Causes of an ad 774–775 14C increase

  title={Causes of an ad 774–775 14C increase},
  author={Adrian L. Melott and Brian C. Thomas},
Arising from F. Miyake, K. Nagaya, K. Masuda & T. Nakamura 486, 240–242 (2012)10.1038/nature11123Atmospheric 14C production is a potential window into the energy of solar proton and other cosmic ray events. It was previously concluded that 14C results from ad 774–775 would require solar events that were orders of magnitude greater than known past events. We find that the coronal mass ejection energy based on 14C production is much smaller than claimed in ref. 1, but still substantially larger… 
Terrestrial effects of possible astrophysical sources of an AD 774‐775 increase in 14C production
This work considers solar proton events (SPEs) with three different fluences and two different spectra, and is able to rule out an event with a very soft spectrum that causes severe ozone depletion and subsequent biological impacts.
A solar super‐flare as cause for the 14C variation in AD 774/5?
We present further considerations regarding the strong 14C variation in AD 774/5. For its cause, either a solar super-flare or a short gamma-ray burst were suggested. We show that all kinds of
The carbon-14 spike in the 8th century was not caused by a cometary impact on Earth
Variations of 14C around AD 775 and AD 1795 – due to solar activity
The motivation for our study is the disputed cause for the strong variation of 14C around AD 775. Our method is to compare the 14C variation around AD 775 with other periods of strong variability.
A review of East Asian reports of aurorae and comets circa AD 775
Author(s): Chapman, J; Neuhauser, DL; Neuhauser, R; Csikszentmihalyi, M | Abstract: © 2015 WILEY-VCH Verlag GmbH a Co. KGaA, Weinheim. Given that a strong 14C variation in AD 775 has recently been
The cosmic-ray events around AD 775 and AD 993 : assessing their causes and possible effects on climate
Miyake et al. (2012, 2013) discovered rapid increases of 14C content in tree rings dated to AD 774-5 and AD 992-3 which were attributed to unprecedented cosmic-ray events. These extreme particle
The AD775 cosmic event revisited: the Sun is to blame
Aims. Miyake et al. (2012, Nature, 486, 240, henceforth M12) recently reported, based on 14 C data, an extreme cosmic event in about AD775. Using a simple model, M12 claimed that the event was too
Multiradionuclide evidence for the solar origin of the cosmic-ray events of ᴀᴅ 774/5 and 993/4
Evidence is provided that these peaks in the atmospheric radiocarbon (14C) concentration at AD 774/5 and 993/4 were most likely produced by extreme solar events, based on several new annually resolved 10Be measurements from both Arctic and Antarctic ice cores.
Another rapid event in the carbon-14 content of tree rings.
New ( 14)C measurements from AD 822 to 1020, and the discovery of a second rapid increase of (14)C content from AD 992 to 993 are reported, suggesting that solar activity is a plausible cause of the (14), and it is highly possible that these events have the same origin.


A signature of cosmic-ray increase in ad 774–775 from tree rings in Japan
It is argued that neither a solar flare nor a local supernova is likely to have been responsible for the increase in 14C concentrations in tree rings of Japanese cedar trees, and the data are consistent with the decadal IntCal 14C data from North American and European trees.
Superflares on solar-type stars
Quasi-periodic brightness modulations observed in the solar-type stars suggest that they have much larger starspots than does the Sun, and the data suggest that superflares occur more frequently on rapidly rotating stars.
Superflares on Ordinary Solar-Type Stars
Short-duration flares are well known to occur on cool main-sequence stars as well as on many types of "exotic" stars. Ordinary main-sequence stars are usually pictured as being static on timescales
Influence of a Carrington-like event on the atmospheric chemistry, temperature and dynamics
Abstract. We have modeled the atmospheric impact of a major solar energetic particle event similar in intensity to what is thought of the Carrington Event of 1–2 September 1859. Ionization rates for
Estimating the frequency of extremely energetic solar events, based on solar, stellar, lunar, and terrestrial records
[1] The most powerful explosions on the Sun – in the form of bright flares, intense storms of solar energetic particles (SEPs), and fast coronal mass ejections (CMEs) – drive the most severe
Observations of the quiet solar corona in the 171 A (~1 MK) passband of the Transition Region and Coronal Explorer (TRACE) often show disruptions of the coronal part of small-scale ephemeral bipolar
Terrestrial Consequences of Spectral and Temporal Variability in Ionizing Photon Events
The effect of many astrophysical events causing atmospheric ionization can be approximated without including time development by generalizing atmospheric computations to include a broad range of peak photon energies and investigating the effect of burst duration.
Astrophysical ionizing radiation and Earth: a brief review and census of intermittent intense sources.
This review estimates the intensities and rates of occurrence of many kinds of strong radiation bursts by astrophysical entities, ranging from gamma-ray bursts at cosmological distances to the Sun itself, and notes for the first time that so-called "short-hard" gamma-rays bursts are a substantial threat, comparable in magnitude to supernovae and greater than that of the higher-luminosity long bursts considered in most past work.
Modeling atmospheric effects of the September 1859 solar flare
We have modeled atmospheric effects, especially ozone depletion, due to a solar proton event which probably accompanied the extreme magnetic storm of 1–2 September 1859. We use an inferred proton
Constraints on solar particle events from comparisons of recent events and million-year averages
  • R. Reedy
  • Physics, Environmental Science
  • 1995
Several sets of measurements of the fluxes of solar energetic particles (SEPs) above 10 MeV have been used to apply limits to huge solar particle events (SPEs) in the past. Direct measurements of