An examination of directional discontinuities and magnetic polarity changes around interplanetary sector boundaries usingE > 2 keV electrons
- 34 Downloads
Past studies of interplanetary magnetic sector boundaries have been based on the assumption that one can determine the field polarities by comparing the field directions with those of the nominal Parker spiral angles. Previous investigators have found evidence for decreases of ∣B∣, the magnitude of the magnetic fieldB, and increases of Θ, the angle betweenB and the ecliptic plane, at sector boundaries. Others have argued that the characteristic thickness of sector boundaries exceeds that of tangential discontinuities, making sector boundaries a separate class of structures.
We use a simple technique for inferring the polarities of interplanetary magnetic fields based on the assumption thatE > 2 keV electrons are always flowing along the magnetic field away from the Sun. Electron data from the UC Berkeley experiment on the ISEE-3 spacecraft are used to examine periods around several apparent sector boundaries in 1978 and 1979. We compare properties of (a) boundaries with field polarity changes and (b) large-angle (ω > 60°) directional discontinuities with no field polarity changes. We find no significant differences between the sector boundaries and the directional discontinuities in terms of associated decreases in ∣B∣ or of values of Θ. These results suggest no significant difference between sector boundaries and directional discontinuities other than the change in field polarities. Within limited statistics we find that about half the polarity changes would not have been identified using a requirement thatω > 90° and that half of theω > 120° discontinuities would have been misidentified as polarity changes.
KeywordsInterplanetary Magnetic Field Magnetic Polarity Field Polarity Ecliptic Plane Sector Boundary
Unable to display preview. Download preview PDF.
- Anderson, K. A., Lin, R. P., Potter, D. W., and Heetderks, H. D.: 1978,IEEE Trans. Geosci. Electron. GE-16, 153.Google Scholar
- Behannon, K. W., Neubauer, F. M., and Barnstorf, H.: 1981,J. Geophys. Res. 86, 3273.Google Scholar
- Crooker, N. U., Siscoe, G. L., Shodan, S., Webb, D. F., Gosling, J. T., and Smith, E. J.: 1993,J. Geophys. Res. 98, 9371.Google Scholar
- Frandsen, A. M. A., Connor, B. V., Van Amersfoort, J., and Smith, E. J.: 1978,IEEE Trans. Geosci. Electron. GE-16, 195.Google Scholar
- Goldstein, H.: 1950,Classical Mechanics, Addison Wesley, Cambridge, U.S.A.Google Scholar
- Gosling, J.T., Birn, J., and Hesse, M.: 1995,Geophys. Res. Letters 22, 869.Google Scholar
- Kahler, S. W. and Hundhausen, A. J.: 1992,J. Geophys. Res. 97, 1619.Google Scholar
- Kahler, S. and Lin, R. P.: 1994,Geophys. Res. Letters 21, 1575.Google Scholar
- Klein, L. and Burlaga, L. F.: 1980,J. Geophys. Res. 85, 2269.Google Scholar
- Lin, R. P., Anderson, K. A., Ashford, S., Carlson, C., Curtis, D., Ergun, R., Larson, D., McFadden, J., McCarthy, M., Parks, G. K., Reme, H., Bosqued, J. M., Coutelier, J., Cotin, F., d'Uston, C., Wenzel, K.-P., Sanderson, T. R., Henrion, J., Ronnet, J. C., and Paschmann, G.: 1995,Space Sci. Rev. 71, 125.Google Scholar
- Mariani, F. and Neubauer, F. M.: 1990, in R. Schwenn and E. Marsch (eds.),Physics of the Inner Heliosphere, Vol. 1, Springer-Verlag, Berlin, p. 183.Google Scholar
- McComas, D. J., Phillips, J. L., Hundhausen, A. J., and Burkepile, J. T.: 1992, in E. Marsch and R. Schwenn (eds.),Solar Wind Seven, Pergamon Press Ltd, Oxford, p. 225.Google Scholar
- Ness, N. F. and Wilcox, J. M.: 1966,Astrophys. J. 143, 23.Google Scholar
- Pilipp, W. G., Miggenrieder, H., Muhlhauser, K.-H., Rosenbauer, H., Schwenn, R., and Neubauer, F. M.: 1987,J. Geophys. Res. 92, 1103.Google Scholar
- Simnett, G. M., Sayle, K., Roelof, E. C., and Tappin, S. J.: 1994,Geophys. Res. Letters 21, 1561.Google Scholar
- Wilcox, J. M. and Ness, N. F.: 1965,J. Geophys. Res. 70, 5793.Google Scholar
- Winterhalter, D., Smith, E. J., Burton, M. E., Murphy, N., and McComas, D. J.: 1994,J. Geophys. Res. 99, 6667.Google Scholar