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.. 

Electron Diffusion by Wave-Particle Interactions in the Radiation Belt

By Oliver Allanson (University of Reading)

The Earth's outer radiation belt is a dynamic and extended radiation environment within the inner magnetosphere, composed of energetic plasma that is trapped by the geomagnetic field. The size and location of the outer radiation belt varies dramatically in response to solar wind variability - orders of magnitude changes in the electron flux can occur on short timescales (~hours). However, it is very challenging to accurately predict, or model, fluxes within the radiation belt. This is a pressing concern given the hundreds of satellites that orbit within this hazardous environment, and so the prediction of its variability is a key goal of the magnetospheric space weather community (e.g. see Horne et al., 2013).

Most physics-based computer models of particle dynamics in the radiation belts rely upon the assumption of slow perturbations to electron distributions due to interactions with low amplitude electromagnetic waves. However, satellite observations have shown that high amplitude waves and correspondingly large changes in electron distributions are not rare (e.g. see a recent example with observations from the ARASE satellite in Kurita et al., 2018). In our novel electromagnetic particle-in-cell numerical experiments, we analyse the diffusion in energy and pitch angle space of 100 million individual high-energy electrons in conditions typical of the radiation belt environment - due to interactions with externally driven electromagnetic waves. The method is illustrated in Figure 1. We present two main conclusions:

(i) On very short timescales (~0.1 second) we observe an initial ‘anomalous’ electron response, for which the rate of diffusion is nonlinear in time.

(ii) After the initial transient phase we observe a normal diffusive response that is consistent with quasilinear theory.

A schematic showing the steps taken by the particle-in-cell numerical experiment.

Figure 1: A schematic illustrating the particle-in-cell numerical experiment.

 The results demonstrate the exciting capabilities of our new experimental technique. Here we prove the concept for conditions that are unlikely to deviate from standard theory, and in future experiments this framework will allow us to investigate the changing nature of the electron response with increased electromagnetic wave amplitude.

For more information, please see the paper:

Allanson, O.,  Watt, C. E. J.,  Ratcliffe, H.,  Meredith, N. P.,  Allison, H. J.,  Bentley, S. N., et al. ( 2019).  Particle‐in‐cell experiments examine electron diffusion by whistler‐mode waves: 1. Benchmarking with a cold plasma. Journal of Geophysical Research: Space Physics,  124. https://doi.org/10.1029/2019JA027088 

On the Calculation of the Effective Polytropic Index in Space Plasmas

by Georgios Nicolaou (MSSL, UCL)

The effective polytropic index of space plasmas γ is crucial for understanding the dynamics of the plasma particles. For instance, numerous theoretical descriptions and simulations of plasmas, demand the knowledge of the effective polytropic index for accurate calculations.  

Several studies, determined γ within different plasma regions, using single spacecraft observations of the plasma density and temperature T. The effective polytropic index γ is typically determined from a linear chi-squared minimization fitting of lnT as a function of lnn.

In this paper, we investigate the accuracy of γ calculations based on the standard fitting analysis, considering plasma n and T measurements with a certain level of uncertainty σn and σT respectively (see Figure 1). We model typical plasmas, and we show that uncertainty in the plasma density measurements introduces a systematic error in the calculation of γ, and potentially leads to artificial isothermal indices (Figure 1, left). On the other hand, uncertainty in the plasma temperature measurements introduces a statistical error in the calculation of γ (Figure 1, right). We analyze Wind spacecraft observations of solar wind protons in order to investigate the propagated uncertainties in real plasma applications, confirming our model predictions (Figure 1).

These results highlight how uncertainties in plasma measurements can lead to erroneous values of the poytropic index. In this study we present a new data-analysis approach for reducing the number of erroneous data-points from future analyses.

Plots showing how the polytropic index varies with uncertainty in density and uncertainty in temperature.

Figure 1. Normalized histograms of (left) γ as a function of σn/n, for σT/T < 15% and (right) γ as a function of σT/T, for σn/n < 1%. The white line is the mean value of the histogram in each column. We display only the range of uncertainties for which we have more than 100 data points. On each panel, we show the predictions of our model (red) for plasma parameters corresponding to the mode values of each parameter for the analyzed intervals.

