29 April, 2004

International Dawn Chorus Day – Sunday 2nd May 2004 Scientists in the Antarctic listen to natural “Dawn Chorus” from Space 29 May 2004 PR No. 5/04 As nature lovers all over the world wake up to enjoy the enthusiastic sounds of birdsongs on International Dawn Chorus Day on 2 May, scientists at British Antarctic Survey’s (BAS) Halley Research Station will listen to a very different Dawn Chorus.

Each morning, as the Earth and its enveloping atmosphere turn towards the Sun, very low frequency radio waves produced in space, travel down to the ground where they can be “heard” using a simple radio receiver. When converted to audible sound waves, they are remarkably like birdsong and for this reason were named “Dawn Chorus” when they were discovered in the mid 20th century. But there is more to this phenomenon than enchanting sounds. Dr Andy Smith and colleagues at BAS believe that ‘chorus waves’ are the accelerating power behind so-called ‘killer electrons’ that damage communications satellites during space storms. Massive eruptions on the Sun, known as Coronal Mass Ejections (CMEs) cause the solar wind to blow harder than usual, which accelerates these electrons to very high speeds. Deep within the Earth’s protective magnetic field lies the van Allen radiation belt – a region of charged particles in space that surrounds the Earth like a doughnut. Scientific opinion is divided on exactly how the so-called “killer electrons” penetrate the belt. Scientists at Halley Research Station record chorus waves in an attempt to understand space weather processes. The ability to anticipate magnetic storms could help insurance, telecommunications and aerospace industries to better protect spacecraft costing upwards of 200 million US dollars. A recent theory by BAS scientists and colleagues, based on measurements in space and Antarctica, has proposed that chorus waves generated by the solar wind interact with and accelerate the electrons. Andy Smith says “by understanding this process we are better informed on how to minimize disruption to satellites”.

Notes to Editors:

Issued by British Antarctic Survey Press Office. Athena Dinar – tel: (01223) 221414, mob:07740 822229, email: a.dinar@bas.ac.uk Linda Capper – tel: (01223) 221448, mob: 07714 233744, email: l.capper@bas.ac.uk

For more information contact. Dr Richard Horne – tel. (01223) 221542, email: r.horne@bas.ac.uk Dr Andy Smith – tel. (01223) 221544, mobile: 07736 921693 email: a.j.smith@bas.ac.uk Antarctica is well placed to observe the dawn chorus, since these very low frequency radio waves are transmitted via the Earth\’s magnetic field to the polar regions. BAS scientists are members of international research teams studying the physics of space storms using satellite-borne and ground-based experiments. In a recent paper in the Journal of Geophysical Research*, Andy Smith and Richard Horne at BAS and Nigel Meredith at the Mullard Space Science Laboratory reported their studies of the chorus observed at Halley during a large number of space storms which occurred over the 11 year interval 1992-2002. They find that the intensity of the chorus increases significantly after storms and argue that their results support the theory that chorus is at least partly responsible for killer electrons. * Smith, A. J., R. B. Horne, and N. P. Meredith (2004), Ground observations of chorus following geomagnetic storms, J. Geophys. Res., 109, A02205, doi:10.1029/2003JA010204. Halley Research Station is the UK\’s most isolated station and is afloat on an ice shelf on the mainland of Antarctica. Halley, lying within the auroral zone, is ideally situated for geospace research. An HF (SHARE) radar, supported by a suite of other powerful radio and optical instruments including remote unmanned Automatic Geophysical Observatories, provides an unparalleled spatial picture of the consequences of geospace interactions in the upper atmosphere over an area of around three million square km above the South Pole. British Antarctic Survey is responsible for most of the UK\’s research in Antarctica. It is a component of the Natural Environment Research Council. More information about the work of the Survey can be found on our website: www.antarctica.ac.uk