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.  

Illustration of the proposed model for the polar hole origin of the fast solar wind by Tu & Marsch (2005)

The solar wind is a stream of plasma that flows radially outwards from the Sun, carrying with it the solar magnetic field. It is a supersonic plasma that is shocked by its encounters with bodies throughout the solar system. The source of the solar wind and its evolution through the solar system are areas of active research within the Space Plasma Physics group at MSSL.

We are the principal investigator institute for the Solar Wind Analyser (SWA) suite of sensors which are selected for inclusion on ESA’s Solar Orbiter Mission.  This mission, targeted for launch in January 2017, is a candidate to be the first component of ESA’s Cosmic Vision 2015-2025 Programme.  As well as leading the international SWA consortium, preparations for this mission at UCL/MSSL include the scientific analysis of current space-based observations of the solar wind, which acts to inform the design and prototyping work for the SWA Electron Analyser System (SWA/EAS), which will be built at UCL/MSSL.

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

We are engaged in the scientific study of the structures and dynamics of a number of regions found within and around the Earths magnetosphere, including the magnetospheric cusps, the magnetopause and the magnetotail. We are particularly interested in magnetic reconnection, and its manifestations at the magnetopause (for example through studies of Flux Transfer Events) and in the magnetotail (in particular the physics of magnetospheric substorm and related phenomena). In addition, recent work concentrates also on the auroral regions, and the physical processes which accelerate particles precipitating from the magnetosphere to the energies needed for auroral activation.

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 Polar, Interball, Geotail, ACE, Wind and THEMIS satellites.  

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. 

MSSL Space Plasma Science Nuggets

Azimuthal electric field PSD values derived from ground-based magnetometer measurements of the D-component magnetic field PSD at L = 7.94, 6.51, 5.40, 4.26, 4.21, 2.98, and 2.55. The dashed lines represent constant fits to these PSD values. From Ozeke et al. (2014)

New and improved analytic expressions for ULF wave radiation belt radial diffusion coefficients

Ozeke et al. [2014] presented analytic expressions for ULF wave-derived radiation belt radial diffusion coefficients, as a function of L and Kp, which can easily be incorporated into global radiation belt transport models. The diffusion coefficients are derived from statistical representations of ULF wave power, electric field power mapped from ground magnetometer data, and compressional magnetic field power from in situ measurements.

An example of the difficulty to visually define an time and location for auroral break-up, but how well an automated algorithm picks out this period of brightening. From Murphy et al. (2014)

Automated determination of auroral breakup during the substorm expansion phase using all-sky imager data

MSSL researchers participated in the development of a novel method for quantitatively and routinely identifying auroral breakup following substorm onset using the THEMIS (Time History of Events and Macroscale Interactions during Substorms) all-sky imagers.

. Field-Aligned currents observed by the AMPERE mission and ground perturbations of the Hall current components  of the substorm current wedge during three substorm expansion phases.  The polarisation ellipses point towards the centre of the substorm current wedge, and the integrated FACs from AMPERE show a significantly complex current structure results in a net upward and downward current structure as first identified by McPherron et al. [1973]. From Murphy et al. (2014)

The detailed spatial structure of field-aligned currents comprising the substorm current wedge

We present a comprehensive two-dimensional view of the field-aligned currents (FACs) during the late growth and expansion phases for three isolated substorms utilizing in situ observations from the Active Magnetosphere and Planetary Electrodynamics Response Experiment and from ground-based magnetometer and optical instrumentation from the Canadian Array for Realtime Investigations of Magnetic Activity and Time History of Events and Macroscale Interactions during Substorms ground-based arrays.

ULF waves in the Van Allen belts. Figure from Mann et al., (2013)

Discovery of the action of a geophysical synchrotron in the Earth’s Van Allen radiation belts

Although the Earth's Van Allen radiation belts were discovered over 50 years ago, the dominant processes responsible for relativistic electron acceleration, transport and loss remain poorly understood. Here we show evidence for the action of coherent acceleration due to resonance with ultra-low frequency waves on a planetary scale.

ULF wave model outputs for a 1 mHz ULF wave source located along the afternoon sector magnetopause (peaked at 1500 h MLT), showing radial electric right (left), azimuthal electric field (centre) and northward magnetic field perturbation (left). Plots were taken at five wave periods after the beginning of the source wave. Figure 1 from Degeling et al. (2013)

The influence of magnetospheric convection and magnetopause motion on Radiation Belt electrons

Understanding the acceleration, transport and loss of relativistic electrons in Earth’s magnetosphere is a high-priority international science objective.  Observations indicate that there are a vast number of effects to be considered in this region ranging from large-scale global effects to effects on the electron gyroscale and from the interaction of electrons with electromagnetic wave processes, to global changes in the Earth’s magnetosphere.   More...

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