A Study of the Possible Mechanism of the Ground Level Enhancement on 28 October 2021
Search citation statements
Paper Sections
Citation Types
Year Published
Publication Types
Relationship
Authors
Journals
Cited by 3 publications
References 75 publications
Characterizing High-Energy Solar Proton Events with Energies Below and Above 100 MeV
We analyzed 58 high-energy proton events that occurred during the years 1996 – 2022. In 32 out of the 58 (55%) events, the proton energies extended up to $\sim 68$ ∼ 68 MeV but did not reach 100 MeV. In the remaining 26 events, the proton energies exceeded 100 MeV. We studied the differences in the characteristics of these proton events and their associations with solar and interplanetary phenomena to improve understanding proton sources and acceleration processes.The coronal mass ejections (CMEs) associated with $>100$ > 100 MeV proton events appeared to be, on average, more energetic than those associated with $< 100$ < 100 MeV proton events. The peak and integrated fluxes (fluence) of the soft X-ray (SXR) flares were higher in > 100 MeV proton events, but there was almost no difference in the rise times of the flares. In a major part of the $> 100$ > 100 MeV proton events, protons were released over the rise phase of the SXR flares, whereas in most of the $<100$ < 100 MeV events the proton releases occurred after the peak of the SXR flares. We established limits for the CME speed VCME and SXR peak flux Fpk or total fluence Fi, which helped us to distinguish the events in the two groups. Solar eruptions with VCME$> 1000$ > 1000 km s−1 and F$_{\mathrm{pk}} > 5 \cdot 10^{-5} $ > pk 5 ⋅ 10 − 5 W m−2 had a high probability to produce proton events of $> 100$ > 100 MeV. On the other hand, eruptions with V$_{\mathrm{CME}} > 900$ > CME 900 km s−1 and F$_{i} <5 \cdot 10^{-4} $ < i 5 ⋅ 10 − 4 J m−2 and eruptions with V$_{ \mathrm{CME}} < 900$ < CME 900 km s−1 irrespective of the SXR total fluence were very likely to produce proton events of $< 100$ < 100 MeV.All proton events were associated with decametric Type III radio bursts, and most of them had Type II bursts associations either in metric or decametric–hectometric (DH) wavelengths or both. Both metric- and DH-Type II emissions were observed in 50% of $<100$ < 100 MeV proton events while they were observed in 88% of $>100$ > 100 MeV events. Our analysis showed that protons in most of the $>100$ > 100 MeV events were released low in the corona ($\leq 3.0$ ≤ 3.0 R⊙) before the onsets of the DH-Type II radio bursts. Conversely, protons in most of the $<100$ < 100 MeV events were released higher in the corona ($>3$ > 3 R⊙) and after the DH-Type II onsets.We conclude that protons in most of the $> 100$ > 100 MeV events are accelerated either by the flare reconnection processes or by shocks low in the corona and could undergo reacceleration higher in the corona in CME shocks manifested in DH-Type II radio emission. In the $<100$ < 100 MeV events, protons are mainly accelerated in CME shocks at coronal heights $>3$ > 3 R⊙.
Characterizing High-Energy Solar Proton Events with Energies Below and Above 100 MeV
We analyzed 58 high-energy proton events that occurred during the years 1996 – 2022. In 32 out of the 58 (55%) events, the proton energies extended up to $\sim 68$ ∼ 68 MeV but did not reach 100 MeV. In the remaining 26 events, the proton energies exceeded 100 MeV. We studied the differences in the characteristics of these proton events and their associations with solar and interplanetary phenomena to improve understanding proton sources and acceleration processes.The coronal mass ejections (CMEs) associated with $>100$ > 100 MeV proton events appeared to be, on average, more energetic than those associated with $< 100$ < 100 MeV proton events. The peak and integrated fluxes (fluence) of the soft X-ray (SXR) flares were higher in > 100 MeV proton events, but there was almost no difference in the rise times of the flares. In a major part of the $> 100$ > 100 MeV proton events, protons were released over the rise phase of the SXR flares, whereas in most of the $<100$ < 100 MeV events the proton releases occurred after the peak of the SXR flares. We established limits for the CME speed VCME and SXR peak flux Fpk or total fluence Fi, which helped us to distinguish the events in the two groups. Solar eruptions with VCME$> 1000$ > 1000 km s−1 and F$_{\mathrm{pk}} > 5 \cdot 10^{-5} $ > pk 5 ⋅ 10 − 5 W m−2 had a high probability to produce proton events of $> 100$ > 100 MeV. On the other hand, eruptions with V$_{\mathrm{CME}} > 900$ > CME 900 km s−1 and F$_{i} <5 \cdot 10^{-4} $ < i 5 ⋅ 10 − 4 J m−2 and eruptions with V$_{ \mathrm{CME}} < 900$ < CME 900 km s−1 irrespective of the SXR total fluence were very likely to produce proton events of $< 100$ < 100 MeV.All proton events were associated with decametric Type III radio bursts, and most of them had Type II bursts associations either in metric or decametric–hectometric (DH) wavelengths or both. Both metric- and DH-Type II emissions were observed in 50% of $<100$ < 100 MeV proton events while they were observed in 88% of $>100$ > 100 MeV events. Our analysis showed that protons in most of the $>100$ > 100 MeV events were released low in the corona ($\leq 3.0$ ≤ 3.0 R⊙) before the onsets of the DH-Type II radio bursts. Conversely, protons in most of the $<100$ < 100 MeV events were released higher in the corona ($>3$ > 3 R⊙) and after the DH-Type II onsets.We conclude that protons in most of the $> 100$ > 100 MeV events are accelerated either by the flare reconnection processes or by shocks low in the corona and could undergo reacceleration higher in the corona in CME shocks manifested in DH-Type II radio emission. In the $<100$ < 100 MeV events, protons are mainly accelerated in CME shocks at coronal heights $>3$ > 3 R⊙.
