The Topology and Polarisation of Subbeams Associated with the `Drifting' Subpulse Emission of Pulsar B0943+10 -- IV. Q-to-B-Mode Recovery Dynamics

Pulsar B0943+10 is well known for its `B' (burst) mode, characterized by accurately drifting subpulses, in contrast to its chaotic `Q' (quiet) mode. Six new Arecibo observations at 327 MHz with durations of 2+ hours each have shed considerable light on the modal dynamics of this pulsar. Of these, three were found to be exclusively `B' mode, and three were discovered to exhibit transitions from the `Q' to the `B' mode. One of these observations has permitted us to determine the circulation time of the subbeam carousel in the `Q' mode for the first time, at some 36.4$\pm$0.9 stellar rotation periods. The onset of the `B' mode is then observed to commence similarly in all three observations. The initial circulation time is about 36 periods and relaxes to nearly 38 periods in a roughly exponential fashion with a characteristic time of some 1.2 hours. This is the longest characteristic time ever found in a mode-switching pulsar. Moreover, just after the `B'-mode onset the pulsar exhibits a symmetrical resolved-double profile form with a somewhat stronger trailing component, but this second component slowly dies away leaving the usual single `B'-mode profile with the longitude of the magnetic axis falling at about its trailing half power point. Thus it would appear that Q-to-B- and B-to-Q-transitions have different characteristic times. Some speculations are given on the nature of this slow modal alternation.Comment: 9 pages, 10 figure

PSR B0809+74: Understanding Its Perplexing Subpulse-separation (P2) Variations

The longitude separation between adjacent drifting subpulses, $P_2$, is roughly constant for many pulsars. It was then perplexing when pulsar B0809+74 was found to exhibit substantial variations in this measure, both with wavelength and with longitude position within the pulse window. We analyze these variations between 40 and 1400 MHz, and we show that they stem primarily from the incoherent superposition of the two orthogonal modes of polarization.Comment: Submitted for publication Astronomy and Astrophysic

Chronicles of nature calendar, a long-term and large-scale multitaxon database on phenology

We present an extensive, large-scale, long-term and multitaxon database on phenological and climatic variation, involving 506,186 observation dates acquired in 471 localities in Russian Federation, Ukraine, Uzbekistan, Belarus and Kyrgyzstan. The data cover the period 1890-2018, with 96% of the data being from 1960 onwards. The database is rich in plants, birds and climatic events, but also includes insects, amphibians, reptiles and fungi. The database includes multiple events per species, such as the onset days of leaf unfolding and leaf fall for plants, and the days for first spring and last autumn occurrences for birds. The data were acquired using standardized methods by permanent staff of national parks and nature reserves (87% of the data) and members of a phenological observation network (13% of the data). The database is valuable for exploring how species respond in their phenology to climate change. Large-scale analyses of spatial variation in phenological response can help to better predict the consequences of species and community responses to climate change.Peer reviewe

Phenological shifts of abiotic events, producers and consumers across a continent

Ongoing climate change can shift organism phenology in ways that vary depending on species, habitats and climate factors studied. To probe for large-scale patterns in associated phenological change, we use 70,709 observations from six decades of systematic monitoring across the former Union of Soviet Socialist Republics. Among 110 phenological events related to plants, birds, insects, amphibians and fungi, we find a mosaic of change, defying simple predictions of earlier springs, later autumns and stronger changes at higher latitudes and elevations. Site mean temperature emerged as a strong predictor of local phenology, but the magnitude and direction of change varied with trophic level and the relative timing of an event. Beyond temperature-associated variation, we uncover high variation among both sites and years, with some sites being characterized by disproportionately long seasons and others by short ones. Our findings emphasize concerns regarding ecosystem integrity and highlight the difficulty of predicting climate change outcomes. The authors use systematic monitoring across the former USSR to investigate phenological changes across taxa. The long-term mean temperature of a site emerged as a strong predictor of phenological change, with further imprints of trophic level, event timing, site, year and biotic interactions.Peer reviewe

Phenomenology of pulsar B0809+74's rotating subbeam system

The basic emission geometry of pulsar B0809+74 is modeled after determinating its polarization position-angle traverse. As the star's profiles are truncated by “absorption” over a broad band, most severely between some 60 and 1500 MHz, the analysis also provides quantitative estimates of the extent of this effect at each frequency. The model's predicted scales are found to agree closely with those determined by correlating pulse sequences observed simultaneously in different bands and by measuring P2 at different frequencies

Phenomenology of pulsar B0809+74's rotating subbeam system

Building on results and analyses of previous works, the structure and polarization of B0809+74's subbeam “carousel” is delimited, but not fully solved. Some 8–10 subbeams are indicated for an equatorward sightline traverse and 25–40 for a polarward one. Either alternative indicates a subbeam circulation time much longer than predicted by theory. Polarized subbeam maps show complex structure and suggest that the star's polarized modes are angularly disjoint

Differences in spatial versus temporal reaction norms for spring and autumn phenological events

For species to stay temporally tuned to their environment, they use cues such as the accumulation of degree-days. The relationships between the timing of a phenological event in a population and its environmental cue can be described by a population-level reaction norm. Variation in reaction norms along environmental gradients may either intensify the environmental effects on timing (cogradient variation) or attenuate the effects (countergradient variation). To resolve spatial and seasonal variation in species' response, we use a unique dataset of 91 taxa and 178 phenological events observed across a network of 472 monitoring sites, spread across the nations of the former Soviet Union. We show that compared to local rates of advancement of phenological events with the advancement of temperature-related cues (i.e., variation within site over years), spatial variation in reaction norms tend to accentuate responses in spring (cogradient variation) and attenuate them in autumn (countergradient variation). As a result, among-population variation in the timing of events is greater in spring and less in autumn than if all populations followed the same reaction norm regardless of location. Despite such signs of local adaptation, overall phenotypic plasticity was not sufficient for phenological events to keep exact pace with their cues-the earlier the year, the more did the timing of the phenological event lag behind the timing of the cue. Overall, these patterns suggest that differences in the spatial versus temporal reaction norms will affect species' response to climate change in opposite ways in spring and autumn