Publication: Physical Correlations Lead to Kappa Distributions
Nov. 23, 2022

The recently developed concept of "entropic defect" is important for understanding the foundations of thermodynamics in space plasma physics, and more generally for systems with physical correlations among their particles. Using this concept, this paper derives the basic formulation of the distribution function of velocities (or kinetic…

Publication: Thermodynamics of the Inner Heliosheath
Oct. 13, 2022

We derive annual sky maps of the proton temperature in the inner heliosheath (IHS), and track their temporal evolution over the years 2009–2016 of Interstellar Boundary Explorer observations. Other associated thermodynamic parameters also determined are the density, kappa (the parameter that characterizes kappa distributions), temperature rate,…

Publication: Oblique and rippled heliosphere structures from the Interstellar Boundary Explorer
Oct. 12, 2022

Past analysis has shown that the heliosphere structure can be deduced from correlations between long-scale solar wind pressure evolution and energetic neutral atom emissions. However, this required spatial and temporal averaging that smoothed out small or dynamic features of the heliosphere. In late 2014, the solar wind dynamic pressure…

Publication: Explanation of Heliospheric Energetic Neutral Atom Fluxes Observed by the Interstellar Boundary Explorer
Oct. 4, 2022

Interstellar neutral atoms propagating into the heliosphere experience charge exchange with the supersonic solar wind (SW) plasma, generating ions that are picked up by the SW. These pickup ions (PUIs) constitute ~25% of the proton number density by the time they reach the heliospheric termination shock (HTS). Preferential acceleration of PUIs…

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…