The article presents results of measurements of radiocarbon (14C) concentration in sub-annual dendrochronologically dated tree rings of English oak (Quercus robur L.) from Grabie village near Kraków (southern Poland). Samples of early wood (EW) and late wood (LW) spanning the years 664–658 BCE. α-cellulose was extracted from each sample and their radiocarbon content was measured at the ATOMKI laboratory in Debrecen, Hungary. The EW and LW data confirm a prolonged increase in Δ14C values around 665–663 as was observed by Park et al. (2017), Rakowski et al. (2019), or Sakurai et al. (2020). In addition, we found that this event may consist of two relatively small events, as was proposed by Sakurai et al. (2020). Based on obtained in this and previous study data we estimate that the occurrence of the two events were between 665 and 664 BCE (Rakowski et al. 2019), and in late spring of 663 BCE (May–June, before beginning of LW formation).

This article presents measurements of the radiocarbon (14C) concentration in sub-annual tree rings. Samples of earlywood (EW) and latewood (LW) from dendrochronologically dated tree rings (English oak, Quercus robur) from Kujawy, near Kraków (Poland), spanning the years of 990–997 CE, are extracted and their 14C content is measured at the Center for Applied Isotope Studies at the University of Georgia, USA. The EW and LW data show a gradual increase in the Δ14C values between 991–995 CE, which are similar to those observed by Rakowski et al. (2018). An increase of 10.3 ± 2.6‰ in Δ14C for the EW data, and 8.6 ± 2.6‰ for the LW data has been recorded for this period. Using this data, it is possible to estimate the time period for when a major historical event occurred, which seems to have been in the late summer (September –2/+1 month) of 993 CE.

A signal of rapid changes in 14C production is logged in annual series of 14C derived from tree rings, which can be associated with diverse effects of cosmic-ray fluxes, including solar burst and supernova events. These 14C signatures may vary in time and space. The intensity and structure of the 14C signal is multifaced, which complicates understanding of the forcing and attribution of the underlying astrophysical events. It was suggested that Δ14C in 1052/53 CE and 1054/55 CE signatures at a 4‰–6‰ range over two years could be caused by the Crab Nebula supernova (SN1054) or/and solar perturbation. The temporal incoherence of the signals in published 14C series is investigated with dynamic time warping (DTW), novel approach for matching time-behavioral patterns in multiple 14C datasets. DTW analysis of four 14C signatures from tree rings of California, Finland and England suggests that 14C spikes between 1052 CE and 1055 CE can be caused by a single event. The flickering fingerprint may result from cross-dating inconformity. Cross-checking of tree-ring records from distant locations is impossible sometimes due to large difference in environmental conditions limiting tree growth. The methodology helps to align the signals and can be applied to other 14C datasets.

This article analyzes a 1969 education reform in Mexico that resulted in the closure of 14 of the then 29 escuelas normales rurales (rural teacher-training colleges) and the annihilation of their internal student organizing structures. I argue that the reform was politically motivated and impelled by the anxieties produced by student politics in the Cold War era. I show also how the Secretaría de Educación Pública (SEP) participated in the authoritarian surveillance of students during the presidency of Díaz Ordaz and in a long campaign to delegitimize the Federación de Estudiantes Campesinos Socialistas de México (FECSM), the federation that united the students from these schools.

The search for life in the Universe is a fundamental problem of astrobiology and modern science. The current progress in the detection of terrestrial-type exoplanets has opened a new avenue in the characterization of exoplanetary atmospheres and in the search for biosignatures of life with the upcoming ground-based and space missions. To specify the conditions favourable for the origin, development and sustainment of life as we know it in other worlds, we need to understand the nature of global (astrospheric), and local (atmospheric and surface) environments of exoplanets in the habitable zones (HZs) around G-K-M dwarf stars including our young Sun. Global environment is formed by propagated disturbances from the planet-hosting stars in the form of stellar flares, coronal mass ejections, energetic particles and winds collectively known as astrospheric space weather. Its characterization will help in understanding how an exoplanetary ecosystem interacts with its host star, as well as in the specification of the physical, chemical and biochemical conditions that can create favourable and/or detrimental conditions for planetary climate and habitability along with evolution of planetary internal dynamics over geological timescales. A key linkage of (astro)physical, chemical and geological processes can only be understood in the framework of interdisciplinary studies with the incorporation of progress in heliophysics, astrophysics, planetary and Earth sciences. The assessment of the impacts of host stars on the climate and habitability of terrestrial (exo)planets will significantly expand the current definition of the HZ to the biogenic zone and provide new observational strategies for searching for signatures of life. The major goal of this paper is to describe and discuss the current status and recent progress in this interdisciplinary field in light of presentations and discussions during the NASA Nexus for Exoplanetary System Science funded workshop ‘Exoplanetary Space Weather, Climate and Habitability’ and to provide a new roadmap for the future development of the emerging field of exoplanetary science and astrobiology.

Our Sun, a magnetically mild star, exhibits space weather in the form of magnetically driven solar explosive events (SEE) including solar flares, coronal mass ejections and energetic particle events. We use Kepler data and reconstruction of X-ray and UV emission from young solar-like stars to recover the frequency and energy fluxes from extreme events from active stars including the young Sun. Extreme SEEs from a magnetically active young Sun could significantly perturb the young Earth's magnetosphere, cause strong geomagnetic storms, initiate escape and introduce chemical changes in its lower atmosphere. I present our recent simulations results based on multi-dimensional multi-fluid hydrodynamic and magnetohydrodynamic models of interactions of extreme CME and SEP events with magnetospheres and lower atmospheres of early Earth and exoplanets around active stars. We also discuss the implications of the impact of these effects on evolving habitability conditions of the early Earth and prebiotic chemistry introduced by space weather events at the early phase of evolution of our Sun.

Kepler observations suggest that G-type stars produce powerful flares suggesting that the early Earth may also have been exposed to frequent and energetic solar explosive events generated by the young Sun. We show that powerful coronal mass ejection (CME) events associated with superflares impacting the Earth magnetosphere with a frequency of 1 event/day. What was the impact of superflares, CMEs and associated solar energetic particle (SEPs) events on the atmospheric erosion of the young Earth and habitability? In this paper we discuss our three-dimensional (3D) magnetohydrodynamic (MHD) simulations that show that frequent and energetic CMEs from the early Sun continuously destroyed the sub-solar parts of Earth's magnetosphere at heights < 1.25 RE. This suggests that CME shock accelerated energetic protons are capable of penetrating into the polar cap region and breaking atmospheric molecular nitrogen, the major ingredient of the early Earth atmosphere, into atomic nitrogen. Photo-collisional dissociation of molecular nitrogen and carbon dioxide creates reactive chemistry that efficiently produces nitrous oxide and hydrogen cyanide, the essential molecule in prebiotic life chemistry. This raises an possibility that frequent super-CMEs could serve as a potential catalyst for the origin of life on early Earth.