Features of the Behavior of SE -Type Emission during a Substorm

A study was made of simultaneous observations of ultra-low-frequency oscillations in the 0.1–5.0 Hz frequency range of the serpentine emissions type (Serpentine Emissions, SE ) observed at the polar cap region and disturbances in the auroral zone. The unique analog magnetic records of the Vostok Antarctic Observatory (corrected geomagnetic coordinates Φ' = –85.41°, Λ' = 69.01°) have been digitized with a high resolution (20 Hz) and are freely available on the website of the World Data Center for Solar-Terrestrial Physics, Moscow. For 1966 (November and December), 1968 (March–July), and 1970–1972, 1973 (January–March) the behavior of “serpentine emissions” was analyzed during the development of 180 isolated substorms identified by variation in AL index. An interruption in the mode of generation of serpentine emissions in the region of the polar cap was found during the active phase of intense isolated substorms (with a maximum magnitude of the AE index of ∼500–600 nT). During the expansion phase of the substorms, broadband noise electromagnetic emission appears with a sharp leading edge in the Pc 1–2 range and is also recorded in the polar cap. Noise emission has a sharp leading edge and occurs approximately 2 hours after reorientation of the Bz -components of the interplanetary magnetic field (IMF) from north to south. The time of the interruption of SE coincides with the beginning this emission and moment of achievement Bz -component of maximum negative IMF values. Interruption of the SE effect is observed against the background of relatively stable other geoeffective parameters of the solar wind and IMF. The average duration of the interruption of emissions is ∼3 hours. Indirect confirmation of the impact of substorm activity on the SE generation regime is found in the coincidence of the patterns of daily and seasonal variation of SE interruption intervals and the probability of observing substorms. Due to the fact that noise emission occurs during the active phase of isolated substorms and ∼2 hours after reorientation of the Bz -components of the IMF in the solar wind, there is reason to believe that it is associated with plasma flows directed towards the Earth from the magnetotail. Apparently, the energy of plasma flows during the active phase of a substorm stimulates the appearance of noise emission, thus interrupting SE.