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 species’ migratory corridor. Gaps in knowledge of the species’ 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 experts’ 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 birds’ 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 Service’s 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

Тепломассоперенос при локальном нагреве и зажигании жидкого топлива сфокусированным потоком излучения

Выполнено численное моделирование комплекса взаимосвязанных процессов тепломассопереноса с фазовыми переходами и химическими реакциями при нагреве и последующем зажигании типичного жидкого топлива сфокусированным потоком излучения. Установлены масштабы влияния процесса поглощения энергии парогазовой смесью и жидкостью на характеристики зажигания