MIST

Magnetosphere, Ionosphere and Solar-Terrestrial

Latest news

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.

Nominations for MIST Council

We are pleased to open nominations for MIST Council. There are two positions available (detailed below), and elected candidates would join Beatriz Sanchez-Cano, Jasmine Kaur Sandhu, Andy Smith, Maria-Theresia Walach, and Emma Woodfield on Council. The nomination deadline is Friday 26 May.

Council positions open for nomination

  • MIST Councillor - a three year term (2023 - 2026). Everyone is eligible.
  • MIST Student Representative - a one year term (2023 - 2024). Only PhD students are eligible. See below for further details.

About being on MIST Council


If you would like to find out more about being on Council and what it can involve, please feel free to email any of us (email contacts below) with any of your informal enquiries! You can also find out more about MIST activities at mist.ac.uk.

Rosie Hodnett (current MIST Student Representative) has summarised their experience on MIST Council below:
"I have really enjoyed being the PhD representative on the MIST council and would like to encourage other PhD students to nominate themselves for the position. Some of the activities that I have been involved in include leading the organisation of Autumn MIST, leading the online seminar series and I have had the opportunity to chair sessions at conferences. These are examples of what you could expect to take part in whilst being on MIST council, but the council will welcome any other ideas you have. If anyone has any questions, please email me at This email address is being protected from spambots. You need JavaScript enabled to view it..”

How to nominate

If you would like to stand for election or you are nominating someone else (with their agreement!) please email This email address is being protected from spambots. You need JavaScript enabled to view it. by Friday 26 May. If there is a surplus of nominations for a role, then an online vote will be carried out with the community. Please include the following details in the nomination:
  • Name
  • Position (Councillor/Student Rep.)
  • Nomination Statement (150 words max including a bit about the nominee and your reasons for nominating. This will be circulated to the community in the event of a vote.)
 
MIST Council contact details

Rosie Hodnett - This email address is being protected from spambots. You need JavaScript enabled to view it.
Mathew Owens - This email address is being protected from spambots. You need JavaScript enabled to view it.
Beatriz Sanchez-Cano - This email address is being protected from spambots. You need JavaScript enabled to view it.
Jasmine Kaur Sandhu - This email address is being protected from spambots. You need JavaScript enabled to view it.
Andy Smith - This email address is being protected from spambots. You need JavaScript enabled to view it.
Maria-Theresia Walach - This email address is being protected from spambots. You need JavaScript enabled to view it.
Emma Woodfield - This email address is being protected from spambots. You need JavaScript enabled to view it.
MIST Council email - This email address is being protected from spambots. You need JavaScript enabled to view it.

RAS Awards

The Royal Astronomical Society announced their award recipients last week, and MIST Council would like to congratulate all that received an award. In particular, we would like to highlight the following members of the MIST Community, whose work has been recognised:
  • Professor Nick Achilleos (University College London) - Chapman Medal
  • Dr Oliver Allanson (University of Birmingham) - Fowler Award
  • Dr Ravindra Desai (University of Warwick) - Winton Award & RAS Higher Education Award
  • Professor Marina Galand (Imperial College London) - James Dungey Lecture

New MIST Council 2021-

There have been some recent ingoings and outgoings at MIST Council - please see below our current composition!:

  • Oliver Allanson, Exeter (This email address is being protected from spambots. You need JavaScript enabled to view it.), to 2024 -- Chair
  • Beatriz Sánchez-Cano, Leicester (This email address is being protected from spambots. You need JavaScript enabled to view it.), to 2024
  • Mathew Owens, Reading (This email address is being protected from spambots. You need JavaScript enabled to view it.), to 2023
  • Jasmine Sandhu, Northumbria (This email address is being protected from spambots. You need JavaScript enabled to view it.), to 2023 -- Vice-Chair
  • Maria-Theresia Walach, Lancaster (This email address is being protected from spambots. You need JavaScript enabled to view it.), to 2022
  • Sarah Badman, Lancaster (This email address is being protected from spambots. You need JavaScript enabled to view it.), to 2022
    (co-opted in 2021 in lieu of outgoing councillor Greg Hunt)

Charter amendment and MIST Council elections open

Nominations for MIST Council open today and run through to 8 August 2021! Please feel free to put yourself forward for election – the voting will open shortly after the deadline and run through to the end of August. The positions available are:

  • 2 members of MIST Council
  • 1 student representative (pending the amendment below passing)

Please email nominations to This email address is being protected from spambots. You need JavaScript enabled to view it. by 8 August 2021. Thank you!

Charter amendment

We also move to amend the following articles of the MIST Charter as demonstrated below. Bold type indicates additions and struck text indicates deletions. Please respond to the email on the MIST mailing list before 8 August 2021 if you would like to object to the amendment; MIST Charter provides that it will pass if less than 10% of the mailing list opposes its passing. 

