Center-to-Limb Variation of Radio Emissions from Thermal-Rich and Thermal-Poor Solar Flares

A statistical analysis of radio flare events was performed by using the event list of Nobeyama Radioheliograph in 1996-2009. We examined center-to-limb variations of 17GHz and 34GHz flux by dividing the flare events into different groups with respect to the 'thermal plasma richness' (ratio of the peak flux of soft X-ray to non-thermal radio emissions) and the duration of radio bursts. It is found that peak flux of 17 and 34GHz tend to be higher toward the limb for thermal-rich flares with short durations. We propose that the thermal-rich flares, which are supposed to be associated with an efficient precipitation of high energy particles into the chromosphere, have a pitch angle distribution of non-thermal electrons with a higher population along the flare loop.Comment: 12 pages, 5 figure

Expansion of signaling genes for adaptive immune system evolution in early vertebrates

<p>Abstract</p> <p>Background</p> <p>The adaptive immune system (AIS) of jawed vertebrates is a sophisticated system mediated by numerous genes in specialized cells. Phylogenetic analysis indicates that emergence of the AIS followed the occurrence of two rounds of whole-genome duplication (2R-WGD) in early vertebrates, but little direct evidence linking these two events is available.</p> <p>Results</p> <p>We examined the relationship between 2R-WGD and the gain of AIS-related functions by numerous genes. To analyze the evolution of the many genes related to signal transduction in the AIS (defined as AIS genes), we identified groups of genes (defined as AIS subfamilies) that included at least one human AIS gene, its paralogs (if any), and its <it>Drosophila </it>ortholog(s). Genomic mapping revealed that numerous pairs of AIS genes and their paralogs were part of paralogons – series of paralogous regions that derive from a common ancestor – throughout the human genome, indicating that the genes were retained as duplicates after 2R-WGD. Outgroup comparison analysis revealed that subfamilies in which human and fly genes shared a nervous system-related function were significantly enriched among AIS subfamilies, as compared with the overall incidence of shared nervous system-related functions among all subfamilies in bilaterians. This finding statistically supports the hypothesis that AIS-related signaling genes were ancestrally involved in the nervous system of urbilaterians.</p> <p>Conclusion</p> <p>The current results suggest that 2R-WGD played a major role in the duplication of many signaling genes, ancestrally used in nervous system development and function, that were later co-opted for new functions during evolution of the AIS.</p

Thermodynamic properties of small flares in the quiet Sun observed by Hα\alpha and EUV: plasma motion of the chromosphere and time evolution of temperature/emission measure

Small flares frequently occur in the quiet Sun. Previous studies have noted that they share many common characteristics with typical solar flares in active regions. However, their similarities and differences are not fully understood, especially their thermal properties. In this study, we performed imaging spectroscopic observations in the H$\alpha$ line taken with the Solar Dynamics Doppler Imager on the Solar Magnetic Activity Research Telescope (SMART/SDDI) at the Hida Observatory and imaging observations with the Atmospheric Imaging Assembly onboard Solar Dynamics Observatory (SDO/AIA). We analysed 25 cases of small flares in the quiet Sun over the thermal energy range of $10^{24}-10^{27}\,\mathrm{erg}$, paying particular attention to their thermal properties. Our main results are as follows: (1) We observe a redshift together with line centre brightening in the H$\alpha$ line associated with more than half of the small flares. (2) We employ differential emission measure analysis using AIA multi-temperature (channel) observations to obtain the emission measure and temperature of the small flares. The results are consistent with the Shibata & Yokoyama (1999, 2002) scaling law. From the scaling law, we estimated the coronal magnetic field strength of small flares to be 5 --15 G. (3) The temporal evolution of the temperature and the density shows that the temperature peaks precede the density peaks in more than half of the events. These results suggest that chromospheric evaporations/condensations play an essential role in the thermal properties of some of the small flares in the quiet Sun, as does for large flares.Comment: 14 pages, 12 figures, accepted for publication in MNRA