``Sticky'' Dusty Plasma Theory

In a dusty plasma, the usual plasma (ionized gas) environment of ions, electrons, and neutral particles is modified by the presence of a fourth species - charged particulates; i.e., the dust particles. The dust particles can range in size from hundreds of nanometers through hundreds of microns. Because the dust particles are charged, they fully interact electrostatically with the other charged species in the surrounding plasma. The presence of the charged dust grains in the plasma modifies many of the properties of the plasma, e.g., charge distributions and potential profiles, and introduces entirely new dust-plasma phenomena, such as the levitation of dust observed in panel one of figure 3.

In this proposed application of dusty plasmas as solar sails, several key questions must be addressed. First, can the mass loading of the dust be sufficiently low to compete effectively against current solar sail technologies? Second, can the dust particles remain sufficiently well-confined within the magnetic balloon and, for sufficient duration, to ensure continuous acceleration? Third, is the reflectivity of the dust particles sufficient to gain the added benefits of a ``black'' plasma? While some preliminary studies have been performed to examine this application of dusty plasma, it is important to note that the focus of this proposed investigation will be to fully assess the feasibility of this idea.

There are two scale lengths that are critical to assessing the feasibility of the dusty plasma solar sail: $a$, the radius of the dust particles and $R$, the radius of the magnetic balloon. If the dust particles are spherical then the mass of an individual particle will scale as $a^3$ and the charge per grain will scale as $a$. The total mass of the system will depend upon the density of the dust grains within the magnetic balloon and will scale as $R^3$. Furthermore, the condition for confinement of the dust particles within the dust cloud will be set by a particle gyroradius less than $R$. In order to resolve these various scaling arguments, it is first necessary to make an estimate of the total charge that accumulates on the dust grain surface.