per cm3 are between 0.005 and 0.5 in the local bubble and G-cloud, respectively meaning that the ISM plasma mass density is . A typical value assumed for approach to Alpha Centauri is the G-cloud value of particle density of 0.1 particles per cm3 corresponding to . The spacecraft velocity is much greater than the ISM velocity at the beginning of a deceleration maneuver so the effective plasma velocity is approximately . Radio emissions of cyclotron radiation due to interaction of charged particles in the interstellar medium as they spiral around the magnetic field lines of a magnetic sail would have a frequency of approximately () kHz, where is the spacecraft velocity and the speed of light. The Earth's ionosphere would prevent detection on the surface, but a space-based antenna could detect such emissions up to several thousands of light years away. Detection of such radiation could indicate activity of advanced extraterrestrial civilizations. In a planetary ionosphere A spacecraft approaching a planet with a significant upper atmosphere such as Saturn or Neptune could use a magnetic sail to decelerate by ionizing neutral atoms such that it behaves as a low beta plasma. The spacecraft velocity is much greater than the planetary ionosphere velocity in a deceleration maneuver so the effective plasma velocity is approximately . In a planetary magnetosphere Inside or near a planetary magnetosphere, a magnetic sail can thrust against or be attracted to a planet's magnetic field created by a dynamo, especially in an orbit that passes over the planet's magnetic poles. When the magnetic sail and planet's magnetic field are in opposite directions an attractive force occurs and when the fields are in the same direction a repulsive force occurs, which is not stable and means to prevent the sail from flipping over is necessary. The thrust that a magnetic sail delivers within a magnetosphere decreases with the fourth power of its distance from the planet's internal magnetic field. When close to a planet with a strong magnetosphere such as Earth or a gas giant, the magnetic sail could generate more thrust by interacting with the magnetosphere instead of the solar wind. When operating near a planetary or stellar magnetosphere the effect of that magnetic field must be considered if it is on the same order as the gravitational field. By varying the magnetic sail's field strength and orientation a "perigee kick" can be achieved raising the