R. A. Bamford

An exploration of the effectiveness of artificial mini-magnetospheres as a potential solar storm shelter for long term human space missions

If mankind is to explore the solar system beyond the confines of our Earth and Moon the problem of radiation protection must be addressed. Galactic cosmic rays and highly variable energetic solar particles are an ever-present hazard in interplanetary space. Electric and/or magnetic fields have been suggested as deflection shields in the past, but these treated space as an empty vacuum. In fact it is not empty. Space contains a plasma known as the solar wind; a constant flow of protons and electrons coming from the Sun. In this paper we explore the effectiveness of a “mini-magnetosphere” acting as a radiation protection shield. We explicitly include the plasma physics necessary to account for the solar wind and its induced effects. We show that, by capturing/containing this plasma, we enhance the effectiveness of the shield. Further evidence to support our conclusions can be obtained from studying naturally occurring “mini-magnetospheres” on the Moon. These magnetic anomalies (related to “lunar swirls”) exhibit many of the effects seen in laboratory experiments and computer simulations. If shown to be feasible, this technology could become the gateway to manned exploration of interplanetary space.

SEP ACCELERATION IN CME DRIVEN SHOCKS USING A HYBRID CODE

We perform hybrid simulations of a super-Alfvenic quasi-parallel shock, driven by a coronal mass ejection (CME), propagating in the outer coronal/solar wind at distances of between 3 to 6 solar radii. The hybrid treatment of the problem enables the study of the shock propagation on the ion timescale, preserving ion kinetics and allowing for a self-consistent treatment of the shock propagation and particle acceleration. The CME plasma drags the embedded magnetic field lines stretching from the sun, and propagates out into interplanetary space at a greater velocity than the in situ solar wind, driving the shock, and producing very energetic particles. Our results show that electromagnetic Alfven waves are generated at the shock front. The waves propagate upstream of the shock and are produced by the counter-streaming ions of the solar wind plasma being reflected at the shock. A significant fraction of the particles are accelerated in two distinct phases: first, particles drift from the shock and are accelerated in the upstream region, and second, particles arriving at the shock get trapped and are accelerated at the shock front. A fraction of the particles diffused back to the shock, which is consistent with the Fermi acceleration mechanism.

Formation of collisionless shocks in magnetized plasma interaction with kinetic-scale obstacles

We investigate the formation of collisionless magnetized shocks triggered by the interaction between magnetized plasma flows and miniature-sized (order of plasma kinetic-scales) magnetic obstacles resorting to massively parallel, full particle-in-cell simulations, including the electron kinetics. The critical obstacle size to generate a compressed plasma region ahead of these objects is determined by independently varying the magnitude of the dipolar magnetic moment and the plasma magnetization. We find that the effective size of the obstacle depends on the relative orientation between the dipolar and plasma internal magnetic fields, and we show that this may be critical to form a shock in small-scale structures. We study the microphysics of the magnetopause in different magnetic field configurations in 2D and compare the results with full 3D simulations. Finally, we evaluate the parameter range where such miniature magnetized shocks can be explored in laboratory experiments.

Modular Space Vehicle Architecture for Human Exploration of Mars using Artificial Gravity and Mini-Magnetosphere Crew Radiation Shield

This paper presents a conceptual Mars Exploration Vehicle (MEV) architecture, which includes two unmanned Mars Lander Transfer Vehicles (MLTVs) and a Mars Crew Transfer Vehicle (MCTV) with a crew of four. The MLTVs and MCTV are assembled in low Earth orbit (LEO) from modules launched by four Space Launch System (SLS) and five Delta IV Heavy rockets. The MLTVs and MCTV individually escape from LEO, transit to Mars, brake into Mars orbit using propulsion and aerobraking, and rendezvous and dock in low Mars orbit (LMO). Each MLTV includes an Earth Departure stage (EDS), Mars Transfer Stage (MTS), Lander Service Module (LSM), and two landers: A Mars Personnel Lander (MPL) provides two-way crew transportation between LMO and the surface. Three unmanned Mars Cargo Landers (MCLs) provide one-way cargo transportation and the functionalities of habitats (MCL-H) (2) and rover (MCL-R). The landers rendezvous and assemble on the surface to form a base. The MCTV includes two EDS, two MTS, and the following: (1) The Multi-Purpose Crew Vehicle (MPCV) transports the crew from Earth to LEO, provides propulsion, and returns the crew to Earth after nominal mission completion or in aborts. (2) Three Deep Space Vehicles (DSVs) provide life support consumables, passive biological radiation shielding, crew habitation space, and propulsion. The DSV design was derived from the MCL-H. (3) An Artificial Gravity Module (AGM) allows the MCTV to rotate and generate artificial gravity for the crew and provides photo-voltaic power generation and deep space communications. A miniature magnetosphere (Mini-Mag), a potential key enabler for human interplanetary exploration, is electromagnetically generated on the AGM and provides active crew biological radiation shielding. The MEV architecture is based on many existing or near-term technologies. It incorporates significant modularity and could provide an economical approach to achieve progressively more ambitious stepping stone missions along a flexible path for human solar system exploration: starting with test flights in Earth and lunar orbit and progressing through missions to nearEarth asteroids and the moons of Mars, and culminating in the Mars landing mission.

Electron energization in lunar magnetospheres

The interaction of the solar wind with lunar surface magnetic fields produces a bow shock and a magnetosphere-like structure. In front of the shock wave energetic electrons up to keV energies are produced. This paper describes how resonant interactions between plasma turbulence in the form of lower-hybrid waves and electrons can result in field aligned electron acceleration. The turbulent wave fields close to the lower-hybrid resonant frequency are excited most probably by the modified two-stream instability, driven by the solar wind ions that are reflected and deflected by the low shock.

Applications of the wave kinetic approach: from laser wakefields to drift wave turbulence

Nonlinear wave-driven processes in plasmas are normally described by either a monochromatic pump wave that couples to other monochromatic waves, or as a random phase wave coupling to other random phase waves. An alternative approach involves a random or broadband pump coupling to monochromatic and/or coherent structures in the plasma. This approach can be implemented through the wave-kinetic model. In this model, the incoming pump wave is described by either a bunch (for coherent waves) or a sea (for random phase waves) of quasi-particles. This approach has been applied to both photon acceleration in laser wakefields and drift wave turbulence in magnetized plasma edge configurations. Numerical simulations have been compared to experiments, varying from photon acceleration to drift mode-zonal flow turbulence, and good qualitative correspondences have been found in all cases.