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..

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..
 

 

Outcome of SSAP priority project review

From the MIST mailing list:

We are writing to convey the outcome of this year’s priority project “light touch” review, specifically with reference to those projects within the remit of SSAP. We would like to thank all the PIs that originally submitted ideas, and those who provided updates to their projects over the summer. SSAP strongly believe that all the projects submitted are underpinned by strong scientific drivers in the SSAP area.

The “light touch” review was undertaken with a unified approach by SSAP and AAP, considering factors that have led to priority project development (in STFC or other research councils) or new funding for priority projects (1/51 projects in the STFC remit) in the last 12 months. After careful discussion, it was agreed by SSAP and AAP not to select any project where the remit clearly overlaps with UKSA (i.e. space missions or TRL 4+), reflecting STFC’s focus on ground-based observations, science exploitation and TRL 0-3 development. Whilst in no way reflecting the excellence of the science, or community scientific wishes, this approach has resulted in some changes to the list of SSAP priority projects. However, now, unlike at the time of the original call, it is clear that such projects cannot move forwards without UKSA (financial) support, and such funds are already committed according to UKSA’s existing programme. SSAP remain strongly supportive of mission-led science in solar-system exploration, so SSAP have strongly recommended that the high-level discussions between UKSA and STFC continue with a view to supporting a clear joint priority projects call in future, more naturally suited to mission and bi-lateral opportunities.

The priority projects (and PIs) identified by SSAP for 2019/20 are:

  • Solar Atmospheric Modelling Suite (Tony Arber)
  • LARES1: Laboratory Analysis for Research into Extra-terrestrial Samples (Monica Grady)
  • EST: European Solar Telescope (Sarah Matthews)

SSAP requested STFC continue to work with all three projects to expand their community reach and continue to develop the business cases for future (new) funding opportunities. In addition, SSAP have requested that STFC explore ways in which the concept of two projects—“ViCE: Virtual Centres of Excellence Programme / MSEMM Maximising Science Exploitation from Space Science Missions”—can be combined and, with community involvement, generate new funding for science exploitation and maximising scientific return in solar-system sciences. Initially this consultation will occur between SSAP and STFC.

We would like to thank the community again for its strong support, and rapid responses on very short timescales. A further “light touch” review will occur in 2020, with a new call for projects anticipated in 2021. SSAP continue to appreciate the unfamiliar approach a “call for proposals with no funding attached” causes to the community and are continuing to stress to STFC that the community would appreciate clearer guidance and longer timescales in future priority project calls.

Yours sincerely,

Dr Helen Fraser on behalf of SSAP

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!

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

 

Effects of VLF transmitter waves on the inner belt and slot region

by Johnathan Ross (British Antarctic Survey)

Signals from man made VLF (Very Low Frequency) transmitters can leak from the Earth-ionosphere wave guide into the inner magnetosphere, where they propagate as electromagnetic waves and contribute to electron dynamics in the inner radiation belt and slot region. These waves are highly localised around the transmitters and are strongest on the nightside. It has been suggested that these waves may be responsible for removing the hazardous MeV energy electrons from this region that can be extremely damaging to satellites. The VLF transmitter waves scatter electrons in pitch angle (the angle between the background field and electron velocity). In an average sense, this scattering can be represented by a diffusion equation, with a diffusion coefficient that can be calculated using quasi-linear theory. In this study we use ~5 years of Van Allen Probesobservations to construct global statistical models of the diffusion coefficients for each individual VLF transmitter, as a function of L*, Magnetic Local Time (MLT) and geographic longitude.

These diffusion coefficients are then incorporated into a 1D pitch-angle diffusion model with longitude and MLT dependence. We find that global averages of the wave power capture the long-term dynamics of the loss process, despite the highly localised nature of the waves in space. We use our model to assess the role of VLF transmitter waves compared to other important loss processes (hiss waves and coulomb collisions) on electron loss in the inner radiation belt and slot region. The figure shows the decay timescales as a function of L value for different combinations of the VLF transmitter (T), coulomb collisions (C), and hiss wave (H) processes. At moderate relativistic energies, E~500 keV (panel d), waves from VLF transmitters have a significant role! They reduce electron lifetimes by an order of magnitude or more, down to the order of 200 days near the outer edge of the inner radiation belt. However, VLF transmitter waves are ineffective at removing multi-MeV electrons (panel f) from either the inner radiation belt or slot region. The results suggest that although the VLF transmitters are important for radiation belt loss, they cannot be responsible for removing the dangerously high energy electrons from the region occupied by satellites.

