December 29, 1999

Adelie penguins porpoising in Arthur Harbor.

We finally had a break in the weather, as the winds died down to an acceptable level to permit zodiac excusions to the islands. The "Lynns" resumed their census counts of giant petrels, while other scientists collected water samples and searched for krill. Steve and I undertook a trial run broadcast to NPR in Washington, DC and made plans to do a dress rehearsal tomorrow for the live New Year's Eve feed. One of the sites that we have chosen to place a wireless, remote microphone is on nearby Torgersen Island--about 1/2 mile from Station. Thousands of Adelie penguin chicks have hatched there over the last few weeks, and the colony is a busy hub of activity. We see adult birds foraging for krill, propoising around Arthur Harbor in groups of a dozen or more. It is remarkable how penguins swim, and this particular technique is reminiscent of dolphins. The sounds of chicks peeping and the general din of the rookery is one of the most lively aspects of the Antarctic soundscape at this tie of year. Steve motored over to the island and positioned the Sennheiser SK250 wireless unit near a community of nests. Back on Station in the studio room, I set up a Sennheiser EK3041 wireless receiver. The Station carpenters, Steve Navarro and Keith Tuley, once again helped out by constructing rugged, weatherproof plexiglass mounts for these delicate electronic instruments. Steve carefully oriented the microphone on the ground within a few feet of the nests. Listening from Palmer, I could hear the most intimate details of chirps, raucous ecstatic calls and the patter of tiny feet across the shards of rock at the rookery.

I have been using Sennheiser microphones for years in the field--they are real work horses and well-suited to the rigours of recording wildlife in extreme conditions. This was my first experience with their wireless technology and, put to the test in such an environment, I have been very impressed with the performance and fidelity. Wow!

The VLF Hut.

The evening brought fresh winds out of the north. The group of elephant seals that has been hauled out by the Bio Lab seems intent on staying. We plan to place a microphone nearby, as they do have a lot to say for themselves between napping. I spent the rest of the evening at T-5 where the VLF Hut is located. The study of Very Low Frequency, or VLF, radio phenomena is one of the many intreguing science projects at Palmer. I had a thorough tour of the T-5 facility by the Science Technician, who oversees and monitors the field work of several science projects. With my orientation at the VLF Hut complete, I hooked up my recorder and had a listen to the sounds of lightning strikes from far and wide. At first, the crackling and popping seemed like static from a radio that was caught between stations. However, each static "pop" sound is a specific lightning event that has occurred somewhere around the world. The faint sound of a descending whistle-like sound, or "atmospheric whistler," is the localized sound of a lightning strike somewhere in the region of the Northeastern United States.

The VLF receiver and monitoring rack.

Think of it this way...

"In the mounting humidity and heat of an approaching summer convection storm, a bolt of lightning splits the sky over the eastern United States. The strike is heard a few seconds later in an associated crash of thunder. Electromagnetic energy from the lightning also propagates through the upper atmosphere and beyond, at the speed of light, so that, in less time than it takes for that clap of thunder to be heard, the breath of a whistler can be picked up through a receiver at Palmer Station. Don Carpenter, professor emeritus at Stanford University's STAR Laboratory, described the phenomenon to me. Waves of energy from the lightning move through layers in the magnetosphere, measured in distances of the earth's radii. They follow lines of force associated with the magnetic field around the planet. These lines of force extend in latitude away from the earth, rounding polar cusps to return along the earth's axis at the poles. Wave energy is channeled in so-called "ducts," to concentrate as atmospheric whistlers in the Arctic and Antarctic. Depending on the distance the waves travel, the media through which they pass (including dense regions of enhanced ionization), as well as the degree of electron precipitation they induce, whistlers will have various pitch, duration, and decay characteristics when they are heard as sound. Carpenter also described other related acoustic events as "hisses," for their broadband noise components, and "dawn choruses," for their indeterminately pitched material, reminiscent of birdsong."*

Apart from a few whistlers, most of the sounds I was hearing came as reflections and transmissions of energy through the ionosphere--at a much lower layer of the earth's atmosphere. It is a pretty amazing vantage point, listening to the world's lightning storms from down here...

Click here to listen to an MP3 sample of Very Low Frequency (VLF) sounds from lightning strikes.