MIST

Magnetosphere, Ionosphere and Solar-Terrestrial

Latest news

New mailing list for Python in space science

A new mailing list for space scientists who use Python has been founded. Angeline Burrell writes: 

There's been a recent push for more community python development and peer-to-peer support. Much of this is focused in the US at the moment, but as the results of the recent survey showed, MIST scientists are active or interested in python as well. If you would like to become involved, you can join the email list by contacting This email address is being protected from spambots. You need JavaScript enabled to view it..

The mailing list will comprise discussion as well as webinars/telecons from Python users, so the list should be useful for a range of abilities with Python. To join, please email This email address is being protected from spambots. You need JavaScript enabled to view it..

New MIST forum via Slack

In the days of yesteryear, there was a MIST forum provided for members of the MIST community to discuss things in a fashion more immediate and informal than email. It has been some years since the fabled MIST forum was a going concern, and in that time, the MIST Council has technically been in violation of the MIST Charter, which states that

MIST will provide an on-line forum to allow ongoing discussions and the formulation of ideas prior to public dissemination. This forum will be private, visible only to registered members; membership is restricted to active MIST scientists and is offered at the discretion of MIST council chair.

As a result of realising that the Charter mandates the maintenance of a forum, MIST Council have chosen to create a Slack workspace for the MIST community. If you would like to join, please This email address is being protected from spambots. You need JavaScript enabled to view it. specifying the email address you would like to use, and you will be invited to join.

MIST Council election results

The polls have closed, and Oliver Allanson (Reading) and John Coxon (Southampton) have been elected to MIST Council. The full results of 2018’s elections are as follows:

  • Oliver Allanson: 56 votes
  • John Coxon: 100 votes
  • Simon Pope: 27 votes
  • Samuel Wharton: 38 votes
  • Darren Wright: 40 votes

121 people cast two votes, and 19 cast a single vote, for a total of 140 responses. This is a turnout of 32.9% against the MIST mailing list, which comprises 426 eligible voters.

The chair of MIST Council, Ian McCrea, said:

I would like to congratulate John on his re-election to MIST Council and to congratulate Oliver on his election – we look forward to you joining us at our next meeting. To the unsuccessful candidates, I would like to say a sincere thank you for taking part and for your interest in being part of MIST Council. Obviously only two candidates can be successful in any given year, but there are elections every year and we hope that you will not be discouraged from standing again at a future date.

MIST Council would like to express their thanks and appreciation to Luke Barnard who is leaving MIST Council, and whose contributions over the last three years have been invaluable. We would also like to thank Q Stanley for handling the technical aspects of the election.

Astronomy/Solar System Advisory Panels call for priority projects

The Astronomy and Solar System Advisory Panels have been asked to identify a few priority projects, comprising 'large scale' (>£50M), ‘medium scale’ (£10-50M) and ‘small scale’ (<£10M) projects that can be started within the next 6 years. The outline business cases put forward by the community will be considered by STFC’s Executive Board and Science Board in September. We will then work with the community and UKRI to identify the best way of taking these ideas forward. 

Interested parties should summarize their ideas for priority projects using the template provided. Only those projects considered to be the most exciting and highest priority (by the Advisory Panels) will be asked to develop an outline business case. Please email your project summary to This email address is being protected from spambots. You need JavaScript enabled to view it. (Astronomy) or This email address is being protected from spambots. You need JavaScript enabled to view it. (Solar System). If your project has overlap with both astronomy and solar system, then please indicate this in your summary and send to both panels. The deadline is Wednesday 18 July 2018. If you have any questions regarding remit, format or submission, please feel free to contact the relevant Advisory Panel.

Jonathan Eastwood wrote, in his email to the MIST mailing list:

STFC has launched a consultation with research communities, designed to identify new world class science and technology proposals for potential future investment. The aim is to develop an ambitious portfolio of outline business cases for priority projects that relate to our strategic scientific and research infrastructure objectives, covering our remit, and driven by our communities… the scope of the projects is very broad – what is needed are exciting and ambitious scientific projects within the broad remit of astronomy and solar system science. Funds for estates and campus development are out of scope, and projects should not be an uplift to the grant/fellowship lines. This exercise is not part of the Evaluation of Astronomy which STFC will undertake in the Autumn (part of its assessment of the wider astronomy, particle and nuclear physics programmes), but projects identified here will be forwarded to that exercise to ensure information is not lost.

