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).



Sun & Princeton Shield

/Space Physics Group

The Space Physics Group

The Space Physics Group

Research News

Publication: Estimates of Proton and Electron Heating Rates Extended to the Near-Sun Environment
Sept. 27, 2023

The differential heating of charged species due to dissipation of turbulent fluctuations plays a key role in solar wind evolution. Measurements from previous heliophysics missions have provided estimates of proton and electron heating rates beyond 0.27 au. Using Parker Solar Probe (PSP) data accumulated during the first 10 encounters, we extend…

Extensive Entropy: The case of Zero Entropy Defect
Sept. 26, 2023

This paper shows that the Rényi and Boltzmann-Gibbs (BG) extensive entropies share the same functional relationship with the nonextensive entropy associated with kappa distributions, which coincides with the well-known Havrda/Charvát/Daróczy/Tsallis (HCDT) entropy. We find that while the relationship between kappa/HCDT and Rényi entropies is…

Publication: Transport equation of kappa distributions in the heliosphere
Aug. 23, 2023

In this paper we develop the transport equation of kappa, the fundamental thermodynamic parameter that labels kappa distributions of particle velocities. Using the recently developed concept of entropy defect, we are able to formulate the transport equation of kappa as a function of a general positive or negative rate of entropy change. Then,…

Publication: Collisional-like dissipation in collisionless plasmas
Aug. 16, 2023

When collisions are strong in a magnetized plasma, standard closures provide simple representations of dissipation in terms of coefficients of viscosity and resistivity. In the opposite limit of weak collisions, the analogous physical effects that lead to dissipation are present, but the simple approximations to describe them, the closures, are…

Publication: Temperature of the Polar Inner Heliosheath - Connection to Solar Activity
June 29, 2023

We study the thermodynamics of the plasma protons in the polar regions of the inner heliosheath (IHS) and its connection with solar activity over solar cycle 24. First, we express the thermodynamic parameters of this plasma with respect to the year of energetic neutral atom (ENA) creation and perform a statistical analysis of temperatures, in…

Publication: Formation, Structure, and Detectability of the Geminids Meteoroid Stream
June 15, 2023

The Geminids meteoroid stream produces one of the most intense meteor showers at Earth. It is an unusual stream in that its parent body is understood to be an asteroid, (3200) Phaethon, unlike most streams, which are formed via ongoing cometary activity. Until recently, our primary understanding of this stream came from Earth-based…

Publication: Proton Equatorial Pitch Angle Distributions in Jupiter's Inner Magnetosphere
June 14, 2023

Protons are seen throughout Jupiter's magnetosphere. Where these protons come from and how they evolve is not well understood. Previous observations by the Galileo spacecraft showed that protons in the vicinity of Europa have properties consistent with charge exchange with a neutral species, which effectively removes the…

Publication: Entropy Defect in Thermodynamics
June 5, 2023

New paper on the axiomatic generalization of thermodynamics for systems with correlations among their constituents, residing either in stationary or nonstationary states.

Analytically, the paper describes the physical foundations of the newly discovered “entropy defect” as a basic concept of thermodynamics. The entropy defect…

Publication: Spherical Harmonic Representation of Energetic Neutral Atom Flux Components Observed by IBEX
June 2, 2023

The Interstellar Boundary Explorer (IBEX) images the heliosphere by observing energetic neutral atoms (ENAs). The IBEX-Hi instrument on board IBEX provides full-sky maps of ENA fluxes produced in the heliosphere and very local interstellar medium through charge exchange of suprathermal ions with interstellar neutral atoms. The first IBEX-Hi…

Publication: Constraints on the IBEX Ribbon's Origin from Its Evolution over a Solar Cycle
June 2, 2023

In 2009, the Interstellar Boundary Explorer (IBEX) discovered a narrow "ribbon" of energetic neutral atom emissions across the sky with properties correlated with the solar wind latitudinal structure and the interstellar magnetic field draped around the heliosphere. It is widely believed that the ribbon is formed from the escape of heliospheric…