Coupling Between the Upper and Lower Atmospheres
The Electrical Connection
Senior Scientist, Laboratory of Extra-Terrestrial Physics, Goddard Space Flight Center
About the Lecture
The Earth’s atmosphere is thought to contain a global electric circuit with an electric current driven by the ever present array of thunderstorms scattered throughout the world. The classical model depicts this circuit to be self contained below the highly conductive ionosphere (below about 70 km), thereby shielding it from external effects such as solar disturbances and Earth magnetospheric storms. Conversely, correlative data have indicated that lower atmospheric electrical parameters do respond to solar and geomagnetic variability, which suggests that electrodynamic coupling processes between the regions must exist. Now mounting experimental and theoretical evidence requires reevaluation of the more traditional concepts. Cosmic rays, relativistic electrons and protons, and recently discovered upward lightning flashes fit into this scenario as strongly perturbing influences. This overview concentrates on the various competing interactions known to occur between the upper and lower atmospheric regions, in an attempt to establish their electrodynamic connection and influence.
About the Speaker
Mr. Goldberg received a B.S. in physics from Rensselaer Polytechnic Institute in 1957 and a Ph.D. in physics from Pennsylvania State University in 1963. He was awarded an NAS/NRC Postdoctoral Associateship at the NASA/Goddard Space Flight Center and is now a senior staff scientist there in the laboratory for Extraterrestrial Physics. From 1989-1991, he served as Director for the Solar-Terrestrial Research Program at the National Science Foundation. He has been actively engaged in problems dealing with solar-terrestrial interactions, including studies of the electrodynamic and neutral states of the atmosphere and their response to extraterrestrial energy sources. To conduct this research, he has been Project Scientist for numerous international scientific rocket/balloon programs and principal investigator for more than 80 sounding rockets. He co-authored the book Sun, Weather, and Climate, edited the book Rocket Techniques in the Middle Atmosphere, and published more than 80 papers in scientific journals. He currently serves as North American editor for the Journal of Atmospheric and Terrestrial Physics. He is a member of Sigma Xi, Sigma Pi Sigma, and several professional societies.
President Spargo called the 2019th meeting to order at 8:15 p.m. on December 3, 1993. The Recording Secretary read the minutes of the 2018th meeting and they were approved.
The speaker for the 2019th meeting was Richard A. Goldberg of the Goddard Space Flight Center, and the title of his talk was “Coupling Between the Upper and Lower Atmospheres: The Electrical Connection”.
Mr. Goldberg opened his very enthusiastic talk by describing the historical view of the electrical circuits in the Earth's atmosphere. He indicated that our environment is highly charged, with the upper atmosphere acting as an infinite conductor, and the circuit between the upper and lower atmospheres being a DC circuit. The electric potential between the upper and lower atmospheres results in about 2000 thunders storms at any one time around the world. Research in the 1920s and '30s showed that the: electrical potential between the upper and lower atmospheres typically increased in the afternoon over continents. More recent weather satellite data has supported this hypothesis by showing that most thunderstorms do occur primarily over continents and in the afternoon.
Since the upper atmosphere is viewed as an infinite conductor, magnetic fields external to the Earth's upper atmosphere should not affect electrical parameters in the lower atmosphere. However, data has not supported this view. Electrical parameters measured in the lower atmosphere have been affected by the sun spot cycle, the Sun's rotating magnetic field, and solar flares. The affect attributed to the sun spot cycle may be the result of solar cosmic rays that increase as sun spot activity decreases. The cosmic rays produce ion pairs in the atmosphere but solar radiation tends to have little effect below an altitude of 70 kilometers. The effects of these outside disturbances are easy to see in the upper atmosphere. The Northern Lights are an example. The effects in the lower atmosphere are not easily observed.
Scientists use a number of methods to measure electromagnetic parameters at various altitudes. Near the Earth's surface in the troposphere, sounders and airplanes easily collect data. Instrumented balloons reach into the stratosphere above an altitude of 18 kilometers. In both of these regions, data can be collected continuously over a lengthy period of time. Above 50 kilometers, these methods do not work, and rockets are needed to reach these altitudes. However, the rockets do not stay aloft long so that the data collected is only instantaneous. A number of data points are achieved by firing a campaign of rockets sequentially. The rockets deploy an instrumented sphere with booms.
Rocket data has shown that the vertical electric field tends to maximize in strength at an altitude of about 65 kilometers. Upsets in the field have magnitudes in the range of a volt per meter when the typical electric field has a magnitude of about a millivolt per meter.
Mr. Goldberg also showed some film of some unusual observations, including upward lightning and airglows in the upper atmosphere just before a lightning flash during the Midwest storms of the past summer. Atmosphere potential has been observed to vary with cosmic ray activity as well as volcano particulate ejection. Mr. Goldberg indicated that the new model of the coupling between the upper and lower atmospheres is an AC circuit, complete with transients. Mr. Goldberg then kindly responded to questions from the audience.
The President thanked the speaker for the Society. The Vice President announced five new members. The President then announced the next meeting, made the usual parking announcement, and adjourned the 2019th meeting to the Social Hour at 9:43 p.m.