MIST
Magnetosphere, Ionosphere and Solar-Terrestrial
Observation of Quiet-Time Mid-Latitude Joule Heating and Comparisons With the TIEGCM Simulation
By Maria-Theresia Walach & Elliot Day (Lancaster University)
Joule heating is a major energy sink in the solar wind-magnetosphere-ionosphere system and modeling it is key to understanding the impact of space weather on the neutral atmosphere. Ion drifts and neutral wind velocities are key parameters when modeling Joule heating, however there is limited validation of the modeled ion and neutral velocities at mid-latitudes. We use the Blackstone Super Dual Auroral Radar Network radar and the Michigan North American Thermosphere Ionosphere Observing Network Fabry-Perot interferometer to obtain the local nightside ion and neutral velocities at ∼40° geographic latitude during the nighttime of 16 July 2014. Despite being a geomagnetically quiet period, we observe significant sub-auroral ion flows in excess of 200 ms−1. We calculate an enhancement to the local Joule heating rate due to these ion flows and find that the neutrals impart a significant increase or decrease to the total Joule heating rate of >75% depending on their direction. As is shown in the figure. Different patches in the ionosphere move at different speeds and therefore create varying Joule heating rates. We compare our observations to outputs from the Thermosphere Ionosphere Electrodynamic General Circulation Model (TIEGCM). At such a low geomagnetic activity however, TIEGCM was not able to model significant sub-auroral ion flows and any resulting Joule heating enhancements equivalent to our observations. We found that the neutral winds were the primary contributor to the Joule heating rates modeled by TIEGCM rather than the ions as suggested by our observations. This presents a gap in TIEGCM's capabilities and care has to be taken when estimating Joule heating rates from models, which make assumptions about ionospheric flows at mid-latitudes.
Panels a, b, c, d and e shows the estimated Joule heating components and total heating for each identified patch of
ionospheric flow, the panel labels correspond to the different patch velocities in the paper.
Each component is plotted according to the legend in panel a.
Panel f shows the Joule heating components and total heating modeled by TIEGCM.
Panel g shows the total Joule heating rate calculated as the average heating rate of all patches in the common area,
while re-plotting TIEGCM's total Joule heating in orange for comparison.
See publication for details:
Day, E. K., Grocott, A., Walach, M.-T., Wild, J. A., Lu, G., Ruohoniemi, J. M., & Coster, A. J. (2024). Observation of quiet-time mid-latitude Joule heating and comparisons with the TIEGCM simulation. Journal of Geophysical Research: Space Physics, 129, e2024JA032578. https://doi.org/10.1029/2024JA032578
On the Association of Substorm Identification Methods
By Christian Lao (UCL, Mullard Space Science Laboratory)
Substorms are a major energy unloading process in the solar wind-magnetosphere-ionosphere system that are capable of processing approximately 10^15J of stored solar wind energy through a complete cycle (Tanskanen et al., 2002). In broad terms, energy is built up and stored in the magnetosphere during substorm growth phases by enhanced reconnection between the solar wind and the magnetosphere on the dayside. Energy is released during substorm expansion and recovery phases by reconnection and other plasma instabilities in the magnetotail, with the start of the expansion phase known as substorm onset. Over the years, numerous signatures and techniques have been used to identify substorm onsets, but these are typically developed or used in isolation. In this study, we quantify the association between the different signatures used for identification of substorms (more specifically, substorm onset). Generally, we found that methods developed and applied to ground magnetometer data achieved the best associations, with events identified at mid-latitude (Chu et al., 2015) and at auroral latitudes (Newell & Gjerloev, 2011) showing the highest levels of coincidence with other substorm indicators. On the other hand, we found that events identified by particle injections (Borovsky & Yakymenko, 2017) showed much poorer associations with other substorm lists, in particular with no improvement over chance agreement with events identified from the aurora. Remarkably, we found less than 50% agreement on the timing and occurrence of substorms between any of the lists studied. As such, any studies dependent upon such lists may come to premature conclusions about substorm dynamics or impacts. Furthermore, a significant number of events in each list may not share multiple substorm signatures, calling into question the legitimacy of each identification. This highlights the need to further cross calibrate our methods or use multiple signatures to evaluate a more robust set of events.