The multi-spacecraft high-energy solar particle event of 28 October 2021
Aims. We studied the first multi-spacecraft high-energy solar energetic particle (SEP) event of solar cycle 25, which triggered a ground level enhancement on 28 October 2021, using data from multiple observers (Parker Solar Probe, STEREO-A, Solar Orbiter, GOES, SOHO, BepiColombo, and the Mars Science Laboratory) that were widely distributed throughout the heliosphere and located at heliocentric distances ranging from 0.60 to 1.60 AU. Methods. We present SEP observations at a broad energy range spanning from ∼10 to 600 MeV obtained from the different instruments. We performed detail modelling of the shock wave and we derived the 3D distribution and temporal evolution of the shock parameters. We further investigated the magnetic connectivity of each observer to the solar surface and examined the shock’s magnetic connection. We performed velocity dispersion analysis and time-shifting analysis to infer the SEP release time. We derived and present the peak proton flux spectra for all the above spacecraft and fluence spectra for major species recorded on board Solar Orbiter from the Suprathermal Ion Spectrograph (SIS). We performed 3D SEP propagation simulations to investigate the role of particle transport in the distribution of SEPs to distant magnetically connected observers. Results. Observations and modelling show that a strong shock wave formed promptly in the low corona. At the SEP release time windows, we find a connection with the shock for all the observers. PSP, STEREO-A, and Solar Orbiter were connected to strong shock regions with high Mach numbers (>4), whereas the Earth and other observers were connected to lower Mach numbers. The SEP spectral properties near Earth demonstrate two power laws, with a harder (softer) spectrum in the low-energy (high-energy) range. Composition observations from SIS (and near-Earth instruments) show no serious enhancement of flare-accelerated material. Conclusions. A possible scenario consistent with the observations and our analysis indicates that high-energy SEPs at PSP, STEREO-A, and Solar Orbiter were dominated by particle acceleration and injection by the shock, whereas high-energy SEPs that reached near-Earth space were associated with a weaker shock; it is likely that efficient transport of particles from a wide injection source contributed to the observed high-energy SEPs. Our study cannot exclude a contribution from a flare-related process; however, composition observations show no evidence of an impulsive composition of suprathermals during the event, suggestive of a non-dominant flare-related process.
On the Possible Mechanisms of the SEP Event and Electron Enhancement over the SEP Decay Phase on 2023 August 5
We carry out this study on the solar energetic particle (SEP) event that occurred on 2023 August 5 over the ascending phase of the current solar cycle 25. It is found that the SEP event might have been initiated by the M1.6 flare, while the SEP peak was caused by the coronal shock manifested in DH-type II radio burst over the propagation phase of a halo coronal mass ejection (CME; ∼1000 km s−1), thus creating a mixed SEP event. There were two enhancements of the electron fluxes lying over the SEP rise and decay phase. It is surprising that, despite a stronger flare (X1.6) and a faster halo CME (∼1647 km s−1), there was no SEP enhancement during the second enhancement of the electron fluxes. In order to investigate this, we make an additional effort to analyze the X1.6 flare based on the availability of the temporal, spectral, and spatial evolution of the electromagnetic radiation components. It is observed that the CME shock was aligned with the flare eruption direction and was close to the western limb (W77°), and thus the radially moving CME shock missed the Earth. In another development, it is observed that the electron impulsive phase lies over the type III radio bursts, indicating that the electrons might have escaped directly during the eruption. The radio flux and radio dynamic spectra of a higher frequency lie over the rise phase of the soft X-ray derivative, indicating that a large number of electrons travelled through magnetic fields.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
Contact Info
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Product
Resources
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
Copyright © 2025 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.
