doi:10.1038/nindia.2014.34 Published online 18 March 2014
Researchers have gained insights into how geomagnetic storms affect airglow — emission resulting from interactions between solar radiation and molecules in the Earth's magnetosphere1.
A geomagnetic storm is a temporary disturbance of the Earth's magnetosphere caused by a shock wave in the solar wind interacting with the Earth's magnetic field. An increase in the solar wind pressure affects the Earth's magnetic field by transferring greater energy and electric current into the magnetosphere. Such a change in the energy and electric current shapes airglow, which can be classified as dayglow and nightglow. Dayglow is the brightest of the two and, as its name suggests, occurs in daylight. Nightglow, on the other hand, is the emission of light resulting from the recombination of molecules that had been split during the day by solar radiation.
To gain a better understanding of the associations between geomagnetic storms, dayglow and nightglow, the researchers developed two neutral atmospheric models (which they called the MSISE-90 and NRLMSISE-00 models) for monitoring emission rates at a low-latitude station (Tirunelveli in Tamil Nadu).
The results they obtained indicate that the emission rate for the MSISE-90 model varies more than for the NRLMSISE-00 model. In the case of the MSISE-90 model, the maximum depletion in the emission rates of dayglow was found to be about 30% at 96 km during the main phase of the one of the geomagnetic storms investigated.
The density of oxygen molecules dropped by about 22% at 96 km during the main phase of the same geomagnetic storm. The NRLSMSISE-00 model did not cause any appreciable change in the number density of oxygen atoms during either of the two events. The present study also showed that geomagnetic storms do not affect the altitude of the peak emission rate.