Solar Flare 1/f Fluctuations from Amplitude-Modulated Five-Minute Oscillation
We first report that the solar flare time sequence exhibits a fluctuation characterized by its power spectral density being inversely proportional to the signal frequency. This is the 1/f fluctuation, or pink noise, observed ubiquitously in nature. Using GOES16 data, we found that low-energy flares...
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MDPI AG
2023-11-01
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| Online Access: | https://www.mdpi.com/1099-4300/25/12/1593 |
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| author | Masahiro Morikawa Akika Nakamichi |
| author_facet | Masahiro Morikawa Akika Nakamichi |
| author_sort | Masahiro Morikawa |
| collection | DOAJ |
| description | We first report that the solar flare time sequence exhibits a fluctuation characterized by its power spectral density being inversely proportional to the signal frequency. This is the 1/f fluctuation, or pink noise, observed ubiquitously in nature. Using GOES16 data, we found that low-energy flares (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>E</mi><mo>≤</mo><msub><mi>E</mi><mrow><mi>m</mi><mi>e</mi><mi>a</mi><mi>n</mi></mrow></msub></mrow></semantics></math></inline-formula>) display 1/f fluctuations, whereas high-energy flares (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>E</mi><mo>></mo><msub><mi>E</mi><mrow><mi>m</mi><mi>e</mi><mi>a</mi><mi>n</mi></mrow></msub></mrow></semantics></math></inline-formula>) show a flat spectrum. Furthermore, we found that the timing sequence of the flares reveals clearer 1/f fluctuations. These observations suggest that the solar flare 1/f fluctuations are associated with low-energy phenomena. We investigated the origin of these 1/f fluctuations based on our recent hypothesis: 1/f fluctuations arise from amplitude modulation and demodulation. We propose that this amplitude modulation is encoded by the resonance with the solar five-minute oscillation (SFO) and demodulated by magnetic reconnections. We partially demonstrate this scenario by analyzing the SFO eigenmodes resolving the frequency degeneration in the azimuthal order number <i>m</i> using the solar rotation and resonance. Given the robust nature of 1/f fluctuations, we speculated that the solar flare 1/f fluctuations may be inherited by the various phenomena around the Sun, such as the sunspot numbers and cosmic rays. In addition, we draw parallels between solar flares and earthquakes, both exhibiting 1/f fluctuations. Interestingly, the analysis applied to solar flares can also be adapted to earthquakes if we read the SFO as Earth’s free oscillation and magnetic reconnections as fault ruptures. Moreover, we point out the possibility that the same analysis also applies to the activity of a black hole/disk system if we read the SFO as the quasi-periodic oscillation of a black hole. |
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| language | English |
| last_indexed | 2024-03-08T20:48:05Z |
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| spelling | doaj.art-c760f974d28f4e36abc70f37620a82fc2023-12-22T14:07:17ZengMDPI AGEntropy1099-43002023-11-012512159310.3390/e25121593Solar Flare 1/f Fluctuations from Amplitude-Modulated Five-Minute OscillationMasahiro Morikawa0Akika Nakamichi1Department of Physics, Ochanomizu University, 2-1-1 Otsuka, Bunkyo, Tokyo 112-8610, JapanGeneral Education, Kyoto Sangyo University, Motoyama Kamigamo Kita-ku, Kyoto 603-8555, JapanWe first report that the solar flare time sequence exhibits a fluctuation characterized by its power spectral density being inversely proportional to the signal frequency. This is the 1/f fluctuation, or pink noise, observed ubiquitously in nature. Using GOES16 data, we found that low-energy flares (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>E</mi><mo>≤</mo><msub><mi>E</mi><mrow><mi>m</mi><mi>e</mi><mi>a</mi><mi>n</mi></mrow></msub></mrow></semantics></math></inline-formula>) display 1/f fluctuations, whereas high-energy flares (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>E</mi><mo>></mo><msub><mi>E</mi><mrow><mi>m</mi><mi>e</mi><mi>a</mi><mi>n</mi></mrow></msub></mrow></semantics></math></inline-formula>) show a flat spectrum. Furthermore, we found that the timing sequence of the flares reveals clearer 1/f fluctuations. These observations suggest that the solar flare 1/f fluctuations are associated with low-energy phenomena. We investigated the origin of these 1/f fluctuations based on our recent hypothesis: 1/f fluctuations arise from amplitude modulation and demodulation. We propose that this amplitude modulation is encoded by the resonance with the solar five-minute oscillation (SFO) and demodulated by magnetic reconnections. We partially demonstrate this scenario by analyzing the SFO eigenmodes resolving the frequency degeneration in the azimuthal order number <i>m</i> using the solar rotation and resonance. Given the robust nature of 1/f fluctuations, we speculated that the solar flare 1/f fluctuations may be inherited by the various phenomena around the Sun, such as the sunspot numbers and cosmic rays. In addition, we draw parallels between solar flares and earthquakes, both exhibiting 1/f fluctuations. Interestingly, the analysis applied to solar flares can also be adapted to earthquakes if we read the SFO as Earth’s free oscillation and magnetic reconnections as fault ruptures. Moreover, we point out the possibility that the same analysis also applies to the activity of a black hole/disk system if we read the SFO as the quasi-periodic oscillation of a black hole.https://www.mdpi.com/1099-4300/25/12/15931/f fluctuationssolar flaresolar five-minute oscillationresonanceamplitude modulation |
| spellingShingle | Masahiro Morikawa Akika Nakamichi Solar Flare 1/f Fluctuations from Amplitude-Modulated Five-Minute Oscillation Entropy 1/f fluctuations solar flare solar five-minute oscillation resonance amplitude modulation |
| title | Solar Flare 1/f Fluctuations from Amplitude-Modulated Five-Minute Oscillation |
| title_full | Solar Flare 1/f Fluctuations from Amplitude-Modulated Five-Minute Oscillation |
| title_fullStr | Solar Flare 1/f Fluctuations from Amplitude-Modulated Five-Minute Oscillation |
| title_full_unstemmed | Solar Flare 1/f Fluctuations from Amplitude-Modulated Five-Minute Oscillation |
| title_short | Solar Flare 1/f Fluctuations from Amplitude-Modulated Five-Minute Oscillation |
| title_sort | solar flare 1 f fluctuations from amplitude modulated five minute oscillation |
| topic | 1/f fluctuations solar flare solar five-minute oscillation resonance amplitude modulation |
| url | https://www.mdpi.com/1099-4300/25/12/1593 |
| work_keys_str_mv | AT masahiromorikawa solarflare1ffluctuationsfromamplitudemodulatedfiveminuteoscillation AT akikanakamichi solarflare1ffluctuationsfromamplitudemodulatedfiveminuteoscillation |