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Algorithm for Detecting an Extreme Solar Flare of September 6, 2017 from its Geomagnetic Precursors

Fri, 06/05/2020 - 00:00

The efficiency of the previously developed algorithm for predicting extreme solar flares from their geomagnetic precursors has been tested on the example of a series of class X flares recorded on September 6, 2017. Over the past few years, these events of the solar flare activity are seen as the most intense. The algorithm consists in comparing the total histograms of the normalized number of synchronization moments for oscillations of long-period pulsations in the horizontal component of the geomagnetic field with extreme solar flare events in the intervals preceding them. The result of the algorithm is that extrema of histograms were detected a few days before the development of intense solar flares and can be considered as markers of the expected extreme flare activity. The study confirms the possibility of using the previously proposed algorithm for a short-term forecast of solar flare activity.

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Radio Emission of Rydberg Atoms in the Upper Atmosphere Modified by High-Power HF Radio Waves

Fri, 06/05/2020 - 00:00

We report on the results of studying the radio emission of the Rydberg states of atoms and molecules in the Earth’s upper atmosphere at ionospheric altitudes when the ionosphere is modified by high-power HF radio waves radiated by the Sura heating facility. Radio emission from the upper atmosphere, caused by the emission of highly excited Rydberg atoms and molecules with the principal quantum number n = 163–169 and n = 225 (decimeter wavelength range) and two spectral features that coincide with the frequencies of transitions between Rydberg states m = 169 → n = 168 with the transition frequency νn = 1375.35 MHz and m = 166 → n = 165 with νn = 1451.5 MHz were detected. Characteristic altitudes of the Rydberg radiation generation region were 150–250 km. The radio emission intensity corresponds to 10–45 K, which is comparable with the intensity of the radio emission generated during solar flares.

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