You will be given a definition of a task first, then some input of the task.
In this task you will be given a text passage from a trivia quiz. You should choose the category this question belongs to from these categories: History, Science, Social Science, Fine Arts, Literature. You can only choose one category, so if in doubt, please choose the closest match.

Pneuman and Kopp provided the first ab initio model of this phenomenon by integrating the MHD equation for a dipole source; their model closely matched Parkers 1956 model. Evidence for this object was provided by Biermanns observations of comets, though it was not observed until Luna 1. Its interaction with the terrestrial magnetic field results in the bow shock. It ceases being supersonic at the termination shock and its velocity falls to zero at the heliopause, where it merges with the interstellar medium. Radiation pressure and pressure from this plasma flow cause comet tails to always face away from the center of the solar system. For 10 points, name this stream of particles constantly emanating from the sun.
Output:
Science