4.1  MIST council is the collective term for the officers of MIST and consists of six individuals and one student representative from the MIST community.

5.1 Members of MIST council serve terms of three years, except for the student representative who serves a term of one year.

5.2 Elections will be announced at the Spring MIST meeting and voting must begin within two months of the Spring MIST meeting. Two slots on MIST council will be open in a given normal election year, alongside the student representative.

5.10 Candidates for student representative must not have submitted their PhD thesis at the time that nominations close.

Nuggets of MIST science, summarising recent papers from the UK MIST community in a bitesize format.

If you would like to submit a nugget, please fill in the following form: https://forms.gle/Pn3mL73kHLn4VEZ66 and we will arrange a slot for you in the schedule. Nuggets should be 100–300 words long and include a figure/animation. Please get in touch!
If you have any issues with the form, please contact This email address is being protected from spambots. You need JavaScript enabled to view it.. 

Transpolar Arcs: Seasonal Dependence Identified by an Automated Detection Algorithm

By Gemma E Bower (University of Leicester)

Transpolar arcs (TPAs) are primarily a northward IMF auroral phenomena. They consist of an arc of auroral emission poleward of the main auroral oval. Their presence suggests that the magnetosphere has a complicated magnetic topology. Currently, TPA formation and evolution have no single explanation that is unanimously agreed upon.

In order to further study the occurrence of TPAs we have developed an automated detection algorithm to determine the occurrence of TPAs in UV images captured by the Defense Meteorological Satellite Program/ Special Sensor Ultraviolet Spectrographic Imager (DMSP/SSUSI) from spacecraft F16, F17, and F18. The detection algorithm identified TPAs as a peak in the average radiance intensity poleward of 12.5° colatitude, in two or more of the wavelengths/bands sensed by SSUSI.

Over 5,000 SSUSI images containing TPAs were identified by the detection algorithm between the years 2010 to 2016. Figure 1a and b shows the seasonal and UT distribution for the F16 TPA images respectively. The occurrence of these TPA images shows a seasonal dependence, with more arcs being visible in the winter hemisphere.  There is also an apparent dependence on time-of-day, especially in the southern hemisphere where no TPAs are seen between 23 and 06 UT.

We investigated the effect that the orbital plane of DMSP has on the area of the detection window scanned, as a possible explanation of the dependences in the results of the detection algorithm. Figure 1c and 1d show the results for F16 for seasonal and UT distribution respectively. It can be seen that the orbital plane of DMSP leads to a preferential observation of the northern hemisphere, and the detection algorithm missing TPAs in the southern hemisphere around 01–06 UT. Hence, we conclude that there is no dependence of TPA occurrence on UT. No seasonal bias in the observations is found, indicating that the seasonal dependence of the TPA occurrence is real. We discuss the ramifications of these findings in terms of proposed TPA generation mechanisms.

Four bar charts showing the number of transpolar arcs identified between 2010 and 2016.

Figure 1: (a-b) Number of transpolar arc (TPA) images identified by F16 between 2010 and 2016. (c-d) Average percent of the detection window poleward of 12.5° colatitude scanned by F16 between 2010 and 2016. (a and c) By month. (b and d) By UT. The northern hemisphere is red and the southern hemisphere is blue

 

Please see paper for full details: Bower, G. E., Milan, S. E., Paxton, L. J., & Imber, S. M. (2022). Transpolar arcs: Seasonal dependence identified by an automated detection algorithm. Journal of Geophysical Research: Space Physics, 127, e2021JA029743. https://doi.org/10.1029/2021JA029743

Variation of Geomagnetic Index Empirical Distribution and Burst Statistics Across Successive Solar Cycles

By Aisling Bergin (University of Warwick)

Geomagnetic indices, based on magnetic field observations at the Earth's surface, provide almost continuous monitoring of Earth’s magnetospheric and ionospheric activity. We analyze two geomagnetic index time series, AE and SMR, which track activity in the auroral region and around the Earth's equator, respectively. We show here that quantiles of the index distributions track solar cycle variation over solar cycles 21–24. The question is then how the likelihood of events varies with solar cycle activity.

In this paper, events are defined as bursts or excursions above a threshold which is either (i) a fixed value or (ii) a quantile of the distribution of the observed index values. We study the solar cycle dependence of the distributions of the burst return periods, R, and the burst durations, τ. A result from the theory of level crossings (LC) [1] constrains how , the ratio of the mean burst duration to return period, depends on the underlying empirical distribution of the observed quantity.

