Magnetic fields (sometimes called `B' fields) occur naturally throughout the universe, but how they affect their surroundings is often unclear. Here on the Earth, magnetic fields align our compasses to north and protect us from harmful particles emitted during solar storms. In regions of star formation, where vast clouds of gas and dust collapse to form young stars, magnetic fields help to determine the direction that the star and its surrounding protoplanetary disk rotate, and may help to create large jets of material that flow away from the star along the rotation axis of the disk. Our own Sun likely went through such a phase in its earliest years, with the disk later becoming the site for the formation of the Earth and the other planets. How jets are launched is one of the key unanswered problems in the study of star formation. Determining the role that magnetic fields play in launching jets from young stars has been difficult. The few existing measurements show weak fields at large distances from the star, but strong fields are needed to drive jets close to the star.
To determine how magnetic fields vary with distance along jets, a team of scientists led by Rice astronomer Patrick Hartigan used a supercomputer to simulate pulsed magnetized flows. The simulations allowed the researchers to follow how shock waves form and evolve along jets. Unlike steady flows, where the field falls relatively gradually with distance, pulsed flows concentrate magnetic fields into a few areas of dense gas, which enables shock waves to form more easily. Shock waves have been observed with images from the Hubble Space Telescope, and the new simulations clarify how these structures evolve in real jets. Click here for full article
Supercomputer simulation of a pulsed magnetized jet
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