For more information, please see the paper:

Nicolaou, G., G. Livadiotis, R. T. Wicks (2019). On the Calculation of the Effective Polytropic Index in Space Plasmas. Entropy, 21, 997. https://doi.org/10.3390/e21100997.

Long-term Correlations of Polytropic Indices with Kappa Distributions in Solar Wind Plasma near 1 AU

by Georgios Nicolaou (MSSL, UCL)

The polytropic process determines a relationship between the plasma density and temperature, during the transition of the plasma from one equilibrium state to another under constant specific heat. This process is described by the effective polytropic index, which can be determined by the analysis of plasma density and temperature measurements, and is a crucial parameter in determining the dynamics of the plasma.

Over the last few decades numerous studies have shown that the velocities of the plasma particles often follow kappa distribution functions. The kappa index that labels and governs these distributions also becomes a key parameter to understand the plasma dynamics.

Interestingly, recent studies have shown that the polytropic indices and kappa indices of space plasmas are related, in the presence of potential energy. Moreover, the relationship between the two indices defines the potential degrees of freedom.

This is the first statistical study to analyze Wind spacecraft observations to derive the polytropic index and the kappa index of solar wind protons and investigate their relationship, over the last two solar cycles. We show that, most of the time, the two indices are related, exactly as predicted by the theory. When able, we quantify the relation in order to derive the potential degrees of freedom. Among others, we show that an enhanced solar activity and/or interplanetary magnetic field, reduces the potential degrees of freedom, and decrease the dimensionality of a typical electric field potential from dr = 3 in solar minimum, to dr = 2 in solar maximum (Figure 1).

Overall, these results identify fundamental properties of the solar wind plasma, that demonstrate clear dependences on solar cycle.

Dimensionality plotted as a function of sunspot number.

Figure 1. Dimensionality dr for a typical interplanetary potential as a function of sunspot number Sn. The linear fit to data points (black dash) is also shown. The results indicate that the potential dimensionality dr reduces with increasing Sn.

For more information, please see the paper:

Nicolaou G. and G. Livadiotis (2019). Long-term correlations of polytropic indices with Kappa distributions in solar wind plasma near 1 AU. The Astrophysical Journal, 884:52, https://iopscience.iop.org/article/10.3847/1538-4357/ab31ad/meta 

The Variation of Geomagnetic Storm Duration with Intensity

By Carl Haines (University of Reading)

Variability in the near-Earth solar wind conditions can adversely affect a number of ground- and space-based technologies.  Some of these space weather impacts on ground infrastructure are expected to increase primarily with geomagnetic storm intensity, but also storm duration, through time-integrated effects. Forecasting storm duration is also necessary for scheduling the resumption of safe operating of affected infrastructure. It is therefore important to understand the degree to which storm intensity and duration are related.

In this study, we use the recently recalibrated aa index, aaH, which provides a global measure of the level of geomagnetic disturbance. We analyse the relationship between geomagnetic storm intensity and storm duration over the past 150 years, further adding to our understanding of the climatology of geomagnetic activity. In particular, we construct and test a simple probabilistic forecast of storm duration based on storm intensity. Using a peak-above-threshold approach to define storms, we observe that more intense storms do indeed last longer but with a non-linear relationship (See Figure 1a).

A plot showing the duration increases with storm intensity and the number of storms decreases with storm intensity.A plot showing the observed probability and the model output, both as a function of storm intensity. The distributions are very similar.

Figure 1 (a) The mean duration (red) and number of storms (blue) plotted as a function of storm intensity. (b) The probability that a storm will last at least 24 hours plotted as a function of storm intensity. The black line shows the observed probability and the red line shows the model output.

