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20 April, 2000

Chris Barrington-Leigh and Stanford's Ionosphere/VLF Research

Question 61: Is all baleen the same?

The weather continues to be extremely stormy. Today there is horizontal rain and the wind is gusting to 55 knots. Definitely no diving. Fortunately, we have plenty to do in the lab!

We spread out into other labs from our two assigned lab spaces (2 and 3) after the LTER group left at the end of March. The only other science group at the station now is made up of one person. Chris Barrington-Leigh is a graduate student from Stanford here to do maintenance on the VLF (very-low-frequency) radio antennae on the glacier. He is also calibrating and updating the instrumentation used by the Stanford group to monitor ionospheric disturbance caused by global lightning.

The ionosphere is the outer part of earth's atmosphere that stretches from an altitude of 30 miles to 300 miles or more. It contains electrically-charged parcticles (ions) that transmit radio waves around the earth. The ionosphere varies in height and ionization with the time of day, season and solar cycle. The disturbances can be observed in the audible portion of the electromagnetic spectrum. This means that the data can be heard and recorded on audio tapes. During most of the year the science technician at Palmer Station maintains the instruments and collects the data tapes to be sent back to the US.

VLF radiation is caused by a variety of sources: standard lightning and sprites (lightning from cloud to atmosphere) traveling along the earth-ionosphere waveguide; whistlers from lightning traveling along the magnetosphere (earth's magnetic field); powerline hum; and Navy VLF transmitters. This data allows scientists to track thunderstorms all over the world, learn how magnetosphere events affect the lower ionosphere, work on models of the global climate, forecast weather, improve aircraft flight planning, and predict certain types of earthquakes.

Palmer Station is an excellent location for gathering this information for several reasons. The atmospheric VLF waves caused by a lightning storm are trapped and bounce between the earth and the ionosphere in all directions from the storm. They travel well over all surfaces except ice. Palmer Station's location gives it clear reception of approximately a third of the world including most of the active lightning areas (Africa, the Pacific, North and South America). Most countries in this coverage area, unlike the United States, do not track every lightening strike in their country. In the United States it took scientists 12 years to develop The National Lightning Detection Network which has now become commercially viable by providing lightning information for forestry, air traffic and power company use. It consists of over 200 high- frequency receivers connected to high-speed data processors that send data about each lightning strike in real time to a central processing location.

The data from the atmospheric VLF waves is compared to the whistlers generated from the same lightning storms. Whistlers are VLF waves that travel along the earth's magnetosphere instead of between the earth and the ionosphere. The curve of the magnetosphere means that the geomagnetic field lines that start near the central US, one of the most active lightning regions on earth, come back to earth near the Antarctic Peninsula, so Palmer is the best location to collect data on the VLF waves that travel along the magnetosphere.

Answer 60: Right whales (and sometimes seis) simply open their mouths and filter plankton as they swim, the forward motion pushing the water through the plates of baleen. Their heads may be partway out of the water when they do this. This is called skimming. The blue, fin, sei, humpback and minke whales take huge mouthfuls of water--their jaws open wide (up to 90 degrees) and their pleated throats expand (balloon-like). When their mouths close, they use their tongues to force the water out through the rows of baleen. In both cases, the plankton are caught in the baleen strands and then swallowed.

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