Variation of Atmospheric Noise with Sunspot Number During the 1600-2000 Hours Time Period at Delhi

Atmospheric noise data collected by the ARN-2 recorder at Delhi were examined to study the effect of sunspot number (SSN) on the year-to-year variations in the noise levels during 1600-2000 h. Since ionospheric propagation characteristics and thunderstorm activity undergo systematic hour-to-hour changes during this time period, the data were analysed on an hourly basis. The burst-noise-level data collected for one complete year were used for determining probable source locations and modes of propagation. The analysis showed that there is dependence on SSN when the noise is received in the burst form via the ionosphere. When the noise is not received in the burst form, the scatter of points is random, and contamination in the data is suspected. When noise is received from local thunderstorms by a ground wave, there is no clear evidence of any relationship between atmospheric noise and SSN.