HAO Eclipse Expedition to Cerro Tololo, Chile

Friday, June 28, 2019

Following its long history of solar eclipse field expeditions, the High Altitude Observatory currently has a team deployed in Cerro Tololo, Chile to conduct solar physics research. On July 2, a total solar eclipse will be visible in South America, fortuitously passing over the NSF's Cerro Tololo Inter-American Observatory. The HAO team comprises Paul Bryans and Ben Berkey (HAO Project Scientists), Austin Monaghan (REU student from the Colorado School of Mines) and Yeimy Rivera (Newkirk Fellow from the University of Michigan).

Image of panel (a) is the intensity of Si X emission
Panel (a) is the intensity of Si X emission
Image of panel (b) the total linear polarization
Panel (b) the total linear polarization

One goal of the eclipse expedition is to determine the coronal magnetic field during the eclipse. To do this, the team will use a cryogenically-cooled infrared camera to measure the polarization of Si X emission in the solar corona. If successful, these will be the first measurements of their kind. We will report on the results after the eclipse but, in the meantime, we can predict what we expect to see.

Built from observations in the weeks prior to the eclipse, Predictive Science Inc. (http://www.predsci.com/corona/jul19eclipse_prelim/home.php) have run MHD models to predict the magnetic structure of the corona at the time of the eclipse. We have used these predictions, along with the HAO FORWARD code, to determine the resultant Si X emission we hope to observe from Chile. The figure below shows a subset of these predictions. Panel (a) is the intensity of Si X emission, panel (b) the total linear polarization, and panel (c) the Stokes U parameter, which shows the direction of the magnetic field. We will know in only a few days if these predictions are accurate!

Image of panel (c) the Stokes U parameter
Panel (c) the Stokes U parameter