Next, we analysed the distribution of storm durations in different intensity classes. We found them to be approximately lognormal, with parameters depending on the storm intensity. On this basis we created a method to probabilistically predict storm duration given peak intensity. Equations are given to find lognormal parameters as a function of storm peak intensity. From these, a distribution of duration can be created and hence a probabilistic estimate of the duration of this storm is available. This can be used to predict the probability a storm will last at least e.g. 24 hours. Figure 1b shows the output of the model for a range of storm peak intensity compared against a test set of the aaH index. The model has good agreement with the observations and provides a robust method for estimating geomagnetic storm duration. The results demonstrate significant advancements in not only understanding the properties and structure of storms, but also how we can predict and forecast these dynamic and hazardous events.

For more information, please see the paper:

Haines, C., Owens, M.J., Barnard, L. et al. Sol Phys (2019) 294: 154. https://doi.org/10.1007/s11207-019-1546-z 

Cassini’s Grand Finale:- Planetary Period Oscillations are everywhere and the dayside field ‘lags’

by Gabby Provan (University of Leicester) 

Saturn’s Planetary Period Oscillations are oscillations at close to Saturn’s planetary period which have been observed to organize all of Saturn’s ionospheric and magnetospheric parameters throughout the Cassini mission.  There are two oscillatory systems, one in the Northern hemisphere and one in the Southern. The enduring mystery is that so far we have yet to understand how a perfectly axisymmetric planetary magnetic field can create such oscillations

In this paper, we study the magnetic field throughout the Cassini Grand Finale orbits.  On these orbits Cassini passed from the northern auroral region in the dawn sector, through the gap between the D ring inner edge and Saturn’s atmosphere, and outbound to the southern auroral region in the dusk sector (See Figure 1). We observe dual PPO modulations on auroral, subauroral, ring-region and intra-ring region field lines – in other words everywhere (see Figure 2).  This is the first time that PPOs have been observed on and inside ring region field lines.  The presence of such field perturbations may provide an explanation for apparent PPO-related phenomena observed in the ring material itself, through the action of these fields on charged dust grains (see e.g. Chancia et al., 2019).

A schematic showing Cassini's pass through key regions of interest.

Figure 1: Plot of the periapsis pass trajectories of the initial and final proximal orbits, Revs 271  (blue) and 292 (red), projected into a meridian plane in cylindrical coordinates.  The darker blue field-aligned area corresponds to field lines mapping through the main ring region in the equatorial plane, between the inner boundary of the C ring and the outer boundary of the A ring, while the lighter blue field-aligned area corresponds to field lines mapping through the D ring.

Next, we considered the residual magnetic field, having discounted the magnetic signature of the PPOs and Saturn’s ring current from the observed magnetic field observations.  We found that the residual azimuthal field had a lagging configuration in the subauroral region with a magnitude ~3-5 nT.  These fields extend essentially unmodified inwards, crossing the ring region and the field lines mapping to Saturn synchronous orbit, to the outer boundary of D ring field lines.  The lagging field indicates a field-aligned current flow of ~0.25 MA rad-1 flowing from the southern ionosphere toward the C and inner B rings. The physical origin of the extended region of lagging dayside fields remains unclear. 

Magnetic field data.

Figure 2: Field data from all the proximal orbit periapsis passes, color-coded  according the northern PPO system phase.  The data are plotted versus time from their field-parallel points taken as t = 0 (central vertical black dotted line), over the interval between -100 and +80 min,  Vertical dashed lines indicate the equatorward boundary of the auroral region.   The green solid lines mark the field line passing through the outer boundary of the A ring, while the green dashed and dotted lines mark the field lines passing through the outer and inner boundaries of the D ring, respectively.  Data in Figures 2a-2c on the left are color-coded by northern PPO phase such that phases near 0°-360° are colored red and phases near 180° blue.  Similarly, data in Figures 2d-2f on the right are color-coded by northern PPO phase such that phases near 90° are colored red and phases near 270° blue.

For more information, please see the paper:

Provan, G.,  Cowley, S. W. H.,  Bradley, T. J.,  Bunce, E. J.,  Hunt, G. J.,  Cao, H., &  Dougherty, M. K. ( 2019). Magnetic field observations on Cassini's proximal periapsis passes: Planetary period oscillations and mean residual fields. Journal of Geophysical Research: Space Physics,  124. https://doi.org/10.1029/2019JA026800