350 research outputs found
Interaction between a fast rotating sunspot and ephemeral regions as the origin of the major solar event on 2006 December 13
The major solar event on 2006 December 13 is characterized by the
approximately simultaneous occurrence of a heap of hot ejecta, a great
two-ribbon flare and an extended Earth-directed coronal mass ejection. We
examine the magnetic field and sunspot evolution in active region NOAA AR
10930, the source region of the event, while it transited the solar disk centre
from Dec. 10 to Dec. 13. We find that the obvious changes in the active region
associated with the event are the development of magnetic shear, the appearance
of ephemeral regions and fast rotation of a smaller sunspot. Around the area of
the magnetic neutral line of the active region, interaction between the fast
rotating sunspot and the ephemeral regions triggers continual brightening and
finally the major flare. It is indicative that only after the sunspot rotates
up to 200 does the major event take place. The sunspot rotates at
least 240 about its centre, the largest sunspot rotation angle which
has been reported.Comment: 4 pages, 6 figures, ApJ Letters inpres
The Significance of Petroleum Bitumen in Ancient Egyptian Mummies
© 2016 The Author(s) Published by the Royal Society. All rights reserved. Mummification was practised in ancient Egypt for more than 3000 years, emerging from initial observations of buried bodies preserved by natural desiccation. The use of organic balms (and other funerary practices) was a later introduction necessitated by more humid burial environments, especially tombs. The dark colour of many mummies led to the assumption that petroleum bitumen (or natural asphalt) was ubiquitous in mummification; however, this has been questioned for more than 100 years. We test this by investigating 91 materials comprising balms, tissues and textiles from 39 mummies dating from ca 3200 BC to AD 395. Targeted petroleum bitumen biomarker (steranes and hopanes) analyses by gas chromatography-mass spectrometry selected ion monitoring (GC-MS SIM, m/z 217 and 191) showed no detectable bitumen use before the New Kingdom (ca 1550-1070 BC). However, bitumen was used in 50% of New Kingdom to Late Period mummies, rising to 87% of Ptolemaic/Roman Period mummies. Quantitative determinations using 14C analyses reveal that even at peak use balms were never more than 45% w/w bitumen. Critically, the dark colour of balms can be simulated by heating/ageing mixtures of fats, resins and beeswax known to be used in balms. The application of black/dark brown balms to bodies was deliberate after the New Kingdom reflecting changing funerary beliefs and shifts in religious ideology
SUMER observations of the inverse Evershed effect in the transition region above a sunspot
Aims. We analyse SUMER spectral scans of a large sunspot within active region
NOAA 10923, obtained on 14-15 November 2006, to determine the morphology and
dynamics of the sunspot atmosphere at different heights/temperatures. Methods:
The data analysed here consist of spectroheliograms in the continuum around
142.0 nm and in the Si iv 140.2 nm, O iii 70.3 nm, N iv 76.5 nm, and O iv 79.0
nm spectral lines. Gaussian-fitting of the observed profiles provides
line-of-sight velocity and Doppler-width maps. Results: The data show an
asymmetric downflow pattern compatible with the presence of the inverse
Evershed flow in a region within roughly twice the penumbral radius at
transition-region temperatures up to 0.18 MK. The motions, highly inhomogeneous
on small scales, seem to occur in a collar of radially directed filamentary
structures, with an average width less than the 1 Mm spatial resolution of
SUMER and characterised by different plasma speeds. Assuming that the flows are
directed along the field lines, we deduce that such field lines are inclined by
10 deg to 25 deg with respect to the solar surface.Comment: 5 pages, 3 figures. Text height reduced for better layout. No changes
in conten
Interpreting ancient food practices:Stable isotope and molecular analyses of visible and absorbed residues from a year-long cooking experiment
Chemical analyses of carbonized and absorbed organic residues from archaeological ceramic cooking vessels can provide a unique window into the culinary cultures of ancient people, resource use, and environmental effects by identifying ingredients used in ancient meals. However, it remains uncertain whether recovered organic residues represent only the final foodstuffs prepared or are the accumulation of various cooking events within the same vessel. To assess this, we cooked seven mixtures of C3 and C4 foodstuffs in unglazed pots once per week for one year, then changed recipes between pots for the final cooking events. We conducted bulk stable-isotope analysis and lipid residue analysis on the charred food macro-remains, carbonized thin layer organic patina residues and absorbed lipids over the course of the experiment. Our results indicate that: (1) the composition of charred macro-remains represent the final foodstuffs cooked within vessels, (2) thin-layer patina residues represent a mixture of previous cooking events with bias towards the final product(s) cooked in the pot, and (3) absorbed lipid residues are developed over a number of cooking events and are replaced slowly over time, with little evidence of the final recipe ingredients
