Edward J. Smith, Pioneer in Space Plasma Research (1927-2019)
Dr. Edward J. Smith, a pioneer of space plasma research, passed away on August 11, 2019, atage 91. Ed received a PhD in physics (his thesis advisor was Robert E. Holzer, also a spaceplasma physicist) from UCLA in 1959. Ed spent 1959 to 1961 at the Space Technologies
Laboratory (now TRW) in El Segundo, California. Then he came to the Jet Propulsion
Laboratory (JPL), California Institute of Technology, Pasadena, California, where he spent theremainder of his scientific life. In his early years at JPL, Ed took a sabbatical at the RoyalInstitute of Technology in Stockholm Sweden with Hannes Alfvén. They became lifelong
friends from that visit.
Ed was typical of scientists of his age, building both the instruments and making major scientificdiscoveries. Ed was unique among his peers in that he was the first to not only fly a fluxgate
magnetometer and vector helium magnetometers in space (VHMs have lower intrinsic noise thanfluxgate magnetometers) but Scalar Helium magnetometers and dual vector/scalar mode
magnetometers. Ed was also the first to build and fly triaxial search coil magnetometers in spacefor electromagnetic plasma wave studies. Ed gave his design of search-coil magnetometers toEurope and Japan where the basic designs were copied and flown in space by other scientists. Ed
was the “father” for all of these space instruments.
Ed was an “experimenter” on the (fluxgate) magnetic field investigation on Mariner 2, the firstsuccessful mission to a planet (Venus, 1962). The other magnetometer experimenters were
Chuck Sonett (NASA), Paul Coleman (NASA) and Leveritt Davis (Caltech). The plasma
instrument experimenters were Marcia Neugebauer and Conway Snyder of JPL. Marcia andConway used the plasma data to confirm Eugene Parker’s prediction of the existence of the solar
wind. Then for the Mariner 4, the first mission to Mars (1965) and Mariner 5, a second mission
to Venus (1967), Ed was the Principal Investigator (P.I.) of the Vector Helium Magnetometer
investigation. From the Mariner 5 interplanetary data, working with Leverett Davis (Caltech)and John Belcher (Davis’ PhD student at the time), they identified Alfvén waves in the solar
wind. Although much more is now known about these waves, the origins and eventual evolutionstill remain a mystery.
Also in the 1960s (launched 1964-1969 and missions extending into the 1970s), Ed was Principal
Investigator of the search-coil magnetometers onboard the Orbiting Geophysical Observatory(OGO) satellites -1, -3 and -5. From these data, Ed and his colleagues were the first to identify
the major electromagnetic plasma waves in the Earth’s magnetosphere: plasmaspheric hiss, outerzone chorus, and magnetosheath lion roars. Ed first worked with Holzer and his students (ChrisRussell was one) and then later with Richard Thorne (UCLA) and Bruce Tsurutani (JPL). These
are the primary magnetospheric electromagnetic wave modes still studied today. An analysis
technique by Ed’s friend Bengt Sonnerup (Dartmouth College) called “minimum varianceanalysis” was found to be extremely useful for analyzing electromagnetic waves. Ed was thefirst to apply this technique, a method which is the main means of studying plasma wave details
today.

The outer heliosphere was next for Ed. He was Principal Investigator of the magnetometer
experiments on the twin spacecraft Pioneers 10 and 11. Pioneer 10 was launched in 1972 andPioneer 11 ~ one year later in 1973. The spacecraft were built by TRW and the mission
managed by NASA Ames. These were the first missions to go to the outer heliosphere, throughthe (then thought) potentially dangerous asteroid belts and to distant planets. The radio isotope
thermoelectric generators (RTGs) gave power to these spacecraft going far from the Sun (a first).
Pioneer 10 encountered the giant planet Jupiter in 1973 going in to a distance of 2.8 Jovian radii(132,000 km). The intense radiation belt fluxes were even higher than predicted, but Pioneer 10
survived. Ed was the first to characterize the planetary magnetic fields and the dynamic everchanging magnetosphere (due to solar wind fluctuations). The bow shock was crossed 17 times
during the encounter.
