|Predicting the Structure
of the Solar Corona
During the 21 June, 2001 Total Solar Eclipse
On Thursday, 21 June, 2001, a total eclipse of the Sun will be visible from within a narrow corridor crossing the Southern Hemisphere, beginning in the South Atlantic, crossing southern Africa and Madagascar, and terminating in the Indian Ocean. A partial eclipse can be seen throughout eastern South America and mid/south Africa. To see a detailed description of the eclipse path, please visit Fred Espenak's 2001 Total Eclipse web site.
On 19 May, 2001, we started an MHD computation of the solar corona, in preparation for our prediction of what the solar corona will look like during this eclipse. We used photospheric magnetic field data from Carrington rotation 1975 (corresponding to the dates April 9 - May 6, 2001) from the National Solar Observatory at Kitt Peak. On June 10, 2001 we updated this prediction by running another MHD simulation in which we evolved the photospheric magnetic field to match data from Carrington rotation 1976 (corresponding to the dates May 6 - June 2, 2001). On June 14, 2001 we attempted to update the photospheric magnetic field once again to match data from Carrington rotations 1976+1977 (corresponding to the dates May 18 - June 14, 2001), but, for technical reasons, this simulation was not successful. The eclipse prediction shown below is thus based on the data from CR1976. If you are curious and wish to compare the coronal predictions for the two simulations based on magnetic field data from CR1975 and CR1976, click here. After the eclipse we will publish comparisons between our prediction and images taken on the day of the eclipse.
||The figure on the left shows the predicted polarization brightness (pB) in the solar corona for the eclipse expected on 21 June, 2001 at 13:10 UT (corresponding to totality in Lusaka, Zambia). The state of the solar corona was computed using a 3D magnetohydrodynamic (MHD) simulation. The pB signal is produced by white light scattered off electrons in the coronal plasma. The image has been radially detrended to account for the fall-off of coronal brightness with distance from the Sun. Vertical (top) is terrestrial (geocentric) north. This is the view of the Sun that would be seen by an observer on Earth with a camera aligned so that vertical is toward the Earth's north pole. To view this image in a coordinate system aligned with solar north, click here. Click the image to see it in more detail.|
|Predicted polarization brightness (top left) together with traces of the magnetic field lines in the solar corona (top right) for the eclipse expected on 21 June, 2001 at 13:10 UT (with terrestrial north up). The Sun's surface shows color contours of the radial component of the measured photospheric magnetic field from Kitt Peak National Solar Observatory, showing the location of active regions (strong magnetic fields). Click the images for higher resolution pictures. To view these images in a coordinate system aligned with solar north, click here.|
(courtesy of Wendy Carlos*)
Magnetic Field Lines
In the figures above we compare our MHD model prediction with a photograph taken in Lusaka, Zambia. The eclipse image is a computer composite and optimization from several negatives taken by Wendy Carlos, merged with images taken with radially graded filters by Jonathan Kern. The images have terrestrial (geocentric) north vertically upward. *Eclipse Image: © 2001 Wendy Carlos and Jonathan Kern - All Rights Reserved. For details, see http://www.wendycarlos.com/eclipse.html and http://www.ligo-la.caltech.edu/~jkern/Eclipse01/.
|The photospheric magnetic field maps we use for our calculations are
built up from daily observations of the Sun during a solar rotation.
These maps give a good approximation of the Sun's magnetic flux if the
large-scale flux is not changing much throughout a rotation. Previously,
we have computed coronal models for an eclipse during the declining phase
of the last solar cycle (November
3, 1994), for two eclipses during solar minimum (October
24, 1995 and March
9, 1997), one eclipse during the the early rising phase of solar cycle
26, 1998), and one eclipse approaching solar maximum (August
11, 1999). The June 21, 2001 eclipse, which is occurring at the
peak of solar maximum, presents a challenge. The photospheric magnetic
field is evolving more rapidly, making synoptic magnetic field data a less
reliable approximation to the true state of the photospheric magnetic field.
The complexity of coronal structures requires high resolution runs (requiring
approximately 1,500,000 grid points in our calculation).
These figures show the photospheric magnetic field maps for three Carrington rotations, CR1975, CR1976, and CR1976+1977, as measured by the National Solar Observatory at Kitt Peak. The maps show the measured photospheric magnetic field as a function of latitude (vertical axis) and Carrington longitude (horizontal axis). Red shows outward directed magnetic flux, and blue shows inward directed flux. Click the images for higher resolution pictures. These maps are considerably more complex than maps during solar minimum.
If your movie player can continuously loop a movie while
playing it, set this option to "on" for the best effect. For example,
on a Silicon Graphics machine, you would use the execute line:
movieplayer -l 0 cr1975.mpg
Z. Mikic, J. A. Linker, D. D. Schnack, R. Lionello, and A. Tarditi, "Magnetohydrodynamic Modeling of the Global Solar Corona," Physics of Plasmas, 6, 2217 (1999).
Z. Mikic, J. A. Linker, P. Riley, and R. Lionello, "Predicting the Structure of the Solar Corona During the 11 August 1999 Total Solar Eclipse," in The Last Total Solar Eclipse of the Millennium, Proceedings of the Conference held in Istanbul, Turkey, 13-15 August, 1999 (W. Livingston and A. Ozguc, eds.), ASP Conferences Series, Vol. 205, p. 162 (2000).