An Inside Look at Sunspot Oscillations with Higher Azimuthal Wavenumbers

Solar chromospheric observations of sunspot umbrae offer an exceptional view of magneto-hydrodynamic wave phenomena. In recent years, a wealth of wave signatures related to propagating magneto-acoustic modes have been presented, which demonstrate complex spatial and temporal structuring of the wave components. Theoretical modelling has demonstrated how these ubiquitous waves are consistent with an m=0 slow magneto-acoustic mode, which are excited by trapped sub-photospheric acoustic (p-mode) waves. However, the spectrum of umbral waves is broad, suggesting that the observed signatures represent the superposition of numerous frequencies and/or modes. We apply Fourier filtering, in both spatial and temporal domains, to extract chromospheric umbral wave characteristics consistent with an m=1 slow magneto-acoustic mode. This identification has not been described before. Angular frequencies of 0.037 +/- 0.007 rad/s (2.1 +/- 0.4 deg/s), corresponding to a period approximately 170 s for the m=1 mode are uncovered for spatial wavenumbers in the range of 0.45<k<0.90 arcsec^-1 (5000-9000 km). Theoretical dispersion relations are solved, with corresponding eigenfunctions computed, which allows the density perturbations to be investigated and compared with our observations. Such magnetohydrodynamic modelling confirms our interpretation that the identified wave signatures are the first direct observations of an m=1 slow magneto-acoustic mode in the chromospheric umbra of a sunspot

Tiesioginio ir daugiataškio žmogaus arterijos pulsines bangos sklidimo laiko matavimo algoritmų palyginimas

The purpose of the study is to compare the accuracy of point-to-point measurement method of pulse wave propagation time from the multi-point. Electroimpedance method recorded pulse waves in the knees and ankles. Both the ECG signal and the digitized 16-bit analog-digital converter with a frequency of 1 kHz per channel. The study was conducted with 18 healthy volunteers, 20-22 years in the supine position for 3-4 minutes. With the help of LabVIEW tools created by the nine algorithms each subject were analyzed 250-300 pulse waves, highlighting the figure of the coefficient of variation. Their comparison showed that the analysis of pulse waves using different algorithms give different results. The most stable were made when times were measured between the highest peaks of the first derivatives of the forward pulse wave fronts. Similar results were found cross-correlation and cross-spectral analysis of second derivatives of the forward pulse wave fronts. It can be argued that the results of these algorithms allow the parameters obtained by averaging closer to the true results