Eugene Parker | |
|---|---|
 Parker in 2019 | |
| Born | Eugene Newman Parker (1927-06-10)June 10, 1927 Houghton, Michigan, U.S. |
| Died | March 15, 2022(2022-03-15) (aged 94) Chicago, Illinois, U.S. |
| Alma mater | Michigan State University (BS) Caltech (PhD) |
| Known for | Solar wind Sweet–Parker model Parker spiral Parker theorem Parker equation Parker instability |
| Awards | See#Awards and honors |
| Scientific career | |
| Fields | Solar physics,heliophysics,plasma physics |
| Institutions | University of Chicago |
| Thesis | The interstellar dust and gas structures (1951) |
| Doctoral advisor | Howard P. Robertson,Leverett Davis[1] |
| Doctoral students | Arnab Rai Choudhuri |
Eugene Newman "Gene" Parker (June 10, 1927 – March 15, 2022) was an Americansolar andplasma physicist, often called the "father" and "founder" ofheliophysics. In 1958 he proposed the existence of thesolar wind and predicted that the magnetic field in theouter Solar System would be in the shape of aParker spiral—predictions initially rejected by reviewers and scientific community, but quickly confirmed by theMariner 2 spacecraft in 1962. Multiple phenomena in solar and plasma physics bear his name, including theParker instability,Parker equation,Sweet–Parker model of magnetic reconnection,Parker limit on magnetic monopoles, andParker theorem. In 1988, he proposed thatnanoflares could explain thecoronal heating problem, a theory that remains a leading candidate.
Parker obtained his PhD fromCaltech in 1951 and spent four years at theUniversity of Utah before joining theUniversity of Chicago in 1955, where he spent the rest of his career at theEnrico Fermi Institute. He wrote more than 400 papers, mostly without co-authors, and received multiple awards including theNational Medal of Science (1989),Gold Medal of the Royal Astronomical Society (1992),Kyoto Prize (2003), andCrafoord Prize (2020). In 2017, NASA renamed its Solar Probe Plus mission toParker Solar Probe in his honor, the first NASA spacecraft named after a living person.
Eugene Newman Parker was born inHoughton, Michigan to Glenn and Helen (née MacNair) Parker on June 10, 1927.[2] Parker's grandfather was a president of theMichigan College of Mines in Houghton[3] and a physicist. Parker's uncle was also a physicist, who worked atBell Laboratories.[4]
Eugene had two younger siblings, a brother and a sister. His father, Glenn, a mining surveyor[5] and then an engineer, worked atConsolidated Aircraft company.[4] When Eugene was seven, the family moved toDetroit, for his father's graduate studies in engineering, and later his work forChrysler.[3] His mother, Helen, got a mathematics degree in Stanford, but didn't pursue a career. By the time Eugene went to university, his parents moved from Detroit to a farm in Arkansas.[5]
Parker became interested in science and engineering from childhood: he was interested in steam trains, and found the mechanical principles of it to be "fascinating".[1] At six, he got his deceased grandfather's 50-power microscope.[4] He became interested in math when it went beyond arithmetics in school, and then in physics.[1]
During the World War II, Parker, then 16, bought a "tax-delinquent property": 40-acre area in the woods ofCheboygan County, around 300 miles from Detroit, for $120 he earned earlier in summer. Together with his brother and cousin, Parker spent three summers building a log cabin there, going by bicycle as there were no other ways to commute. The log cabin with no electricity and running water was in use by Parker's family for almost 80 years.[6][3][5]
Parker received hisBachelor of Science degree inphysics fromMichigan State University in 1948 and aDoctor of Philosophy (PhD) degree from Caltech in 1951.[7] He had a tuition scholarship at Michigan, but not at Caltech. To earn money for the first semester, he worked as a technician at the Physics Laboratory at Chrysler Engineering[4] for six months in 1948. Parker later wrote thatWilliam Smythe's year-long course inelectricity and magnetism was the most demanding course in his first year at Caltech, but noted that after several weeks the problems became easier and he "aced" the exam. Parker later got a teaching assistantship with the help ofWilliam A. Fowler. Parker worked withHoward P. Robertson, who suggested him to study dynamics of the interstellar medium. When Robertson left Caltech, Parker continued to work withLeverett Davis, who became his PhD advisor.[1][4]
Parker's PhD thesis was of two parts: a dynamical analysis of interstellar gas clouds and a study of dust structures in the Pleiades. In the first, gas clouds were idealized as self-gravitating Hamiltonian systems, leading to the result that they either disperse to infinity or collapse into compact objects such as stars, a result accepted for publication without controversy; Parker later called the idea "a dubious assumption". The second part proposed that "the long thin curved dust striations observed in the Pleiades" require an interstellar magnetic field of at least a microgauss to prevent dust grains, driven by interstellar winds, from smearing out into diffuse clouds. Because the grains are photoelectrically charged, they can remain tied to magnetic field lines, preserving the observed narrowstriations.[4]
