Abstract
At solar maximum, the large-scale structure of the heliospheric magnetic field (HMF) reflects the complexity of the Sun's coronal magnetic fields. The corona is characterised by mostly closed magnetic structures and short-lived, small coronal holes. The axis of the Sun's dipole field is close to the solar equator; there are also important contributions from the higher order terms. This complex and variable coronal magnetic configuration leads to a much increased variability in the HMF on all time scales, at all latitudes. The transition from solar minimum to solar maximum conditions, as reflected in the HMF, is described, as observed by Ulysses during its passage to high southern heliolatitudes. The magnetic signatures associated with the interaction regions generated by short-lived fast solar wind streams are presented, together with the highly disordered period in mid-1999 when there was a considerable reorganisation in coronal structures. The magnetic sector structure at high heliolatitudes shows, from mid-1999, a recognisable two-sector structure, corresponding to a highly inclined Heliospheric Current Sheet. A preliminary investigation of the radial component of the magnetic field indicates that it remains, on average, constant as a function of heliolatitude. Intervals of highly Alfvénic fluctuations in the rarefaction regions trailing the interaction regions have been, even if intermittently, identified even close to solar maximum.
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References
Alfvén, H. and Felthammar, C.-G.: 1963, Cosmical Electrodynamics, Oxford University Press, Oxford, 228 pp.
Balogh, A., Beek, T. J., Forsyth, R. J., Hedgecock, P. C., Marquedant, R. J., Smith, E. J., Southwood, D. J., and Tsurutani, B. T.: 1992, ‘The Magnetic Field Investigation on the Ulysses Mission: Instrumentation and Preliminary Scientific Results’, Astron. Astrophys. Suppl. Ser. 92, 221.
Belcher, J. W. and Davis, L., Jr.: 1971, ‘Large-Amplitude Alfvén Waves in the Interplanetary Medium’, J. Geophys. Res. 76, 3534.
Forsyth, R. J., Balogh, A., Horbury, T. S., Erdos, G., Smith, E. J., and Burton, M. E.: 1996, ‘The HeliosphericMagnetic Field at Solar Minimum: Ulysses Observations from Pole to Pole’, Astron. Astrophys. 316, 287.
Forsyth, R. J., Balogh, A., Smith, E. J., and Gosling, J. T.: 1997, ‘Ulysses Observations of the Northward Extension of the Heliospheric Current Sheet’, Geophys. Res. Lett. 24, 3101.
Forsyth, R. J., Balogh, A., and Smith, E. J.: 2001a, ‘Latitudinal Variation of the Underlying Heliospheric Magnetic Field Direction: Comparison of the Ulysses First and Second Orbits’, Space Sci. Rev. 97, 161–164 (this issue).
Forsyth, R. J., Rees, A., Balogh, A., and Smith, E. J.: 2001b, ‘Magnetic Field Observations of Transient Events at Ulysses, 1996–2000’, Space Sci. Rev., 97, 217–220 (this issue).
Gosling, J. T. and Forsyth, R. J.: 2001, ‘CME-driven solar wind disturbances at high heliographic latitudes’, Space Sci. Rev. 97, 87–98 (this issue).
Gosling, J. T., McComas, D. J., Skoug, R. M., and Forsyth, R. J.: 2001, ‘Stream Interaction Regions at High Heliographic Latitudes During Ulysses‘ Second Polar Orbit’, Space Sci. Rev. 97, 189–192 (this issue).
Hoeksema, J. T., Wilcox, J. M., and Scherrer, P. H.: 1982, ‘Structure of the Heliospheric Current Sheet in the Early Portion of Sunspot Cycle 21’, J. Geophys. Res. 87, 10 331.
Jokipii, J. R. and Kóta, J.: 1989, ‘The Polar Heliospheric Magnetic Field’, Geophys. Res. Lett. 16 (1), 1–4.
McComas, D. J., Gosling, J. T., and Skoug, R. M.: 2000, ‘Ulysses Observations of the Irregularly Structured Mid-Latitude Solar Wind During the Approach to Solar Maximum’, Geophys. Res. Lett. 27 (16), 2437.
Smith, E. J.: 1993, in C. P. Sonett, M. S. Giampapa and M. S. Mathews (eds), ‘The Sun and Interplanetary Magnetic Field’, The Sun In Time, University of Arizona Press, Tucson.
Smith, E. J. and Balogh, A.: 1995, ‘Ulysses Observations of the Radial Magnetic Field Component: Absence of a Latitude Gradient’, Geophys. Res. Lett. 22, 3317.
Smith, E. J., Balogh, A., Neugebauer, M., and McComas, D.: 1995, ‘Ulysses Observations of Alfvén Waves in the Southern and Northern Solar Hemispheres’, Geophys. Res. Lett. 22, 3381.
Suess, S. T. and Smith, E. J.: 1996, ‘Latitudinal Dependence of the Radial IMF Component-Coronal Imprint’, Geophys. Res. Lett. 22, 3267.
Wang, Y.-M., Sheeley, N. R., Jr., and Rich, N. B.: 2000a, ‘Evolution of Coronal Stream Structure During the Rising Phase of Solar Cycle 23’, Geophys. Res. Lett. 27, 149.
Wang, Y.-M., Lean, J., and Sheeley, N. R., Jr.: 2000b, ‘The Long Term Variation of the Sun's Open Magnetic Flux’, Geophys. Res. Lett. 27, 505.
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Balogh, A., Smith, E.J. The Heliospheric Magnetic Field at Solar Maximum: Ulysses Observations. Space Science Reviews 97, 147–160 (2001). https://doi.org/10.1023/A:1011854901760
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DOI: https://doi.org/10.1023/A:1011854901760