After the successful Pioneer 10 encounter, NASA and the scientists started planning for thePioneer 11 encounter with Jupiter. If Pioneer 11 were sent even closer to the planet than Pioneer
10, Pioneer 11could be directed to an encounter with Saturn! NASA made the decision to send
Pioneer 11 in to a distance 1/3 that of Pioneer 10. The trajectory was planned so that thespacecraft would miss the magnetic equator where the particle radiation was most intense. Themission was successful and Ed and his colleagues made even better (closer) measurements of theplanetary magnetic fields.
The mission to Saturn was not without controversy. NASA asked the Pioneer 11 scientists todecide the trajectory of the Pioneer 11 Saturnian flyby: either go outside the Saturnian rings
where the satellite would be safe, or go inside the rings where there was the danger of collisions
with unseen ring particles. The vote of the P.I.s was not unamimous, but Ed’s (and others)arguments and votes to go inside held the day. Pioneer 11 was sent into a distance of only 21,000
km from Saturn’s cloud tops. Ed and colleagues were the first to characterize the planetary
magnetic fields and the Saturnian magnetosphere.
During the transit to these distant planets, Ed and his colleagues made other discoveries. WithJohn Wolfe, they were the first to identify an interaction between high speed solar wind streams
and slow streams, a region they named “Corotating Interaction Regions” or CIRs. CIRs havebeen shown to be important for causing geomagnetic activity on Earth. With Pioneers 10 and 11
energetic particle experimenters (John Simpson of the University of Chicago, James Van Allenof the University of Iowa and Frank McDonald of the Goddard Space Flight Center), they
discovered that fast forward and fast reverse collisionless shocks bounding the CIRs wereaccelerating energetic particles in deep interplanetary space between 3 and 10 AU. With Marcia
Neugebauer and Bruce Tsurutani, Ed studied and characterized different types of interplanetary
discontinuities.
Because of Pioneer 11’s close encounter with Saturn, the satellite received a gravitational boost
to become the first spacecraft to get out of the ecliptic plane. Although it only attained anangular distance of 17°, it was enough for Ed and colleagues to determine the shape of theheliospheric current sheet (HCS). Ed remembered a somewhat obscure prediction by his oldfriend Hannes Alfvén. The HCS became known as the “Alfvén ballerina skirt”. As the ballerina
spins, her skirt will fluctuate up and down with warps in it.
The International Sun-Earth-Explorers were the first joint NASA-ESA mission to be flown.
There were 3 spacecraft. ISEE-3 was a solar wind monitor placed in orbit around the L1libration point (first to have achieved this orbit) and ISEE-1 and -2 were magnetospheric orbiting
spacecraft. Ed Smith was the magnetometer P.I. on the ISEE-3 spacecraft and a Co-I on theplasma wave experiments on ISEE-1, -2 and -3.
With combined ISEE-3 magnetometer and plasma data Ed and colleagues identified andcharacterized what are now called Coronal Mass Ejections (CMEs), one of the causes ofmagnetic storms on Earth. Ed and Bruce Tsurutani of the ISEE-3 magnetometer team andmembers of the Los Alamos, New Mexico plasma team (Jack Gosling and Ron Zwickl; the P.I.
was Sam Bame) were the first to identify and characterize interplanetary fast shocks using
observational data.
The ISEE -1, -2, and -3 team were the first to collectively study the Earth’s foreshock regions
where back-streaming energetic electrons and ions propagated into the solar wind generatingplasma waves through in situ instabilities. Ed was also strongly involved in identifying afundamental magnetosheath wave mode at Earth, Jupiter and Saturn called the mirror mode.
With Charlie Kennel (UCLA), Ferd Coroniti (UCLA) and Fred Scarf (TRW) (and many othercolleagues), Ed studied quasiparallel shock particle acceleration for the first time.