After Caltech, Parker got a job as an instructor at the Department of Mathematics at theUniversity of Utah. After two years there, he found out that he wouldn't be offered a permanent position and that he would be fired soon. After a talk withWalter Elsasser he was proposed "a position as a one-third time assistant professor in the Physics Department and a two-thirds time research associate with him". He worked with Elsasser for two years.[1] In 1955,John Simpson invited Parker to theUniversity of Chicago as a theoretician to studycosmic rays; Parker spent the rest of his career there, at theEnrico Fermi Institute. He became full professor in 1962, and served as a head of the physics department in 1970-1972, and of the department of astronomy and astrophysics in 1972–1978. Parker retired in 1995, but continued to work and publish papers.[6] Parker had 14 PhD students.[1]
I always looked upon myself as a physicist learning new tricks by looking at nature. Space, the whole galaxy, the whole Universe — I know no better place to find new physics.
Parker is often called the "father", "unquestioned founder", and a "legendary figure" inheliophysics.[8][9][3] AstrophysicistAngela Olinto noted that "Gene's name is quite literally written in our star", referencing multiple phenomena discovered by Parker: "theParker instability, which describes magnetic fields in galaxies; theParker equation, which describes particles moving through plasmas; theSweet-Parker model of magnetic fields in plasmas; and theParker limit on the flux of magnetic monopoles."[7]
Parker wrote more than 400 papers and four books.[9] Most of his papers are single authored; Parker never wrote papers with his students, "urging them to be independent".[6] Parker never co-authored a paper if he didn't reproduce all calculations, and he never used computers for research.[5] Parker's research relied onclassical physics likeMaxwell's equations andmagnetohydrodynamics, he didn't use methods fromquantum mechanics ortheory of relativity.[2][3][5]
AstrophysicistArnab Rai Choudhuri, Parker's PhD student, wrote that "it is impossible for one person to fully understand the significance of all of Parker’s works at a technical level, unless that person also happens to be almost as brilliant as Parker himself!"[5]
Choudhuri described Parker as a very independent researcher:[5]
Parker’s papers are always marvels of scientific composition and bear the stamp of a scientific autocrat who enjoyed doing science in his own terms. He would always pay particular attention to the logical structure of the paper. Since Parker often dealt with complex ideas years before others paid attention to them, it may not always be easy to read his papers. But a reader with the prerequisite technical knowledge can always follow the clear thread of scientific logic. Nothing would be fuzzy or obscure.
ConfrontingCowling'santidynamo theorem, Parker showed that in a rotating, convecting conductor, turbulence becomes helical, enabling large-scale field growth when averaged ("mean-field" theory). He wrote down a tractable dynamo equation and identified wave-like solutions (dynamo waves) that offered a physical picture for the sunspot belt’s equatorward drift across a cycle. Parker's paper established the feasibility of MHD dynamos, showed turbulence can build global order, and sketched a solar-cycle model.[5][a]
Parker explained how strong toroidal flux generated in the solar interior becomes lighter than its surroundings due to magnetic pressure, making segments buoyant and able to rise to the surface as Ω-shaped loops that produce bipolar sunspot pairs. He later showed buoyancy is enhanced in the convection zone but suppressed just below, naturally “anchoring” loop footpoints—consistent with the observed morphology. This framework led to thin-flux-tube and full-MHD simulations and clarified links toJoy’s law tilts and toroidal field strengths at depth.[5][b]
Building onSweet's neutral-sheet model, Parker derived the canonical inflow rate for resistive reconnection in a long, thin current sheet—now called Sweet–Parker scaling. Historical publication delays meant Parker’s paper appeared first but credited Sweet’s mechanism. While crucial, the Sweet–Parker rate is too slow for flare rise times, motivating later fast-reconnection scenarios and modern numerical/kinetic work. The classical rate remains a baseline against which faster mechanisms are compared.[5][c]