True positive rate “heatmap” showing the percentage of events from the Reference (Horizontally labelled)
substorm list a Comparison substorm list (Vertically labelled) also observes. These are the best
performing methods on the datasets they are leveraging. A higher score/lighter colour indicates better association.
References:
Tanskanen et al. 2002: https://doi.org/10.1029/2001JA900153
Chu et al., 2015: https://doi.org/10.1002/2015JA021104
Newell & Gjerloev, 2011: https://doi.org/10.1029/2011JA016779
Borovsky & Yakymenko, 2017: https://doi.org/10.1002/2016JA023625
See publication for details:
Lao, C. J., Forsyth, C., Freeman, M. P., Smith, A. W., & Mooney, M. K. (2024). On the association of substorm identification methods. Journal of Geophysical Research: Space Physics, 129, e2024JA032762. https://doi.org/10.1029/2024JA032762
Autumn MIST 2024
Autumn MIST this year will be held on Friday 29th November at The Exchange in Birmingham (3 Centenary Square, Birmingham, B1 2DR - near Birmingham New Street). We are hosting Autumn MIST outside of London for the first time, allowing us to use a venue that will be able to accommodate our growing community.
Abstract submission and registration are now closed.
Venue Information (https://www.birmingham.ac.uk/the-exchange):
The Exchange is a 10-15 minute walk from Birmingham New Street station, which is the recommended mode of transport for attendance.
There is no on site parking at the venue - the closest parking is (limited) on street parking on Bridge Street. To find accessible parking, please check this website: https://www.birmingham.ac.uk/the-exchange/plan-your-visit. We would also like to note that there is a clean air zone in place around the centre of Birmingham, that comes with associated costs for driving.
Food will be provided in the form of welcome refreshments, two coffee breaks and a buffet lunch.
Poster and Talk Presentations:
Talks will be 12 minutes in length, including questions. We suggest that talks should target 10 minutes, allowing two for questions. Due to a packed schedule we will have to stick to time throughout the day, please plan your talks accordingly.
There will be two poster sessions during the day, and the poster boards will support portrait A0 posters only. As the poster sessions are not as long as we’d like, we are putting together a repository of posters online for people to browse. This will only be available to registered attendees, and only until the 31st December 2024.
Please check your emails to find the links to submit your talk and poster online. Talks must be submitted online (by the 28th November), while posters may be uploaded to a secure repository if you wish to share your work with the community.
MIST Buddies:
We are aware that Autumn MIST welcomes a range of attendees, many of whom are new to the community and may be attending their first conference. Following last years success, we will be running a "MIST Buddies" scheme this year that informally partners new members with their peers, with an emphasis on PhD students. The purpose of the partnerships is to give new community members a contact point for the day and someone that can give them a helping hand in networking and getting to know the community. We would love to hear from you if you are (a) a new member that would like a partner or (b) willing to be a MIST Buddy.
To get involved please complete the online form (supplied by email) by Friday 22 November. Thank you in advance for helping make the community more welcoming and supportive.
Name Tags:
As trialed last year, we will not be providing name badges and lanyards. Instead we would like for everyone to bring your favourite lanyard and name badges and reuse those. We would also like to have a lanyard amnesty where people can bring a spare lanyard for those who may have forgotten or do not have a lanyard. There will be a small number of stickers available on the day to make your own name tag if needed.
Code of Conduct:
All attendees must follow the MIST/RAS Code of Conduct, which can be found here: https://www.mist.ac.uk/community/conduct-and-support. Details on reporting breaches of the code of conduct will be provided on the day. Thank you in advance for contributing to a safe and enjoyable experience for everyone.
Tips for students:
Last year's student rep on MIST council, Sophie Maguire, wrote an excellent article with lots of advice for first time attendees: https://mist.ac.uk/students-corner/344-tips-for-autumn-mist-2023.
The pub:
After events such as Autumn MIST, it is usually the case that people move to a local pub once the conference has finished. Please do not feel intimidated by this. Everyone is more than welcome to come along and it is a really great platform to get to know people and have some more informal discussions. The official pub for Autumn MIST will be the Purecraft Bar & Kitchen (https://maps.app.goo.gl/QpkyEa9SGnsgqQKb6).