Type of Project: Numerical Simulation, Data Analysis, Statistics

Skills/Interest Required:A successful student will have an interest in computer programming, satellite observations, statistics, and/or the physics of solar phenomena.

Mentors:Henry (Trae) Winter and Piet Martens

Point of Contact:Trae Winter Email:hwinter_at_cfa.harvard.edu

A surprising result from high-resolution solar imaging missions has been the apparent, near constant width of coronal loops. These loops structures are defined by the corona's complex magnetic field and their constant width has been interpreted by some as a sign that the magnetic field does not expand in the solar atmosphere as rapidly as previously thought [1]. The fact that the characteristic length scale of these loop structures is curiously the same as the instrument resolution of the TRACE satellite telescope has lead some scientists to show that the constant loop width can be explained as an artifact of the background signal and instrumental resolution [2]. DeForrest [2] simulated the effects of expanding yet sub-resolution loops on TRACE instrument response and found no discernible difference between the expanding and constant loop width case. Later López Fuetes et al. engineered a statistical method to determine if apparently constant width loops were expanding sub-resolution loops or constant width loops at the instrument resolution. Simulations showed this method to be effective and application of this method found that loops observed in TRACE were of constant width. Both of the previously mentioned works noted that the intensity scale height for expanding loops would be higher for expanding loops than their constant width counterparts, and left the investigation of this effect to future study. It is this effect of increased intensity scale heights that will be investigated by this work.

During the summer the student will simulate wide variety of loops using the HyLoop simulation suite available at CfA. This code provides a hydrodynamic simulation of a coronal loop of arbitrary 3D geometry and provides simulated instrument responses that take 1) Instrument spatial resolution, 2) Point spread functions of arbitrary shapes and sizes and 3) Inclination angle dependent line of sight, path length integrals. The student will simulate loops with various expansion parameters and heating profiles and create synthetic TRACE images with measured background levels and monitor the intensity scale height of each. The student will then use the method of López Fuentes et al [3] to analyze the loop widths and perform a statistical analysis to determine if any parameters in the loop construction are strongly correlated with inferred loop width.

Caption: An image of a series of solar coronal loops as seen in the TRACE 171 bandpass. The apparent constant width of the loops remains puzzling.

Caption: Simulated coronal loops as seen by different instruments. The leftmost images is observed by the XRT instrument's Al-Poly bandpass but with a 2 arc-second pixel size. The middle picture is in the same bandpass but with a 0.5'' pixel size. The image on the right shows the AIA 335 bandpass with a 0.1''. The student working on this project will be making simulated images like this and analyzing them.

[1] "Cross-Sectional Properties of Coronal Loops"

[2] "On the Size of Structures in the Solar Corona"

[3] "Are Constant Loop Widths an Artifact of the Background and the Spatial Resolution?"

The TRACE satellite home page