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William Matthaeus is a space plasma physicist who joined the UD faculty in 1983.
not easy to be a student of the sun. Your subject is roughly 93 million
miles away. You cant go there because you dont have that kind of
ride. You cant look at it because youd go blind. You cant touch it
because youd be incinerated long before you got close. And you cant
get close because it is surrounded by high-velocity streams of hot
plasma emanating from all directions. Even if you found a way to get
into that firehose of plasma, some of it reaching speeds of 1.8 million
miles per hour, you would experience such chaotic turbulence that you
would want to go anywhere else fast.
This thing we call the sun is mysterious in all its ways.
But if you want to study it, as NASA most definitely does, its a great idea to have the University of Delawares William Matthaeus, Unidel Professor of Physics and Astronomy,
at the drawing board. As a space plasma physicist, he thinks about some
of the most intangible questions ever raised. He calculates how things
would work and interact according to the laws of physics as we
understand them. He would help you figure out if this study was worth
all the brainpower and effort and money it would require.
He has done that kind of thinking for NASA, which is about to launch its most ambitious sun-related mission ever the Parker Solar Probe Mission
from Cape Canaveral, Fla. Matthaeus was part of the Science and
Technology Definition Team that informed the plans for this mission,
which will send a spacecraft into the hot plasma of the suns corona for
the first time. The corona is the outermost edge of the suns
Move this whole section up, swapping places with the section above it.
A NASA artist's rendering of the Parker Solar Probe approachimg the sun.
The launch date changed several times, but everything came together
on Sunday, Aug. 12. The mission had to go by Aug. 19, astronomers said,
because of its reliance on a certain interaction with Venus and the
impact that interaction has on its velocity and energy consumption.
Matthaeus, who has been on UDs faculty since 1983 and also is director of the Delaware Space Grant
program, hopes to be present with several UD colleagues, postdoctoral
researchers and students to witness the launch of the car-sized
spacecraft that is meant to orbit the sun for at least the next seven
The first step was designing the heat shields and thermal control
systems, Matthaeus said. The technology has made it feasible for the
last 10 years or so, but were finally going to do it. And the little
state of Delaware has a little piece of a billion-dollar mission.
Zooming at speeds that will exceed 400,000 miles per hour, the Parker
Solar Probe (called PSP for short) will be the fastest spacecraft ever
and get within 4 million miles of the sun more than five times closer
than the previous record set by the Helios-B spacecraft, which got about
27 million miles away.
It will provide our first glimpse of several regions of the solar
wind the powerful streams of scorching plasma coming from the suns
corona and help us understand more about how things work in the suns
atmosphere and beyond. That, in turn, will help us understand how the
sun changes the space environment, where space weather affects
astronauts, satellites, electronics and, for the strongest events, even
electric power grids on the Earths surface.
The Solar Probe will test calculations and predictions made over the
past six decades since University of Chicago physicist Eugene Parker
first theorized about the solar wind.
And it may help to answer significant questions that have puzzled scientists for decades.
One major question deals with the counterintuitive fact that the
lower corona, where solar wind is born, is far hotter than the surface
of the sun. The corona, the part that is visible in a total eclipse, can
reach temperatures approaching several million degrees Fahrenheit. The
surface of the sun is about 10,000 degrees Fahrenheit.
Rohit Chhiber, who recently earned his doctorate and is a student of
Matthaeus, spent long hours calculating conditions the spacecraft may
encounter at three important stages of its journey through the solar
wind. That study was the crux of his dissertation and he was the lead
author of an article for Astrophysical Journal that reported on the model he created.
Three landmarks of great interest include:
The point (closest to the sun) at which the solar wind reaches supersonic speed.
The point at which the solar wind reaches super-Alfvenic speed (the speed of magnetic waves).
The point at which the solar wind reaches the beta-1 location
(where the mechanical pressure equals the magnetic pressure). When the
solar wind passes this point, the suns magnetic fields no longer
dominate and govern its motion.
When the wind passes these points and exceeds these speed
thresholds, the magnetic field starts to curve away in a spiral,
Matthaeus said. So were very interested to see what happens when the
Parker Solar Probe passes through these regions. Were trying to find
out why the solar wind is here, how it is heated and propelled.
UDs Bennett Maruca, assistant
professor of physics and astronomy, has a keen interest in the mission,
too. His thesis advisor Justin Kasper, formerly of the
Harvard-Smithsonian Center for Astrophysics and now at the University of
Michigan made the only instrument that will be outside the
spacecraft, encountering the intense elements without a heat shield.
Chhiber and NASA research scientist Arcadi Usmanov created a video
simulation of these calculations to show how PSPs orbits are likely to
unfold. Each orbit takes about 100 days and the spacecraft is expected
to make 33 orbits. The spacecrafts sensors will collect data that will
be transmitted to Earth as the mission unfolds.
Every orbit it records the data from the instruments and at a
certain point that data goes to big antennas that use microwave
transmissions from the spacecraft to receive information from the
onboard instruments, Matthaeus said. There are times when it is
absolutely impossible to send anything back because of this big object
in the way.
When its on the far side of the sun, that is.
Chhiber has analyzed the character of gas dynamics and changes in
plasma dynamics across these regions and has made estimates of the
conditions that will be encountered.
The amount of time PSP spends in different regions tells you the
kind of science youll be discovering in those different regions,
Matthaeus, UD colleague and Professor Michael Shay and research
associate Tulasi Parashar shared some of their studies of the
heliosphere and the magnetosphere during workshops at the SHINE (Solar
Heliospheric & Interplanetary Environment) Conference, held in Cocoa
Beach, Florida., in late July.
Article by Beth Miller; photos
by Evan Krape and courtesy of NASA
The Parker Solar Probe will fly directly into the suns corona, the part that can easily be seen during a total solar eclipse.