Variations in number of lightning discharge radio pulses by observations in Yakutsk

The main natural source of very low-frequency radiation (LFR: 3–30 kHz) is a lightning discharge which generates radio pulses, namely atmospherics. The atmospherics were registered in the period from 2001–2015 30 km away from Yakutsk (62N; 129,72 E) in the context of industrial noise-free environment. A receive path corresponds to a band of ground lightning discharge's energy concentration: 0,3–10 kHz. The threshold level of a field, received by a frame antenna $\sim$2 mV/m, which provides an opportunity to register radio pulses at night propagation conditions is up to $\sim$6 000 km. The specific period of a daily variation: minimum 3–7 UT (minimum thunderstorm activity, maximum radio signal attenuation); the summer maximum 8–12 UT (influence of local thunderstorms, maximum signal attenuation); the winter and summer maximum 15–19 UT (minimum attenuation in radio signal propagation). The variation of maximums 17 h (UT) – 230 % (summer to winter) and 9 h (UT) — 2 600 % (local thunderstorms in summer). The 11-year variation is a half-wave with the maximum of 1 year earlier than the minimum of solar activity. The flow of atmospherics is in an antiphase with the solar activity and in a phase with the variation of cosmic rays. From the maximum to the minimum of the solar activity (2001–2007) the change of radio pulse flow 3–7 UT has comprised 59 and 13 times; 15–19 UT comprised 38 and 5 times; 8–12 UT comprised 34 and 8 in winter and summer, respectively. According to our observations, by registering radio signals of a radio navigation system RSDN-20, in the radio path Novosibirsk–Yakutsk the change of attenuation from the minimum to the maximum of the solar activity is 120 %. Taking into account the propagation, the ratio between the number of atmospherics, accepted in the minimum of the solar activity (2009) and the maximum (2013) for summer months is 159 %.