MIST

Magnetosphere, Ionosphere and Solar-Terrestrial

Latest news

Representing the MIST Community in award nominations

MIST Council has recently launched an effort to create an award nominations task force with the following aims:

  1. Actively contribute towards more equal representation and a diverse range of nominees for awards
  2. Recognise and promote the work of overlooked members of the community
  3. Provide a means for students and ECRs to gain experience in preparing an effective nomination package

The initial plan is to start by considering those awards given out by the Royal Astronomical Society. This is so there will be sufficient time to prepare nomination packages by the RAS deadline (July 2020), and the wide range of awards will allow us to consider the entire MIST community. The task force is spearheaded by Oliver Allanson, Jasmine Sandhu, and Maria-Theresia Walach.

This task force is inspired by Liz MacDonald, a heliophysicist at NASA’s Goddard Space Flight Center. Liz Macdonald organized the Nomination Task Force within AGU’s Space Physics and Aeronomy (SPA) section, which has been summarised in an article in Eos. We plan to work in a manner similar to that described in the article, as we believe that by having a community task force we will be able to achieve community-wide representation in a timely manner.

If you would like to be part of the task force then please sign-up using our Google Form by Friday 4th October. At this stage we are not soliciting for specific ideas for nominees. Instead we are seeking to gauge support and receive feedback. We would like to emphasise that all members of the MIST community are welcome, and indeed encouraged, to sign-up to to join this task force, from PhD student to Emeritus Professor.

New MIST Chair and Vice-Chair elected

Congratulations to John Coxon on becoming MIST Chair, and to Jasmine Sandhu on becoming MIST Vice-chair in a unanimous vote at a Council meeting last week.
 
MIST Council elects a new Chair whenever the previous Chair steps down, and in addition this year, the council has decided to elect a Vice-Chair for the first time.
 
On behalf of the MIST community, we would like to thank Ian McCrea for doing a superb job as Chair during his tenure on the Council.

EGU elections now open

The call for candidates for the EGU 2019 elections is currently open, with a deadline of 15 September 2019. The following roles are up for election: Union President, General Secretary, and the Division Presidents. More details about these roles and how you can nominate yourselves/colleagues can be found on the EGU website. 
 
MIST Council would like to emphasise that this is an excellent opportunity to contribute to and shape the field on an international scale, and we hope to see members from the MIST community putting themselves forward.

Summer Science Exhibition 2020

The Royal Society is currently accepting proposals for the Summer Science Exhibition 2020, and the deadline for proposals is 10 September 2019. Further details on applying can be found here.
 
MIST Council would like to highlight that this is an excellent opportunity for cross-institutional collaborations! The MIST community is involved in a number of projects with a particularly timely aspect (e.g. Solar Orbiter and SMILE), which would be very appropriate to propose to the Royal Society. If you are currently preparing a proposal that you are happy to invite community members to join or you have an idea for a proposal that you would like to work with the community on, then please email This email address is being protected from spambots. You need JavaScript enabled to view it. with a short outline by 9 August 2019. We hope to then share these projects with the community to build support for the proposals and involve the wider community!
 
We will be discussing this further and sharing ideas on the #public-engagement channel on the MIST Slack workspace. If you aren’t on the MIST Slack workspace then click here for details.

2019 Rishbeth prize winners announced

We are pleased to announce that the Rishbeth Prizes this year are awarded to Affelia Wibisono and Michaela Mooney , both of the Mullard Space Science Laboratory (UCL).
 
Affelia Wibisono wins the prize for the best MIST student talk, entitled “Jupiter’s X-ray Aurorae as seen by XMM-Newton concurrently with Juno”. Michaela wins the best MIST poster prize, for a poster entitled “Evaluating auroral forecasts against satellite observations”.
 
MIST Council would like to congratulate both Affelia and Michaela. As prize winners, Affelia and Michaela have been invited to write articles for Astronomy & Geophysics, which we look forward to reading.

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!

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.

Nugget: Statistical characterisation of the growth and spatial scales of the substorm onset arc

By Nadine Kalmoni, UCL Mullard Space Science Laboratory, Holmbury St. Mary, Dorking, Surrey, UK

During southward IMF reconnection on the dayside leads to a build up of magnetic energy in the tail. As flux is piled into the tail the configuration becomes unstable leading to an explosive release in magnetic energy, termed a substorm. The rearrangement of the magnetic field is accompanied by highly dynamic substorm aurora.

The relatively high temporal and spatial resolution of the THEMIS mission All Sky Imagers have allowed recent observations of small scale azimuthal structures, auroral beads, which form in the minutes leading to auroral onset [e.g. Rae et al., 2009]. Conjugate observations in the Northern and Southern hemisphere suggest that the beads have a common magnetotail driver and are the ionospheric signature of a magnetospheric instability [Motoba et al., 2012].

Kalmoni et al. [2015] statistically analyse the growth and spatial scales of clear signatures of auroral beads observed in the minutes leading to substorm onset. The statistical observations are compared with the Shear-Flow Ballooning Instability (SFBI) [Voronkov et al., 1997] and the Cross-Field Current Instability [Lui, 2004 and references therein] which have both been proposed to play a role in substorm onset. Our observations conclude that the SFBI initiated in the near-Earth plasma sheet is the most likely explanation.

Kalmoni, N. M. E., I. J. Rae, C. E. J. Watt, K. R. Murphy, C. Forsyth, and C. J. Owen (2015), J. Geophys. Res. Space Physics, 120, doi:10.1002/2015JA021470.

kalmoni nugget

Normalised growth rate as a function of spatial scale in comparison to (a) the Cross-Field Current Instability for inner-edge and mid-tail plasma sheet parameters and (b) the Shear-Flow Ballooning Instability for varying shear-flow widths.