Flow Field Evolution of a Decaying Sunspot
We study the evolution of the flows and horizontal proper motions in and
around a decaying follower sunspot based on time sequences of two-dimensional
spectroscopic observations in the visible and white light imaging data obtained
over six days from June~7 to~12, 2005. During this time period the sunspot
decayed gradually to a pore. The spectroscopic observations were obtained with
the Fabry-P\'{e}rot based Visible-Light Imaging Magnetograph (VIM) in
conjunction with the high-order adaptive optics (AO) system operated at the 65
cm vacuum reflector of the Big Bear Solar Observatory (BBSO). We apply local
correlation tracking (LCT) to the speckle reconstructed time sequences of
white-light images around 600 nm to infer horizontal proper motions while the
Doppler shifts of the scanned \FeI line at 630.15 nm are used to calculate
line-of-sight (LOS) velocities with sub-arcsecond resolution. We find that the
dividing line between radial inward and outward proper motions in the inner and
outer penumbra, respectively, survives the decay phase. In particular the moat
flow is still detectable after the penumbra disappeared. Based on our
observations three major processes removed flux from the sunspot: (a)
fragmentation of the umbra, (b) flux cancelation of moving magnetic features
(MMFs; of the same polarity as the sunspot) that encounter the leading opposite
polarity network and plages areas, and (c) flux transport by MMFs (of the same
polarity as the sunspot) to the surrounding network and plage regions that have
the same polarity as the sunspot.Comment: 9 pages, 7 figures, The Astrophysical Journal, accepted September,
200
Main Sequence Masses and Radii from Gravitational Redshifts
Modern instrumentation makes it possible to measure the mass to radius ratio
for main sequence stars in open clusters from gravitational redshifts. For
stars where independent information is available for either the mass or the
radius, this application of general relativity directly determines the other
quantity. Applicable examples are: 1) measuring the radii of solar metallicity
main sequence stars for which the mass - luminosity relation is well known, 2)
measuring the radii for stars where model atmospheres can be used to determine
the surface gravity (the mass to radius squared ratio), 3) refining the mass -
radius relation for main sequence stars, and 4) measuring the change in radius
as stars evolve off the main sequence and up the giant branch.Comment: 7 pages, latex, no figures, to be published in ApJ Letter
Holocene lake sediment core sequences from Lochnagar, Cairngorm Mts., Scotland - UK final report for CHILL-10,000
The CHILL 10,000 research objective at Lochnagar is to examine proxy data for temperature
and climate conditions. Changes in lake sediment stratigraphical data can be used to reconstruct
past conditions. These proxies include organic and minerogenic matter as a bulk proxy for
catchment and within-lake productivity, chironomids as a proxy for air temperature, diatoms as
an indicator for lake water pH, pollen as an indicator of catchment vegetation and finally
biomarkers to help determine changes in proportions of organic source material within the lake
mud
The Evershed Effect with SOT/Hinode
The Solar Optical Telescope onboard Hinode revealed the fine-scale structure
of the Evershed flow and its relation to the filamentary structures of the
sunspot penumbra. The Evershed flow is confined in narrow channels with nearly
horizontal magnetic fields, embedded in a deep layer of the penumbral
atmosphere. It is a dynamic phenomenon with flow velocity close to the
photospheric sound speed. Individual flow channels are associated with tiny
upflows of hot gas (sources) at the inner end and downflows (sinks) at the
outer end. SOT/Hinode also discovered ``twisting'' motions of penumbral
filaments, which may be attributed to the convective nature of the Evershed
flow. The Evershed effect may be understood as a natural consequence of thermal
convection under a strong, inclined magnetic field. Current penumbral models
are discussed in the lights of these new Hinode observations.Comment: To appear in "Magnetic Coupling between the Interior and the
Atmosphere of the Sun", eds. S.S. Hasan and R.J. Rutten, Astrophysics and
Space Science Proceedings, Springer-Verlag, Heidelberg, Berlin, 200
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