MIST Council would like to urge members of the MIST community to engage with this exercise in order to make sure that MIST science is well-represented in STFC strategy in the future.

Petition to eliminate harassment and bullying

MIST council is committed to fostering an open and inclusive scientific environment.

Many people will have seen the recent reports of bullying and harassment in Universities are becoming more and more widespread. In one of many steps to highlight the need for these actions to stop, an open letter and petition has been prepared by members of the wider community, including faculty from Imperial, UCL, and other UK and international institutions. This cross-institute example underlines the importance of eliminating harassment and bullying from the university and research environments. If you wish to sign the petition, you can find it by clicking here.

Our community is a big part of the RAS, which has a Code of Conduct and a Diversity, Equality and Inclusion Policy that we must adhere to:

  1. Promoting an inclusive environment for all.
    2. Promoting equality of opportunity.
    3. Welcoming applications from all backgrounds.
    4. Supporting and developing careers for all.
    5. Recruiting and promoting staff based on merit, rather than absence or presence of underrepresented characteristics.

We would strongly encourage our community to continue to participate in eradicating these issues from our scientific and every day lives.

Solar Wind Dependence of Magnetospheric Ultra-Low Frequency Plasma Waves

By Sarah Bentley, Department of Meteorology, University of Reading, UK

Ultra-low frequency plasma waves (ULF, 1-15 mHz) are implicated in the energisation and transport of radiation belt electrons. Therefore a description of magnetospheric ULF wave power in terms of driving parameters is highly desirable for radiation belt forecasting; in particular, we want to describe power in terms of solar wind properties, as the solar wind is the dominant driver behind these waves.

However, identifying solar wind driving parameters is severely hampered by the nature of the solar wind. All solar wind parameters are highly interrelated due to their common solar sources and the interactions within the solar wind between the Sun and Earth, resulting in the effect that all solar wind properties correlate so strongly with speed vswthat investigating their relationship to magnetospheric properties is difficult.

To circumvent analysis techniques that require properties such as a linear interdependence between these parameters, we use a series of simple yet systematic two-parameter plots (e.g. Figure 1) to identify which parameters are causally correlated to ULF wave power, rather than just correlated via a relationship with speed vsw. We find that speed, the southward component of the interplanetary magnetic field and summed power in proton number density perturbations (vsw, Bz < 0 and δNp) are the three dominant parameters driving power in magnetospheric ultra-low frequency waves. These parameters can be used in future modelling but are also of interest because there is clearly a threshold at Bz = 0, and because ULF wave power depends more on perturbations δNp than the number density Np itself.

For more information, see the paper below or an informal blog post here.

Bentley, S. N., Watt, C. E. J., Owens, M. J., & Rae, I. J. (2018). ULF wave activity in the magnetosphere: Resolving solar wind interdependencies to identify driving mechanisms. Journal of Geophysical Research: Space Physics, 123. https://doi.org/10.1002/2017JA024740

Figure 1: A two-parameter plot taken from Bentley et al., 2018. We bin the ULF power observed at one station (roughly corresponding to geostationary orbit) at one frequency (2.5mHz) and observe whether it increases with increases in solar wind speed vswand/or the component Bz of the interplanetary magnetic field, using fifteen years of data. Cut-throughs at constant speed and Bz are shown in (b) and (c). ULF power increases with speed and with more strongly negative Bz for Bz<0, but only with speed for Bz>0.  

The Role of Proton Cyclotron Resonance as a Dissipation Mechanism in Solar Wind Turbulence

By Lloyd Woodham, Mullard Space Science Laboratory, University College London, UK

The solar wind contains turbulent fluctuations that are part of a continual cascade of energy from large scales down to smaller scales. At ion-kinetic scales, some of this energy is dissipated, resulting in a steepening in the spectrum of magnetic field fluctuations and heating of the ion velocity distributions, however, the specific mechanisms are still poorly understood. Understanding these mechanisms in the collisionless solar wind plasma is a major outstanding problem in the field of heliophysics research.