For more information, please see the paper:

Ross, J. P. J.,  Meredith, N. P.,  Glauert, S. A.,  Horne, R. B., &  Clilverd, M. A. ( 2019).  Effects of VLF transmitter waves on the inner belt and slot region. Journal of Geophysical Research: Space Physics,  124, 5260– 5277. https://doi.org/10.1029/2019JA026716

Electron decay timescales considering a combination of different loss processes.

Figure: Electron decay timescales from the 1D model with MLT and longitude averaging. The lines correspond to: black - Coulomb collisions; green - hiss and Coulomb collisions; blue - VLF transmitters and Coulomb collisions; red - VLF transmitters, hiss and Coulomb collisions.

How does substorm activity affect the ring current?

by Jasmine Kaur Sandhu (MSSL, UCL)

Earth’s magnetosphere is highly dynamic and due to coupling with the solar wind huge amounts of energy can be stored in the stretched magnetotail. Substorms (impulsive bursts of nightside reconnection) rapidly close large amounts of the tail flux and, through enhanced convection and injection of plasma, substorms can significantly energise the ring current population.

Do substorms with different properties affect the ring current differently?

Substorms can occur as an isolated event (preceded and followed by quiet periods) or as part of a compound event (multiple substorms occurring one directly after the other). A statistical analysis of ion observations from the Van Allen Probes was conducted to identify the similarities and differences in the ring current population during isolated substorms and the first compound substorm in a sequence. Figure a,b,d,e shows L-MLT maps of the median ring current energy content for both isolated and compound substorms, as well as before substorm onset (growth phase) and after substorm onset (expansion phase). Figure c,f shows statistically significant changes following onset and Figure g,h shows the difference in energy content for compound substorms compared to isolated.

Both types of substorms are associated with an enhancement post-onset, where the total enhancement is larger for a compound substorm. We also observed that the ring current energy content is elevated during compound substorms compared to isolated substorms, both before and after onset. Analysis shows that a key driver of these differences is the enhanced and prolonged solar wind driving prior to onset of compound substorms. Plasma is more effectively circulated to the inner magnetosphere and the density of injections are increased.

Overall the work demonstrates the importance of solar wind driving for the substorm – ring current relationship and suggests that compound substorms are able to very effectively energise the ring current to a high degree.

For more information, please see the paper:

Sandhu, J. K.,  Rae, I. J.,  Freeman, M. P.,  Gkioulidou, M.,  Forsyth, C.,  Reeves, G. D., et al. (2019). Substorm‐ring current coupling: A comparison of isolated and compound substorms. Journal of Geophysical Research: Space Physics,  124. https://doi.org/10.1029/2019JA026766

Plots showing the spatial distribution of ring current energy content.

Figure: Values for each L‐MLT bin are plotted at the bins' location in the L‐MLT domain for the H+ ions. The mean energy values, E (J), are shown for (a) growth phases of isolated substorms, (b) expansion phases of isolated substorms, (d) growth phases of compound substorms, and (e) expansion phases of isolated substorms. The difference in the mean values, ΔE (J), for the expansion phase relative to the growth phase is shown for (c) isolated substorms and (f) compound substorms. The difference in mean values for the compound substorms relative to the isolated substorms is shown for (g) the growth phase and (h) the expansion phase. It is noted that, for the difference plots (c, f, g, h), the difference in mean values is only plotted if the distributions are identified to be statistically different according to the Kolmogorov‐Smirnov test with p<0.01. MLT = magnetic local time.

 

First evidence for multiple-harmonic standing Alfvén waves in Jupiter’s equatorial plasma sheet

By Harry Manners (Imperial College London)

Ultra-low-frequency (ULF) magnetohydrodynamic waves carry energy and momentum through planetary magnetospheres, corresponding to perturbations on large spatial-scales. These perturbations can lead to global oscillations of the magnetic field known as field line resonances (FLRs). While ULF waves and FLRs have been studied extensively in the terrestrial magnetosphere, relatively little literature exists concerning the same phenomena in magnetospheres of the outer planets.

