ABOUT THE ALBUM

In our first album we heard a day of low geomagnetic activity at the Halley Station. In contrast, here, in In Aurora’s Garden, we experience the solar storm of 17th June 2012. A few days prior to this, on the 13th and 14th June, two large explosions on the surface of the Sun released bursts of charged particles and magnetic field which travelled outwards and towards the Earth. The material reached the Earth on the 17th June, the day chosen for our album, tearing open the Earth’s magnetic field, leading to a geomagnetic storm. Particles were injected into near Earth space giving rise to radio emissions including chorus and plasmaspheric hiss. At lower altitudes electrons rained down on the Earth’s upper atmosphere leading to some beautiful and stunning displays of the aurora.

In a musical sense In Aurora’s Garden is quite different to Aurora Musicalis. This album is more like our second album Celestial Incantations, which allows a broad musical response to the ‘sounds’ of space. The range of ‘sounds’ offered here are significant, offering the chance for interplay between sonification, music and art (the images of Scarborough are both integral to and deeply profound within this project), which we detail in the individual tracks.

Cunio spent a number of days in the percussion room at the Australian National University, recording gongs, wood blocks, bells, vibraphones, and glockenspiels, as with his piano and his synthesis rig. Percussion virtuoso Tunji Beier lent his collection of crystal bowls for track Of Bats and Bowls and the cellist Imogen Granwal played on Cosmic Introspection. There are also a number of lesser-known instruments, the Japanese shakuhachi is played by Master Bronwyn Kirkpatrick in a piece Cunio wrote specially for her. The tabla is played by emerging virtuoso Samarai Cunio. There is a multi-tracked orchestra on Sunlight Reverie. We again hear soprano Heather Lee, in Cunio’s setting of a traditional Chinese text, as well as a new version of the Joni Mitchell classic Both Sides Now, which concludes the album.

Meredith, who has a profound knowledge of the constituent ‘sounds’ captured at Halley, chose a 24-hour period on 17th June 2012, the day of the peak of the solar storm. This a great mythological year, the same year as Aurora Musicalis, but something we contemplated in more detail for this project.

2012 marked the ending of the Mayan calendar, and which prompted soul searching for many, and more than a few conspiracies, and in some ways a doubting of science in some elements of society. It was like one of our great thought archetypes had ended. At the same time the solar storm offered us the chance to look at the effects of the Sun on our planet in both a mythological and scientific way – allowing our art / science collaboration to deepen again, where multiple praxes and methodologies can work together. If Halley and our sounds of space project teaches us one thing it might be that we are not nearly as important as might think.

What does the Halley receiver offer us? Put simply it provides us with a sonic time lapse series of recordings in a manner similar to a time lapse videos. Sound is not sped up as with images, it is culled, with a 1 minute sample provided every 15 minutes, leading to 96 minutes of sound for each day. Each sound file was combined together on a time line then stitched together to make a continuous project, that plays seamlessly from beginning to end, or as individual tracks. We include this sound file so that you may experience the project as we did at its outset. We hope that these sounds will be part of the fields of acoustic ecology and sonic archaeology, where we critically listen to the sounds of the word as they were. There is more detail about Halley and these ‘sounds’ at the end of these notes.

This album, as a cross disciplinary co-creative art-science project, offers up an opportunity to contemplate the majesty of Antarctica as it still exists and to fill ourselves with admiration for our wondrous planet. May we always care.

Kim Cunio, Diana Scarborough and Nigel Meredith

ABOUT THE 'SOUNDS'

To appreciate this project we invite you to read about and experience the ‘sounds’ from the VLF receiver at Halley. Below are definitions and descriptions of the ‘sounds’ you will hear.

SPHERICS The main signals a ground-based VLF receiver will detect are from lightning activity. Each lightning flash emits a short radio pulse, known as a spheric, which covers a wide range of frequencies. These are heard as short cracks and appear as vertical lines in a spectrogram. Spherics can be detected from lightning that is up to 10,000 km away !

TWEAKS Spherics may travel even further, up to half way around the globe. Higher frequencies travel slightly faster than lower frequencies, so these signals undergo dispersion. These signals are known as tweaks and have a pronounced ringing nature.

WHISTLERS Some of the radio waves associated with lightning leave the atmosphere and leak into space. The signals may be guided by the Earth’s magnetic field and received in the opposite hemisphere. They may even be reflected in the opposite hemisphere and be detected in the same hemisphere as the original lightning strike. As a general rule the higher frequency waves travel faster than lower frequency waves. The waves have a characteristic descending tone and are known as whistlers.

TRIGGERED EMISSIONS Sometimes the whistlers can excite additional radio waves. These are known as triggered emissions.

CHORUS Another prominent signal type, known as chorus, is generated deep within the magnetosphere itself. Energetic electrons enter the magnetosphere during geomagnetic storms driven by the Sun, causing the Earth’s beautiful aurora and generating chorus emissions. The most common form consists of a multitude of rising tones in the frequency range 1 to 5 kHz. The emissions are known as chorus because they often resemble the twittering of birds in the dawn chorus. Chorus can accelerate electrons to very high energies. Studying these effects is important since these so-called “killer” electrons can damage satellites.

PLASMASPHERIC HISS is another important magnetospheric emission. It is largely responsible for the slot region between the Earth’s inner and outer radiation belt. Unlike chorus, plasmaspheric hiss is a broadband, structureless signal and resembles audible hiss.

THE HALLEY VLF RECEIVER

The Halley Very Low Frequency (VLF) receiver consists of two, orthogonal, 58m^2 single loop antennae, designed to detect the magnetic fluctuations of the Earth’s low frequency radio waves. The weak signals are amplified, processed electronically and subsequently digitised at 96 kHz.

At BAS we use the radio wave data recorded by the VLF receiver to study the science of space weather storms, to help understand potential space weather impacts on the climate system and for lightning detection. We also convert the data directly to audible sound, revealing a series of weird and wonderful noises, known as the ‘sounds' of space.

FURTHER READING

1. ‘Sounds of space’ project page at the British Antarctic Survey
www.bas.ac.uk/project/sounds-of-space/

2. Meredith, N. P., K. Cunio, D. Scarborough and A. D. Wynne, Music of the Spheres, Astronomy and Geophysics, 63, 1, doi.org/10.1093/astrogeo/atac013, 2022.

3. Meredith, N. P., Turning the sounds of space into art, Astronomy and Geophysics, 60, 2, doi.org/10.1093/astrogeo/atz097, 2019.


FURTHER LISTENING

1. Listen to Nigel Meredith’s invited talk in the session “Dialogues between space science and art” at the 44th COSPAR Scientific Assembly, 21st July 2022. www.youtube.com/watch?v=iHE_7fi6Pmk

2. Listen to Nigel Meredith speaking to the Cambridge University Astronomical Society about the ‘sounds of space’, 8th February 2022. www.youtube.com/watch?v=f33DdOOrqkc