Sources of magnetic fields in recurrent interplanetary streams

Abstract

We examined the sources of magnetic fields in recurrent streams observed by the Imp 8 and Heos spacecraft at 1 AU and by Mariner 10 en route to Mercury between October 31, 1973, and February 9, 1974, during Carrington rotations 1607–1610. Most fields and plasmas at 1 AU were related to coronal holes, and the magnetic field lines were open in those holes. However, some of the magnetic fields and plasmas at 1 AU were related to open field line regions on the sun which were not associated with known coronal holes, indicating that open field lines may be more basic than coronal holes as sources of the solar wind. Magnetic field intensities in five equatorial coronal holes, estimated by projecting the measured interplanetary magnetic fields back to the sun by using the principle of flux conservation, ranged from 2 to 18 G with an average of 9 G. Average measured photospheric magnetic fields along the footprints of the corresponding unipolar fields on circular equatorial arcs at 2.5 RS had a similar range and average, but in two cases the intensities were approximately 3 times higher than the projected intensities. The coronal footprints of the sector boundaries on the source surface at 2.5 RS, determined by a potential field extrapolation of the measured photospheric fields, meandered between −45° and +45° latitude, and their inclination with respect to the solar equator ranged from near 0° at some longitudes to near 90° at others. It is possible that sector boundaries are related to convergence surfaces of the flow near the sun. The high densities observed near sector boundaries between streams might be due in part to the convergence of flows from adjacent coronal holes.

Reconstruction and Prediction of Variations in the Open Solar Magnetic Flux and Interplanetary Conditions

“…To eliminate the possibility that such simple harmonic expansions would result in all of the magnetic field lines returning to the Sun within a small heliospheric distance, the coronal field was required to become radial at the outer boundary, the source surface. Despite its many assumptions and obvious limitations, PFSS has been very successful in the study of a wide range of solar and heliospheric phenomena, including: coronal structure as seen during eclipses (e.g., Smith and Schatten, 1970), end-to-end modelling of Earth-impacting coronal mass ejections (CMEs, e.g., Luhmann et al, 2004), coronal null points and CME release (e.g., Cook et al, 2009), interplanetary magnetic fields (e.g., Burlaga et al, 1978), heliospheric current sheet structure (e.g., Hoeksema et al, 1982), waves in the corona (e.g., Uchida et al, 1973), solar wind acceleration (e.g., Neugebauer et al, 1998;Marsch, 1999), stellar coronal fields (e.g., Jardine et al, 2002), coronal hole and fast solar wind stream evolution (e.g., Wang and Sheeley Jr, 1990), co-rotating interaction regions and associated cosmic ray modulation (e.g., Rouillard et al, 2007), solar wind speed prediction (e.g., Arge et al, 2002), solar wind density structure (e.g., Rouillard et al, 2010), pseudostreamers (e.g., , and quantifying the open solar flux (discussed below). The method has also generated results that compare well with images that reveal field line structure in the corona and with the results of MHD modelling (see the Living Review by Mackay and Yeates, 2012).…”

The shape and location of the sector boundary surface in the inner solar system

“…Such a correspondence has also been discussed by other authors (see the review by Hundhausen, 1977). Burlaga et al, (1978a) …”

Connecting the Sun and the Solar Wind: Comparison of the Latitudinal Profiles of Coronal and [ITAL]Ulysses[/ITAL] Measurements of the Fast Wind

“…Recent analyses of Ulysses measurements using modeling based on the distribution of the large-scale photospheric magnetic field (e.g., Neugebauer et al 1998;Linker et al 1999) mapped the fast solar wind roughly back to polar coronal holes and reached similar conclusions. However, whether coronal holes are the sole source of the fast solar wind has often been questioned (e.g., Hundhausen 1977;Burlaga et al 1978;Zhao & Hoeksema 1995;.…”