Energetic and relativistic nuclei and electron experiment of the SOHO mission

Валтонен, Э.; Peltonen, J.; Peltonen, P.; Eronen, T.; Hoisko, E.; Louhola, M.; Lumme, M.; Nieminen, A.-L.; Riihonen, E.; Teittinen, M.; Torsti, J.; Ahola, Kimmo; Holmlund, Christer; Kelhä, Väinö; Leppälä, Kari; Ruuska, Pekka; Strömmer, Esko; Verkasalo, Raimo; Koivula, E.; Moilanen, Marko

doi:10.1016/s0168-9002(97)00469-5

Cited by 14 publications

(8 citation statements)

References 12 publications

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“…At high energies these cases can be better distinguished because of a more rapid fall of the proton intensities. However, the ERNE High Energy Detector has a very large geometric factor (∼20-40 cm 2 sr; Valtonen et al 1997;Torsti et al 1995) often causing saturation during very large SEP events. Therefore, events following larger events before the recovery of the instrument may be missed.…”

Section: Proton Event Selectionmentioning

confidence: 99%

Properties of solar energetic particle events inferred from their associated radio emission

Kouloumvakos

Nindos

Валтонен

et al. 2015

A&A

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Aims. We study selected properties of solar energetic particle (SEP) events as inferred from their associated radio emissions. Methods. We used a catalogue of 115 SEP events, which consists of entries of proton intensity enhancements at one AU, with complete coverage over solar cycle 23 based on high-energy (∼68 MeV) protons from SOHO/ERNE. We also calculated the proton release time at the Sun using velocity dispersion analysis (VDA). After an initial rejection of cases with unrealistic VDA path lengths, we assembled composite radio spectra for the remaining events using data from ground-based and space-borne radio spectrographs. We registered the associated radio emissions for every event, and we divided the events in groups according to their associated radio emissions. In cases of type III-associated events, we extended our study to the timings between the type III radio emission, the proton release, and the electron release as inferred from VDA based on Wind/3DP 20-646 keV data. Results. The proton release was found to be most often accompanied by both type III and II radio bursts, but a good association percentage was also registered in cases accompanied by type IIIs only. The worst association was found for the cases only associated with type II. In the type III-associated cases, we usually found systematic delays of both the proton and electron release times as inferred by the particles' VDAs, with respect to the start of the associated type III burst. The comparison of the proton and electron release times revealed that, in more than half of the cases, the protons and electrons were simultaneously released within the statistical uncertainty of our analysis. For the cases with type II radio association, we found that the distribution of the proton release heights had a maximum at ∼2.5 R . Most (69%) of the flares associated with our SEP events were located in the western hemisphere, with a peak within the well-connected region of 50• -60• western longitude. Conclusions. Both flare-and shock-related particle release processes are observed in major proton events at >50 MeV. Typically, the protons are released after the start of the associated type III bursts and simultaneously or before the release of energetic electrons. Our study indicates that a clear-cut distinction between flare-related and CME-related SEP events is difficult to establish.

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Section: Proton Event Selectionmentioning

confidence: 99%

Properties of solar energetic particle events inferred from their associated radio emission

Kouloumvakos

Nindos

Валтонен

et al. 2015

A&A

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“…As a second criterion we want to select the high energy (E > 20 MeV nuc −1 ) range both for H, as the basic SEP reference element, and for the most common hi-Z elements. We use H data from the SOHO/Energetic and Relativistic Nuclei and Electron (ERNE) experiment [19]. Two sensors comprise the ERNE experiment and were designed to measure lower-energy particles (≤ 12 MeV nuc −1 , the LED) and higher energy particles (≥ 12 MeV nuc −1 , the HED).…”

Section: Data Analysis 21 Instrument Selectionmentioning

confidence: 99%

“…Two sensors comprise the ERNE experiment and were designed to measure lower-energy particles (≤ 12 MeV nuc −1 , the LED) and higher energy particles (≥ 12 MeV nuc −1 , the HED). Energy ranges for both H and He in the HED are 13.5-25.8 MeV nuc −1 and 25.8-50.7 MeV nuc −1 [19]. Only two-hour averaged H and He data are available via the public ERNE database, from which we select the combined 13.5-50.7 MeV H channels as the basic H energy range for SEP events.…”

Section: Data Analysis 21 Instrument Selectionmentioning

confidence: 99%

Variations of Heavy Ion Abundances Relative to Proton Abundances in Large Solar Energetic (E > 10 MeV) Particle Events.

