A bright impulsive solar burst detected at 30 THz

Ground- and space-based observations of solar flares from radio wavelengths to gamma-rays have produced considerable insights but raised several unsolved controversies. The last unexplored wavelength frontier for solar flares is in the range of submillimeter and infrared wavelengths. Here we report the detection of an intense impulsive burst at 30 THz using a new imaging system. The 30 THz emission exhibited remarkable time coincidence with peaks observed at microwave, mm/submm, visible, EUV and hard X-ray wavelengths. The emission location coincides with a very weak white-light feature, and is consistent with heating below the temperature minimum in the atmosphere. However, there are problems in attributing the heating to accelerated electrons. The peak 30 THz flux is several times larger than the usual microwave peak near 9 GHz, attributed to non-thermal electrons in the corona. The 30 THz emission could be consistent with an optically thick spectrum increasing from low to high frequencies. It might be part of the same spectral component found at sub-THz frequencies whose nature remains mysterious. Further observations at these wavelengths will provide a new window for flare studies.Comment: 9 pages, 11 figures, accepted by Astrophysical Journal, March 23, 201

Mycelial compatibility and aggressiveness of Sclerotinia sclerotiorum isolates from Brazil and the United States.

ABSTRACT: The objective of this work was to evaluate the genetic diversity among Sclerotinia sclerotiorum isolates from Brazil and the USA, assess their aggressiveness variability, and verify the existence of an isolate-cultivar interaction. Isolate variability was determined by mycelial compatibility grouping (MCG), and isolate aggressiveness by cut-stem inoculations of soybean cultivars. Two experiments for MCGs and two for aggressiveness were conducted with two sets of isolates. The first set included nine isolates from the same soybean field in Brazil and nine from the Midwest region of the USA. The second set included 16 isolates from several regions of Brazil and one from the USA. In the first set, 18 isolates formed 12 different MCGs. In the second set, 81% of the isolates from Brazil grouped into a single MCG. No common MCGs were observed among isolates from Brazil and the USA. The isolates showed aggressiveness differences in the first set, but not in the second. Although aggressiveness differed in the first set, soybean cultivars and isolates did not interact significantly. Cultivar rank remained the same, regardless of the genetic diversity, aggressiveness difference, and region or country of origin of the isolate. Results from screening of soybean cultivars, performed by the cut-stem method in the USA, can be used as reference for researchers in Brazil. RESUMO: O objetivo deste trabalho foi avaliar a diversidade genética entre isolados de Sclerotinia sclerotiorum do Brasil e dos EUA, determinar sua variabilidade quanto à agressividade e verificar a existência de interação isoladocultivar. A variabilidade dos isolados foi determinada por agrupamento de compatibilidade micelial (ACM), e a agressividade dos isolados, por meio de inoculações, com corte da haste, em cultivares de soja. Dois experimentos de ACM e dois de agressividade foram realizados, com dois conjuntos de isolados. O primeiro conjunto incluiu nove isolados, do mesmo campo de soja no Brasil, e nove da região Meio?Oeste dos EUA. O segundo conjunto incluiu 16 isolados de várias regiões do Brasil e um dos EUA. No primeiro conjunto, 18 isolados formaram 12 ACMs diferentes. No segundo conjunto, 81% dos isolados do Brasil formaram um único ACM. Nenhum ACM comum foi observado entre os isolados do Brasil e dos EUA. Os isolados apresentaram diferenças quanto à agressividade no primeiro conjunto de isolados, mas não no segundo. Embora a agressividade tenha diferido no primeiro conjunto, as cultivares de soja e os isolados não interagiram significativamente. A classificação das cultivares permaneceu a mesma, independentemente da diversidade genética, da diferença quanto à agressividade e da região ou país de origem do isolado. Resultados da seleção de cultivares de soja, realizada pelo método de inoculação de corte da haste nos EUA, podem ser utilizados como referência para pesquisadores no Brasil