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The Origin of Time Delays between Sub-Terahertz and Soft X-ray Emission from Solar Flares

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Abstract—

The time delays between sub-terahertz (sub-THz) and soft X-ray (SXR) emission from solar flares with a positive spectrum slope at frequencies of >100 GHz are considered. Based on a cross-correlation analysis of the time profiles of sub-THz and SXR emission from 11 flare events obtained from the KOSMA (230 GHz), SST (212 GHz), and RT-7.5 (93 GHz) telescopes, as well as the GOES satellite in channel 1–8 Å, we identified two main types of sub-THz events. Type I includes four X-class events with a well-defined Neupert effect, i.e., the sub-THz flux outpaces the SXR flux by 2–9 min. Type II includes seven M-class flares, in which the time profiles behave similarly and the delays do not exceed 30 s. The different mechanisms of radio emission in different layers of the solar atmosphere may be responsible for the positive slope of the sub-THz spectrum of flares.

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Funding

This work was supported by the Russian Foundation for Basic Research, project no. 20-52-26 006, Ministry of Education and Science, project no. 0831-2019-0006, and project nos. RVO:67985815 and 21-16508J (Grant Agency of the Czech Republic).

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Authors and Affiliations

  1. Crimean Astrophysical Observatory, Russian Academy of Sciences, Nauchnyi, Russia

    V. V. Smirnova & Yu. T. Tsap

  2. Central Astronomical Observatory at Pulkovo, Russian Academy of Sciences, 196140, St. Petersburg, Russia

    A. S. Morgachev & G. G. Motorina

  3. Astronomical Institute, Czech Academy of Sciences, 251 65, Ondřejov, Czech Republic

    G. G. Motorina & M. Bárta

Authors
  1. V. V. Smirnova
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  2. Yu. T. Tsap
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  3. A. S. Morgachev
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  4. G. G. Motorina
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  5. M. Bárta
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Corresponding author

Correspondence to V. V. Smirnova.

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Translated by O. Pismenov

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Smirnova, V.V., Tsap, Y.T., Morgachev, A.S. et al. The Origin of Time Delays between Sub-Terahertz and Soft X-ray Emission from Solar Flares. Geomagn. Aeron. 61, 993–1000 (2021). https://doi.org/10.1134/S0016793221070173

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  • DOI: https://doi.org/10.1134/S0016793221070173

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