I began my career in magnetospheric physics by analyzing plasma data from the Magnetospheric Plasma Analyzers (MPA) on the Los Alamos National Laboratory geosynchronous satellites. The main focus of my Master's Thesis research was the characterization of low energy (< 200 eV) electron distributions. Correlations were made between the electron pitch angle distributions and plasma regimes and local time of occurrence. Ultimately, this work had ramifications for the plasmaspheric refilling process [Fillingim et al., J. Geophys. Res., 104, 4457, 1999]. Subsequently, I moved to higher altitudes utilizing plasma data from the Three-Dimensional Plasma and Energetic Particle Investigation (3DP) on the Wind spacecraft. My research concentrated on observations in the plasma sheet during substorm periods during Wind perigee passes through Earth's magnetosphere. Most passes occurred in the near-Earth plasma sheet between 10 to 20 RE, though some passes extended up to altitudes of 90 RE.

Global Auroral Imaging and Its Connection to Magnetospheric and Plasma Sheet Dynamics

By combining Wind 3DP plasma sheet observations with global auroral images from the Ultraviolet Imager (UVI) onboard the Polar spacecraft, I have been able to explore the connection between the plasma sheet and the aurora and to determine what plasma sheet processes are associated with auroral activity. The results of some of my work have shown that plasma sheet disturbances composed of large ion velocity moments (also known as bursty bulk flows), electron temperature enhancements, energetic particle flux increases, and high frequency magnetic field fluctuations and dipolarizations have a one-to-one correspondence with and occur at the the same time as auroral brightenings [Fillingim et al., Geophys. Res. Lett., 27, 1379, 2000]. Also, the same types of disturbances are observed in the plasma sheet during small, localized auroral displays (pseudobreakups) and during large scale substorms, indicating that the physical processes occurring in the plasma sheet are the same for both types of auroral activity [Fillingim et al., Phys. Plasmas, 8, 1127, 2001]. Additionally, the plasma measurements show that kinetic effects are important; the ion distribution functions often show multiple components, revealing more complexity in the plasma dynamics than the moments alone indicate [Fillingim et al., in Disturbances in Geospace: The Storm-Substorm Relationship, Geophys. Monogr. Ser., 142, 45, 2004]. Quantitative comparisons between the observed precipitating electron flux in the magnetosphere and the precipitating electron flux inferred from the auroral images have also allowed me to estimate the potential drop between the plasma sheet and ionosphere necessary to bring the two measurements into agreement [Fillingim et al., in Sixth International Conference on Substorms, 382, 2002].

Conjugate Auroral Studies

As the Polar apogee latitude has moved to the southern hemisphere, I have combined Polar UVI images of the southern aurora with IMAGE Far Ultraviolet (FUV) images from the north in order to investigate auroral conjugacy. Using data from these two spacecraft, I have been able to address the issue of auroral conjugacy statistically on a synoptic scale. Some of my recent work, which focuses on auroral bright spots on the day side, have shown that the time variation and even the gross morphology of the aurora can be different in the opposite hemispheres. These differences appear to be correlated with the interplanetary magnetic field conditions [Fillingim et al., Geophys. Res. Lett., 2005 (in press)]. Since the dayside magnetopause and boundary layer are magnetically connected to the dayside aurora, hemispheric asymmetries in the dayside aurora imply asymmetries in the solar wind-magnetosphere coupling processes. The next step is to correlate the auroral differences with other ionospheric and low altitude measurements such as convection patterns and field aligned currents with the ultimate goal of relating external conditions, high altitude processes, and low altitude processes leading to the formation of aurora.

Wave-Particle Interactions in the Plasma Sheet

Recently, I have started to work with members of the Wind Radio and Plasma Wave Investigation (WAVES) team in order to directly relate electron and ion particle distribution functions in the plasma sheet measured by Wind 3DP to waveforms observed by the Time Domain Sampler (TDS) component of WAVES. So far we have found solitary waves and waves near the electron cyclotron and plasma frequencies associated with strongly peaked field-aligned electron distributions and beams [Fillingim et al., Geophys. Res. Abstracts, 5, abstract 07964, 2003]. This work has the potential to quantitatively explore the interactions between the waves and particle distribution functions and to study basic plasma physics under conditions (density, temperature, magnetic configuration) only possible in the natural laboratory of Earth's magnetosphere.