A variety of metals (e.g. Na, Fe, Mg, K, Ca and Si) are deposited in the mesosphere and lower thermosphere (MLT) region of the Earth’s atmosphere between 70 and 120 km, through the process of meteoric ablation (Figure 1). Ablation occurs because cosmic dust particles enter the atmosphere at high velocities (11-72 km s‑1), which causes sputtering and flash heating through collisions with air molecules, followed by rapid evaporation of metal atoms and oxides once the particles melt (Plane et al., 2015). This source of metals gives rise to layers of metal atoms centred around 85 – 92 km which can be observed by the ground-based lidar (laser radar) techniques, as well as by satellite-borne optical spectroscopy. Metallic ions at higher altitudes are also measured by mass spectrometry on sub-orbital rockets. These metals provide a unique tracer of the physics and chemistry of the atmosphere at the interface with geospace (Plane et al., 2015).
At the University of Leeds, in close collaboration with the US National Center for Atmospheric Research (NCAR) and NASA Goddard Space Flight Center (GSFC), we have added the chemistry of six metals (Na, Fe, K, Mg, Si and Ca) into the three-dimensional Whole Atmosphere Community Climate Model (WACCM) (e.g. Marsh et al., 2013; Feng et al., 2013, 2015; Plane et al. 2014, 2015, 2016; Langowski et al. 2015). This is the first global atmospheric model of meteoric metals, which allows us to better understand the meteor astronomy, chemistry and transport processes that control the different metal layers in the MLT.
However, the standard version of WACCM only extends up to 140 km, and recent lidar observations have shown that neutral Fe, Na and K layers occur up to at least 170 km (e.g. Chu et al., 2011; Dou et al., 2013; Tsuda et al. 2015). Furthermore, metallic ions have been observed at heights of over 500 km (Carter and Forbes, 1999; Plane et al., 2015), and WACCM does not yet contain some important electodynamical processes. A new version of the next generation model (WACCM-X, an extended version of WACCM which couples the ionosphere up to 600 km (Liu et al., 2010)), is being developed at NCAR in Boulder, Colorado. One aim of this DTP project will be to include metal chemistry in WACCM-X which we have recently successfully incorporated the Fe chemistry into an earlier version of WACCM-X. The student will have the opportunity to work at NCAR with Dr Daniel Marsh (a co-supervisor).
Since late 2014, NASA’s MAVEN spacecraft has been in orbit around Mars (Figure 2). Metallic ions in the Martian atmosphere are measured by two instruments: the Imaging Ultra-Violet Spectrograph (IUVS) (Schneider et al., 2015; Crismani et al., 2017) and the Neutral Gas and Ion Mass Spectrometer (Benna et al., 2015; Grebowsky et al., 2017). The IUVS measures Mg+ ions between 80 and 150 km by remote sensing, and the NGIMS measures ions down to 120 km when the spacecraft performs a “deep dip” manouvre. The lead supervisor of this DTP project is a member of the MAVEN Science Team, which provides access to data from both instruments. The data-set gathered so far has produced significant surprises, suggesting that our understanding of chemistry and dynamics in planetary ionospheres is flawed. Metallic ions in the Martian atmosphere will be modelled using the Laboratoire de Météorologie Dynamique (LMD) Mars general circulation model, through a collaboration with a group at the Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS) in Paris.
The project will therefore explore and contast the coupling of atmospheric chemistry and dynamical processes in the upper atmospheres of Earth and Mars. The PhD student will have an opportunity to visit NCAR and LATMOS.
The goal of this project is to answer a number key questions about the upper atmospheric metal layers: why do neutral metal atoms occur in the ionosphere above 100 km? What are the chemical and physical processes which control their distribution? Why do the metallic ions in the Martian atmosphere show a strong diurnal variation, and have the same scale height as the neutral atmosphere, unlike Earth? What is the role of the very different magentic fields on the two planets? How are the layers affected by long-term trends such as the solar cycle and climate change? Which important processes are missing in the current whole atmosphere models?
In this project, you will work with leading scientists at Leeds, NCAR and LATMOS to develop a comprehensive global models of the metallic ion layers, and then validate the new models using available lidar and satellite measurements. Specific goals will include:
- Learning to run the existing WACCM and WACCM-X models, analyzing model output and comparing with general observations of meteorology and chemical composition;
- Incorporating metal chemistry into the WACCM-X and LMD models;
- Collecting available lidar data from observatories in China, the US and Germany, and then comparing with the developing WACCM-X metal model;
- Modelling MAVEN IUVS and NGIMS observations of metallic ions in the Martian atmosphere using the LMD model.
Potential for high impact outcome:
This project addresses the coupling of the atmosphere to the geospace environment. Metallic species provide a unique tracer of dynamics in the neutral and ionized atmosphere, on a range of temporal (seconds to years) and spatial (400 km vertical, global horizontal) scales. The Chinese Academy of Sciences have recently recognized this as their highest priority research area in geophysics, and have made significant investments in a chain of lidar stations at low geomagnetic latitudes. The data that they will provide will be the first of its kind and – combined with a new state-of-the-science whole atmosphere model up to 600 km being developed at NCAR- will likely to lead to some high impact discoveries. The MAVEN satellite uniquely performs deep dip orbits into a planetary atmosphere, and this has uncovered a goldmine of data against which models can be tested.
