STANFORD UNIVERSITY
EE 350 RADIOSCIENCE SEMINAR
Professor Leonard Tyler
Autumn 2002-2003

Date: Wednesday, October 2, 2002
Time: 4:15-5:30 PM; Refreshments at 4:00 PM
Location: Bldg. TCSeq, Rm. 101

Discovery at Stanford of the Plasmapause, An Unexpected Boundary in Space

Professor Donald L. Carpenter, Emeritus

STAR Lab, Stanford University

Abstract

In the 1950s and early 1960s Stanford was the setting for several pioneering studies of the Earth's space environment. The work was based upon ground recordings of natural very low frequency signals from lightning (whistlers) that propagated from hemisphere to hemisphere along geomagnetic-field-aligned paths that reached several Earth radii in altitude. From data recorded at spaced stations, including Antarctic locations, Stanford researchers were able to map important properties of the light ion plasma surrounding the Earth, accomplishing this several years before the corresponding high altitude regions were probed by satellites. One of the discoveries, made following key earlier contributions by Owen Storey at Cambridge University and Bob Helliwell and Bob Smith at Stanford, concerned the upward extension of the Earth's ionosphere, later called the plasmasphere. That region was found to have a sharp, geomagnetic-field-aligned boundary, a boundary that had not been predicted by theory. There was supporting evidence from the 1959 USSR Lunik I rocket experiment of Konstantin Gringauz and later a spirited debate as to the reality of "Carpenter's Knee" between the Stanford group and a satellite group at Goddard Space Flight Center led by Sig Bauer. The plasmasphere, long regarded as well understood, is now being "rediscovered," thanks to global views obtained for the first time by the EUV instrument (Bill Sandel, U. of Tucson) on the IMAGE satellite.