1,470 research outputs found
Thermal to Nonthermal Energy Partition at the Early Rise Phase of Solar Flares
In some flares the thermal component appears much earlier than the nonthermal
component in X-ray range. Using sensitive microwave observations we revisit
this finding made by Battaglia et al. (2009) based on RHESSI data analysis. We
have found that nonthermal microwave emission produced by accelerated electrons
with energy of at least several hundred keV, appears as early as the thermal
soft X-ray emission indicative that the electron acceleration takes place at
the very early flare phase. The non-detection of the hard X-rays at that early
stage of the flares is, thus, an artifact of a limited RHESSI sensitivity. In
all considered events, the microwave emission intensity increases at the early
flare phase. We found that either thermal or nonthermal gyrosynchrotron
emission can dominate the low-frequency part of the microwave spectrum below
the spectral peak occurring at 3-10 GHz. In contrast, the high-frequency
optically thin part of the spectrum is always formed by the nonthermal,
accelerated electron component, whose power-law energy spectrum can extend up
to a few MeV at this early flare stage. This means that even though the total
number of accelerated electrons is small at this stage, their nonthermal
spectrum is fully developed. This implies that an acceleration process of
available seed particles is fully operational. While, creation of this seed
population (the process commonly called `injection' of the particles from the
thermal pool into acceleration) has a rather low efficiency at this stage,
although, the plasma heating efficiency is high. This imbalance between the
heating and acceleration (in favor of the heating) is difficult to reconcile
within most of available flare energization models. Being reminiscent of the
tradeoff between the Joule heating and runaway electron acceleration, it puts
additional constraints on the electron injection into the acceleration process.Comment: 11 pages, 12 figures, accepted for Ap
Expert elicitation of seasonal abundance of North Atlantic right whales Eubalaena glacialis in the mid-Atlantic
This work was supported in part by US Office of Naval Research (ONR) grants to E.F.: N00014-09-1-0896 at University of California, Santa Barbara and N00014-12-1-0274 at University of California, Davis. This work was also supported by ONR grant N000141210286 to the University of St Andrews. In addition, we gratefully acknowledge funding for this work from The Marine Alliance for Science and Technology for Scotland (MASTS). MASTS is funded by the Scottish Funding Council (grant reference HR09011) and contributing institutions.North Atlantic right whales (Eubalaena glacialis; henceforth right whales) are among the most endangered large whales. Although protected since 1935, their abundance has remained low. Right whales occupy the Atlantic Ocean from southern Greenland and the Gulf of St. Lawrence south to Florida. The highly industrialized mid-Atlantic region is part of the speciesβ migratory corridor. Gaps in knowledge of the speciesβ movements through the mid-Atlantic limit informed management of stressors to the species. To contribute to filling of these gaps, we elicited estimates of the relative abundance of adult right whales in the mid-Atlantic during four months, representing each season, from ten experts. We elicited the minimum, maximum, and mode as the number of individuals in a hypothetical population of 100 right whales, and confidence estimates as percentages. For each month-sex combination, we merged the ten expertsβ answers into one distribution. The estimated modes of relative abundances of both sexes were highest in January and April (females, 29 and 59; males, 22 and 23) and lowest in July and October (females, five and nine; males, three and five). In some cases, our elicitation results were consistent with the results of studies based on sightings data. However, these studies generally did not adjust for sampling effort, which was low and likely variable. Our results supplement the results of these studies and will increase the accuracy of priors in complementary Bayesian models of right whale abundances and movements through the mid-Atlantic.Publisher PDFPeer reviewe
