Searcharxiv⌕ Search

arXiv subjects

Ian Cohen

Publications and source records attributed to Ian Cohen.

8 recordsLinked to original sources
arXiv2025

The Uranus Flagship: Investigating New Paradigms for Outer Solar System Exploration Workshop Summary Report

This white paper is a summary of the Uranus Flagship Workshop that took place 21 to 23 May 2024 at NASA's Goddard Space Flight Center. Co-led by Goddard and Johns Hopkins Applied Physics Lab conveners, we had a broad, international, Science Organizing Committee, and a largely early career Local Organizing Committee from APL and GSFC. From prior workshops, it was apparent that the community was wildly enthusiastic about starting a mission, but lacked focus on what was possible or where to begin. Thus, the purpose of our workshop was to discuss practical aspects of the next planetary flagship and how we can employ new paradigms to better enable robust outer planet exploration. To enable this goal, we introduced the community to the best practices and lessons learned from previous missions and NASA-commissioned studies, and discussed the challenges involved with a mission so far from the Earth/Sun. The underlying workshop purpose was to steward the community towards a more practical mission design approach that will enable the development of this mission, as well as future missions, on a shorter cadence by setting expectations and having difficult discussions early in development. Because of the time scales involved in this mission, special effort was made towards early career inclusion and participation.

astro-ph.IM↗
arXiv2025

Uranus Flagship Science-Driven Tour Design: Community Input Poll

The highest priority Planetary Flagship from the Planetary Science and Astrobiology Decadal Survey is the Uranus Orbiter and Probe. This mission enables broad, cross-disciplinary science of an ice giant system, including the planet, moons, rings, and magnetosphere. The ice giants represent a size class of planet that is largely unexplored but that is common among extrasolar planet systems. At the same time, Uranus is unique, possessing a regular satellite system, rings, and a complex magnetosphere surrounding a planet tilted over for extreme seasonal variation. Exploration of the Uranian system is guided by a broad suite of science Objectives and through remote sensing, in situ probe, and fields and particles experiments. Due to the rapid nature of the Decadal concept study, the orbital tour could not be perfectly optimized, but a best effort was made to include orbit insertion, probe release and relay, and multiple satellite flybys; some Objectives were necessarily better met than others by this tour. The mission's tour trajectory can be optimized to meet any of the Decadal Science Objectives, by focusing on a particular system target, for example magnetosphere, satellites, or planet interior, but the best tour will simultaneously meet the highest priority measurements for every Objective. The community-led (with no institutional or NASA sponsorship) poll described here was designed to collect broad science inputs on the tour parameters required for each Decadal Science Objective. Here we present results aggregated by Objective, as well as compared longitudinally, of the highest priority tour needs identified across all Objectives. Both the raw and aggregated data are made publicly available for future white papers, tour and trajectory work, as well as mission and instrument design teams, but the results are not binding nor decisional in any way.

astro-ph.IM↗
arXiv2024

Earth's Alfv\'en wings driven by the April 2023 Coronal Mass Ejection

We report a rare regime of Earth's magnetosphere interaction with sub-Alfv\'enic solar wind in which the windsock-like magnetosphere transforms into one with Alfv\'en wings. In the magnetic cloud of a Coronal Mass Ejection (CME) on April 24, 2023, NASA's Magnetospheric Multiscale mission distinguishes the following features: (1) unshocked and accelerated cold CME plasma coming directly against Earth's dayside magnetosphere; (2) dynamical wing filaments representing new channels of magnetic connection between the magnetosphere and foot points of the Sun's erupted flux rope; (3) cold CME ions observed with energized counter-streaming electrons, evidence of CME plasma captured due to reconnection between magnetic-cloud and Alfv\'en-wing field lines. The reported measurements advance our knowledge of CME interaction with planetary magnetospheres, and open new opportunities to understand how sub-Alfv\'enic plasma flows impact astrophysical bodies such as Mercury, moons of Jupiter, and exoplanets close to their host stars.

physics.space-ph↗
arXiv2023

Small Platforms, High Return: The Need to Enhance Investment in Small Satellites for Focused Science, Career Development, and Improved Equity

In the next decade, there is an opportunity for very high return on investment of relatively small budgets by elevating the priority of smallsat funding in heliophysics. We've learned in the past decade that these missions perform exceptionally well by traditional metrics, e.g., papers/year/\$M (Spence et al. 2022 -- arXiv:2206.02968). It is also well established that there is a "leaky pipeline" resulting in too little diversity in leadership positions (see the National Academies Report at https://www.nationalacademies.org/our-work/increasing-diversity-in-the-leadership-of-competed-space-missions). Prioritizing smallsat funding would significantly increase the number of opportunities for new leaders to learn -- a crucial patch for the pipeline and an essential phase of career development. At present, however, there are far more proposers than the available funding can support, leading to selection ratios that can be as low as 6% -- in the bottom 0.5th percentile of selection ratios across the history of ROSES. Prioritizing SmallSat funding and substantially increasing that selection ratio are the fundamental recommendations being made by this white paper.

astro-ph.IM↗
arXiv2023

The Persistent Mystery of Collisionless Shocks

Collisionless shock waves are one of the main forms of energy conversion in space plasmas. They can directly or indirectly drive other universal plasma processes such as magnetic reconnection, turbulence, particle acceleration and wave phenomena. Collisionless shocks employ a myriad of kinetic plasma mechanisms to convert the kinetic energy of supersonic flows in space to other forms of energy (e.g., thermal plasma, energetic particles, or Poynting flux) in order for the flow to pass an immovable obstacle. The partitioning of energy downstream of collisionless shocks is not well understood, nor are the processes which perform energy conversion. While we, as the heliophysics community, have collected an abundance of observations of the terrestrial bow shock, instrument and mission-level limitations have made it impossible to quantify this partition, to establish the physics within the shock layer responsible for it, and to understand its dependence on upstream conditions. This paper stresses the need for the first ever spacecraft mission specifically designed and dedicated to the observation of both the terrestrial bow shock as well as Interplanetary shocks in the solar wind.

astro-ph.IM↗
arXiv2020

The Science Case for Spacecraft Exploration of the Uranian Satellites

The five classical Uranian moons are possible ocean worlds that exhibit bizarre geologic landforms, hinting at recent surface-interior communication. However, Uranus' classical moons, as well as its ring moons and irregular satellites, remain poorly understood. We assert that a Flagship-class orbiter is needed to explore the Uranian satellites.

astro-ph.IM↗
arXiv2018

Solar System Ice Giants: Exoplanets in our Backyard

Future remote sensing of exoplanets will be enhanced by a thorough investigation of our solar system Ice Giants (Neptune-size planets). What can the configuration of the magnetic field tell us (remotely) about the interior, and what implications does that field have for the structure of the magnetosphere; energy input into the atmosphere, and surface geophysics (for example surface weathering of satellites that might harbour sub-surface oceans). How can monitoring of auroral emission help inform future remote observations of emission from exoplanets? Our Solar System provides the only laboratory in which we can perform in-situ experiments to understand exoplanet formation, dynamos, systems and magnetospheres.

astro-ph.EP↗