Scientists at the University of California, Los Angeles present new research on a curious cosmic phenomenon known as “whistlers”—very low frequency packets of radio waves that race along magnetic field lines. This first-of-its-kind study, appearing in the Physics of Plasmas, provides new insights into the nature of whistlers and space plasmas—regions of energized particles trapped by Earth’s magnetic fields. These studies could one day aid in the development of practical plasma technologies with magnetic fields, including spacecraft thrusters that use charged particles as fuel.