Archiving of data on occurrence of breeding birds associated with fire treatments and controls
Since 2001, we have collected data on occupancy and relative abundance of Greater Sage- Grouse (Centrocercus urophasianus) and other species of breeding birds in the central Great Basin, and characterized the vegetation structure and composition of breeding birdsβ habitats, through four projects supported by the Joint Fire Science Program (00-2-15, 01B-3-3-01, 05-2-1- 94, and 09-1-08-4). These projects collectively have generated dozens of refereed publications, dozens of invited papers or presentations, multiple M.S. theses and Ph.D. dissertations, and many workshops and field tours. Bird data included in refereed publications to date were based on point counts with a fixed radius of 75 or 100 m and a duration of 5 minutes per visit. These data previously were archived with the USDA Forest Serviceβs Research Data Archive. Since 2004, however, we also have conducted 100-m fixed-radius point counts with a duration of 8 minutes per visit. Furthermore, starting in 2002, we recorded birds detected beyond the fixed radius and during travel among point-count locations or at other times of day or night. We archived data on the incidental and longer-distance detections of birds, which included more than 22,600 records. We also archived all data on vegetation structure and the composition of dominant trees and shrubs collected through 2012. There are few sets of long-term, spatially extensive data on distributions and abundance of fauna or extensive characterizations of vegetation in the Great Basin. These data have considerable capacity to inform understanding and management of fire dynamics; changes in land cover, including conversion of native vegetation to cheatgrass (Bromus tectorum); and the status of species proposed for listing under the Endangered Species Act
Strongest coronal magnetic fields in solar cycles 23-24: probing, statistics, and implications
Strong coronal magnetic field, when present, manifests itself as bright
microwave sources at high frequencies produced by gyroresonant (GR) emission
mechanism in thermal coronal plasma. The highest frequency at which this
emission is observed is proportional to the absolute value of the strongest
coronal magnetic field on the line of sight. Although no coronal magnetic field
larger than roughly 2,000 G was expected, recently the field at least twice
larger has been reported. Here, we report a search for and statistical study of
such strong coronal magnetic fields using high-frequency GR emission. A
historic record of spatially resolved microwave observations at high
frequencies, 17 and 34 GHz, is available from Nobeyama RadioHeliograph for more
than 20 years (1995-2018). Here we employ this data set to identify sources of
bright GR emission at 34 GHz and perform a statistical analysis of the
identified GR cases to quantify the strongest coronal magnetic fields during
two solar cycles. We found that although active regions with the strong
magnetic field are relatively rare (less than 1% of all active regions), they
appear regularly on the Sun. These active regions are associated with prominent
manifestations of solar activity
Π’Π΅ΠΏΠ»ΠΎΠΌΠ°ΡΡΠΎΠΏΠ΅ΡΠ΅Π½ΠΎΡ ΠΏΡΠΈ Π»ΠΎΠΊΠ°Π»ΡΠ½ΠΎΠΌ Π½Π°Π³ΡΠ΅Π²Π΅ ΠΈ Π·Π°ΠΆΠΈΠ³Π°Π½ΠΈΠΈ ΠΆΠΈΠ΄ΠΊΠΎΠ³ΠΎ ΡΠΎΠΏΠ»ΠΈΠ²Π° ΡΡΠΎΠΊΡΡΠΈΡΠΎΠ²Π°Π½Π½ΡΠΌ ΠΏΠΎΡΠΎΠΊΠΎΠΌ ΠΈΠ·Π»ΡΡΠ΅Π½ΠΈΡ
ΠΡΠΏΠΎΠ»Π½Π΅Π½ΠΎ ΡΠΈΡΠ»Π΅Π½Π½ΠΎΠ΅ ΠΌΠΎΠ΄Π΅Π»ΠΈΡΠΎΠ²Π°Π½ΠΈΠ΅ ΠΊΠΎΠΌΠΏΠ»Π΅ΠΊΡΠ° Π²Π·Π°ΠΈΠΌΠΎΡΠ²ΡΠ·Π°Π½Π½ΡΡ
ΠΏΡΠΎΡΠ΅ΡΡΠΎΠ² ΡΠ΅ΠΏΠ»ΠΎΠΌΠ°ΡΡΠΎΠΏΠ΅ΡΠ΅Π½ΠΎΡΠ° Ρ ΡΠ°Π·ΠΎΠ²ΡΠΌΠΈ ΠΏΠ΅ΡΠ΅Ρ
ΠΎΠ΄Π°ΠΌΠΈ ΠΈ Ρ
ΠΈΠΌΠΈΡΠ΅ΡΠΊΠΈΠΌΠΈ ΡΠ΅Π°ΠΊΡΠΈΡΠΌΠΈ ΠΏΡΠΈ Π½Π°Π³ΡΠ΅Π²Π΅ ΠΈ ΠΏΠΎΡΠ»Π΅Π΄ΡΡΡΠ΅ΠΌ Π·Π°ΠΆΠΈΠ³Π°Π½ΠΈΠΈ ΡΠΈΠΏΠΈΡΠ½ΠΎΠ³ΠΎ ΠΆΠΈΠ΄ΠΊΠΎΠ³ΠΎ ΡΠΎΠΏΠ»ΠΈΠ²Π° ΡΡΠΎΠΊΡΡΠΈΡΠΎΠ²Π°Π½Π½ΡΠΌ ΠΏΠΎΡΠΎΠΊΠΎΠΌ ΠΈΠ·Π»ΡΡΠ΅Π½ΠΈΡ. Π£ΡΡΠ°Π½ΠΎΠ²Π»Π΅Π½Ρ ΠΌΠ°ΡΡΡΠ°Π±Ρ Π²Π»ΠΈΡΠ½ΠΈΡ ΠΏΡΠΎΡΠ΅ΡΡΠ° ΠΏΠΎΠ³Π»ΠΎΡΠ΅Π½ΠΈΡ ΡΠ½Π΅ΡΠ³ΠΈΠΈ ΠΏΠ°ΡΠΎΠ³Π°Π·ΠΎΠ²ΠΎΠΉ ΡΠΌΠ΅ΡΡΡ ΠΈ ΠΆΠΈΠ΄ΠΊΠΎΡΡΡΡ Π½Π° Ρ
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