X-ray studies of planets in our solar system

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The Chandra and XMM-Newton observatories have revealed the beauty and multiplicity of X-ray emissions from planets and comets in our solar system. The project focuses on Jupiter, with the possibility of extending to studies of our own Earth. Jupiter's polar regions show bright soft X-ray aurorae, with a line-rich spectrum arising from the charge exchange interactions of atmospheric neutrals with local and/or solar wind high charge-state heavy ions, accelerated in the planet's powerful magnetic environment. Jupiter's atmosphere also scatters solar X-rays, so that at low latitudes the planet's disk displays an X-ray spectrum that closely resembles that of solar flares. The project will make use of Chandra and XMM-Newton data to extend our current studies of the role that the solar wind plays in the X-ray aurora generation on Jupiter. Most of the data are already in hand and more will be obtained in the near future, while the JUNO spacecraft is orbiting the planet, allowing unprecedented multi-wavelength studies as well as correlated remote and in situ measurements.The process of charge exchange takes place also at Earth. Solar wind charge exchange (SWCX) X-ray emission is produced in the interaction of highly charged ions of the solar wind with neutral hydrogen in the Earth's exosphere: the emission's intensity is proportional to the ion and neutral densities, so is brightest in the dayside magnetosheath and the magnetospheric cusps. MSSL, in collaboration with other institutes in the UK, Europe, Canada, China and the European Space Agency, are developing a space mission called SMILE (www.mssl.ucl.ac.uk/SMILE) dedicated to studying this emission as a means to reach a better understanding of how the Earth's magnetosphere responds to the impact of the solar wind. Depending on progress, the student could investigate in particular the expected spectral characteristics of the SWCX X-ray emission.