The comet 67P Churyumov-Gerasimenko amazes us again

A Scandinavian study guide, based on some observations of ionized gas around the comet 67P, allows for the first time to follow the development of cometary magnetosphere as the body approaches the Sun and interacts with the solar wind.
Rosetta is probing the comet 67P Churyumov-Gerasimenko, robotically in every way possible, and we have already begun to get to know its body and its ancestral humid and dusty metabolism. This week, the journal Science dedicated a special issue to the ESA mission, a set of scientific results that can be considered as a kind of medical records of the comet, prepared by most specialists.


Credit: ESA/Rosetta/RPC-ICA

One of these reports, compiled by an international research team led by the Swedish Institute of Space Physics, it shows how the magnetosphere around a comet does exist. The instrument RPC-ICA on board Rosetta was in fact able to record the embryonic stages of formation of the magnetosphere surrounding a 67P, while the comet approached more and more to the Sun and began to interact with the solar wind.
As the comet is heated, volatile substances – mainly water – evaporate from the surface and form an atmosphere around the comet. The solar ultraviolet radiation and collisions with particles of the solar wind cause ionization of the atmosphere comet. Newly formed ions are influenced by the electric and magnetic fields in the solar wind, being able to come accelerated to high speeds. When the comet gets close enough to the Sun, its atmosphere becomes sufficiently dense and ionized to be electrically conductive. When this happens, the atmosphere begins to resist the solar wind, creating a region around the comet and the solar wind sheltered represent here the newly magnetosphere.
The measuring device of ions ICA Rosetta (Ion Composition Analyzer, one of five instruments Rosetta Plasma Consortium, RPC) found water ions of low speed data collected in August 7, 2014, one day after the arrival of the Rosetta 100 km away from the comet 67P. “It was a clear sign of the comet, a clear identification of cometary ions in the atmosphere,” says Hans Nilsson, Swedish Institute of Space Physics (IRF) in Kiruna, responsible for the product Ion Composition Analyser, developed and built right in Kiruna.
“Rosetta is a unique space mission – said Nilsson.



Previous probes that have studied comets you have scooted in front of distance and speed of tens of kilometers per second. Moreover, at the time of the previous meetings, the magnetosphere comet was in a fully developed stage. “On the contrary, says researcher, Rosetta currently orbiting 67P low speed and at a distance of a few tens of kilometers. Fundamental to the fact, then, that the mission has come to the comet in time to observe the early stages of the formation of the magnetosphere.
“For the first time, we were able to see what happens before the atmosphere of the comet begins to resist the solar wind – explains Nilsson. We found that the atmosphere of the comet resists solar wind than we thought he would do at this early stage. We also were surprised by the property that our data we glimpse: the atmosphere of the comet appears to be distributed in a very uneven around the nucleus. ”
As the comet gets closer to the Sun in its orbit, researchers can follow live the transition of the magnetosphere from this early stage to a more mature and well-established. “The transition is probably the most interesting part – concludes Nilsson. It can occur at any time from now on. Every morning, while we give a quick glance at the new data just arrived we wonder if it is not what we find again today. “

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