Imperial College London


Faculty of Natural SciencesDepartment of Physics

Professor in Planetary Science



m.galand Website




Huxley BuildingSouth Kensington Campus





Publication Type

132 results found

Stephenson P, Galand M, Deca J, Henri P, Carnielli Get al., Cooling of Electrons in a Weakly Outgassing Comet

<jats:p>&amp;lt;p&amp;gt;The plasma instruments, Mutual Impedance Probe (MIP) and Langmuir Probe (LAP), part of the Rosetta Plasma Consortium (RPC), onboard the Rosetta mission to comet 67P revealed a population of cold electrons (&amp;lt;1eV) (Engelhardt et al., 2018; Wattieaux et al, 2020; Gilet et al., 2020). This population is primarily generated by cooling warm (~10eV) newly-born cometary electrons through collisions with the neutral coma. What is surprising is that the cold electrons were detected throughout the escort phase, even at very low outgassing rates (Q&amp;lt;1e26 s&amp;lt;sup&amp;gt;-1&amp;lt;/sup&amp;gt;) at large heliocentric distances (&amp;gt;3 AU), when the coma was not thought to be dense enough to cool the electron population significantly.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;&amp;amp;#160;Using a collisional test particle model, we examine the behaviour of electrons in the coma of a weakly outgassing comet and the formation of a cold population through electron-neutral collisions. The model incorporates three electron sources: the solar wind, photo-electrons produced through ionisation of the cometary neutrals by extreme ultraviolet solar radiation, and secondary electrons produced through electron-impact ionisation.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;The model includes different electron-water collision processes, including elastic, excitation, and ionisation collisions.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;&amp;amp;#160;The electron trajectories are shaped by electric and magnetic fields, which are taken from a 3D collisionless fully-kinetic Particle-in-Cell (PIC) model of the solar wind and cometary plasma&amp;amp;#160; (Deca 2017, 2019). We use a spherically symmetric coma of pure water, which gives a r&amp;lt;sup&amp;gt;-2&amp;lt;/sup&amp;gt; profile in the neutral density. Throughout their lifetime, electrons undergo stochast

Journal article

Rymer A, Mandt K, Hurley D, Lisse C, Izenberg N, Smith HT, Westlake J, Bunce E, Arridge C, Masters A, Hofstadter M, Simon A, Brandt P, Clark G, Cohen I, Allen R, Vine S, Hansen K, Hospodarsky G, Kurth W, Romani P, Lamy L, Zarka P, Cao H, Paty C, Hedman M, Roussos E, Cruikshank D, Farrell W, Fieseler P, Coates A, Yelle R, Parkinson C, Militzer B, Grodent D, Kollmann P, McNutt R, André N, Strange N, Barnes J, Dones L, Denk T, Rathbun J, Lunine J, Desai R, Cochrane C, Sayanagi KM, Postberg F, Ebert R, Hill T, Mueller-Wodarg I, Regoli L, Pontius D, Stanley S, Greathouse T, Saur J, Marouf E, Bergman J, Higgins C, Johnson R, Thomsen M, Soderlund K, Jia X, Wilson R, Englander J, Burch J, Nordheim T, Grava C, Baines K, Quick L, Russell C, Cravens T, Cecconi B, Aslam S, Bray V, Garcia-Sage K, Richardson J, Clark J, Hsu S, Achterberg R, Sergis N, Paganelli F, Kempf S, Orton G, Portyankina G, Jones G, Economou T, Livengood T, Krimigi S, Szalay J, Jackman C, Valek P, Lecacheux A, Colwell J, Jasinski J, Tosi F, Sulaiman A, Galand M, Kotova A, Khurana K, Kivelson M, Strobel D, Radiota A, Estrada P, Livi S, Azari A, Yates J, Allegrini F, Vogt M, Felici M, Luhmann J, Filacchione G, Moore Let al., Solar System Ice Giants: Exoplanets in our Backyard

Future remote sensing of exoplanets will be enhanced by a thoroughinvestigation of our solar system Ice Giants (Neptune-size planets). What canthe configuration of the magnetic field tell us (remotely) about the interior,and what implications does that field have for the structure of themagnetosphere; energy input into the atmosphere, and surface geophysics (forexample surface weathering of satellites that might harbour sub-surfaceoceans). How can monitoring of auroral emission help inform future remoteobservations of emission from exoplanets? Our Solar System provides the onlylaboratory in which we can perform in-situ experiments to understand exoplanetformation, dynamos, systems and magnetospheres.

Working paper

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