MIST

Magnetosphere, Ionosphere and Solar-Terrestrial

Latest news

STFC Policy Internship Scheme now open

This year has proved the critical importance of science having a voice within Parliament. But how does scientific evidence come to the attention of policy makers? If you are a STFC-funded PhD student, you can experience this first-hand through our Policy Internship Scheme, which has just opened for applications for 2020/21. During these three-month placements, students are hosted either at the Parliamentary Office of Science and Technology (POST) or the Government Office for Science (GO Science).

POST is an independent office of the Houses of Parliament which provides impartial evidence reviews on topical scientific issues to MPs and Peers. Interns at POST will research, draft, edit and publish a briefing paper summarising the evidence base on an important or emerging scientific issue. GO Science works to ensure that Government policies and decisions are informed by the best scientific evidence and strategic long-term thinking. Placements at GO Science are likely to involve undertaking research, drafting briefing notes and background papers, and organising workshops and meetings.

The scheme offers a unique opportunity to experience the heart of UK policy making and to explore careers within the science-policy interface. The placements are fully funded and successful applicants will receive a three-month extension to their final PhD deadline.

For full information and to see case studies of previous interns, please see our website. The closing date is 10 September 2020 at 16.00.

Applied Sciences special issue: Dynamical processes in space plasmas

 

Applied Sciences is to publish a special issue on the topic of dynamical processes in space plasmas which is being guest edited by Georgious Nicolaou. Submissions are welcome until 31 March 2021, and submission instructions for authors can be found on the journal website. For general questions, This email address is being protected from spambots. You need JavaScript enabled to view it..

MIST elections in 2020

The election for the next MIST councillors opens today, and will run until 23:59 on 31 July 2020. The candidates are Michaela Mooney, Matt Owens, and Jasmine Kaur Sandhu. 

If you are subscribed to this mailing list you should receive a bespoke link which will let you vote on the MIST website, which will be sent by This email address is being protected from spambots. You need JavaScript enabled to view it.. If you don’t receive this link, please check your junk folder! The candidates’ platforms are on the voting platform, and also reproduced below for your convenience. 

Michaela Mooney

I’m a final year PhD student at MSSL standing for MIST Council as a student representative. During my PhD, I’ve been actively engaged in the department as a Student Rep in the Staff Student Consultation Committee and in the Equality, Diversity and Inclusion Committee. I’m an active member of the MIST research community through proposals for RAS Discussion meetings and NAM sessions on geomagnetic activity. 

My main goals as a MIST Council representative would be to:

  • lobby funding bodies to reduce the impact of the pandemic on PhD students.
  • facilitate the organisation of virtual conferences and careers days to ensure that students continue to have opportunities to present research and access to careers information.
  • support good practises in equality, diversity and inclusion within the MIST community.

My key priority would be to limit the impact of the pandemic on students and ensure equality of opportunities.

Matt Owens

Now, more than ever, it’s vital our community address its diversity problems. If anyone is standing for MIST council from an underrepresented demographic, I’d encourage you to vote for them; MIST needs their experience and insight. If not, I’ll seek to ensure MIST council continues to promote equality of opportunity and diversity in science.

MIST’s primary role is to represent our solar-terrestrial science within the wider discipline. I’m predominantly a heliospheric scientist, but keep a toe in the solar physics community. E.g., I’ve served in editorial capacities for both JGR and Solar Physics, and have a good deal of experience with both NERC and STFC funding. As such, I’d hope to see MIST working closely with UKSP, as we have a lot of common interest. I am also keen that the MIST community coordinate to make the most of the industrial and operational forecasting opportunities that are open to it. Finally, I’m a very recent convert to open science. I would seek to increase the prevalence of research code publication and use of community tools within our field, for reasons of both efficiency and reproducibility.

Jasmine Kaur Sandhu

I am a post-doctoral research associate at the Mullard Space Science Laboratory, UCL, with a research focus on inner magnetospheric physics. During my time as a Council member I have led a number of initiatives, primarily the MIST Student’s Corner, the MIST Nugget Series, and the MIST online seminar series. If elected, I will continue to focus on supporting early career researchers in ways that promote diversity of both science and the scientists within our community. This will include developing a set of up-to-date, comprehensive, and informative resources on funding opportunities available to early career researchers for travel funding and fellowships. This will be supported by a mentor-like scheme for assistance and guidance on applications.

