Modeling ion conics in space

Space Plasma Physicists have measured energetic, positively charged ionospheric ions at auroral and polar cusp latitudes. These ions gyrate around the geomagnetic field lines at extremely high speeds (with energies ranging from tens of eV to tens of keV) while flowing upward from the low altitude ionosphere into the magnetosphere. Such populations of ions have been christened ion conics. The term conic refers to the fact that these ion distributions are strongly peaked in pitch angle, so that they are concentrated on a cone in velocity space. The discovery of conics was somewhat surprising, largely because no mechanism for transversely accelerating ionospheric ions to what are essentially magnetospheric energies had been anticipated. It is probable that these ions were accelerated transversely by the plasma waves that are omnipresent in the turbulent region of the high latitude ionosphere or magnetosphere. Since the geomagnetic field decreases with altitude, as the ions drift to higher altitudes, some of the transverse energy is converted to upwards motion, thereby transforming the shape of these distributions into velocity space conics. In this talk, the authors describe two possible wave particle interaction mechanisms that may be responsible for the transverse acceleration of ions: lower hybrid and ion cyclotron resonance heating. Theories and modeling efforts developed at MIT will be reviewed