In the 19th and early 20th century the prevailing view was that the Sun is a static object, connected to planets and minor bodies only via gravity.[10] The first evidence of a constant particle flow was found incomets; itstails always point away from the Sun. In 1950s, the German astrophysicistLudwig Franz Biermann studied how comet tails interact with the Sun. Biermann stated that "solar corpuscular radiation" was needed to explain the observed behavior. In 1956, he came to the University of Chicago, where he discussed his results with Parker. Parker also discussed thesolar corona with mathematicianSydney Chapman, who mentioned that "the corona is so hot that it should extend clear to the orbit of the Earth". Parker then conjectured that "the corona and solar corpuscular radiation must be the same thing". When he wrote hydrodynamic equations for this extended atmosphere, his solution showed him the existence ofsolar wind.[11] Parker himself said that the math needed for the solar wind discovery was just "four lines of algebra".[8]
I called it the solar wind because I felt that solar corpuscular radiation gives the wrong idea. With that term, one thinks of individual particles being shot out, which was the original picture we had. But it really is an ordinary flow of gas.[11]
The plasma flow velocity equation; one of the solutions led Parker to the solar wind:[12]
Parker theory of supersonic solar wind predicted the shape of the solar magnetic field in theouter Solar System. Parker argued that a million-degree corona cannot remain static: pressure forces must drive a radially expanding flow that accelerates from subsonic near the Sun to supersonic beyond a critical point. He further noted that solar rotation winds outward-advected magnetic field lines into a spiral pattern in the ecliptic, now called theParker spiral.[5]
His theoretical modeling was not immediately accepted by the astronomical community: when he submitted the results toThe Astrophysical Journal in 1958,[d] two reviewers recommended its rejection. One reviewer commented on the paper: "Well I would suggest that Parker go to the library and read up on the subject before he tries to write a paper about it, because this is utter nonsense."[6] The editor of the journal,Subrahmanyan Chandrasekhar, finding no obvious errors in the paper, overruled the reviewers and published the paper, even though he disagreed with Parker's theory.[2][6] At the time, no spacecraft took measurements of space medium, and Parker himself was an unknown 31-year-old professor from Chicago.[13] One of the most vocal critics of solar wind wasJoseph W. Chamberlain, also from the University of Chicago, who published a paper in 1960 with an alternative solution of the equation that led Parker to solar wind.[12] Chamberlain's subsonic solution was called "solar breeze".[14]
Parker wrote to his parents about the solar wind theory rejection:[3]
It is amazing that everyone who has had his formal training in astronomy refuses to accept the idea of a solar wind. They will argue like mad that any child knows that the Sun is a static object. Even when you whip them with a bit of both theory and observations, they won’t go along with it. They discount the observations and won't study the theory.
Parker's theoretical predictions were confirmed by satellite observations: in 1959, the flow of particles from the Sun was detected by the Soviet'sLuna 2. In 1962, four years after the original publication,Mariner 2 mission carried out observations with a specifically designed instrument.[13][15][16][17] It is called to be "a unique example in astrophysics, due to its immediate and brief confirmation by observations".[9] Mariner 2 data revealed two types of solar wind, a low- and a high-speed components.[14] The paper became Parker's most famous publication.[6][e]
After establishing the solar wind, Parker modeled cosmic-ray propagation as diffusion through wind-borne magnetic irregularities combined with advection by the outflow. He wrote a Fokker–Planck transport equation and estimated anisotropic diffusion coefficients (easier along the mean field than across it).[5]
With Jokipii, he quantified how scattering produces cross-field spread along Parker-spiral lines, consistent with observations, cementing the modern transport framework used in heliophysics and space weather.[5][f]
Parker treated the interstellar gas, magnetic field, and cosmic rays as a coupled system in a galactic disk. He showed that horizontal fields are buoyantly unstable: gas drains downward, magnetized “arches” rise, and dense clumps collect in valleys—an undular mode now called theParker instability. Nonlinear evolution produces structures reminiscent of observed gas clumping along spiral arms. He also formulated a local αΩ dynamo for spiral galaxies, with helical turbulence and differential rotation amplifying toroidal fields on timescales shorter than galactic ages, aligning with observed large-scale patterns.[5][g]
Reasoning that abundantmonopoles would short out galactic magnetic fields, Parker related monopole density and drift to magnetic-field decay and demanded consistency with field persistence/growth, obtaining a stringent upper bound—theParker limit. The estimate, first offered in a Russell lecture as a " back-of-the-envelope calculation", later guided experimental monopole searches across particle physics and cosmology.[5][h]