A Summary of the SWIMMR Kick-Off Meeting

The kick-off event for the Space Weather Innovation, Measurement, Modelling and Risk Study (one of the Wave 2 programmes of the UKRI Strategic Priorities Fund) took place in the Wolfson Library of the Royal Society on Tuesday November 26th. Seventy-five people attended the event, representing a range of academic institutions, as well as representatives from industry, government and public sector research establishments such as the UK Met Office. 

The morning session of the meeting consisted of five presentations, introducing the programme and its relevance to government, the Research Councils and the Met Office, as well as describing details of the potential calls. The presentations were as follows:

  •  Prof John Loughhead (Chief Scientific Advisor to BEIS) - Space Weather Innovation, Measurement, Modelling and Risk Programme (a governmental perspective). The slides from Prof John Loughhead's talk are available here.
  • Prof Chris Mutlow (Director of STFC RAL Space) - SWIMMR: Project funded by the Strategic Priorities Fund (a perspective from STFC).  The slides from Prof Chris Mutlow's talk are available here.
  • Jacky Wood (Head of Business Partnerships at NERC) - Space Weather Innovation, Measurement, Modelling and Risk (SWIMMR) - A NERC perspective.  The slides from Jacky Wood's talk are available here.
  • Dr. Ian McCrea (Senior Programme Manager for SWIMMR) -  SWIMMR: Space Weather Innovation, Measurement, Modelling and Risk: A wave 2 programme of the UKRI Strategic Priorities Fund.  The slides from Dr Ian McCrea's talk are available here.
  • Mark Gibbs (Head of Space Weather at the UK Met Office) - SWIMMR (Met Office perspective and detailed description of the calls.  The slides from Mark Gibb's talk are available here.

During the lunch break, the Announcement of Opportunity for the five NERC SWIMMR calls was issued on the NERC web site.  The afternoon therefore began with a brief introduction by Jacky Wood to the NERC Announcement of Opportunity, and the particular terms and conditions which it contained.

The remainder of the afternoon session was spent in a Question and Answer session in which attendees were able to ask questions to the speakers about the nature of the programme and the potential timing of future calls, and finally to an informal discussion session, in which participants gathered into groups to discuss the opportunities for funding which had been outlined. 

2019 RAS Council elections

As you may have seen, the nominations for RAS Council are currently open with a deadline of 29 November. MIST falls under the “G” (Geophysics) category and there are up to 3 councillor positions and one vice-president position available. MIST Council strongly encourages interested members of the MIST community to consider standing for election.
 
Clare Watt (University of Reading) has kindly volunteered to be a point of contact for the community for those who may wish to talk more about being on council and what it involves. Clare is a councillor on RAS Council, with her term due to complete in 2020, and This email address is being protected from spambots. You need JavaScript enabled to view it..
 

 

Nuggets of MIST science, summarising recent MIST papers in a bitesize format.

If you would like to submit a nugget, please contact This email address is being protected from spambots. You need JavaScript enabled to view it. 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!

Determining the Nominal Thickness and Variability of the Magnetodisc Current Sheet at Saturn

By Ned Staniland (Imperial College London)

The presence of an internal plasma source (the moon Enceladus) coupled with the rapid rotation rate of Saturn (~10 hrs) results in an equatorially confined layer of plasma that stretches the dipolar planetary magnetic field into what is known as a magnetodisc. This structure is found at both gas giants and so understanding its formation and how it responds to different drivers reveals the dynamics of these magnetospheres and how the geologically active moons affect them. We explore the thickness of the equatorial current sheet that is associated with the stretched field geometry. We use 66 fast, high inclination crossings of the current sheet made by Cassini, where a clear signature in the magnetic field data (Figure 1a shows a sharp reversal in the radial field during the crossing) allows for a direct determination of its thickness and offset.

We find that the current sheet is thinner than previously calculated but identify several sources of spatial and temporal variability. For instance, the current sheet is 50% thicker in the nightside inner magnetosphere compared to the dayside (Figure 1b). This is consistent with the presence of a noon‐midnight convection electric field at Saturn that produces a hotter plasma population on the nightside, resulting in a thicker current sheet. However, the current sheet becomes thinner with radial distance on the nightside, while staying approximately constant on the dayside (Figure 1b), reflecting the solar wind compression of the magnetosphere and the stretching of the field in the tail. Some of the variability is well characterized by the planetary period oscillations (PPOs). But we also find evidence for non‐PPO drivers of variability, highlighting the interplay between different drivers that shape the Saturnian system.  

