Space Plasma Research at UCL/MSSL

We are active in a number of areas of Space Plasmas Research, driven by our current and future participation in international space science missions for which we have, or will provide instrument hardware.  These include interests in the solar wind, and the terrestrial and planetary magnetospheres.  


The solar wind is a continuous supersonic outflow of plasma from the Sun that fills the space between the planets. The solar wind is turbulent, and collisions between solar-wind particles are very rare. This leads to many effects that are counter-intuitive to our everyday experience with neutral gases like the air. Although we know that the solar wind is launched in the solar corona, the acceleration mechanisms, the heating of the solar wind, the role of non-equilibrium physics, as well as the effects of waves and turbulence are still areas of very active research. 

Members of the Space Plasma Physics group at MSSL work on answering these questions using spacecraft measurements of the particles and the electromagnetic fields in the solar wind as well as plasma theory and simulations. We want to understand the origin of the solar wind, its propagation through interplanetary space, and its interaction with celestial bodies. 

We are the principal investigator institute for the Solar Wind Analyser (SWA) instrument suite on board the upcoming Solar Orbiter mission. This mission will launch in 2020 and investigate the connection between the Sun and the solar wind in great detail. In addition to leading the SWA consortium, we built the Electron Analyser System (EAS) for SWA at MSSL. We also use data from past and present space missions such as Helios, Cluster, Wind, and MMS to study the solar wind.

We work in close collaboration with the UCL/MSSL Solar Physics group in order to better our understanding between phenomena on the Sun and their propagation into the solar system.

Artist's impression of plasma regions of the magnetosphere

Earth's magnetosphere describes the region around our planet controlled by the global magnetic field. This region, populated by plasma from both the lower atmosphere and the solar wind, is a highly complex and variable system. The magnetosphere responds strongly to external driving from the solar wind and internal dynamics. How dynamic processes, such as storms and substorms, are driven and the response of the system to these processes are current open questions for the field. 

Through use of spacecraft and ground based observations, we are exploring the features of the magnetosphere and the key processes that occur. In particular, we study the source and loss processes of the radiation belt population during geomagnetic storms, the triggering of the substorm process and the substorm energy budget. 

The principal tool we use for magnetospheric research is data from the ESA 4-spacecraft Cluster mission and China/ESA 2-spacecraft Double Star mission. UCL/MSSL is the Principal Investigator Institute for the Electron Spectrometer instrument (PEACE) flown on all 6 of these spacecraft.  We also use data from the GOES, THEMIS, and the Van Allen Probes, and from a range of ground based instruments (e.g. the CARISMA magnetometer array).

Artist impression of Jupiter and its moons. Image courtesy John Spencer

Often in close collaboration with members of the UCL/MSSL Planetary Group, members of the Space Plasmas Group regularly participate in studies of the plasma environments (magnetospheres, ionospheres, plasma wakes, etc.) of other solar system bodies.

Our expertise in studying the plasma environment around the Earth and the abundance of data available allow us to study the similarities and differences between the different planetary systems throughout the solar system. Through these comparisons, we can further our understanding of the fundamental physics of plasmas. 

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MSSL Space Plasma Science Highlights

Figure 3 from Forsyth et al. [2018]. Superposed epoch analysis results with respect to substorm onset of the substorm FACs (SU‐MLT and SD‐MLT) from AMPERE, calculated by removing the median current in the hour before onset. The top and bottom rows show the upward substorm FAC (SU) and downward substorm FAC (SD), respectively, in each MLT sector. As per the above, the results are subdivided into seasons of 90 days centered on the solstices and equinoxes.

Seasonal and Temporal Variations of Field‐Aligned Currents and Ground Magnetic Deflections During Substorms

Earth is surrounded by electrical currents flowing in space. These currents, which can be 10,000 times greater than domestic electrical supplies, can flow along the Earth's magnetic field and into the upper atmosphere and are linked to aurora. The size of this current depends on atmospheric conditions, with the upper atmosphere being a better conductor when it is sunlit, and the interaction between particles flowing from the Sun and the Earth's magnetic field. During space weather events known as substorms, which happen several times per day on average, the aurora brightens massively and the currents flowing into the upper atmosphere increase. Using data from the Iridium communications satellites, measured these currents during substorms. More...


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

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. More...

NHDS: The New Hampshire Dispersion relation Solver

NHDS: Calculating the properties of plasma waves

Waves are a very important mechanism to transfer energy in a plasma and to heat the particles efficiently. These processes occur in astrophysical, space, and laboratory plasmas. Like all electric charges, the plasma particles react on electric and magnetic fields, while they also change the electric and magnetic fields themselves. This makes plasmas a lot more complicated than normal (neutral) gases. As a consequence of this behaviour, there are many different types of waves that can exist in a plasma, while a gas like the air we are breathing only carries one type of wave (the sound wave).  More...

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Understanding Waves and Instabilities in Collisionless Plasmas with ALPS

The solar wind is a plasma in which collisions are very rare. Many plasmas in the universe are in this so-called "collisionless" state. This applies, for example, to a common type of accretion disks around black holes in the centres of galaxies, the very dilute medium between galaxies, magnetospheres around planets and comets, as well as pulsar winds in supernova remnants. In all collisionless plasmas, the behaviour of plasma waves, which are the fundamental building blocks of many important plasma processes, is more complicated to understand than in a collision-dominated plasma. Therefore, we have to rely on computer models to calculate the properties of plasma waves. With their help, it is also possible to calculate whether the plasma is in a stable or unstable state, a question of great importance for understanding the plasma behaviour. More...

The role of localised compressional Ultra-Low Frequency waves in energetic electron precipitation

Global-scale electromagnetic wave activity known as Ultra-Low Frequency (ULF) waves have been historically discussed as playing an indirect role in the acceleration and loss of radiation belt electrons. This is primarily due to the fact that ULF waves cannot easily interact with the gyration of electrons causing acceleration, or their bounce motion causing them to be lost. However, certain assumptions on the global-scale nature of these ULF wave fields are made to arrive at this conclusion. In this paper, we explore the validity of the assumptions that go into our current thinking, and provide a thought experiment on how a localised, large-amplitude electromagnetic wave field could interact with relativistic particles and play a direct role in radiation belt losses as a result. We conclude that localized ULF wave fields may provide an additional and, importantly, complementary means to more established processes that are known to precipitate electrons from the radiation belts during geomagnetic storms. More...

Page last modified on 08 sep 11 09:26