Investigating Pre-flare Signatures in Spectroscopic Observations of an X9-class Solar Flare
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| Format: | Preprint |
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2026
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| _version_ | 1866911724136824832 |
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| author | Seyfritz, Louis Kazachenko, Maria French, Ryan |
| author_facet | Seyfritz, Louis Kazachenko, Maria French, Ryan |
| contents | On October 3rd, 2024, the Sun emitted an X9.0-class flare from active region NOAA 13842. The event was recorded by multiple space-based instruments, beginning hours before the eruption, granting a unique opportunity to provide insight into the flare's pre-flare phase. In this study, we employ analysis of Interface Region Imaging Spectrograph (IRIS) spectroscopic data to investigate pre-flaring phenomena associated with this flare. We present time-series and wavelet analysis of non-thermal velocity, Doppler velocity, and line intensity quantities of the IRIS Si IV 1403 angstrom line. We find two ranges of periodic oscillations during the pre-flare phase: ~7-10 min and ~18-21 min oscillations, with local enhancements occurring near the polarity inversion line. We also find a steady rise in Si IV line parameters beginning 3 hours before the flare in the same region, transitioning into strong non-thermal velocities and blueshifts ~15 minutes before onset. These findings are consistent with a slow destabilization of the coronal magnetic field, possibly driven by the gradual activation of a flux rope, followed by a rapid shift to intense reconnection activity leading to flare onset. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2605_07889 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Investigating Pre-flare Signatures in Spectroscopic Observations of an X9-class Solar Flare Seyfritz, Louis Kazachenko, Maria French, Ryan Solar and Stellar Astrophysics Plasma Physics Space Physics On October 3rd, 2024, the Sun emitted an X9.0-class flare from active region NOAA 13842. The event was recorded by multiple space-based instruments, beginning hours before the eruption, granting a unique opportunity to provide insight into the flare's pre-flare phase. In this study, we employ analysis of Interface Region Imaging Spectrograph (IRIS) spectroscopic data to investigate pre-flaring phenomena associated with this flare. We present time-series and wavelet analysis of non-thermal velocity, Doppler velocity, and line intensity quantities of the IRIS Si IV 1403 angstrom line. We find two ranges of periodic oscillations during the pre-flare phase: ~7-10 min and ~18-21 min oscillations, with local enhancements occurring near the polarity inversion line. We also find a steady rise in Si IV line parameters beginning 3 hours before the flare in the same region, transitioning into strong non-thermal velocities and blueshifts ~15 minutes before onset. These findings are consistent with a slow destabilization of the coronal magnetic field, possibly driven by the gradual activation of a flux rope, followed by a rapid shift to intense reconnection activity leading to flare onset. |
| title | Investigating Pre-flare Signatures in Spectroscopic Observations of an X9-class Solar Flare |
| topic | Solar and Stellar Astrophysics Plasma Physics Space Physics |
| url | https://arxiv.org/abs/2605.07889 |