Conjugate Studies of ULF Waves and Magnetospheric Dynamics Using Ground-Based Induction Magnetometers at Four High-Latitude Manned Sites

Augsburg University, Minneapolis MN

Investigators

Abstract

Since the beginning of the space age increasingly sophisticated efforts have been made to explore and understand Earth's space environment. Scientists now understand much about the configuration of the ionosphere and the region above it, the magnetosphere, but much remains to be done before we fully understand the dynamical processes involved in transferring energy and momentum from the rapidly changing solar wind (driven by both quiescent and explosive processes near the surface of the Sun) into Earth's magnetosphere, ionosphere, and upper atmosphere. It is increasingly understood that doing so requires the coordinated use of multiple data sets, including both a variety of individual spacecraft and strategically located ground observatories. Because those parts of Earth's field that reach farthest out into space intersect the ground at high latitudes, arrays of ground magnetometers have long been a valued means of monitoring processes in remote parts of the magnetosphere. This proposal requests support to continue to operate and analyze data from four search coil magnetometers located at high latitude sites in the North American sector, two in Antarctica (South Pole and McMurdo) and two in the Arctic (Sondrestromfjord, Greenland, and Iqaluit, Nunavut, Canada). South Pole and Iqaluit provide close magnetic conjugacy near-cusp latitudes, while Iqaluit and Sondrestromfjord provide data at similar northern latitudes but with a local time separation of 1.5 hours. During daytime hours these locations provide a window to the magnetospheric boundary and the interactions of the magnetosheath with the magnetosphere, and during nighttime hours they provide an increasingly appreciated high-latitude perspective on the development of substorm activity. The proposers are also involved in analysis of data from other high latitude arrays of ground-based instruments, including the multi-instrument U.S. and British AGO (Automated Geophysical Observatory) and developing autonomous magnetometer arrays in Antarctica, and the MACCS and CANOPUS magnetometer arrays in Arctic Canada. The 10 Hz sampling rate of the search coil magnetometers in this project provide an important complement to the more limited sampling rates of other search coil and fluxgate magnetometer systems (= 2 Hz) in these regions. Taken together, these instruments make it possible to study the entire range of ULF variations, from Pc 1 and Pi 1 pulsations down to Pc 5 pulsations, with high sensitivity. In conjunction with data from other instruments located at the Antarctic sites and with both low-altitude and high-altitude satellites, these magnetometers have played, and we expect will continue to play, a significant role in a variety of studies of geospace phenomena. During the next three years we expect our scientific efforts to focus on (a) studies of several classes of Pc 1 and 2 waves (0.2-1 Hz), including waves observed poleward of the cusp, so-called "mantle waves"; (b) the propagation of Pc 3-4 pulsations and the generation of quasiperiodic (QP) emissions, a class of ELF/VLF emissions modulated at Pc 3-4 frequencies (15-60 mHz); and (c) studies of both short-period and long-period irregular ULF waves, especially during substorms and magnetic storm periods. Analysis and data processing efforts associated with these data sets are highly suitable for undergraduate as well as graduate research participation, and build on continuing strong programs of faculty and undergraduate student research.