The Position of a Type I Storm Source in the Magnetic Field of an Active Region

Type I storms generally occur in association with large sun-spots and the radiation is usually circularly polarized. Statistically it has been found that the sense of polarization, right-hand (RH) or left-hand (LH), usually corresponds to the ordinary magneto-ionic mode in the field of the dominant spot of the active region; when a following spot dominates, the polarization tends to be determined by this spot rather than by the leading field. One-dimensional position measurements show that the type I sources are usually not radially above the active region but are displaced by a few minutes of arc. The source sizes are about l‧.2 to 4‧.5 at 169 MHz and the sources frequently contain double, multiple or bipolar structure at 80 and 160 MHz.