February 26, 1998 SwRI Eclipse Expedition


Scientists from Southwest Research Institute in Boulder, Colorado and San Antonio, Texas were part of a team of scientists to study the total solar eclipse on February 26 on Curacao in the Netherland Antilles. The total eclipse was visible from a narrow corridor which began in the Pacific, continued through the Caribbean and ended off the Atlantic coast of Africa.

Total solar eclipses provide scientists with unique opportunities to study our nearest star, the Sun, and learn about the outer atmosphere of the Sun, called the corona which is the source of the solar wind, "space weather", and large solar storms which sometimes engulf the earth and play havoc with satellites, radio communications, and electric power grids here on earth. Even today, with modern satellites and spacecraft, a total solar eclipse still provides scientists with a unique opportunity to study the detailed fine scale structure of the inner corona in a way not otherwise possible.

On the northern tip of the island of Curacao, Dr. Don Hassler and Dr. Dave Slater from Southwest Research Institute (SwRI), worked in collaboration with a team led by Dr. Steve Tomczyk from the National Center for Atmospheric Research (NCAR) in Boulder, Colorado to study the detailed fine scale magnetic structure of the corona with new, large format, high speed electronic detectors called CCDs. SwRI scientists recorded high resolution time series images, or movies, of a portion of the solar corona to study the smallest scale observable structures, which appear as light and dark "threads", analogous to studying individual strands of hair on a person's head. Knowledge of this detailed small-scale structure will help scientists understand the physical conditions of the Sun's corona and the magnetic field which controls its structure.

Sample results:

The purpose of these observations were to record high spatial resolution observations and movies of a portion of the solar corona with high temporal resolution to study small scale structures. Evidence of movement or wiggling of these structures might be a sign of hydromagnetic waves or Alfven waves travelling along magnetic field lines and heating the atmosphere.

Figure 1 (above left) shows an image of the moon beginning to occult or "swallow" the limb of the Sun. Figure 2 (above, 2nd from left) shows an image of "Bailey's beads", or bright beads of sunlight along the moon's limb, caused by sunlight shining between the mountains of the moon. Also visible are giant magnetic loops of plasma called prominences. Figures 3 and 4 (above, right two images) show sample images of the corona above the southwest limb of the Sun during the eclipse (taken one minute apart), showing both open and closed-loop magnetic structures. These images have been processed with an unsharp masking technique to increase the contrast of subtle features. The field-of-view of these images is 6 x 18 arcminutes, with roughly 1.4 arcsecond per pixel spatial resolution. More than 120 images were taken roughly 1.6 seconds apart to form a time series, or movie, to look for changes or wiggling of the small scale structures, which might be a sign of waves travelling along the magnetic field lines and heating the atmosphere.

The movies available below are a one (1) minute sample of the observations from 18:12 UT with a time cadence of roughly 1.6 seconds per image and spatial resolution of roughly 1.4 arcsec per pixel. These are preliminary QUICKLOOK images which have not yet been co-registered. They have been processed with an unsharp masking technique to increase the contrast of subtle features. They are presented here as 5-loop sequence animated gifs which can be viewed with most web browsers.

Click here for "Mondongo Soup, Carnaval and Eclipse Saros 130: Impressions of the Eclipse from Curacao" by Don Hassler.
Click here for a press release describing the eclipse expedition.

This project is a collaboration with the High Altitude Observatory (HAO/NCAR). The image shown at the left is a polarized brightness (pB) image obtained with the HAO/NCAR POISE experiment using a 2k x 2k CCD camera. This link to the HAO Eclipse Homepage shows preliminary results from this experiment as well as the HAO/NCAR polar plume imager (PEPPI) and the daily Mk3 coronal image from Mauna Loa Solar Observatory.

SwRI GAP Group's Homepage

SwRI Homepage
This is http://www.boulder.swri.edu/~hassler/eclipse98/. Last modified: March 17, 1998