Current Projects

Evolution of the Earth's Van Allen Radiation Belts

The evolution of the Earth's Van Allen Radiation Belts is being modeled by following test particle trajectories in 2D and 3D simulations using 3D magnetohydrodynamic fields from the Lyon-Fedder-Mobarry MHD code driven by measured plasma parameters from spacecraft in the solar wind upstream from Earth. Global electric and magnetic field structure and computed particle distributions in momentum and spatial location are compared with measurements from the recently launched (August 30, 2012) Van Allen Probes satellites. This work is supported by the NASA Heliophysics Directorate. Separate work on the access, trapping and loss of solar energetic protons in Earth's 'magnetosphere' is funded by NSF.


Green Cube

The undergraduates in the JPL-sponsored GreenCube project of the Lynch Rocket Lab, are developing a CubeSat-class autonomous sensor payload, which they fly on balloons across New Hampshire and this spring will be floating in an array down the Connecticut (and other) River(s). ``Cubesat'' is a small satellite prototype established by CalPoly and Stanford Universities. Similar satellites have been used by many other universities and student satellite programs because of its relatively easy and inexpensive design. Our 3UCubeSat payloads fly on bursting balloons that reach approximately 90,000 ft. in the air before falling back to earth with a parachute. The total flight takes approximately two hours. We have flown 6 such flights across NH so far. This spring we will be floating an array of 20 Arduino-based GPS-enabled GreenCube payloads down rivers to study river transport of large woody debris, an important parameter in geography studies of fluvial morphology and of recent importance in Vermont given the damage done by Hurricane Irene last year.



The upcoming ISINGLASS sounding rocket mission (February 2017, Poker Flat Rocket Range, Alaska) will sample multiple locations simultaneously in the auroral ionosphere to take gradient measurements of plasma parameters. Two identical rockets will be flown into two separate events (ie, quiet early evening arc vs dynamic rayed arc); each rocket has a large subpayload, and four small deployable payloads. 

Mechanism for higher harmonic radio emission from aurorae

It has long been known that the aurora emit radio waves at the second and third harmonics of the electron cyclotron frequency. A detailed theory explaining these emissions has been developed and tested in many experiments. However, recently (in 2012) the fourth and fifth harmonics were observed for the first time. While it is possible that the same theoretical explanation applies to them, there is some evidence that their polarization may be inconsistent with the mechanism that generates the lower harmonics. Colleagues have proposed and alternative, non-linear mechanism to explain the higher harmonics. We are working on observations as well as theoretical calculations to determine whether the polarization is indeed inconsistent with the mechanism established for the lower harmonics, and in either case to design experiments to establish the generation mechanism.


Understanding wave-particle interactions in Earth's polar cusps

The polar cusps are two funnel-like regions near the poles of Earth's approximately dipolar magnetic field, one in each hemisphere, where the Earth's magnetic field may directly connect to that of the solar wind. The interaction of the solar wind and its magnetic field with Earth's magnetic field gives rise to unusual effects in the cusp leading to particular distributions of accelerated and non-accelerated charged particles, which in turn generate plasma waves and interact with pre-existing plasma waves. Some of the wave-particle interactions resemble those observed elsewhere in Earth's ionosphere, such as in the nightside aurora. However, not enough measurements have been made in the cusp to determine how the its wave-particle processes differ. Together with collaborators at several other universities, we are leading an effort to launch a rocket into the cusp in November-December, 2015.

Seeking the generation mechanism for Bursty radio emissions from Earth's ionosphere

For almost twenty years, bursty radio emissions at 1.5-4.5 MHz, originating in Earth's high latitude ionosphere, have been described and probed with multiple experiments. The emission mechanism remains a mystery, though recently a theory has been proposed. We have set up arrays of antennas attached to sensitive digital receivers at several Arctic and Antarctic locations, to perform measurements needed to test the theory. In addition, we are investigating signals similar to the burst emissions detected by NASA satellites. Since it is unlikely that the emission mechanism is unique to Earth's ionosphere, its identification will probably lead to predictions or explanations of radio emissions from other space plasmas, in addition to providing a passive method to remotely sense plasma properties and processes in Earth's ionosphere.


Polarization, fine structure and occurrence rates of ground-level AKR

Auroral Kilometric Radiation is the most powerful natural radio emission from Earth's environment, carrying away up to a percent of the energy of the aurora. Our group and others have found evidence that the radiation is not only beamed away from the Earth, as previously known, but occasionally leaks to low altitudes. We have experiments in place at several locations, primarily in Antarctica, to measure the polarization and fine structure of these leaked AKR emissions, which should help establish that they indeed are related to the AKR observed in space and should provide clues about the mechanism by which the energy penetrates the ionosphere to reach the ground.


Simulations of whistler chorus waves

Electromagnetic ion cyclotron and whistler chorus waves occur in the Earth's inner magnetosphere at a distance of about 4 to 7 Earth radii from the Whistler chorus waves occur in the Earth's inner magnetosphere at a distance of about 4 to 7 Earth radii from the center of the earth. These waves are thought to provide a mechanism for energization and loss of particles in the Earth's radiation belt. Two-dimensional simulations of these waves are revealing the structure of the waves, their evolution, and their effects on particle populations including the radiation belts.


BARREL (Balloon Array for RBSP Relativistic Electron Losses)

BARREL uses stratospheric balloons to study the loss of high energy electrons from Earth's Van Allen radiation belts. The electrons in this region of near-Earth space are relativistic, moving very close to the speed of light. BARREL balloons measure x-rays produced by these particles when they are scattered into Earth's atmosphere. BARREL balloon campaigns have been conducted in Antarctica in January-February 2013 and 2014 during which 20 small (~20 kg) balloon payloads were launched, and in Sweden in 2015 (7 launches). BARREL works closely with the Van Allen Probes, two NASA satellites, launched in August 2013 to study the radiation belts.


Quantum Simulation with Cold Atoms in Engineered Optical Potentials

Many-body quantum systems can be very difficult to handle theoretically, and in some important cases the true nature of the phase diagram is not yet accurately known. One possible path to gain deeper understanding of these incredibly rich physical systems is to engineer a "synthetic" many body quantum system that maps onto a particular system of interest, but has more conveniently tunable properties. Ultracold atoms in engineered optical potentials are one platform for such an approach. We are developing optical trapping and manipulation techniques to create (and examine the properties of) various strongly correlated and "topological" quantum phases of matter.