2002-2003 Science Planning Summary

Aeronomy & Astrophysics

Dr. Vladimir Papitashvili
Program Manager

AO-128-O

NSF/OPP 00-90545
Station: South Pole Station
RPSC POC: Paul Sullivan
Research Site(s): Cusp Lab

A versatile electromagnetic waveform receiver for South Pole Station
Dr. James W. LaBelle
Dartmouth College
Department of Physics & Astronomy
jlabelle@einstein.dartmouth.edu
http://www.dartmouth.edu/artsci/physics/spacephy/
Dr. Allan Weatherwax
Siena College Physics

Deploying Team Members: James W Labelle . Shengyi Ye
Research Objectives: The Earth's aurora naturally emits a rich variety of radio waves at low, medium, and high frequencies (LM/MF/HF) which are signatures of the interaction between the auroral electron beam and the ionospheric plasma. Yet some of the mechanisms that generate plasma waves are not well understood. This project focuses on several types of signals detectable at ground level, including auroral hiss, which occurs primarily at very low frequencies but often extends into the LF/MF range, and auroral roar, a relatively narrow band emission generated near or at the second and third harmonics of the electron cyclotron frequency.

This group uses a versatile electromagnetic waveform receiver deployed at South Pole Station. Only recently has it been possible to conceive of an inexpensive, versatile receiver of this type for the South Pole. An antarctic location is essential for ground-based observations of LF auroral hiss because the broadcast bands usually found in the northern hemisphere are typically absent in Antarctica. Further, the absence of broadcast bands improves the effectiveness of automatic wave-detection algorithms.

Researchers can use the receiver to address many issues. For example, it has recently been discovered that auroral roar is sometimes modulated at frequencies between 7 and 11 Hertz, a phenomenon called flickering auroral roar. This receiver will enable researchers to discover how common flickering auroral roar is, the conditions under which it occurs, what the frequencies are, and how the amplitude and frequency vary over time.

Between 15 percent and 30 percent of auroral hiss events are not observable at very low frequencies. The receiver will determine whether LF auroral hiss consists exclusively of relatively unstructured broadband impulses or whether it sometimes displays a fine structure similar to that of auroral kilometric radiation and whistler mode waves in the same frequency range detected in the lower ionosphere. Project team members will also define and test auroral roar and auroral hiss mechanisms. Despite its extensive application for communications, the LF/MF/HF band has been relatively little investigated as a source of natural radio emissions detectable at ground level.

A complete knowledge of our geophysical environment requires understanding the physics of these emissions. Further, electron beam–plasma interactions analogous to the terrestrial aurora occur in many space physics and astrophysics applications. Often, the electromagnetic radiation emitted by these systems is our only source of knowledge about them. The local auroral plasma provides an opportunity to view some plasma radiation processes at close range.


Field Season Overview:
A complete system upgrade is scheduled for the 2002-2003 austral summer. This includes a new electromagnetic waveform receiver and computer in the Cusp Lab at South Pole Station. Station science technicians will operate and maintain the equipment throughout the 2003 austral-winter.