We use magnetic field and ion moment data from the MFI and SWE instruments on-board the Wind spacecraft to study the nature of solar wind turbulence at ion-kinetic scales. We analyse the spectral properties of magnetic field fluctuations between 0.1 and 5.5 Hz over 2012 using an automated routine, computing high-resolution 92 s power and magnetic helicity spectra. To ensure the spectral features are physical, we make the first in-flight measurement of the MFI ‘noise-floor’ using tail-lobe crossings of the Earth's magnetosphere during early 2004. We utilise Taylor's hypothesis to Doppler-shift into the spacecraft frequency frame, finding that the spectral break observed at these frequencies is best associated with the proton-cyclotron resonance scale, 1/kc, compared to the proton inertial length di and proton gyroscale ρi. This agreement is strongest when we consider periods where βi,perp ~ 1, and is consistent with a spectral break at di for βi,par « 1 and ρi for βi,perp » 1.

Histograms for 2012 of the estimated helicity onset frequency, fb, versus the three characteristic plasma scales, converted into frequencies using Taylor's hypothesis - fL represents fkc, fdi, and fρi, for each column respectively. The data used are for periods where 0.95 ≥ βi,perp ≥ 1.05. The colour-bar represents the column-normalised number of spectra. The black dashed lines represent fb = fL and similarly, the red dashed lines are fb = fL√2 and fb = fL√2, which give the resolution of the wavelet transform about the line fb = fL due to the finite width of the Morlet wavelet in frequency space. We see the best agreement between fb and fkc during these periods.

We also find that the coherent magnetic helicity signature observed at these frequencies is bounded at low frequencies by 1/kc and its absolute value reaches a maximum at ρi. These results hold in both slow and fast wind streams, but with a better correlation in the more Alfvénic fast wind where the helicity signature is strongest. We conclude that these findings are consistent with proton-cyclotron resonance as an important mechanism for dissipation of turbulent energy in the solar wind, occurring at least half the time in our selected interval. However, we do not rule out additional mechanisms.

Woodham et al., 2018, The Role of Proton Cyclotron Resonance as a Dissipation Mechanism in Solar Wind Turbulence: A Statistical Study at Ion-kinetic Scales, ApJ, 856, 49, DOI: 10.3847/1538-4357/aab03d

 

The Broadband Excitation of 3-D Alfvén Resonances (FLRs) in a MHD Waveguide

By Tom Elsden, Department of Mathematics and Statistics, University of St. Andrews, St. Andrews, UK

Field line resonance (FLR) has been the theoretical mechanism used to explain a myriad of ground and spaced based observations of ultra low frequency (ULF) waves in Earth’s magnetosphere. FLR is a plasma physics process whereby energy from a global oscillation (fast mode) can be transferred to local oscillations along magnetic field lines (Alfvén mode), where the fast mode frequency matches the local Alfvén frequency. This process was first studied analytically where the plasma was only inhomogeneous in the radial direction (mathematically 1D) [Southwood, 1974, Chen and Hasegawa, 1974] and has since been extended both analytically and numerically to more complicated systems [e.g. Lee and Lysak, 1989, Chen and Cowley, 1989, Wright and Thompson, 1994, Russell and Wright, 2010].

A feature of FLRs in complicated geometries, such as a dipole, is that the poloidal (radial) and toroidal (azimuthal) Alfvén frequencies are different [e.g. Radoski, 1967]. This infers that the location where the FLR will occur is dependent on the polarisation of the Alfvén wave. This property has recently been explored theoretically in 3D [Wright and Elsden, 2016] and forms the basis of this current work. The magnetosphere is asymmetric and therefore requires an understanding of FLR in 3D. We look at wave coupling in an excessively asymmetric waveguide in order to study the physics clearly.

The figure below taken from Elsden and Wright [2018], displays cuts in the equatorial plane from a 3D MHD waveguide simulation using a 2D dipole magnetic field geometry. In each panel, the x-axis is the radial direction (α) and the y-axis the azimuthal direction (β), and the density varies with azimuth. The left panel shows the energy density (dimensionless units) integrated along a field line, showing an accumulation of energy along curved resonance paths, where the FLR polarisation is between poloidal and toroidal. The middle and right panels show the square root of the kinetic energy in the equatorial plane, revealing ridges which develop by phase mixing in 3D. We find that with a broadband driver it is the natural fast waveguide modes which drive FLRs. Such modes are fairly insensitive to the form of the driver, and hence the resonances are seen at the same locations for many different driving stimuli. This means that the resonances are a property of the medium, and can hence be used as a seismological tool to infer properties of the equilibrium. Finally, the key point is that traditionally FLRs are regarded as having a strictly toroidal polarisation. However, here we have shown in 3D that they can have other polarisations.

