Using orbital tethers to remediate geomagnetic radiation belts

Abstract

The Van Allen radiation belts pose a hazard to spacecraft and astronauts, and similar radiation belts around other planets pose a hazard to interplanetary probes. We discuss a method of remediating these radiation belts first proposed by Danilov and Vasilyev, and recently improved by Hoyt, Minor, and Cash, where a long, charged tether is placed in orbit inside a radiation belt. In this approach, an electric field of the tether scatters the belt particles into a pitch angle loss cone leading to absorption of the particles in the atmosphere. A test particle calculation is presented which computes the scattered pitch angle of belt particles as a function of initial pitch angle and gyrophase for different particle energies. The moments of the resulting distribution of scattered angle versus initial pitch angle are used to compute the number density of the belt as a function of time using a Fokker‐Planck diffusion approximation. Finally, we use the characteristic timescales of scattering for particles of different energies to discuss the feasibility of using such a system of tethers as a long and short‐term remediation solution.

Active Experiments in Space: The Future

“…More space experiments are needed to further understand the interactions of electrodynamic tethers with the plasma environment (e.g., Choiniere et al, 2001;Siguier et al, 2013;Janeski et al, 2015) and to explore wave launching by tethers (Estes, 1988;Luttgen and Neubauer, 1994;Sanchez-Arriaga and Sanmartin, 2010). One suggested active experiment is to use a kV-charged tether to electrostatically pitchangle scatter radiation-belt particles into the atmospheric loss cone as the particles pass through the tether's sheath (Hoyt and Minor, 2005;Huboda de Badyn et al, 2016), although estimated time scales for remediation appear too long (∼1 yr). Another interesting active experiment involving a tape tether used to explore the upper atmosphere has been suggested by Sanmartin (Sanmartin et al, 2006;Sanmartin, 2010): ambient ions would be accelerated into a long, negatively biased tape producing secondary electrons which are then accelerated off the tape to excite an artificial aurora in the upper atmosphere.…”