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Accueil > A propos du LPP > Communication > Actualités archivées > 2019 > First discoveries of the Parker Solar Probe mission

First discoveries of the Parker Solar Probe mission

Data from the first solar encounter of the Probe published by Nature reveal large amplitude solar wind bursts which may play a role in the heating of the solar corona together with an unexpected co-rotation of the wind with the Sun.

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Parker Solar Probe
©NASA/JHUAPL

With the first analysis of Parker Solar Probe data, with LPP involvement, Icarus dream sort of became reality. Among the ten mission concepts that were defined in 1958 at the dawn of space age, Solar Probe was the single missing corner-stone of the edifice. Neil Armstrong walked on the Moon but mankind never « touched the Sun ». After many aborted attempts, NASA eventually took up the technological challenge in 2010 when the Parker Solar Probe project was initiated. The Probe was launched on 12 August 2018 from the Cape with 4 instruments onboard. Minimizing the mass of the payload allows reaching the required speed to get as close as possible to the star and still being able to escape after each encounter.

One of the big mysteries of solar physics is the heating of the solar corona whose 2 milions degrees temperature is so much higher than the 6000 degrees temperature of the photosphere. None of the proposed explanations could be confirmed so far due to the lack of in situ measurements below 65 solar radii. Today, Parker Solar Probe fills this important gap in our knowledge of the solar system. Onboard the spacecraft, two electron spectrometers use an innovative detection system whose design closely follows the one developed by LPP for the european Solar Orbiter mission. Benefiting from CNES support, LPP Space Plasmas Physics team developed a specific integrated circuit used to detect electrons. The rad-hard component works as expected in the harsh solar environment. It was a key element to miniaturize Parker Solar Probe electron spectrometers.

The Nature paper describes the surprising discovery of an extremely structured plasma with series of solar wind bursts spread over the two weeks of the first two solar encounters of the Probe that reached 35 solar radii. During these events, the flow speed would suddenly increase from 300 to 450 km/sec while plasma density would almost double, and the magnetic field would rotate and may even reverse its polarity locally. Data from the electron spectrometers show that the magnetic connectivity of these structures to the Sun remains unchanged, which raises the question of their origin.

A second surprise comes from the unexpected measurement of a very significant transverse deflection of the wind associated with these bursts. At times reaching 30 to 50 km/sec, these flows by far exceed the expected co-rotation of the solar wind plasma (typically by a factor 15 or more). The induced loss of angular momentum, when confirmed by further data acquisition closer to the Sune, needs to be explained and compared with long term predictions of stellar evolution. Parker Solar Probe first discoveries open a new era for solar physics with forthcoming measurements of the always more elusive solar wind closer to its source, down to 10 solar radii in 2024 after series of gravity assist by Mercury.

Reference : Kasper, J.C., Bale, S.D., Belcher, J.W., Berthomier, M. et al. Alfvénic velocity spikes and rotational flows in the near-Sun solar wind. Nature (2019) doi:10.1038/s41586-019-1813-z

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