Discovery Magazine

Photo Credit: Sterling & Farid (2008)

Astrophysical Plasmas and Detector Development

Solar plasmas emit far-ultraviolet and extreme-ultraviolet radiations that are important energy sources for driving the Earth’s upper atmosphere. Emission from these solar plasmas photoionize, dissociate, and excite atmospheric species participating in the formation of both the ozone layer and the ionosphere. They interact strongly with oxygen and nitrogen establishing the atmosphere’s chemical composition, its thermal structure, and vertical composition. Absorption of these radiations further initiate the atmospheric chemical cycles of nitric oxide and water vapor.

Human activities are affected by the FUV and EUV radiations from solar plasmas. The FUV and EUV radiations from solar plasmas influence Earth’s atmosphere through their effects on radio communications, electric power distribution, satellite orbital parameters, and the health and safety of astronauts and spacecraft. These radiations from solar plasmas are extremely variable and are influenced by several solar cycles including the passage of active regions across the solar disk and the 11?year solar cycle. Understanding the sources of FUV and EUV radiation from solar plasmas as well as their variability are important goals for Sun-Earth system science.

In order to understand the sources of FUV and EUV emission from solar plasmas and their variability, it is necessary to study the individual structures that constitute the solar plasmas  from which this emission arises. It is also necessary to understand the distribution and dynamics of the solar magnetic field, including the emerging flux and their interactions with pre?existing flux distributions. We are executing a multi-faceted program of research with the goal of identifying the discrete sources of solar FUV (100-200 nm) and EUV (10-100 nm) emission and their variability. We seek to understand the mechanisms which generate and energize these structures.

Another goal of this research is to advance CCD detector technologies for observing solar plasmas that emit FUV and EUV radiation.  Generally detectors, the devices which convert light energy to electrical signals, are the single most important technology to determine the ultimate performance of our observatories. The large imaging format, high sensitivity, compact size, ease of operation and maturity of CCDs have led instrument designers to choose them for most visible-light imagers and spectrometers. This remains true also in the FUV, EUV and soft x-ray range. However, problems with sensitivity and radiation damage (in space-based applications) have left the full potential of silicon based FUV, EUV and soft x-ray detectors unrealized. We propose to contribute to the development of an innovative low-power CCD that offers superior soft x-ray, EUV, and FUV response as well as superior radiation tolerance and point spread function (PSF) control compared to standard astronomical CCDs. The proposed technology will strengthen the position of silicon-based sensors and yield a more ideal deployable device.

This research is undertaken utilizing data analyses and observational and theoretical techniques including the development of semi-supervised, machine learning based software that can identify, measure, analyze and classify a plethora of dynamic solar phenomena. Integrated with the research program is a comprehensive program of education and public outreach, which is primarily aimed at addressing problems of minority and female under?representation in physics and astronomy. Our EPO component includes individual K–12, undergraduate, and graduate student education components.