Elsden, T. and A. N. Wright (2018), The Broadband Excitation of 3D Alfvén Resonances in a MHD Waveguide, J. Geophys. Res. Space Physics, 123, doi:10.1002/2017JA025018

Figure: Left: Energy density integrated along a field line. Black dashed line represents a theoretical prediction of the main FLR location. Middle: Square root of the the kinetic energy in the equatorial plane. Right: Same as middle but annotated for use in other plots in the paper.



AuroraWatch UK: An Automated Aurora Alert System

By Nathan A. Case, Department of Physics, Lancaster University, Lancaster, UK

The aurora borealis, though most often visible from more northerly latitudes, can occasionally be seen from the UK too. To help the public in their endeavour to see the northern lights from the UK, Lancaster University’s AuroraWatch UK issues alerts of when the aurora might be visible.

As the currents driving the aurora intensify, they produce disturbances to the local magnetic field. Since its inception in September 2000, AuroraWatch UK has been using its own suite of magnetometers to record these disturbances and issue real-time alerts about where in the UK an aurora might be seen.

We have now combined and standardised these alerts, using the latest alert algorithm to produce a 17-year dataset of UK aurora alerts. This dataset, along with the real-time data, is freely available for the community and the general public to use. We find that the alerts match well with the wider Kp index and the solar cycle.

Case, N. A., Marple, S. R., Honary, F., Wild, J. A., Billett, D. D., & Grocott, A. 2017. AuroraWatch UK: An automated aurora alert system. Earth and Space Science, 4, 746–754. https://doi.org/10.1002/2017EA000328

(left) A pie chart illustrating the number of hours spent at each AuroraWatch UK activity level, as a percentage of the total number of hours. (right) A histogram of the percentage of hours spent at an elevated alert level (i.e., yellow or above) per year. Also plotted are (solid line) the percentage of time per year where Kp ≥ 4 and (dashed line) the mean daily sunspot number per year (as a proxy for solar activity). The sunspot number is divided by 10 for scale.

Nugget: Are steady magnetospheric convection events prolonged substorms?

By Maria-Theresia Walach, Department of Physics and Astronomy, University of Leicester, Leicester, UK

The large scale convection of magnetic flux within the Earth’s magnetosphere due to reconnection, also known as the Dungey cycle [Dungey, 1961; 1963], is partially driven by the solar wind. During southward IMF reconnection at the subsolar magnetopause opens flux, which is then added to the magnetotail. Depending on the strength of solar wind-driving, the magnetospheric response can be delayed, episodic or prolonged, also known as “magnetospheric modes” [e.g. Pulkkinen et al., 2007].

Walach and Milan [2015] produced a statistical analysis of the event progression of steady magnetic convection events (intervals where the dayside reconnection is balanced by nightside reconnection [e.g. DeJong et al., 2008]), substorms (dominant dayside reconnection is followed by a delayed interval of dominant nightside reconnection [e.g. Baker et al., 1996]), and sawtooth events (signatures appearing to be quasi-periodic and quasi-global substorms [e.g. Henderson, 2004]). Superposed epoch analyses show that 58% of the studied steady magnetospheric convection events are part of prolonged substorms, where dayside reconnection is at first dominant. Then nightside reconnection is initiated as part of a substorm, but as the solar wind-driving continues the Earth’s magnetosphere then progresses into a state of steady magnetospheric convection, after which the substorm recovery continues.

Walach, M.-T., S. E. Milan (2015), J. Geophys. Res. Space Physics, 120, doi:10.1002/2014JA020631.

walach nugget

Superposed epoch analysis of substorms (red), sawtooth events (orange), steady magnetospheric convection events with preceding substorms (blue) and steady magnetospheric convection events without preceding substorms (green). The onset of the steady magnetospheric convection events with preceding substorms has been shifted to match the preceding substorm onset. The time of the event duration for the steady magnetospheric convection events in superposed epoch analyses in the right column has been normalised.