Doctor of Philosophy (Ph.D.)
Physics
University of Alabama
2010
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Faculty
Faculty
Dragana Tankosic, Ph.D.
Lecturer
Department/Office
- Physics and Astronomy
School/College
- College of Arts & Sciences
Biography
Dragana Tankosić, Ph.D., is a lecturer in the Department of Physics and Astronomy at Howard University. She earned her doctorate in physics from the University of Alabama in Huntsville and holds both a master's degree and bachelor's degree in physics from the University of Belgrade in Serbia, with her master's studies completed jointly through the University of Alabama in Huntsville. Before joining Howard University in 2022, Tankosić held teaching appointments at Southeastern Louisiana University and Motlow State Community College and completed research appointments at NASA's Marshall Space Flight Center, the University of Alabama in Huntsville and the Astronomical Observatory in Belgrade.
Tankosić's research focuses on dusty plasma physics, laboratory astrophysics, planetary and lunar dust, space physics and radiation-matter interactions. During nearly 14 years of research at NASA and the University of Alabama in Huntsville, she investigated the physical and optical properties of lunar, planetary and interstellar dust, conducting experiments on dust charging, photoelectric emission, radiation pressure and condensation processes. Her research has been published in leading peer-reviewed scientific journals and presented at international conferences. She also received a NASA Postdoctoral Fellowship and was named Young Scientist of the Year by the Astronomical Observatory in Belgrade.
Her teaching integrates extensive research experience with student-centered instruction, emphasizing hands-on scientific inquiry, critical thinking and inclusive learning environments that prepare students for careers in physics and related fields.
Education & Expertise
Education
Master of Science (M.S.)
Physics
University of Belgrade
Bachelor of Science (B.S.)
Physics
University of Belgrade
Academics
Academics
General Physics I and II
General Astronomy
Observational Astronomy
Research
Research
Specialty
Dusty plasma physics, Planetary and lunar dust, Space physics, Experimental plasma physics, Laboratory astrophysics, Radiation–matter interactions, Physics educationGroup Information
Member of a NASA-MSFC research team that conducted fundamental investigations into the optical and physical characteristics of lunar dust grains, including the following:
- Conducted laboratory experiments measuring photoelectric emission from individual micron-size cosmic and lunar dust grains.
- Preformed laboratory investigations of lunar dust grain charging driven by solar-wind electrons.
Accomplishments
Accomplishments
NASA Postdoctoral Fellowship
Young Scientist of the Year, Astronomical Observatory, Belgrade
Publications and Presentations
Publications and Presentations
Study of the Effects of the Electric Field on Charging Measurements of Individual Micron-Size Dust Grains by Secondary Electron Emissions
The dust charging by electron impact is an important dust charging process in Astro-physical, Planetary, and the Lunar environments. Low energy electrons are reflected or stick to the grains charging the dust grains negatively. At sufficiently high energies electrons penetrate the grain leading to excitation and emission of electrons referred to as secondary electron emission (SEE). Available theoretical models for the calculation of SEE yield applicable for neutral, planar or bulk surfaces are generally based on Sternglass Equation (1954) [1]. However, viable models for charging of individual dust grains do not exist at the present time. Therefore, the SEE yields have to be obtained by some experimental methods at the present time.
Experimental Investigation of Charging Properties of Interstellar-Type Silica Dust Grains by Secondary Electron Emissions
At the present time, very limited experimental data are available for charging of individual micron-size dust grains, particularly for low energy electron impact. Our laboratory measurements on individual, positively charged, micron-size dust grains levitated carried out in a unique facility at NASA-MSFC, based on an electrodynamic balance, indicate that the SEE by electron impact is a complex process. The electron impact may lead to charging or discharging of dust grains depending upon the grain size, surface potential, electron energy, electron flux, grain composition, and configuration (Abbas et al, 2010, 2012). In this paper, we discuss SEE charging properties of individual micron-size silica microspheres that are believed to be analogs of a class of interstellar dust grains. The measurements indicate charging of the 0.2 micron silica particles when exposed to 25 eV electron beams and discharging when exposed to higher energy electron beams. Relatively large size silica particles (5.2-6.82 micron) generally discharge to lower equilibrium potentials at both electron energies. These measurements conducted on silica microspheres are qualitatively similar in nature to our previous SEE measurements on lunar Apollo missions dust samples.
Laboratory Studies of Charging Properties of Dust Grains in Astrophysical and Planetary Environme
Laboratory Studies of Charging Properties of Dust Grains in Astrophysical and Planetary Environments
Dust grains immersed in ambient plasmas and radiation, are charged and coupled to the plasma through electric and magnetic fields. Dust grains in various astrophysical/planetary environments are generally charged by: (a) photoelectric emissions with incident radiation at photon energies higher than the work function of the material and (b) sticking of low energy electrons and ions of the surrounding plasma or by secondary electron emissions induced by incident electrons/ions at sufficiently high energies. Consequenly, the particle charge is an important parameter that influences physical and dynamical processes in the interplanetary and interstellar medium, planetary rings, interstellar dust clouds, comets and the outer atmospheres of planets. The charging properties of individual micron-size dust grains are expected to be substantially different from the bulk materials. However, no viable models for calculation of the charging properties of individual micron size dust grains are available at the present time. Currently, very limited experimental data are available for charging of individual micron-size dust grains. In this paper we give a review of the results of the measurements on charging of analogs of the interstellar as well as Apollo 11 and 17 lunar dust grains carried out on the Electrodynamic Balance Facility at the NASA-MSFC.
Charging of Individual Micron-Size Interstellar/Planetary Dust Grains by Secondary Electron Emissions
Dust grains in various astrophysical environments are generally charged electrostatically by photoelectric emissions with UV/X-ray radiation, as well as by electron/ion impact. Knowledge of physical and optical properties of individual dust grains is required for understanding of the physical and dynamical processes in space environments and the role of dust in formation of stellar and planetary systems. In this paper, we discuss experimental results on dust charging by electron impact, where low energy electrons are scattered or stick to the dust grains, thereby charging the dust grains negatively, and at sufficiently high energies the incident electrons penetrate the grain leading to excitation and emission of electrons referred to as secondary electron emission (SEE). Currently, very limited experimental data are available for charging of individual micron-size dust grains, particularly by low energy electron impact. Available theoretical models based on the Sternglass equation (Sternglass, 1954) are applicable for neutral, planar, and bulk surfaces only. However, charging properties of individual micron-size dust grains are expected to be different from the values measured on bulk materials. Our recent experimental results on individual, positively charged, micron-size lunar dust grains levitated in an electrodynamic balance facility (at NASA-MSFC) indicate that the SEE by electron impact is a complex process. The electron impact may lead to charging or discharging of dust grains depending upon the grain size, surface potential, electron energy, electron flux, grain composition, and configuration (e.g. Abbas et al, 2010). Here we discuss the complex nature of SEE charging properties of individual micron-size lunar dust grains and silica microspheres.