PRL-IAPT Dr. Vikram Sarabhai Lecture

Space has always fascinated humans. Especially, the sight of the stars, the galaxies, and the planets have kindled curiosity in the minds of many a scholars, thinkers as well as children since these objects can be seen with a naked eye. There is yet another light in the near earth region which an unaided eye cannot “see”, but understanding the variations in its brightness is important for fundamental investigations of the physics of sun-earth interactions as well as for several aspects of applications in our day-to-day life – as we are increasingly dependent on space-based technologies. Scientists have invented and developed innovative methods to remotely sense the behavior of the atmospheric regions ‘up above the sky’ using this light called the “airglow” or the “aurora” as the tracer of the medium. The behavior of these airglow or auroral emissions tell us about the weather at that altitudes in terms of the wave propagations, temperatures, winds, etc. These optical airglow emissions are present not only in the night but also in the daytime, just as do the stars, galaxies, and planets. PRL has pioneered the development of innovative techniques for the measurement of airglow in the daytime, akin to seeing the stars in the broad daylight, which have resulted in several new insights on the behavior of the near-earth space. This talk will attempt to give a flavor of the recent developments made in the measurement techniques and the discoveries made in the understanding of solar-terrestrial interactions. Some such optical techniques are being developed for space based research of not only the Earth’s upper atmosphere but also of the atmospheres of several other planets in forthcoming ISRO’s space missions. This is one of the frontier areas of research for the young physicists who are planning on taking up research as their career.