WHISTLING CHARACTERISTICS DURING PERIODS OF IONOSPHERIC DISTURBANCES

Abstract

The results of observations of whistlers in obs. Karymshina (Kamchatka) in the period November-December 2008 are presented. This period was characterized by an excess of f0F2 values and a decrease in hF2 compared to the usual level. This effect was most clearly observed in Irkutsk, however, it also manifested itself in Kamchatka, although it was less pronounced. Such an event is explained [4] by both a change in the composition of the thermosphere and the appearance of the western component of the electric field and the electron concentration gradient at the maximum of disturbances. The latter is also associated with a change in the direction of the northern component of the interplanetary magnetic field [4]. Under normal conditions, the refractive index of VLF waves in daytime conditions is higher than at night [7], and the number of whistlers, on the contrary, is higher at night than during the day. On December 18-19, the appearance of whistling atmospherics in the daytime was observed in Kamchatka in the same amount as at night, about 10 1/min. At the same time, in the periods following the maximum changes in the ionosphere characteristics (23, 24, 27, 29, 30 December), there was a sharp increase in the number of whistles in the daytime to ∼50 1/min. It is possible that in this case the source of whistles were atmospheric discharges initiated in a typhoon, which were observed near the conjugate region in the southern hemisphere. The increase in the number of whistlers is associated with a change in the conditions of capture on the force line L = 2.4.

Keywords

• whistlers
• magnetic field
• electromagnetic radiation
• ionosphere.