This work shows the necessity for considering the variable structure of the largest current system in the Saturnian magnetosphere, which is essential particularly for future modelling efforts.

Plots showing (a) magnetic field signatures of a current sheet crossing for a example pass and (b) statistical distribution of the current sheet thickness comparing dayside and nightside crossings and inner and magnetodisc crossings.

Figure 1a) shows Cassini magnetic field data during a current sheet crossing. We determine the current sheet boundaries by identifying spikes in the variance of the cylindrical radial field component (green line, top panel). Figure 1b) shows box plots calculated from the 66 crossings that highlight the radial profile and day-night asymmetry of the current sheet thickness.

For more information, please see:

Staniland, N. R., Dougherty, M. K., Masters, A., & Bunce, E. J. (2020). Determining the nominal thickness and variability of the magnetodisc current sheet at Saturn. Journal of Geophysical Research: Space Physics, 125, e2020JA027794. https://doi.org/10.1029/2020JA027794

Random forest model of ultra‐low frequency magnetospheric wave power

By Sarah Bentley (Northumbria University)

Parameterised (statistical) models are being increasingly used in space physics, both as an efficient way to use large amounts of data and as an important step in real-time modelling, to capture physics on scales not incorporated in numerical modelling. We have used machine learning techniques to create a model for the power in ultra low frequency (1-15mHz, ULF) waves throughout Earth’s magnetosphere. Capturing the power in these global-scale waves is necessary to determine the energisation and transport of high energy electrons in Earth’s radiation belts, and the model can also be used to test how individual wave driving processes combine throughout the magnetosphere.

The model is constructed using ensembles of decision trees (i.e. a random forest). Each decision tree iteratively partitions the given parameter space into variable size bins to reduce the error in the predicted output values. These variable bins mitigate several difficulties inherent to space physics data (sparseness, interdependent driving parameters, nonlinearity) to produce an approximation of ULF wave power in our chosen parameter space: physical driving parameters (solar wind speed vsw, magnetic field component Bz and variance in proton number density var(Np)) and spatial parameters of interest (magnetic local time MLT, magnetic latitude and frequency band).

[frequency, latitude, component, MLT, vsw, Bz, var(Np)] → ULF wave power

It is not always possible to extract all physical processes from parameterised models such as this. Instead we suggest a hypothesis testing framework to examine the physics driving ULF wave power. This formalises the approach taken in full statistical surveys, beginning with dominant driving processes, testing how they manifest in the model, and then examining remaining power.

Plots showing how ULF wave power varies with MLT and a given parameter. Each panel considers a different parameter.

Figure 1: Variation of ULF wave power at one station, 5mHz. Model-predicted power spectral density is shown by magnetic local time at quantiles of (a) speed (for median Bz < 0 and var(Np)), (b) Bz < 0 (for median speed and var(Np)) and (c) var(Np) (for median speed and Bz < 0). Median values for speed, Bz < 0 and var(Np) are 421 km s−1, −1.8 nT and var(Np) = −0.716 log10(cm−3) respectively. (d)-(f) also show variation of wave power with speed, Bz and var(Np) but for Bz > 0 (with a median value of Bz = 1.7 nT held constant for (d) and (f)). Radius of each quantile corresponds to the power spectral density in log10(nT2/Hz) predicted for those solar wind values, at that station, frequency and magnetic local time.

In the paper we demonstrate how this method of iteratively considering smaller scale driving processes applies to magnetic local time asymmetries in ULF wave power. In Figure 1 we can see the wave power predicted by the model when we change one driving parameter and keep the others constant, for Bz<0 and Bz>0 separately. The MLT asymmetries in power clearly change with both driving parameter and there are two separate behaviour regimes for Bz>0, Bz<0. Digging deeper into these results using the framework, we conclude that

  • The dawn-dusk wave power asymmetry is a combined effect of the different radial density profiles and wave driving from magnetopause (“external”) perturbations such as Kelvin-Helmholtz instabilities.
  • We cannot account for the effects of a compressed magnetosphere, but var(Np) does not represent wave driving by magnetopause perturbations.
  • Nor does Bz, which likely represents wave power increases with substorms. 

