMF conditions at the end of the event. A southward turning of the IMF ends five events, two end with positive By dominated IMF and four with negative By dominance. The figure shows one of the studied events that ends with a southward turning of the IMF. Under positive (negative) By the arcs move duskward (dawnward) in the northern hemisphere with the opposite true in the southern hemisphere. Under a southward turning the arcs move equatorward. These results are in agreement with previously proposed models. Understanding the evolution of HCA will allow DLR to be studied in more detail.

Figure 1: One of the studied events. The top panels show the keograms of the ASC and the relevant interplanetary magnetic field (IMF) data for the event. The first row of the columns shows the DMSP/IDM flows with an inset showing the IMF clock angle at the time of the SSUSI image. The second row is the LBHs SSUSI image on a log scale. The third row is the SSUSI image centred on the Taloyoak ASC station with the available ASC images projected on top. The final rows are the ASC images with north located at the top of each image plotted on a log scale. The UT given is the time of the ASC image and the most poleward point of the DMSP pass.
Figure 1: One of the studied events. The top panels show the keograms of the ASC and the relevant interplanetary magnetic field (IMF) data for the event. The first row of the columns shows the DMSP/IDM flows with an inset showing the IMF clock angle at the time of the SSUSI image. The second row is the LBHs SSUSI image on a log scale. The third row is the SSUSI image centred on the Taloyoak ASC station with the available ASC images projected on top. The final rows are the ASC images with north located at the top of each image plotted on a log scale. The UT given is the time of the ASC image and the most poleward point of the DMSP pass.


Please see paper for full details: Bower, Bower, G. E., Milan, S. E., Paxton, L. J., Spanswick, E., & Hairston, M. R. (2023). Formation and motion of horse collar aurora events. Journal of Geophysical Research: Space Physics, 128, e2022JA031105. https://doi.org/10.1029/2022JA031105

Related articles: Nuggets

Winners of Rishbeth Prizes 2023

We are pleased to announce that following Spring MIST 2023 the Rishbeth Prizes this year are awarded to Sophie Maguire (University of Birmingham) and Rachel Black (University of Exeter).

Sophie wins the prize for the best MIST student talk which was entitled “Large-scale plasma structures and scintillation in the high-latitude ionosphere”. Rachel wins the best MIST poster prize, for a poster entitled “Investigating different methods of chorus wave identification within the radiation belts”. Congratulations to both Sophie and Rachel!

As prize winners, Sophie and Rachel will be invited to write articles for Astronomy & Geophysics, which we look forward to reading.

MIST Council extends their thanks to the University of Birmingham for hosting the Spring MIST meeting 2023, and to the Royal Astronomical Society for their generous and continued support of the Rishbeth Prizes.

Related articles: News

Will Space Weather Delay Your Train? – Modelling the Impact of Geomagnetically Induced Currents on Electrified Railway Signaling Systems in the United Kingdom

By Cameron Patterson (Lancaster University)

Railway signalling is one of the many ground-based systems that are susceptible to the impacts of space weather. A popular signalling system is the track circuit, where a line is split into smaller sections called ‘blocks’, each containing a power supply and a relay that sets the signal based on the level of current. Currents induced in the rails during geomagnetic events disrupt this balance, and have the potential to cause signalling misoperations, which can create delays and/or possibly be hazardous. Using recent theoretical work and parameters from industry standards documents, we have developed realistic models of two railway lines in the United Kingdom to study the impacts that geomagnetically induced currents have on signalling systems. In this study, we have focused on right side failures, which is when there are no trains occupying the blocks and green signals are turned red. Our results show that the susceptibility of a track circuit to induced currents is dependent on its length, orientation and position along the line. We found that the threshold electric field strength for a misoperation to occur is approximately what would arise during a storm expected to occur once every 30 years. Finally, we showed that with a 1 in 100 year extreme electric field, there would be a significant number of misoperations across the line.

 

Figure 1. The current through each of the track circuit relays between Glasgow to Edinburgh with (a) no geoelectric field applied, (b) at the threshold for misoperation, and (c) at the estimated electric field strength for a 1 in 100 year event. The green circles indicate the current of each relay, the red (solid) line shows the current value below which the track circuit would de-energize and display an incorrect signal, and the green (dashed) line shows the level that the current would need to rise above to re-energize if de-energized. An unfilled green circle means normal operation, and a filled red circle indicates a misoperation.

 

Please see the following paper for a more in depth look: Patterson, C. J., Wild, J. A., & Boteler, D. H. (2023). Modeling the impact of geomagnetically induced currents on electrified railway signaling systems in the United Kingdom. Space Weather, 21, e2022SW003385. https://doi.org/10.1029/2022SW003385.

Related articles: Nuggets