Why is solar cycle 24 an inefficient producer of high-energy particle events?

Vainio, R.; Raukunen, Osku; Tylka, A. J.; Dietrich, William F.; Afanasiev, Alexandr

doi:10.1051/0004-6361/201730547

Cited by 24 publications

(22 citation statements)

References 28 publications

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“…Recently, Sandberg et al (2014) developed a method for cross-calibrating the medium energy GOES/EPS channels with corresponding channels of the science-level IMP-8/GME instrument. The effect of this cross-correlation was validated by Rodriguez et al (2017) using STEREO observations (Mewaldt et al, 2008;von Rosenvinge et al, 2008). Sandberg et al (2014) also noted some problems with the low energy IMP-8 data, attributed to the gradual failing of the LED instrument between 1984 and 1990.…”

Section: Summary and Discussionmentioning

confidence: 82%

“…The agreement suggests that during the solar cycles 19-24, on average, GLEs have been responsible for a major portion of fluence even at low energies. On shorter timescales this is not necessarily the case; for example, during the first eight years of cycle 24 the total proton fluence at >10 MeV from sub-GLEs, calculated with the Band-fits (parameters given in Vainio et al, 2017), was about 7.9 ⋅ 10 8 cm À2 sr À1 , whereas the only GLE of the period produced a fluence of about 6.6 ⋅ 10 6 cm À2 sr À1 , i.e., two orders of magnitude smaller.…”

Section: Summary and Discussionmentioning

confidence: 99%

“…The spectral parameters (and their uncertainties) for sub-GLEs occurring in solar cycles 20-22 are given in Table 3. The parameters for the sub-GLEs occurring in cycles 23 and 24 are listed in Vainio et al (2017). Figure 10 shows the response (number of counts measured) of a high-latitude NM, DN, (in arbitrary units) for both GLEs and sub-GLEs, calculated with the equation…”

Section: Small Glesmentioning

confidence: 99%

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Two solar proton fluence models based on ground level enhancement observations

Raukunen

Vainio

Tylka

et al. 2018

J. Space Weather Space Clim.

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158

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-Solar energetic particles (SEPs) constitute an important component of the radiation environment in interplanetary space. Accurate modeling of SEP events is crucial for the mitigation of radiation hazards in spacecraft design. In this study we present two new statistical models of high energy solar proton fluences based on ground level enhancement (GLE) observations during solar cycles 19-24. As the basis of our modeling, we utilize a four parameter double power law function (known as the Band function) fits to integral GLE fluence spectra in rigidity. In the first model, the integral and differential fluences for protons with energies between 10 MeV and 1 GeV are calculated using the fits, and the distributions of the fluences at certain energies are modeled with an exponentially cut-off power law function. In the second model, we use a more advanced methodology: by investigating the distributions and relationships of the spectral fit parameters we find that they can be modeled as two independent and two dependent variables. Therefore, instead of modeling the fluences separately at different energies, we can model the shape of the fluence spectrum. We present examples of modeling results and show that the two methodologies agree well except for a short mission duration (1 year) at low confidence level. We also show that there is a reasonable agreement between our models and three well-known solar proton models (JPL, ESP and SEPEM), despite the differences in both the modeling methodologies and the data used to construct the models.

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Section: Summary and Discussionmentioning

confidence: 82%

Section: Summary and Discussionmentioning

confidence: 99%

Section: Small Glesmentioning

confidence: 99%

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Two solar proton fluence models based on ground level enhancement observations

Raukunen

Vainio

Tylka

et al. 2018

J. Space Weather Space Clim.

Self Cite

158

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“…This variability is present only in the inner corona (below~3 solar radii). In addition, there is strong lateral variability in seed particledensities in the corona which have been shown to be important factor controlling the highest energies obtained from the shock acceleration (Vainio et al, 2017). These factors give rise to very localised regions Fig.…”

Section: Cumulative Fluence Model Progressionmentioning

confidence: 99%

Updated Model of the Solar Energetic Proton Environment in Space

Jiggens

Heynderickx

Sandberg³

et al. 2018

J. Space Weather Space Clim.

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-The Solar Accumulated and Peak Proton and Heavy Ion Radiation Environment (SAPPHIRE) model provides environment specification outputs for all aspects of the Solar Energetic Particle (SEP) environment. The model is based upon a thoroughly cleaned and carefully processed data set. Herein the evolution of the solar proton model is discussed with comparisons to other models and data. This paper discusses the construction of the underlying data set, the modelling methodology, optimisation of fitted flux distributions and extrapolation of model outputs to cover a range of proton energies from 0.1 MeV to 1 GeV. The model provides outputs in terms of mission cumulative fluence, maximum event fluence and peak flux for both solar maximum and solar minimum periods. A new method for describing maximum event fluence and peak flux outputs in terms of 1-in-x-year SPEs is also described. SAPPHIRE proton model outputs are compared with previous models including CREME96, ESP-PSYCHIC and the JPL model. Low energy outputs are compared to SEP data from ACE/EPAM whilst high energy outputs are compared to a new model based on GLEs detected by Neutron Monitors (NMs).

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“…The GLE dataset spans high-energy SEP events over almost seven solar cycles providing sufficient basis for statistical studies (e.g. Gopalswamy et al, 2014;Raukunen et al, 2017;Vainio et al, 2017). Since the beginning of systematic ground-based measurements of cosmic rays, over 70 GLEs have been "officially" registered so far (see the International GLE Database gle.oulu.fi).…”

Section: Introductionmentioning

confidence: 99%

GLE and Sub-GLE Redefinition in the Light of High-Altitude Polar Neutron Monitors

et al. 2017

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The conventional definition of ground level enhancement (GLE) events requires detection of solar energetic particles (SEP) by at least two differently located neutron monitors. Some places are exceptionally suitable for ground-based detection of SEP -high-elevation polar regions with negligible geomagnetic and reduced atmospheric energy/rigidity cutoffs. At present, there are two neutron-monitor stations in such locations on the Antarctic plateau: SOPO/SOPB (at Amundsen-Scott station, 2835 m elevation) and DOMC/ DOMB (at Concordia station, 3233 m elevation). Since 2015, when the DOMC/ DOMB station started continuous operation, a relatively weak SEP event, not detected by sea-level neutron-monitor stations, was registered by both SOPO/ SOPB and DOMC/DOMB and accordingly classified as a GLE. This would lead to a distortion of the homogeneity of the historic GLE list and the corresponding statistics. To address this issue, we propose to modify the GLE definition so that it keeps the homogeneity: A GLE event is registered when there are near-time coincident and statistically significant enhancements of the count rates of at least two differently located neutron monitors including at least one neutron monitor near sea level and a corresponding enhancement in the proton flux measured by a space-borne instrument(s). Relatively weak SEP events registered only by highaltitude polar neutron monitors, but with no response from cosmic-ray stations at sea level, can be classified as sub-GLEs.

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Why is solar cycle 24 an inefficient producer of high-energy particle events?

Cited by 24 publications

References 28 publications

Two solar proton fluence models based on ground level enhancement observations

Two solar proton fluence models based on ground level enhancement observations

Updated Model of the Solar Energetic Proton Environment in Space

GLE and Sub-GLE Redefinition in the Light of High-Altitude Polar Neutron Monitors

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