We also found significant remaining uncertainty with mild solar wind driving, suggesting that the internal state of the magnetosphere should be included in future models.

Please see the paper for full details:

Bentley, S. N., Stout, J., Bloch, T. E., & Watt, C. E. J. (2020). Random forest model of ultra‐low frequency magnetospheric wave power. Earth and Space Science, 7, e2020EA001274. https://doi.org/10.1029/2020EA001274

Accounting for variability in ULF wave radial diffusion models

By Rhys Thompson (University of Reading)

The Van Allen outer radiation belt is a region in near‐Earth space containing mostly high‐energy electrons trapped by the Earth's geomagnetic field. It is a region populated by satellites that are vulnerable to damage from the high‐energy environment. Many modern outer radiation belt models simulate the long‐time behaviour of high‐energy electrons by solving a three‐dimensional Fokker‐Planck equation for the drift‐ and bounce‐averaged electron phase space density that includes radial, pitch‐angle, and energy diffusion.

Radial diffusion is an important process, driven by ultralow frequency (ULF) waves, where electrons are drawn from the outer boundary and accelerated toward Earth, or pushed away from the outer radiation belt and lost to interplanetary space. All of the physics is contained in the radial diffusion coefficient, DLL, often deterministically parameterized to provide a single output from the specified inputs which does not allow for any variability in the underlying ULF wave power. 

We perform idealized numerical ensemble experiments on radial diffusion, introducing temporal and spatial variability to a widely used DLL, based on the median of statistical ultralow frequency (ULF) wave power for a particular geomagnetic index Kp, through stochastic parameterization constrained by statistical properties of its underlying observations. Results for one of the experiments is shown below in Figure 1. Our results demonstrate the sensitivity of radial diffusion over a long time period to the full distribution of the radial diffusion coefficient, highlighting that information is lost when only using median ULF wave power. A better understanding of temporal and spatial variations of ULF wave interactions with electrons, and being able to characterize these variations to a good level of accuracy, is vital to produce a robust description of radial diffusion over long timescales in the outer radiation belt.


Electron phase space density as a function of L value for different temporal variability timescales for a 2 day experiment.

Figure 1: Ensemble results for the electron phase space density (PSD) at the end of a 2 day radial diffusion experiment, where ensemble DLL time series over the duration of the experiment are formulated by applying (lognormal) variability to a constant deterministic DLL (Kp=3) over a range of temporal variability scales (1, 3, 6, 12, and 24 hr, respectively). When variability is applied it persists until to the next hour of variability (relative to the temporal variability scale) where the process is repeated. The median (dashed), mean (dash‐dot) ensemble profiles are shown, as well as the initial PSD profile (dotted) and the deterministic solution with constant deterministic DLL (solid). Ensemble kernel density estimates of the resulting electron PSD are also shown.

Please see the paper for full details:

Thompson, R. L.Watt, C. E. J., & Williams, P. D. (2020). Accounting for variability in ULF wave radial diffusion modelsJournal of Geophysical Research: Space Physics125, e2019JA027254. https://doi.org/10.1029/2019JA027254

Multi‐scale observation of two polar cap arcs occurring on different magnetic field topologies

By Jade Reidy (University of Southampton & British Antarctic Survey)

Polar cap arcs (auroral arcs occurring at high latitudes) have been under debate since they were first discovered over 100 years ago. Although reports present conflicting evidence of the arcs forming on open field lines whilst others argue they are formed on closed field lines, recent work suggests that more than one polar cap arc formation mechanism potentially exists (e.g. Reidy et al., 2017, 2018).

Two events containing polar cap arcs occurring over Svalbard have been investigated using multiscale ground‐based and spacecraft instrumentation. Figures 1a and 2a show UV images from each event from the Special Sensor Ultra-Violet Imager (SSUSI) on board low-orbiting spacecraft (DMSP). These auroral images have been projected onto magnetic local time grids with noon at the top and dawn to the right. On both SSUSI images, we have projected an all sky camera image from Svalbard; this demonstrates how the ground-based and global-scale observations are related and allowed us to find an interval where the arc passes through the small field of view of the Auroral Structure and Kinetics (ASK) instrument (shown in Figures 1b and 2b for each event). Key features of each event are summarised below:

Event 1 – A Closed Event

  • Electron and ion precipitation observed in both hemispheres.
  • Highly dynamic small scale structure is observed (Figure 1b), similar to features in the main auroral oval.

