THREE-DIMENSIONAL EVOLUTION OF SOLAR WIND DURING SOLAR CYCLES 22–24

摘要: This paper presents an analysis of three-dimensional evolution solar wind density turbulence and speed at various levels activity between cycles 22 24. The data used in this study have been obtained from the interplanetary scintillation (IPS) measurements made Ooty Radio Telescope, operating 327 MHz. Results show that (1) on average, there was a downward trend maximum cycle to deep minimum phase 23; (2) scattering diameter corona around Sun shrunk steadily toward Sun, starting 2003 smallest size deepest minimum, it corresponded reduction ~50% phases (3) latitudinal distribution significantly different minima 23. At 22, when underlying magnetic field simple nearly dipole nature, high-speed streams were observed poles ~30° latitudes both hemispheres. In contrast, long-decay 23, sources poles, accordance with weak polar fields, occupied narrow latitude belts ~60° latitudes. Moreover, agreement large amplitude heliospheric current sheet, low-speed prevailed low- mid-latitude regions heliosphere. (4) transition 23 24, high close equator extended equatorial-to-mid-latitude regions. above results comparison Ulysses other situ suggest source has changed globally, important implication supply mass energy space reduced prolonged period low activity. IPS are consistent onset growth middle 2009. However, width northern almost disappeared indicates ascending reached hemisphere Sun. southern part hemisphere, yet develop and/or increase.