Parker theorem', also known as the fundamental magnetostatic theorem, was formulated in 1972. It describes how magnetic fields behave in perfectly conducting fluids, particularly in space plasmas. The theorem states that three-dimensional magnetic fields naturally form infinitesimally thin current sheets – regions where the magnetic field direction changes abruptly. These sheets arise from the fundamental interaction between magnetic fields that are "frozen" into the conducting fluid.[18][i]
Parker argued that random footpoint motions in thephotosphere inevitably tangle coronal fields, making smooth equilibria topologically unattainable. The corona relaxes via ubiquitous current sheets where reconnection dissipates energy, supplying heat. Initial skepticism gave way to broader interest as stellar coronal X-rays were established; Parker then estimated the energy budget and introduced the nanoflare concept—many small events rather than single large releases. The field converged on a mixed picture: closed-loop regions likely dominated by current-sheet heating; open-field regions more wave-driven.[5]
Seeking to address thecoronal heating problem, in 1988 Parker proposed that the solar corona might be heated by myriad tiny "nanoflares", miniature brightenings resemblingsolar flares that would occur all over the surface of the Sun. Parker's theory became a leading candidate to explain the problem.[5][19][20][j]
In 1960, a Space Science Board report recommended a solar spacecraft mission to study the origins of solar wind, and another mission to the outer Solar System "to study the interaction of the heliosphere with the interstellar medium". In 2010, NASA approved the Solar Probe Plus mission; Parker was invited as an advisor.[21]
In 2017,NASA renamed the Solar Probe Plus toParker Solar Probe in Parker's honor, the first NASA spacecraft named after a living person.[2] In October 2017, Parker visited the spacecraft at theJohns Hopkins Applied Physics Laboratory in Laurel, Maryland.[22] In 2018, Parker and his family traveled toCape Canaveral to watch the PSP's launch.[2]
PSP's science teams sent preprints and publications to Parker, who was excited about the mission.[2][21]
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In aNational Geographic article, "Dear Parker Solar Probe", Parker wrote:[23]
Dear Solar Probe:
I think there’s a point that’s not widely appreciated, but it’s fundamental: The Sun is an ordinary star of middling mass and middling brightness, but it’s a model for almost all stars—and the only one we’re going to see up close enough to do a whole lot of measurements. There are stars that are oddballs, the ones that interest the astrophysics types. But the fact that the sun supports life on one of its planets is already a unique designation.
I’m in love with the sun for that reason. Somehow, in many circles, solar physics is looked upon as old, dusty, dried-up problems that don’t really have new solutions. On the contrary, it’s the one star where we know what we’re talking about!
Parker Solar Probe used repeatedgravity assists fromVenus to develop an eccentric orbit, approaching within 9.86solar radii (6.9 million km or 4.3 million miles)[24][25] from the center of the Sun. At its closest approach in 2024, its speed relative to the Sun was 690,000 km/h (430,000 mph) or 191 km/s (118.7 mi/s), which is 0.064% thespeed of light.[26] It is the fastest object ever built onEarth.[27] PSP is the first spacecraft that entered the solar atmosphere, which was described by NASA as "touching the Sun". It was done when PSP passed theAlfven surface which marks the end of the solar atmosphere and beginning of the solar wind.[28]
Parker met his future wife, Niesje, in Utah. Her family was from Netherlands, she emigrated to the US after World War II. She had a degree in bacteriology. They married in 1954. In Chicago, Niesje got a job at the University of Chicago Graduate School of Business, and later became an Associate Director of Computing Services.[5] Parkers were married for 67 years and had two children, a son and a daughter. Parker's hobbies included woodworking, sailing and hiking; at 76, he went to theNorth Pole with his son.[3]
Parker was described as a humble man with a "genial personality". Henever drank alcohol or coffee, "always drove at 55 miles per hour", never seek attention, and was rarely critical of other scientists' works. The only scientist he was openly critical of wasHannes Alfvén, who later was awarded the Nobel Prize in Physics: "Parker did not think the man dug deeply enough into problems and sometimes had been quite wrong". Parker published several papers "challenging and even undercutting Alfven’s conclusions".[3]
Parker died in Chicago on March 15, 2022, at the age of 94.[2][7] His body was cremated, and half of the ashes buried near his log cabin in the woods.[5]
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