The solar coronal sheet during the period of sunspot maximum

Abstract

It is demonstrated that the outer corona extends radially in the form of a sheet from the neutral line on the source surface (a spherical surface of 2.5 solar radii) or from an even lower level during the period of sunspot maximum, as well as during the period of sunspot minimum. During the period of sunspot maximum the neutral line lies nearly at right angles to the heliographic equator. Assuming that the long coronal streamers extend from the neutral line (as is known to be the case during the period of sunspot minimum), the expected geometry is constructed and is compared with coronal photographs taken during the eclipse. It resembles the observed coronal photographs seen from the Earth on July 11, 1991. In particular, the expected geometry can explain details of the observed features, including highly inclined (with respect to the heliographic equator) long coronal streamers and polar plumelike features. It is also explained why in the past the corona was believed to be nearly spherical during the period of sunspot maximum.

Reconstruction of the Heliospheric Current Sheet Tilts Using Sunspot Numbers

“…The HCS divides the interplanetary space into two parts with oppositely directed open magnetic field lines and is a framework of the heliosphere. The orientation and the shape of the HCS are also known to change with the 11-year solar cycle (Hoeksema, 1991b;Hoeksema, Wilcox, andScherrer, 1982, 1983;Gulyaev and Filippov, 1992;Gulyaev and Vanyarkha, 1992;Ivanchuk and Pishkalo, 2002;Saito et al, 1993).…”

Trajectories of microwave prominence eruptions

“…We made white-light synoptic maps for individual events using all of the C2 full-resolution images available (processing level-0.5) by taking a slice of each image at a specified heliocentric distance above both east and west, or northern and southern limbs. Because the large-scale coronal morphology becomes highly complicated toward the solar maximum (e.g., Saito et al 1993;Wang et al 2000), we focus on the corona relatively close to the Sun so that the solar disturbances observed at different heights can be identified. We select three heliocentric distances of 2.5, 3.5, and 4.5 Rs for the synoptic maps with a latitudinal resolution of 0.28, 0.20, and 0.16 degree per pixel, respectively ( Fig.…”

“…Since the 1970s, it has been recognized 2 The "streamer blowout" and "spike" CMEs defined in Howard et al (1985) might correspond to our group (a) while their "double spike" and "multi spike" CMEs would be included in our group (b). that large-scale coronal streamers can be represented by an edge-on view of a single warped heliospheric current sheet (HCS), encircling the Sun (e.g., Saito et al 1993;Wang et al 1997). This single-sheet interpretation, however, seems to fail for the CMEs that progressively occurred within multiple layers of streamers with a discontinuity across one of the streamers (e.g., the 8 February 1999 event); these CME outflows might have been separated by a sheet structure.…”

Three-dimensional reconstruction of the streamer belt and other large-scale structures of the solar corona

“…To validate our procedure, we considered the model of electron density described by the analytic expression given by Saito (1993) for an axi-symmetric, homogeneous K-corona of the minimum type and calculated two radiance images, one using the classical procedure of los integration as specified by Eq. (7), the other using our method and with the size of the root cube ranging from 24 to 30 R sun (Fig.…”

“…The matter was pursued further by systematically comparing drawings of the white-light corona (obtained from photographs) with calculated configurations of the coronal magnetic field (Saito et al 1993;Ambroz & Sykora 1994;Sykora et al 2002).…”