Research Assistant Professor Carlos Martinis
Ionospheric Physics, Space Physics, Thermosphere/Ionosphere plasma irregularities
Professor Martinis studies the low and midlatitude ionosphere using all-sky optical imagers built in-house and distributed worlwide. Naturally occurring chemical reactions in the nighttime upper atmosphere produce very tenuous light at different wavelength. These emissions, known as airglow, can be studied with very sensitive cameras and narrow band filters to give information on processes occurring at different heights. The optical analysis is complemented and augmented with in-situ satellite measurements and ground-based GPS and radar data. One of the processes studied, known as equatorial Spread-F, is related to large scale plasma irregularities that can have serious effects on propagation of radio signals. The research involves the investigation of the climatology of low and midlatitude ionospheric processes, electrodynamical coupling between ionospheric regions, and inter-hemispheric studies of processes affected by the presence of Earth’s magnetic field.
Professor Michael Mendillo (AST)
Space physics; planetary atmospheres; observations and models.
We design, build and field state-of-the-art All Sky Imagers (ASI) located at twelve mini-observatories on six continents. These instruments study the sub-visual emissions from features in the Earth’s upper atmosphere (80-400 km above the surface). These include: (1) stable auroral red arcs at sub-auroral latitudes, (2) travelling ionospheric disturbances at middle latitudes, (3) ionospheric irregularities at low latitudes, and (4) waves in the Mesosphere at all latitudes. Many of our ASI observations are made at sites selected because they are at opposite ends of the same geomagnetic field lines (called Conjugate Points). Boston University is the only institution world-wide to have conjugate images linking North American to South America and Antarctica, and Europe to Africa. Our ASI studies contribute to understanding how disturbances on the Sun cause effects at Earth—Space Weather—by combining our images with data from ground-based radars, GPS systems, and satellites in the geospace environment.
Our team includes faculty, post-doctoral associates, staff scientists, research fellows, graduate students and undergraduate research assistants.
View Professor Michael Mendillo’s Profile Here
Research Associate Professor Toshi Nishimura (ECE)
Aurora, Solar wind-Magnetosphere-Ionosphere Interaction, Ionosphere-Thermosphere Interaction at Earth, Optical and Radar Imaging, Space Weather
Toshi Nishimura’s group studies Solar wind-Magnetosphere-Ionosphere-Thermosphere interaction of the Earth using NASA’s satellites and ground-based imaging and radar observatories. The research topics include aurora, plasma and electromagnetic energy transport, magnetic reconnection, ion-neutral interaction. His group identified the sequence of events leading to substorm auroral onset, which had been a long-standing debate over 40 years in the magnetosphere-ionosphere coupling community and became a potential resolution to a long-standing debate in the substorm community. They have also investigated the cause of a certain type of aurora, called pulsating aurora. Although different wave modes had been discussed in the community, he uniquely determined by using a cross correlation method that the lower band chorus waves are the mode of waves for driving pulsating aurora. This discovery has been published in the journal Science and highlighted by news media. Other recent highlights include auroral responses to the solar wind, magnetic reconnection dynamics, plasma flow-neutral wind interaction, and polar cap dynamics.
View Research Associate Professor Toshi Nishimura’s Profile Here
Professor Meers Oppenheim (AST)
Computational and theoretical space plasma physics; dymanics of the E-region ionosphere; particle-wave interactions in the auroral ionosphere and magnetosphere; physics and observations of meteoroids and meteor plasmas
Professor Oppenheim studies space plasma physics using supercomputer simulations, theory, and data. He works on a range of topics, including ionospheric and solar collisional plasmas, particle-wave interactions, and the physics of meteor trails. In 2016, he has been working to incorporate the important effects of ionospheric turbulence into planetary scale simulations of the coupled magnetosphere, ionosphere and atmosphere. He has also been trying to model wave heating of the solar chromosphere. Most recently, he has also been working on understanding the effects of UV photoelectrons on the ionosphere and their observational consequences. Improving our understanding of these systems enables us to better characterize energy flows in the upper atmosphere.
View Professor Meers Oppenheim’s Profile Here
Professor Josh Semeter (ECE)
Ionospheric and space-plasma physics; radar signal processing; spectroscopy of atmospheric airglow and aurora; optical sensors; image reconstruction and tomography
Dr. Semeter’s research concerns interactions between the Earth’s ionized outer atmosphere (the ionosphere) and the space environment. One manifestation is the aurora-borealis, produced by the release of electromagnetic energy stored in the distant magnetosphere. The ionosphere is electrically conducting, and so it absorbs, refracts, and modulates radio waves. Understanding these effects is essential for the design and operation of global navigation (GPS) and communication systems. Electric currents flowing in the ionosphere also affects terrestrial technologies, such as power grids and pipelines, via induction. Ionospheres are inherent to all stellar-planetary systems, and their connection with the absorption of ionizing radiation suggests a fundamental connection with the evolution of habitable environments in the universe.
Activities in Dr. Semeter’s lab include the development of optical and magnetic sensor technologies, radar experiment design and signal processing (with focus on incoherent scatter radar), and the application of tomographic and other inversion techniques to the analysis of distributed, multi-mode measurements of the space environment.
View Professor Joshua Semeter’s Profile Here
Associate Professor Paul Withers (AST)
Planetary atmospheres and ionospheres; radio science instruments; accelerometer instruments
Our group’s interests lie in planetary atmospheres, particularly upper atmospheres, and ionospheres. An ionosphere is a weakly ionized plasma embedded within an upper atmosphere, generally produced by solar photoionization. The properties of an upper atmosphere and ionosphere are determined by chemistry, energetics, dynamics, coupling to the lower atmosphere and solid surface below, and coupling to the solar wind and magnetosphere above. Upper atmospheres and ionospheres form highly-integrated systems in which common processes operating in different environments produce different outcomes.
They aim to characterize how atmospheres and ionospheres behave, then understand the physical processes responsible for these behaviors. Their focus is generally on acquiring and interpreting spacecraft observations of these environments, with numerical models playing a supporting role.
Involvement in spacecraft instrument teams enables the research group to maintain a long-term focus on a scientific question and strongly influence how that question is investigated. It also offers superb opportunities for undergraduate and graduate research projects. Assoc. Prof. Withers has been involved in over a dozen spacecraft radio science and accelerometer investigations and aims to be involved in many more in the future.
View Associate Professor Paul Withers’ Profile Here