Our main results are as follows:

  1. At fixed value burst thresholds, is peaked in the declining phase for AE annual samples and follows the sunspot number double peak for SMR.
  2. Bursts are identified in samples at three distinct phases of the solar cycle. At fixed quantile thresholds the distributions of τ and R fall on single empirical curves for each of (i) the AE index at solar minimum, maximum, and declining phase and (ii) the SMR index at solar maximum. This goes beyond the constraint on average from LC theory.
  3. The tail of the empirical cumulative distribution functions of the observed values of the AE and SMR indices collapse onto common functional forms specific to each index and cycle phase when normalized to the first two moments of their exceedance distributions.

Taken together, these results may combine to offer important constraints in the quantification of overall space weather activity levels.

 

Three panels showing how the theory of level crossings relates the empirical cumulative distribution function (cdf) to the ratio of the mean duration to mean return period for bursts above a specified threshold in a timeseries.
The theory of level crossings relates the empirical cumulative distribution function (cdf) to the ratio of the mean duration to mean return period for bursts above a specified threshold in a timeseries. Panels (a) - (c) illustrate this relationship for the SuperMAG 1-min ring current index (SMR) from 1975 to 2017. (a) Cdf values, C(x), and highlighted quantiles of interest (black lines) for nonoverlapping 1-year (-)SMR samples are seen to track the 13-month smoothed monthly sunspot number (red, shifted). (b) Bursts (grey) are identified where the SMR index (black) is below a given threshold, u (blue). Burst parameters duration (τ) and return period (R) are quantified. (c) The ratio of mean burst duration to mean return period for bursts in nonoverlapping 1-year (-)SMR samples over thresholds of 40 nT (purple), 60 nT (blue), and 100 nT (green) follows the sunspot number double peak (grey).

Please see the paper for full details: Bergin, A., Chapman, S. C., Moloney, N. R., & Watkins, N. W. (2022). Variation of geomagnetic index empirical distribution and burst statistics across successive solar cycles. Journal of Geophysical Research: Space Physics, 127, e2021JA029986. https://doi.org/10.1029/2021JA029986

[1] Lawrance, A., & Kottegoda, N. (1977). Stochastic modelling of riverflow time series. Journal of the Royal Statistical Society: Series A, 140(1), 1–31. https://doi.org/10.2307/2344516

Saturn's Weather‐Driven Aurorae Modulate Oscillations in the Magnetic Field and Radio Emissions

By Nahid Chowdhury (University of Leicester)

Planetary parameters at Saturn have exhibited mysterious time variabilities and periodicities for almost two decades. After the first Voyager measurements of the 1980s led to a determination of a rotation rate for the ringed planet, the advent of the Cassini mission in the 2000s showed that the measured length of a day at Saturn was subject to change. Numerous theories were proposed to explain the time variabilities seen in planetary parameters ranging from the radio emission through to the energies of neutral atoms and these fell into one of two general categories. The first was that a driving mechanism for the observed periodic behaviour would be situated externally to the planet, within the magnetosphere. The second was that a driving mechanism would be situated within the planet’s atmosphere.

Using infrared observations of Saturn’s northern polar auroral H3+ emission taken with Keck-NIRSPEC in 2017, we investigated ion flows in our search for a signature of the twin-vortex mechanism in the planet’s upper atmosphere that was purported to drive the observed periodicities. H3+ is an ion found in the ionosphere of gas giant planets and measurements of its line-of-sight velocity are indicative of the more general motion of constituents in the planet’s atmosphere.

By grouping our spectral data into quadrants of local northern planetary magnetic phase, we set up our experiment to probe the ion flows driven by the planetary period current. This led to the astonishing detection of the proposed ionospheric twin-vortices that are considered to be responsible for the periodicities witnessed throughout Saturn’s planetary and magnetospheric environments. Our observations show that local atmospheric weather effects at Saturn drive the twin-vortex flows while also generating some auroral emissions. This result has far-reaching implications for both other planets in our Solar System and exoplanetary systems.

 

Figure caption: Shown here is an example of the type of winds within the upper atmosphere that are driving the ionosphere to move in the way observed in this new paper. This set of two vortices rotate around the pole of the planet, driving currents within the ionosphere, which then reach out into the surrounding magnetosphere, producing the bright aurora and magnetic field changes observed by Cassini. This weather system was originally proposed by Chris Smith in a paper in Monthly Notices of the Royal Astronomical Society in 2011 (doi:10.1111/j.1365-2966.2010.17602.x) – and it is these modelled flows that we show here.

Please see paper for full details: Chowdhury, M.N., Stallard, T.S., Baines, K.H., Provan, G., Melin, H., Hunt, G.J., Moore, L., O’Donoghue, J., Thomas, E.M., Wang, R. and Miller, S., 2022. Saturn's Weather‐Driven Aurorae Modulate Oscillations in the Magnetic Field and Radio Emissions. Geophysical Research Letters49(3), p.e2021GL096492. DOI: https://doi.org/10.1029/2021GL096492.