Spacecraft and ground-based images of the auroral arc showing both the global structure and the small-scale structuring.

Figure 1: Observations of the polar cap arc occurring on 04 February 2016. (a) SSUSI and the all sky imager observations. (b) ASK instrument observations of the auroral arc.

Event 2 – An Open Event

  • An electron-only particle signature.
  • Very dim auroral features that are consistent with the low plasma density of the magnetotail lobes (Figure 2b).

Spacecraft and ground-based images of the auroral arc showing both the global structure and the small-scale structuring.

Figure 2: Observations of the polar cap arc occurring on 15 December 2015, in the same format as Figure 1.

In the full paper we investigate the different formation mechanisms further by comparing to observations from different instrumentation (including a ground-based spectrograph, located on Svalbard, and the Super Dual Auroral Radar Network). We conclude both events to be consistent with different and distinct formation mechanisms and that this is reflected in the small scale observations.

Please see the paper for full details:

Reidy, J. A.,  Fear, R. C.,  Whiter, D. K.,  Lanchester, B. S.,  Kavanagh, A. J.,  Price, D. J., et al. (2020).  Multi‐scale observation of two polar cap arcs occurring on different magnetic field topologies. Journal of Geophysical Research: Space Physics,  125, e2019JA027611. https://doi.org/10.1029/2019JA027611

Dipole Tilt Effect on Magnetopause Reconnection and the Steady‐State Magnetosphere‐Ionosphere System: Global MHD Simulations

By Joseph Eggington (Imperial College London)

The Earth's dipole axis is tilted with respect to the Sun; the extent of this tilt, given by the ‘dipole tilt angle’, changes both diurnally and seasonally as the planet orbits and rotates. This introduces numerous variabilities in the coupled magnetosphere‐ionosphere system, such as altering the location and intensity of magnetic reconnection, allowing the tilt angle to strongly influence magnetospheric convection. In this study, we perform global magnetohydrodynamic (MHD) simulations of the steady‐state magnetosphere‐ionosphere system using the Gorgon MHD code. We drive the system with purely southward Interplanetary Magnetic Field (IMF) conditions for tilt angles from 0–90°, exploring hypothetical configurations beyond the actual extreme of ~30° to elucidate the underlying tilt angle dependence of the system. We identify the location of the magnetic separator (the 3-D reconnection X-line) with increasing tilt angle, showing how the shift of the separator southward on the magnetopause and the resulting changes in the reconnection rate lead to weaker and more time-dependent coupling with the solar wind at large tilt angles.

These trends map down to the ionosphere, with the polar cap contracting as the tilt angle increases, and the region I field‐aligned current (FAC) system migrating to higher latitudes with changing morphology. As shown in the Figure, the hinging of the magnetotail current sheet towards the equator in a tilted configuration results in a longer convection pathway for open field lines in the Northern hemisphere, as the reconnection site on the nightside is shifted more weakly than on the dayside. This introduces a North‐South asymmetry in magnetospheric convection, driving more FAC in the Northern ionosphere for large tilt angles than in the South independent of hemispheric differences in conductance. These results highlight the strong sensitivity to onset time in the potential impact of a severe space weather event, since the intensity of stormtime FACs at a given location on the ionosphere will depend closely on the orientation of the dipole axis.

Animation showing the response of field configuration and current density to changing dipole tilt angle. The corresponding FACs response is also shown.

Figure: Animation of the effect of a changing dipole tilt angle on the magnetosphere-ionosphere system. The left panel shows a contour map of the magnetospheric current density in the noon-midnight meridian plane, with magnetic field lines in black. The orange crosses mark the approximate location of the dayside and nightside reconnection sites; the white dashed line shows the magnetopause location, and the solid white line represents the magnetic equator. The two right panels show contours of the FAC in the northern and southern ionosphere, with the open-closed boundary as a black dotted line.

Please see the paper for full details:

Eggington, J. W. B., Eastwood, J. P., Mejnertsen, L., Desai, R. T., & Chittenden, J. P. (2020). Dipole tilt effect on magnetopause reconnection and the steady‐state magnetosphere‐ionosphere system: Global MHD simulations. Journal of Geophysical Research: Space Physics, 125, e2019JA027510. https://doi.org/10.1029/2019JA027510