Research Areas

Space@VT studies the influence of the Sun on the Earth and the flow of energy through the geospace system. The center has leadership roles in numerous collaborative experiments in ground- and space-based, in situ, and remote sensing of Earths atmosphere and the geospace environment. The interdisciplinary work involves strong modeling, theoretical, and instrumentation efforts.

Current Research

Upper atmospheric variations

The influence of solar radiation and solar wind driving on the global distribution of density.

High levels of auroral activity produce large levels of heating, on the order of hundreds of gigawatts, that increase the temperature of the upper atmosphere, so that densities in low-Earth orbit are enhanced. Empirical models of the energy flux into the ionosphere developed by Space@VT are used to accurately calculate changes in the global exospheric temperature. These changes in temperature are related to changes in the density of the upper atmosphere, or thermosphere, that perturb the orbits of satellites in low-Earth orbit. A key parameter in the temperature calculation is the amount of nitric oxide within the thermosphere, which rises in proportion to heating in the ionosphere, and in turn causes the thermosphere to cool off at a faster rate through optical emissions. Measurements of the nitric oxide emissions were found to be highly correlated with the temperature produced by the model.

Ionospheric Remote Sensing

The Super Dual Auroral Radar Network (SuperDARN) is an international collaboration of 10 countries that cooperatively operate more than 30 High-Frequency (HF) radars distributed around the world to conduct research on Earth's near-space environment. The SuperDARN group at Virginia Tech operates six of these radars and leads the U.S. portion of the collaboration. Areas of research include radar techniques for remote sensing of the ionosphere and upper atmosphere, the interaction of the solar wind with Earth's magnetosphere, and the range of disturbance effects in near-space that are known as space weather. Space@VT faculty and students have recently focused on modeling the performance of the SuperDARN twin-terminated folded dipole antenna, as well as optimization of the HF radar signal processing techniques. They are applying the SuperDARN observations toward understanding the formation and dynamics of ionospheric irregularities and large-scale ionospheric plasma structures, among other phenomena.

Extreme Solar Wind Coupling

Space@VT researchers are looking at polar electric potential saturation during periods of extreme solar wind coupling. This research utilizes satellites, incoherent scatter radar, and the SuperDARN radars. New results reveal unusual observations of extreme driving during northward interplanetary magnetic field that shows no saturation of the ionospheric electric field. This is very unusual. Additionally, numerous instances of magnetospheric response to solar wind transient events (pressure changes or field orientation changes) are being investigated using conjugate northern and southern measurements. One very interesting event shows nearly the same response in both hemispheres, although our understanding would indicate that this should not be the case due to summer/winter conductivity differences in the respective ionospheres.

The Aeronomy of Ice in the Mesosphere (AIM) satellite was launched in 2007 and is the first satellite dedicated to the study of Polar Mesospheric Clouds (PMCs). Space@VT researchers use AIM data to study Atmospheric Gravity Waves (AGWs). These small-scale waves get their name because their restoring force is gravity, they are ubiquitous in the atmosphere, and they play an important role in atmospheric variability. Due to their small scales, they are parameterized in global climate models, and there is a need for measurements. Studying AGWs helps us understand the coupling between the lower and upper atmospheric regions.

Signatures of gravity waves are observed in AIM PMC images as circular rings, bands, and solitary waves. Circular wave structures have been used to study coupling between atmospheric regions by understanding the gravity wave propagation from their source in the troposphere to the upper atmosphere.

Space@VT recently completed development of the first retarding potential analyzer built for use on a CubeSat. This instrument will launch next year, and be deployed by the International Space Station as part of Space@VT's LAICE satellite project. Two other Virginia Tech instruments are part of LAICE, and are in the final stages of development and testing.

Ground Station

The Virginia Tech Ground Station (VTGS) is currently under development, and the first of four major subsystems will be brought online in October 2015. The VTGS is intended to be a space communications laboratory for teaching purposes, but also to provide a platform for research activities related to space communications and space science. It consists of four primary subsystems: a VHF/UHF subsystem; 3m and 4.5m dish antennas; and a NOAA weather satellite subsystem. The VHF/UHF subsystem will primarily communicate with spacecraft such as CubeSats and other smallsats. The 3 m subsystem will receive high rate mission data from smallsats and other spacecraft as well as live streaming video of astronauts and cosmonauts at scheduled times from the International Space Station via an Amateur Radio transmitter known as ISS-HAMTV. The 4.5 m dish antenna subsystem will primarily be used for Earth-Moon-Earth communications (bouncing radio waves off the moon to communicate around the world). The NOAA weather satellite subsystem will receive weather satellite imagery broadcasts.

Probing the Ionosphere through Artificial Heating

Our researchers have made a number of new scientific discoveries in the area of stimulated electromagnetic radiation and turbulence produced when heating the near-Earth space environment with high-power, high-frequency radio waves. Experimental observations have been made in both Alaska and Norway. These discoveries have elucidated basic nonlinear physics of the space environment, as well as provided new practical remote-sensing diagnostics that can be used to measure density, mass, and temperature of constituent species. We have also developed techniques for accessing charged dust characteristics in the space environment by using radio wave heating. All of these discoveries have been aided by the development of state-of-the-art advanced computational models aided by High-Performance Computing (HPC) techniques.