Modelling the Varying Location of Field Line Resonances During Geomagnetic Storms

By Tom Elsden (University of Glasgow)

Field line resonances (FLRs) are the manifestation of a magnetohydrodynamic (MHD) wave coupling process where energy is transferred from a global to local field-aligned wave. The ‘resonance’ comes from a frequency matching between these waves and being a resonant process, can result in a significant accumulation of energy on a given field line. These waves play an important role in magnetospheric wave-particle interactions, the generation of aurora and can further be used as a seismological tool to remote sense the magnetosphere from ground-based observations.

The location where FLRs occur is intrinsically linked to the current state of the magnetosphere, with the magnetic field structure, plasma density and solar wind driving conditions all being key factors. Given the drastic effect of a geomagnetic storm on the morphology of the magnetosphere, we considered how such changes impact where FLRs form between storm and non-storm times.

We used ground magnetometer data to determine how the fundamental Alfven frequency of field lines varies over the course of a storm on average. These frequencies were then used to infer a plasma density profile to be used in a numerical MHD model to investigate where the FLRs would form under broadband solar wind driving conditions.

Figure 1 shows results from these simulations, displaying the field-aligned current density as an indication of FLRs, mapped from the ionosphere to the equatorial plane to display the radial structure. The left panel is from a simulation modelling the initial phase of a storm, with the right panel modelling the main phase. We show that for an average storm, the FLR moves radially inward by ~1.7RE (compare vertical line locations). This is caused by a decrease in the fundamental Alfven frequency as well as an increase in the global (fast) wave frequency which drives the FLRs.

The important aspect of the results is the overall trend of more Earthward FLR formation during storms. Particularly if extrapolated to more severe storms, this could have an impact on storm-time wave-particle interactions in the radiation belts.

 Colour contours of field-aligned current density from near the ionospheric end of field lines, mapped to the equatorial plane. Left: simulation modelling storm initial phase. Right: simulation modelling storm main phase. Vertical lines indicate field line resonance locations.

Figure 1 Caption: Colour contours of field-aligned current density from near the ionospheric end of field lines, mapped to the equatorial plane. Left: simulation modelling storm initial phase. Right: simulation modelling storm main phase. Vertical lines indicate field line resonance locations.


Please see paper for full details: Elsden, T., Yeoman, T. K., Wharton, S. J., Rae, I. J., Sandhu, J. K., Walach, M.-T., et al. (2022). Modeling the varying location of field line resonances during geomagnetic storms. Journal of Geophysical Research: Space Physics, 127, e2021JA029804. https://doi.org/10.1029/2021JA029804

 

Resolving Magnetopause Shadowing Using Multimission Measurements of Phase Space Density

 By Frankie Staples (formerly at MSSL UCL, now at UCLA)

Loss mechanisms act independently or in unison to drive rapid loss of electrons from the radiation belts. Electrons may be lost by precipitation into the Earth’s atmosphere, or through the magnetopause into interplanetary space – a process known as magnetopause shadowing. The mechanisms by which electrons are lost may be identified through changes to electron phase space density (PSD). This method considers the number of particles at given adiabatic coordinates (𝝁, K, and L*), which relate the electron energy, pitch angle, and location in the magnetic field. The characteristics of PSD evolution as a function of L* can be used to identify which loss mechanism is acting. However, the rapid nature of electron flux dropouts make it extremely difficult to resolve PSD dynamics at the necessary timescales to identify the contributions of either loss mechanism.

 

In this study we used a new multimission dataset of PSD observations from 36 satellites to resolve the dynamics of a magnetopause shadowing induced flux dropout in September 2017. We showed that by using Van Allen Probe data alone, the physical processes causing the dropout could be misinterpreted due to limited time and/or spatial resolution. Using multimission observations provided unprecedented time and spatial resolution necessary to correctly interpret PSD dynamics. 

 

The labelled Figure shows the magnetopause shadowing characteristics identified in PSD observations. Each panel shows PSD as a function of L* for fixed μ = 900 MeV/G and K = 0.1 G0.5RE at 1-hour intervals through phases of the storm. Symbol colours indicate when measurements were taken within the hour period, and dotted lines show the minimum and maximum L* of the last closed drift shell (LCDS) before the magnetopause. 

 A figure showing three scatter plots. The labelled Figure shows the magnetopause shadowing characteristics identified in PSD observations. Each panel shows PSD as a function of L* for fixed μ = 900 MeV/G and K = 0.1 G0.5RE at 1-hour intervals through phases of the storm.

Please see paper for full details: 

Staples, F. A., Kellerman, A., Murphy, K. R., Rae, I. J., Sandhu, J. K., & Forsyth, C. (2022). Resolving magnetopause shadowing using multimission measurements of phase space density. Journal of Geophysical Research: Space Physics, 127, e2021JA029298. https://doi.org/10.1029/2021JA029298