Jeremy Emmett edited Method.md  over 9 years ago

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The simulation was coded in FORTRAN 90 and paralellized to run on 16 cores. Aside from small-scale simuations to to ensure that the code functioned as expected, I ran a single 30,000 particle simulation, which produced the main results presented in this project. The simulation was run over the course of about 1000 initial orbital periods of Neptune. The initial shape and parameters of the system were as follows:  _Initial Coordinates_  The initial 'disk' of particles was created by randomly generating x and y coordinates between 0 and 1, with the constraint that every random point must lie no further from the origin than 1. Viewed top-down, the result was a roughly circular collection of 30,000 points with a uniform number density per unit area. The disk was given some 'thickness' by assigning each coordinate a random z-component between 0 and 0.1. The first two such points represented the coordinates of the Sun and Neptune, respectively. The initial position of the Sun was set to [0,0,0] for convenience. The initial position of Neptune was set to [0,-0.5,0], and thus at an initial distance of 0.5 from the Sun. This radius was chosen so as to immerse Neptune deep within the protoplanetary disk in which it would have formed. Interior material represented that from which planets and asteroids interior to the orbit of Neptune might form. Outlying material represented an initially close-in 'Kuiper Belt' of sorts. _Initial Masses_  Mass was allocated between the Sun, the disk particles, and Neptune such that the total mass of the system summed to 1. Though it actually constitutes over 99% of the total mass of the solar system, the mass of the sun was ar  btrarily set to a value of 0.9. The mass of Neptune was set to a value of $4.5\times 10^-5$\textsuperscript{,t} so that the ratio of the mass of Neptune to the mass of the Sun was a realistic value (0.005\%). The disk particles, with a combined mass of 0.099955, constituted the remainder of the total mass of the system, which was equally distributed among them (mass of an individual disk particle = 0.099955/30,000 = $3.33 10^-6$.  _Initial Velocities_  Though the combined mass of disk particles and that of Neptune constituted a significant portion of the total mass of the system, the Sun was the dominant mass. Therefore, since it ies at the center of the system, the mass enclosed by the Neptune's initial  radius of each particle was assumed to be that of also determined  theSun alone in calculating  initial circular velocities. Due to the large number of particles and they way in orbit period,  which they were initially randomly distributed, the disk was assumed to have a uniform mass density in served as  the xy-plane. Under these assumptions, every particle was assigned an initial velocity vector which would kick them, more or less, into a circular orbit about time unit for  the Sun. simulation.  This was accomplished calculated  with the following equation: equation.  \begin {equation}  V_c=\sqrt{\frac{GM}{R}} \2 \Pi \sqrt{a^3/M}  \end {equation}  _Initial Masses_  Mass was allocated between the Sun, the disk particles, and Neptune such that the total mass of the system summed to 1. Though it actually constitutes over 99% of the total mass of the solar system, the mass of the sun was ar  btrarily set to a value of 0.9. The mass of Neptune was set to a value of $4.5\times 10^-5$\textsuperscript{,t} so that the ratio of the mass of Neptune to the mass of the Sun was a realistic value (0.005\%). The disk particles, with a combined mass of 0.099955, constituted the remainder of the total mass of the system, which was equally distributed among them (mass of an individual disk particle = 0.099955/30,000 = $3.33 10^-6$.  The _Initial Velocities_  Though the combined mass of disk particles and that of Neptune constituted a significant portion of the total mass of the system, the Sun was the dominant mass. Therefore, since it ies at the center of the system, the mass enclosed by the radius of each particle was assumed to be that of the Sun alone in calculating  initial orbit period circular velocities. Due to the large number  of Neptune, particles and they way in which they were initially randomly distributed, the disk was assumed to have a uniform mass density in the xy-plane. Under these assumptions, every particle was assigned an initial velocity vector  which would be used as kick them, more or less, into a circular orbit about  the simulation's time unit, Sun. This  was calculated via accomplished with  the following formula: equation:  \begin {equation}  \2 \Pi \sqrt{a^3/M} V_c=\sqrt{\frac{GM}{R}}  \end {equation}Where $\M$ = enclosed mass and $\a$ = semi-major axis  Neptune was initially placed into a circular orbit about t