Energy Spectra, Composition, and Other Properties of Ground-Level Events During Solar Cycle 23

Mewaldt, R. A.; Looper, M. D.; Cohen, C. M. S.; Haggerty, D. K.; Labrador, A. W.; Leske, R. A.; Mason, G. M.; Mazur, J. E.; Rosenvinge, T. T. von

doi:10.1007/s11214-012-9884-2

Cited by 159 publications

(171 citation statements)

References 67 publications

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“…The Band function is constructed in such a way that both the function and its first derivative are continuous. Recently, the Band function has been shown to approximate well the energetic particle spectra in the GLEs of solar cycle 23 measured by instruments on the ACE, GOES, SAMPEX and STEREO spacecraft (Mewaldt et al, 2012) and GLE71 measured by the PAMELA experiment (Asvestari et al, 2017), as well as proton and heavy ion spectra of large SEP events measured by instruments on the ACE, SAMPEX, SOHO and GOES spacecraft (Desai et al, 2016a, b). The original Tylka and Dietrich (2009) GLE analysis was extended through 2012 using data from GOES spacecraft 2 and the worldwide NM network.…”

Section: Previous Models Of Sepsmentioning

confidence: 97%

Two solar proton fluence models based on ground level enhancement observations

Raukunen

Vainio

Tylka

et al. 2018

J. Space Weather Space Clim.

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: Previous Models Of Sepsmentioning

confidence: 97%

Two solar proton fluence models based on ground level enhancement observations

Raukunen

Vainio

Tylka

et al. 2018

J. Space Weather Space Clim.

158

View full text Add to dashboard Cite

show abstract

“…(Mewaldt 2006;Mewaldt et al 2012) 10 cm −2 s −1 for cycle 21 up to 70 cm −2 s −1 for cycle 19 (Reedy 2012). Moreover, estimates of the SEP flux were quite uncertain during the earlier years of space-borne measurements because of two effects, which are hard to account for (e.g., Reeves et al 1992;Tylka et al 1997).…”

Section: Solar Energetic Particles In the Pastmentioning

confidence: 99%

A history of solar activity over millennia

Usoskin

2017

Living Rev Sol Phys

359

235

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Presented here is a review of present knowledge of the long-term behavior of solar activity on a multi-millennial timescale, as reconstructed using the indirect proxy method. The concept of solar activity is discussed along with an overview of the special indices used to quantify different aspects of variable solar activity, with special emphasis upon sunspot number. Over long timescales, quantitative information about past solar activity can only be obtained using a method based upon indirect proxies, such as the cosmogenic isotopes 14 C and 10 Be in natural stratified archives (e.g., tree rings or ice cores). We give an historical overview of the development of the proxy-based method for past solar-activity reconstruction over millennia, as well as a description of the modern state. Special attention is paid to the verification and cross-calibration of reconstructions. It is argued that this method of cosmogenic isotopes makes a solid basis for studies of solar variability in the past on a long timescale (centuries to millennia) during the Holocene. A separate section is devoted to reconstructions of strong solar energetic-particle (SEP) events in the past, that suggest that the present-day average SEP flux is broadly consistent with estimates on longer timescales, and that the occurrence of extra-strong events is unlikely. Finally, the main features of the long-term evolution of solar magnetic activity, including the

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“…It was found that the GLE spectra tend to be slightly harder than non-GLE spectra and that they are consistent with double power laws (Mewaldt et al 2012;Kühl et al 2016). Also, the authors found that the composition of GLEs tends to have higher Fe/O ratios, enrichments in 3 He (Wiedenbeck 2013) and highly-ionized charge-states of heavy elements such as Fe.…”

Section: Introductionmentioning

confidence: 85%

“…1 and 2 for details) also confirms the conclusion that gradual SEP events are accelerated by large CMEdriven shocks . These events produce some of the highest intensity events observed at Earth at energies up to several GeV (Mewaldt et al 2012;Kühl et al 2016).…”

Section: Introductionmentioning

confidence: 99%