The student will work under the supervision of Professor John Plane and Dr Wuhu Feng at the University of Leeds, and Dr Daniel Marsh at the world-leading US National Center for Atmospheric Research. This project will provide a high level of specialist scientific training in: (i) the application of world-leading atmospheric chemistry-climate models to two planets; (ii) analysis and synthesis of large datasets; (iii) use of advanced High Performance Computing facilities (e.g. the UK national supercomputer archer.ac.uk, and the N8 HPC n8hpc.org.uk). The successful PhD student will have an opportunity to visit NCAR and LATMOS for collecting observations and model development, as well as training organised by the Doctoral Training Programme, the National Centre for Atmospheric Science, and attendance at national/international conferences.
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Plane, J. M. C.; J. D. Carrillo-Sanchez, T. P. Mangan, M. M. J. Crismani, N. M. Schneider, and A. Määttänen (2018), Meteoric Metal Chemistry in the Martian Atmosphere, Journal of Geophysical Research – Planets, 123, 695-707.
Benna, M., P. R. Mahaffy, J. M. Grebowsky, J. M. C. Plane, R. V. Yelle, and B. M. Jakosky (2015): Metallic ions in the upper atmosphere of Mars from the passage of comet C/2013 A1 (Siding Spring), Geophys. Res. Lett., 42, 4670-4675.
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Chu, X. Z., Z. B. Yu, C. S. Gardner, C. Chen and Fong (2011), Lidar observations of neutral Fe layers and fast gravity waves in the thermosphere (110-155 km) at McMurdo (77.8oS, 166.7oE), Antarctica, Geophys. Res. Lett., 38, doi:10.1029/2011GL050016.
Crismani, M. M. J.; N. M. Schneider; J. M. C. Plane; J. S. Evans; S. K. Jain; M. S. Chaffin; J. D. Carrillo-Sanchez; J. I. Deighan; R. V. Yelle; A. I. F. Stewart; W. McClintock; J. Clarke; G. M. Holsclaw; A. Stiepen; F. Montmessin; B. M. Jakosky (2017), Detection of a persistent meteoric metal layer in the Martian atmosphere, Nat. Geosci., 10, 401–404, doi.org/10.1038/ngeo2958.
Dou, X. K., S. C. Qiu, X. H. Xue, T. D. Chen, and B. Q. Ning (2013), Sporadic and thermospheric enhanced sodium layers observed by a lidar chain over China, J. Geophys. Res. Space Physics, 118, 6627–6643, doi:10.1002/jgra.50579.
Feng, W., D. R. Marsh, M. P. Chipperfield, D. Janches, J. Hoffner, F. Yi, and J. M. C. Plane (2013), A global atmospheric model of meteoric iron, J. Geophys. Res- Atmos., 118, 9456–9474, doi:10.1002/jgrd.50708.
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Grebowsky J. M.; M. Benna; J. M. C. Plane; G. A. Collinson; P. R. Mahaffy; B. M. Jakosky (2017), Unique, non-Earthlike, meteoritic ion behavior in upper atmosphere of Mars, Geophys. Res. Lett., 44, 3066-3072, 10.1002/2017GL072635.
Langowski, M. P., C. von Savigny, J. P. Burrows, W. Feng, J. M. C. Plane, D. R. Marsh, D. Janches, M. Sinnhuber, A. C. Aikin, and P. Liebing (2015), Global investigation of the Mg atom and ion layers using SCIAMACHY/Envisat observations between 70 and 150 km altitude and WACCM-Mg model results, Atmos. Chem. Phys., 15, 273-295, doi:10.5194/acp-15-273-2015.
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Plane, J. M. C., W. Feng, E. C. R. Dawkins, M.P.C. Chipperfield, J. Hoffner, D. Janches, D. R. Marsh (2014), Resolving the strange behaviour of extra-terrestrial potassium in the upper atmosphere, Geophys. Res. Lett., doi:10.1002/2014GL060334.
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Plane, J. M. C., J. C. Gómez-Martín, W. Feng, and D. Janches (2016), Silicon chemistry in the mesosphere and lower thermosphere, J. Geophys. Res. Atmos., 121, 3718–3728, doi:10.1002/2015JD024691.
Schneider, N. M., Deighan, J. I., Stewart, A. I. F., McClintock, W. E., Jain, S. K., Chaffin, M. S., Stiepen, A., Crismani, M., Plane, J. M. C., Carrillo-Sanchez, J. D., Evans, J. S., Stevens, M. H., Yelle, R. V., Clarke, J. T., Holsclaw, G. M., Montmessin, F., and Jakosky, B. M. (2015): MAVEN IUVS observations of the aftermath of the Comet Siding Spring meteor shower on Mars, Geophys. Res. Lett., 42, 4755-4761.
Tsuda, T. T., X. Chu, T. Nakamura, M. K. Ejiri, T. D. Kawahara, A. S. Yukimatu and K. Hosokawa (2015), A thermospheric Na layer event observed up to 140 km over Syowa Station (69.0oS, 39.6oE) in Antarctica, Geophys. Res. Lett., 42, (10), 3647 – 3653, doi:10.1002/2015GL064101.