Radio waves reveal birth of gravity waves during solar eclipse
doi:10.1038/nindia.2015.28 Published online 26 February 2015
Using very low frequency radio waves, astrophysicists have discovered that solar eclipses trigger atmospheric gravity and planetary waves in the lower ionosphere of the atmosphere1. The radio waves can be used as a remote sensing tool for studying the lower ionosphere, which is difficult to probe with balloons or satellites.
To better understand how atmospheric gravity and planetary waves contribute to atmospheric balance, the researchers tracked signals of very low frequency radio waves that travelled from the Indian Naval Transmitter in South India to three Indian receiving stations in Kolkata, Malda and Raiganj and one in Kathmandu, Nepal. In addition, they gathered ozone and temperature data to investigate how the gravity and planetary waves mix gases between different layers in the upper atmosphere.
All the receiving stations except one recorded much higher wave-like oscillations on the day of a solar eclipse than on other days. This may indicate the formation of gravity waves with periods of between 10 and 40 minutes.
Sunrise and sunset triggered drastic changes in the temperature, electron and ion densities and the chemical composition of the ionosphere, which gave rise to gravity and planetary waves. “Our analysis clearly gives the strength and periodicity of the gravity and planetary waves by reading out the amplitude of the reflected radio waves,” says lead research Sandip Chakrabarti.
The authors of this work are from: Indian Centre for Space Physics and S. N. Bose National Centre for Basic Sciences, Kolkata, India and The University of Electro-Communication, Tokyo, Japan.
1. Pal, S. et al. On the use of very low frequency transmitter data for remote sensing of atmospheric gravity and planetary waves. Adv. Space Res. 55, 1190−1198 (2015)