Round¹,

Loper²,

Nava³

et al. 2019

Proceedings of 36th International Cosmic Ray Conference — PoS(ICRC2019)

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The elemental composition of heavy ions (with atomic number Z > 2) (hi-Z) in large gradual E > 10 MeV nuc −1 SEP events has been extensively studied in the 2-15 MeV nuc −1 range to determine the acceleration processes and transport properties of SEPs. These studies invariably are based on abundances relative to those of a single element such as C or O and often neglect H and He, the elements of primary interest for space weather. The total radiation of an SEP event is determined not only by the H and He properties but also by those of hi-Z ions whose abundances and variations relative to H from one event to another are unknown. We report a study to determine those variations in a group of 15 large SEP events over the period 2000 to 2015. Five hi-Z ions (He, C, O, Mg, & Fe) were selected to determine variations of their fluences relative to those of H in the 13.5-50.7 MeV nuc −1 energy range for each SEP event. Our average hi-Z abundance ratios slightly exceed those reported by [1] at lower energies, with the Fe event abundances showing the largest standard deviation of an order of magnitude. The event abundances were weakly correlated with H fluences and strongly correlated with speeds Vcme of associated coronal mass ejections (CMEs). These correlations may be evidence of streaming limits in the shock regions of H in the largest events.

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“…The particle observations were made with the Energetic and Relativistic Nuclei and Electron (ERNE) instrument onboard the Solar and Heliospheric Observatory (SOHO) (Torsti et al 1995;Valtonen et al 1997). ERNE consists of two particle detectors, the Low Energy Detector (LED) and High Energy Detector (HED).…”

Section: Observationsmentioning

confidence: 99%

Iron-rich solar particle events measured by SOHO/ERNE during two solar cycles

Raukunen

Валтонен

Vainio

2016

A&A

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Aims. We study the differences in the heavy ion composition of solar energetic particle (SEP) events between solar cycles 23 and 24. Methods. We have surveyed the SOHO/ERNE heavy ion data from the beginning of solar cycle 23 until the end of June 2015, that is, well into the declining phase of cycle 24. We used this long observation period to study the properties of heavy ions (from C to Fe) and to compare the two solar cycles in this respect. We surveyed the data for SEP events with enhancements in the Fe/C and Fe/O intensity ratios in the energy range 5-15 MeV per nucleon, and associated the events with solar flare and coronal mass ejections (CME) when possible. We studied the properties of heavy ions in these events and compared the average relative abundances of heavy ions between the two solar cycles. Results. We found that fewer days had C and O intensities higher than~10 −3 cm −2 sr −1 s −1 (MeVn −1 ) −1 during solar cycle 24 than during cycle 23. For Fe this difference was clear even at lower intensities. We also found that fewer days had Fe/(C+O) > 0.183 during cycle 24. We identified 86 SEP events with at least one Fe-rich day, 65 of which occurred during cycle 23 and only 21 during cycle 24. We found that impulsive events have been almost completely absent during cycle 24. Mean abundances of heavy ions in the events were found to be significantly lower during cycle 24 than in cycle 23. Our results reflect the reduced solar activity in cycle 24 and indicate lower efficiency of particle acceleration processes for both gradual and impulsive SEP events in cycle 24.

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Energetic and relativistic nuclei and electron experiment of the SOHO mission

Cited by 14 publications

References 12 publications

Properties of solar energetic particle events inferred from their associated radio emission

Properties of solar energetic particle events inferred from their associated radio emission

Variations of Heavy Ion Abundances Relative to Proton Abundances in Large Solar Energetic (E > 10 MeV) Particle Events.

Iron-rich solar particle events measured by SOHO/ERNE during two solar cycles

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