A comparative study on 3-D solar wind structure observed by Ulysses and MHD simulation
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During Ulysses’ first rapid pole-to-pole transit from September 1994 to June 1995, its observations showed that middle-or high-speed solar winds covered all latitudes except those between -20° and +20° near the ecliptic plane, where the velocity was 300–450 km/s. At poleward 40°, however, only fast solar winds at the speed of 700–870 km/s were observed. In addition, the transitions from low-speed wind to high-speed wind or vice versa were abrupt. In this paper, the large-scale structure of solar wind observed by Ulysses near solar minimum is simulated by using the three-dimensional numerical MHD model. The model combines TVD Lax-Friedrich scheme and MacCormack II scheme and decomposes the calculation region into two regions: one from 1 to 22 Rs and the other from 18 Rs to 1 AU. Based on the observations of the solar photospheric magnetic field and an addition of the volumetric heating to MHD equations, the large-scale solar wind structure mentioned above is reproduced by using the three-dimensional MHD model and the numerical results are roughly consistent with Ulysses’ observations. Our simulation shows that the initial magnetic field topology and the addition of volume heating may govern the bimodal structure of solar wind observed by Ulysses and also demonstrates that the three-dimensional MHD numerical model used here is efficient in modeling the large-scale solar wind structure.
KeywordsUlysses observation solar wind structure numerical simulation
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- 2.Lu, X. H., Wei, F. S., Yang, Z. L. et al., Ulysses observations and discussions of acceleration mechanisms for the solar wind, Acta Geophysica Sinica, 1998, 41(4): 437-z43.Google Scholar
- 8.Shi, Y., Wei, F. S., Feng, X. S. et al., Three-dimensional MHD simulation for the solar wind structure observed by Ulysses, Chi-nese Science Bulletin, 2001, 46(16): 1354–1357.Google Scholar
- 15.Feng, X. S., Wu, S. T., Fan, Q. L., A class of TVD type combined numerical scheme and its application in MHD simulation, Chinese Journal of Space Science (in Chinese), 2002, 4: 300–308.Google Scholar
- 16.Feng, X. S., Wu, S. T., Wei, F. S. et al., A class of TVD type com-bined numerical scheme for MHD equations with a survey about numerical methods in solar wind simulations, Space Science Re-views, 2003, 43: 107–110.Google Scholar