Broken Power-law Energy Spectra of the Accelerated Electrons Detected in Radio and Hard X-Rays during the SOL2013-05-13 Event

Author(s)

da Silva, Douglas Felix ^{[1, 2]} ; Valio, Adriana ^[2]

Affiliation

^[1] Chinese Acad Sci, NSSC, Lab Space Weather, Beijing - Peoples R China

^[2] Univ Prebiteriana Mackenzie, Ctr Radio Astron & Astrophys Mackenzie, Sao Paulo - Brazil

• Document type: Journal article
• Source: Astrophysical Journal Letters; v. 915, n. 1 JUL 2021.
• Web of Science Citations: 0

Abstract

Solar flares, resulting from magnetic activity of the Sun, are among the most energetic events in the solar system and in extreme cases directly affect our highly technological society. In this work, we analyze a solar flare detected at millimeter and centimeter wavelengths, as well as X-rays above 1 MeV. Observations of solar flares at these energy bands provide diagnostics of the energetic accelerated electrons and the magnetic fields where the emission is produced. During the SOL2013-05-13 solar flare, radio data were obtained by the telescope system POlarisation Emission of Millimeter Activity at the Sun, which observes the Sun at 45 and 90 GHz with polarization measurements, and at microwaves (1-15 GHz) by the Radio Solar Telescope Network. For the same event, X-ray emission was detected by the RHESSI and Fermi satellites. Spectra at both wavelengths were constructed and fit separately to yield the accelerated electron energy distribution that produced the emission. The optically thin radio spectral index was calculated by fitting the Ramaty model of gyrosynchrotron emission to the observed radio spectrum, whereas the hard X-ray spectral index was obtained from the spectral fit assuming a thermal emission model plus a nonthermal broken power-law distribution. Finally, both spectral indexes were compared and confirmed that the index obtained from the radio spectrum agrees with the index of the X-ray spectrum for energies above the break energy of similar to 600 keV. Thus, the hard X-rays more energetic than 600 keV and high radio frequencies of solar flares are emitted by the same population of high-energy accelerated electrons. This result indicates that the accelerated electrons have an energy distribution best represented by a broken power law, with a breakup above energies around 1 MeV. (AU)

• FAPESP's process: 09/50637-0 - Solar patrol polarization telescopes at 45 and 90 GHz
• Grantee: Adriana Benetti Marques Valio
• Support type: Regular Research Grants
• FAPESP's process: 13/10559-5 - Investigation of high energy and plasma astrophysics phenomena: theory, numerical simulations, observations, and instrument development for the Cherenkov Telescope Array (CTA)
• Grantee: Elisabete Maria de Gouveia Dal Pino
• Support type: Research Projects - Thematic Grants
• FAPESP's process: 13/24155-3 - Solar flare diagnostic in an unprecedented frequency range from microwaves to THz frequencies: challenges for interpretation (flat)
• Grantee: Carlos Guillermo Giménez de Castro
• Support type: Research Projects - Thematic Grants