Solar Intern Program Project:
 Title:Searching for the source of the solar wind in coronal holes

Type of Project: Data Analysis

Skills/Interest Required: Interest in analyzing imaging and spectral data obtained by space missions. No advanced programming skills required.

Mentor: Dr. Hui Tian and Dr. Steve Cranmer



The Sun is continuously releasing ionized particles to the interplanetary space in the form of solar wind. Coronal holes, which are regions of reduced X-Ray emission on the surface of the Sun, are believed to be the major source regions of the solar wind. The solar transition region is a thin layer between the cool chromosphere and hot corona. The transition region in coronal holes plays a crucial role in the mass and energy supply to the solar wind. Detailed analysis of the dynamics and wave activities in the transition region is important for the study of solar wind origin.


The project will mainly involve analysis of the transition region images and spectral line profiles obtained by NASA's IRIS mission, which was launched in June 2013. Coronal holes will be identified from the full-disk images taken in the 193 filter of the AIA instrument onboard NASA's SDO mission. The IRIS data reveal unprecedented details and dynamics of the solar transition region. Using the IRIS data of coronal holes, the student will mainly study dynamics such as flows, brightenings, and various types of waves in the transition region. Such an investigation will likely provide important implications for the origin of the solar wind. The student will learn about the behavior of the solar transition region and the technique of solar ultra-violet spectroscopy.


Figure 1: Origin regions of the solar wind from coronal holes. The figure illustrates the location and geometry of three-dimensional magnetic field structures in the solar atmosphere. In the lower plane the magnetic field vertical component at the photosphere is shown. The Ne VIII Doppler shift is placed in the upper plane. The hatched area indicates where the outflow speed of highly charged neon ions is larger than 7 km s-1. The figure is adapted from Tu et al. (Science, 308, 519, 2005).

Figure 2: Solar wind outflows guided by expanding and merging magnetic funnels. The Ne VIII Doppler shift image is placed at the bottom. The positive and negative values represent red shifts and blue shifts, respectively. The map of the vertical component of the extrapolated magnetic field at 20 Mm is placed at the height of 20 Mm. The figure is adapted from Tian et al. (A&A, 478, 915, 2008).


Section Photo