Space Physics at Princeton

Welcome to Space Physics at Princeton

The Space Physics group in the Department of Astrophysical Sciences:

  • Educates Princeton University undergraduate and graduate students through hands-on work in an active space instrument laboratory and with scientific data from space
  • Conceives, designs develops, calibrates, and flies cutting-edge space instrumentation on NASA missions
  • Analyzes space data from the Sun and Solar Corona through to the Solar Wind and terrestrial and planetary magnetospheres, including the global heliosphere and its interaction with the local interstellar medium
  • Discovers scientific secrets of our space environs through integrated observations, data analysis, and theoretical understanding

We are the lead institution for numerous NASA Heliophysics missions and instruments that Prof. David J. McComas serves as the principal investigator for:

Interstellar Mapping and Acceleration Probe (IMAP) mission – under development and launching in 2025 to explore the details of particle acceleration and the Sun’s interaction with the local interstellar medium;

Parker Solar Probe (PSP), Integrated Science investigation of the Sun (ISʘIS) instrument suite – launched 8/12/2018 to measure energetic particles as close in as nine solar radii from the Sun’s surface;

Interstellar Boundary Explorer (IBEX) mission – launched in 2008 and still exploring the boundaries of our heliosphere and its interaction with the local interstellar medium;

New Horizons, Solar Wind Around Pluto (SWAP) instrument – launched in 2006, measured the plasma environments of Pluto and the Jovian magnetosphere and continues to make unprecedented observations of interstellar pickup ions;

Advanced Composition Explorer (ACE), Solar Wind Electron Proton Alpha Monitor (SWEPAM) instrument – launched in 1997 and still providing solar wind data from the Sun-Earth Lagrangian point (L1);

Two Wide-angle Imaging Neutral-atom Spectrometers (TWINS) mission – returned the first stereo imaging of the Earth’s dynamic magnetosphere (operational from 2008-2017);

Ulysses, Solar Wind Observations Over the Poles of the Sun (SWOOPS) instrument – discovered the three-dimensional structure of the solar wind from the first and only mission to fly over the poles of the Sun (operational from 1990 - 2009).



Research News

Publication: Beta-Dependent Constraints on Ion Temperature Anisotropy in Jupiter's Magnetosheath
Aug. 5, 2022

Most space plasmas are weakly collisional. Due to the low collision rate, the plasmas are routinely out of local thermal equilibrium and often exhibit non-Maxwellian velocity distributions. The charged particles typically exhibit anisotropy in temperature measurements, that is, distinct temperatures are observed perpendicular and parallel (

Publication: First High-resolution Observations of Interstellar Pickup Ion Mediated Shocks in the Outer Heliosphere
Aug. 2, 2022

This study reports the first high-time-resolution observations of interstellar pickup ions (PUIs) in the outer heliosphere, including the first high-resolution observations of PUIs mediating shocks collected anywhere. These new data were enabled by a clever flight software reprogramming of the Solar Wind Around Pluto (SWAP) instrument on New…

Publication: Galactic Cosmic Rays Throughout the Heliosphere and in the Very Local Interstellar Medium
July 22, 2022

We review recent observations and modeling developments on the subject of galactic cosmic rays through the heliosphere and in the Very Local Interstellar Medium, emphasizing knowledge that has accumulated over the past decade. We begin by highlighting key measurements of cosmic-ray spectra by Voyager, PAMELA, and AMS and discuss advances in…

Publication: Taylor Microscale and Effective Reynolds Number near the Sun from PSP
July 2, 2022

The Taylor microscale is a fundamental length scale in turbulent fluids, representing the end of fluid properties and onset of dissipative processes. The Taylor microscale can also be used to evaluate the Reynolds number in classical turbulence theory. Although the solar wind is weakly collisional, it approximately behaves as a…

Professor David J. McComas receives the 2022 EGU Hannes Alfvén Medal
June 3, 2022

Congratulations to Princeton University Professor David McComas, he received, Hannes Alfvén Medal at the 2022 EGU General Assembly in Austria.

The European Geosciences Union (EGU) awarded 50 recipients at this year’s General Assembly, with Union Medals and Awards, Division Medals, and Division Outstanding Early Career Scientist Awards…

Space Physics Students Graduate as class of 2022
May 23, 2022

Congratulations to Sydney Evans, Grace Gong, and Nina Arcot as they successfully graduate as part of the class of 2022.

They have successfully completed a number of different projects with the group, and we would like to thank them for their dedication and for the important contributions that they have made.

To find out more…

Publication: In Situ Observations of Interstellar Pickup Ions from 1 au to the Outer Heliosphere
May 9, 2022

Interstellar pickup ions are an ubiquitous and thermodynamically important component of the solar wind plasma in the heliosphere. These PUIs are born from the ionization of the interstellar neutral gas, consisting of hydrogen, helium, and trace amounts of heavier elements, in the solar wind as the heliosphere moves through the local…

Publication: Water-Group Pickup Ions From Europa-Genic Neutrals Orbiting Jupiter
May 4, 2022

Water-group gas continuously escapes from Jupiter's icy moons to form co-orbiting populations of particles or neutral toroidal clouds. These clouds provide insights into their source moons as they reveal loss processes and compositions of their parent bodies, alter local plasma composition, and act as sources and sinks for magnetospheric…

Publication: Closed Fluxtubes and Dispersive Proton Conics at Jupiter's Polar Cap
May 3, 2022

Two distinct proton populations are observed over Jupiter's southern polar cap: a ~1 keV core population and ~1-300 keV dispersive conic population at 6–7 RJ planetocentric distance. We find the 1 keV core protons are likely the seed population for the higher-energy dispersive conics, which are accelerated from
a distance of ∼3-5 RJ…

Publication: Sub-Alfvénic Solar Wind Observed by the Parker Solar Probe: Characterization of Turbulence, Anisotropy, Intermittency, and Switchback
Feb. 11, 2022

In the lower solar coronal regions where the magnetic field is dominant, the Alfvén speed is much higher than the wind speed. In contrast, the near-Earth solar wind is strongly super-Alfvénic, i.e., the wind speed greatly exceeds the Alfvén speed. The transition between these regimes is classically described as the "Alfvén point" but may in…

Sun & Princeton Shield