Plasma magnet

A plasma magnet is a spacecraft propulsion device that captures energy from the solar wind. It uses a magnetic field to capture energy. The field acts as a sail, using the captured energy to propel the spacecraft analogously to how the wind propels a sailing vessel. It accelerates the vessel as it moves away from the sun and decelerates as it approaches (at the end of an interstellar journey). Thrust vectoring can be achieved by manipulating the sail size.
Solar wind.
The solar wind is a stream of energetic charged particles released from the upper atmosphere of a star, called the corona. This plasma mostly consists of electrons, protons and alpha particles with kinetic energy between 0.5 and 10 keV. The solar wind travels at velocities greater than 105 m/s. Its dynamic pressure is roughly 2x10-9 N/m2 at 1 AU. A properly designed system allows the spacecraft to accelerate to near the speed of the solar wind. The thrust provided from the solar wind remains constant, regardless of the distance from the star, because the plasma expands in size as the distance from the star increases.
Design.
The basic principle is that a rotating magnetic field, driven by alternating current in a crossed pair of coils, creates a circulating current, and that current then expands in radius until it creates a dipolar magnetic field much larger than the coils' radius.
To achieve sufficient thrust for a spacecraft (0.1-1 N), the "sail" must be at least 4 km in radius. The magnetic field strength must be 50nT.
To create such a field using an electromagnet requires large-scale engineering. A circular electromagnet would reach 300m in radius, carrying 105 amp-turns. Such an electromagnet would likely be so massive that the captured thrust would barely move it. 
A travel-relevant balance requires a vessel mass of a few 100 kg and power of at least a few kW.
Phased antennas operating in the radio frequency range produce a rapidly rotating magnetic field. This field preferentially accelerates electrons within a plasma to produce a direct current that can generate a steady state magnetic field that is much larger than can be sustained by practical electromagnets.
Drag device.
A drag device is one that is pushed by an external energy source. The classic drag device is a sailing vessel. By contrast, an airplane or a rocket use a fuel source to supply their own energy.