We have used magnetometer data from the Galileo spacecraft to search for ULF wave-power at Jupiter, specifically in the thin, dense equatorial plasma sheet (see panel a of Figure). By removing the background magnetic field we were able to isolate perturbations in the direction transverse to the background field (panel b). We obtained frequency-time information via wavelet transforms of the magnetic-field residuals.

We found evidence for a multiple-harmonic wave structure isolated in the equatorial plasma sheet, on 8th November 1996. Four harmonics were detected, with periods ranging from 4 to 22 minutes (panel c).

We band-pass filtered the transverse field components to obtain a ~1 nT contribution from each harmonic. Subsequent polarization analysis revealed reversals in handedness in each signal consistent with the structure of a multiple-harmonic standing Alfvén wave (panel d). The same analysis suggests all of the detected harmonics are odd modes, with no evidence to support the presence of even modes. We currently have no explanation for the absence of the even modes, but speculate that it is a consequence of the symmetry of the driving mechanism with respect to the magnetic equator.

For more information, please see the paper:

Manners, H. A., & Masters, A. (2019). First evidence for multiple‐harmonic standing Alfvén waves in Jupiter's equatorial plasma sheet. Geophysical Research Letters, 46. https://doi.org/10.1029/2019GL083899

Galileo magnetometer data showing the presence of multiple harmonics and reversals in the handedness.

Figure: a) Magnetic field data from the Galileo spacecraft during 8th November 1996. b) Transverse magnetic field residuals, showing ULF wave packets. c) Wavelet transform of one of the transverse components, showing coincident enhancements in wave power at 22, 14, 7 and 4 minutes. d) Reversals in the handedness of the 22 minute wave signal, consistent with standing Alfvén waves.

 

Timescales of Birkeland Currents Driven by the IMF

By John Coxon (University of Southampton)

Birkeland currents are the mechanism by which information is communicated from Earth’s magnetopause to the ionosphere. Understanding the timescales of these currents is very useful for understanding the ionosphere’s reaction to magnetopause phenomena. We use the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) dataset, which uses magnetometers on 66 spacecraft in low Earth orbit to derive Birkeland current density on a grid of colatitude and magnetic local time. The current densities are derived in a ten minute sliding window, evaluated every two minutes.

We use the SPatial Information from Distributed Exogenous Regression (SPIDER) technique (Shore et al, 2019), which treats each coordinate of a global dataset (e.g. AMPERE or SuperMAG) independently, regressing the time series in each coordinate against some external driver to find the time lag that maximises the correlation of the two. 

The figure below shows the correlation (left) and lag (centre) of the current densities with Interplanetary Magnetic Field (IMF) Bz. We focus on the R1 and R2 regions (right) here. Southward (negative) Bdrives Birkeland current as a result of magnetic reconnection, as shown by the correlations. Looking at the lags on the dayside, the poleward lags are 10–20 minutes, reflecting the time taken for the Birkeland currents to start to react to magnetic reconnection. At all MLT, the equatorward lags are 60–90 minutes, reflecting the time at which the polar cap is largest. On the nightside, the poleward lags are 90–150 minutes, reflecting how long it takes the polar cap to contract during nightside reconnection. More details on the R1/R2 correlations, and other correlations between Birkeland current and IMF Band By, are available in the full study.

For more information, please see the paper: 

Coxon, J. C., Shore, R. M., Freeman, M. P., Fear, R. C., Browett, S. D., Smith, A. W., et al. ( 2019). Timescales of Birkeland currents driven by the IMF. Geophysical Research Letters, 46, 78937901. https://doi.org/10.1029/2018GL081658

Polar plots showing the correlation and lag of AMPERE current density data. A schematic illustrating the key regions is also shown.

Figure: Correlation (left) and lag (centre) of AMPERE current density with IMF Bz in March 2010. A key to the regions visible is presented in the right-hand panel, to allow easy references in the text above.