Tribute to Eugene Parker, NASA’s great solar physicist

NASA has just announced that one of the great pioneers of solar physics, Eugene Parker, has died at the age of 94. He was the first scientist to witness the launch of the space probe that bears his name, namely Solar Probe Parker in August 2018.

Born in 1927 in Houghton, Michigan (USA).astrophysicist therefore belongs to the same generation as his colleagues in France, also deceased, Evry Shatzman as well as Jean-Claude Peckerthey too physics solar. Thus, he is one of those young researchers who, at the end of the Second World War, will benefit from the dazzling progressastrophysics nuclear and astronautics to explore the territory of astrophysics, which was discovered in the 1930s by such geniuses as Subrahmanyan Chandrasekhar as well as Arthur Eddington with his work on internal structure of stars.

Thus, Eugene Parker will receive the equivalent of a master’s degree in physics in Michigan State University in 1948 and his PhD from Caltech in 1951, where the Nobel Prizes in Physics would shine from the same decade Richard Feynman as well as Murray Gell Mannbefore accepting a position in 1955 at the University of Chicago, where he remained for the rest of his career and remained active after his retirement in 1995.

At that time, the boom in nuclear astrophysics was not the only one, because plasma astrophysics was also developing, as evidenced by the publications of Chandrasekhar at the same timealso working at the University of Chicago.

supersonic particle flow

In 1957, Eugene Parker received a revelation. He understands that there must be something like the solar wind, i.e. a plasma flow consisting mainly ofions (mainly fromatoms fromhydrogen and D’helium) and D’electrons who are expelled from high atmosphere from Sun. Dynamics in speed and the temperature of this plasma explosion should also change with time in accordance with solar activity, which has been increasing since 1931.astronomer as well as optometrist French Bernard Lyot started shooting spectacular films showing solar flares in slow motionthanks to his observations on the Pic du Midi with a completely new instrument he has just developed: coronograph.

Presentation of the Parker solar probe and its discoveries. For a fairly accurate French translation, click on the white box in the lower right corner. After that, English subtitles should appear. Then click on the nut to the right of the rectangle, then on “Subtitles” and finally on “Translate automatically”. Select “French”. © NASA

But when he sends an article for publication in the same year, where he develops his theory of a supersonic flow of particles emitted from the surface of the Sun, the first expert who evaluates the article, as expected, anonymous, returns an incendiary report to the editors. Well, I would advise Parker to go to the library and do a little research before writing an article about it, because this is complete nonsense! “.

Chandrasekhar is the editor, and is also not at all convinced by Parker’s article, but finding no flaws in reasoning and calculations, he allows publication, perhaps reminding himself that his own theory about the limiting mass of white dwarfs was also rejected by Eddington over two decades ago.

When Parker was later asked for advice to the young, aspiring scientists no doubt marked by this story, he said: If you are doing something new or innovative, expect trouble. But think about it critically, because if you’re wrong, you want to be the first to know! “.

If for some time the idea of ​​the solar wind actually met only skepticism and even ridicule, then it is imposed in 1962, when the instruments of the Mariner 2 probe were sent to Venus indicates the existence of the solar wind.

From solar plasma to galactic plasma

Parker’s own work subsequently contributed to the revolution in plasma astrophysics. magnetic fields so much so that in a statement from the University of Chicago regarding Parker’s death, Nicky Fox, director of NASA’s Heliophysics Division, said: ” I do not think it is an exaggeration to say that the field of heliophysics today is largely due to the work of Dr. Eugene Parker. Although Dr. Parker is no longer with us, his discoveries and legacy will live on forever. »

Eugene Parker also went beyond solar wind astrophysics because we owe his work in origin cosmic rays, generation of cosmic and stellar magnetic fields due to the dynamo effect and magnetic fields in galaxies. Therefore, we find its trace in many branches of astrophysics, as we are quickly convinced when we learn about the existence of the Parker instability, which describes the magnetic fields in galaxies; belonging’the equation Parker, who describes the motion of particles in a plasma; the Sweet-Parker model of magnetic fields in plasma; and the Parker constraint on the flow magnetic monopoles in Milky Way.

In the same press release, Robert Rosner, professor of astronomy and astrophysics, adds: Eugene seemed to me the ideal physicist – brilliant and experienced, personable, eloquent, but at the same time modest. I will never forget the pleasure he took in investigating a scientific problem and his colossal knowledge of physics, which was then reinforced by his analytical abilities. And we must never forget the support that he provided to everyone with whom he interacted – his students and doctoral students, as well as his colleagues. His passing is indeed a great loss for all of us. »

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