The Solar Photon Random Walk Model simulates the path of photons in radiative transport as they escape from the Sun. Photons do not travel in a straight line, but rather collide with larger particles and get redirected in a fashion. This simulation models that process using a random walk in polar coordinates. The step size for this random walk are determined by the mean free path, the average distance the photon will travel before colliding with another particle. This mean free path (l) is equal to the inverse of the product of the density (p) and the opacity (k): l = 1/(k*p). The density and opacity of the Sun are not constant throughout, but rather change at different distances from the center. However, these values are not agreed upon among the scientific community. Using different values of the mean free path, physicists give the average escape time of photons anywhere from between 100,000 years and 1,000,000 years. As a result, the program was designed not only to take into account a few different physicists' values (both average and linearly decreasing values) but it also allows the user to input their own values.

The Solar Photon Random Walk Model was developed as a final project in a sophomore-level Computational Physics course (Phy 200) using the Easy Java Simulations (EJS) modeling tool.  It is distributed as a ready-to-run (compiled) Java archive.  Double clicking the ejs_comp_phys_photon_random_walk.jar file will run the program if Java is installed.

Please note that this resource requires at least version 1.5 of Java (JRE).