The ISEE-3 space mission had a very clever design engineer named Bob Farquhar. Bob foundthat by storing extra hydrazine gas onboard (this gas was used to keep ISEE-3 in orbit about thelibration point), after the prime mission was accomplished, the spacecraft could be moved toother regions in space. This was an extremely novel concept at the time! The ISEE-3 teamvoted (the vote was again not unanimous) to move the spacecraft from the L1 orbit to a series ofdeep magnetotail passes reaching ~240 Earth radii (Re). To accomplish this a series of lunar
gravitational assists had to be planned and executed. From this new mission, Ed and colleagues
determined that the magnetotail was not “fragmented” but still maintained a two-lobe structure
all the way to 240 Re. They also discovered slow shocks bounding the lobe-plasmasheetboundary and “plasmoids” flowing down the tail. With Fred Scarf, Charlie Kennel and Ferd
Coroniti, Ed and colleagues identified electrostatic plasma wave modes in the tail andmagnetosphere.
After the deep tail passes, there was still hydrazine gas available for further spacecraft
maneuvers. Farquhar identified an opportunity to go through a comet’s tail. The ISEE-3
mission was renamed the International Cometary Explorer (ICE) which encountered comet
Giacobini-Zinner in 1985. Ed showed that the cometary magnetic tail had a structure of draped
magnetic fields as predicted (again) by Hannes Alfvén.

One of the biggest surprises with the cometary encounter was the detection of highly nonlinear
plasma waves associated with neutral gas sublimated from the comet nucleus. As the neutral
H2O molecules become ionized by either photoionization or charge exchange from the solarwind, the newly formed ions are instantaneously affected by the solar wind electric fields and areaccelerated so that they collectively are unstable and generate the waves. Ed and Bruce were thefirst to make this discovery. A theory by Ching Wu and Ron Davidson of the University ofMaryland had clearly predicted this but was missed by the experimenters.
After the encounter of ICE with comet Grigg-Skjellerup, a spacecraft “armada” was sent tocomet Halley (1986 encounter), the most famous of all comets. ICE was a distant participant ~1
million km away, but still managed to detect pickup ion waves. Hiroshi Oya (Tohoku University,Japan) invited Ed and Bruce to become Co-Is on the Japanese Sakigake plasma wave
investigation going to Halley.
For the joint NASA-ESA Ulysses mission Ed not only supplied the Vector Helium
Magnetometer as Co-I (Peter Hedgecock of Imperial College was the first P.I. and then later
André Balogh), but he was also the NASA Project Scientist for the mission. Ed worked inconjunction with Peter Wenzel, the ESA Project Scientist to make the mission scientifically
successful. By using the magnetometer data, Ed was able to determine that the Sun’s magnetic
field does not simply disappear and then reverse polarity or simply rotate its dipole every 11
years but a more complex field dominates during the field reversal interval.
Ed supplied the (Dual Sensor Scalar) magnetometer for the Argentine Science Application
Satellite (SAC-C) in 2000 and a vector/scalar helium magnetometer on the NASA/ESA Cassini
mission which orbited Saturn. Ed also was a Co-I of the JUNO mission to Jupiter (arrival date2016).
Ed was a member and Fellow of the American Geophysical Union, and a member of theAmerican Association for the Advancement of Science and the American Astronomical Union.
He was a recipient of two NASA medals for Exceptional Scientific Achievement and a NASA
Distinguished Service medal. He was elected a Fellow of the American Geophysical Union. In
2005, he received the Arctowski medal from the U.S Academy of Sciences in recognition ofcontributions to solar-terrestrial research. Ed was the author or co-author of over 500 scientificarticles. His research interests included Planetary Magnetism and Magnetospheric and SolarHeliospheric physics. The achievements of Dr. Edward J. Smith as a pioneer of space science are
truly remarkable.
Bruce T. Tsurutani , COSPAR Space Science Award 2018 (bruce.tsurutani@gmail.com)
Marcia M. Neugebauer, University of Arizona, Tucson, COSPAR Space Science Award 1998
(mneugeb@lpl.arizona.edu)