Type of Project: Numerical modeling and data analysis

Skills/Interest Required: Interest in use of advanced computer modeling tools in the analysis of space based and ground based observations. No advanced programming skills required.

Mentors: Drs. Ed DeLuca and Aad Van Ballegooijen

Point of Contact: Dr. Ed DeLuca Email: edeluca_at_cfa.harvard.edu

Background: The solar atmosphere (that region above the photosphere) is controlled by magnetic fields rooted in the convection zone and penetrating the surface. Magnetic field from different parts of the photosphere expand and interact with each other creating a complex set of surfaces. The gas in the corona is fully ionized plasma, as a result it is an extremely good electrical conductor. In these circumstances the plasma is tied to the magnetic field, when the plasma radiates it outlines the magnetic field line. The only place in the universe where we can see this process is on the sun (similar processes take place in the Earth ionosphere but the coupling to field lines is not as strong the the radiative signature is much weaker). The solar atmosphere is a plasma physics laboratory where we can observe structures that remain stable for many days and those that erupt in minutes (resulting in flares and solar storms).

Project: For this project the student will begin by becoming familiar with the observations needed to create a mathematical model of the magnetic field in an active region. Ground based magnetic field measurements from SOLIS and GONG are used to define the boundary conditions of the magnetic field. The observations are used as input to a Non-linear force-free field calculating program, written in IDL (Van Ballegooijen (2004)) There are many possible coronal models that are consistent with the photospheric observations. To constrain the models we compare field lines in the model with coronal observations from Hinode/XRT. Once we have a model that is consistent with the coronal observation, we can study the relationships between the magnetic structure and the heating of plasma in the corona.

Caption: These images show the magnetogram and field lines from the magnetic model. (a) XRT image at the flare onset overlaid with red and green contours representing positive and negative polarities. Image (b) is a side view of (a). The Field Of View (FOV) of (a) and (b) is 0.2 R .