9 research outputs found
Evidence of Non-Thermal Particles in Coronal Loops Heated Impulsively by Nanoflares
The physical processes causing energy exchange between the Sun's hot corona
and its cool lower atmosphere remain poorly understood. The chromosphere and
transition region (TR) form an interface region between the surface and the
corona that is highly sensitive to the coronal heating mechanism. High
resolution observations with the Interface Region Imaging Spectrograph (IRIS)
reveal rapid variability (about 20 to 60 seconds) of intensity and velocity on
small spatial scales at the footpoints of hot dynamic coronal loops. The
observations are consistent with numerical simulations of heating by beams of
non-thermal electrons, which are generated in small impulsive heating events
called "coronal nanoflares". The accelerated electrons deposit a sizable
fraction of their energy in the chromosphere and TR. Our analysis provides
tight constraints on the properties of such electron beams and new diagnostics
for their presence in the nonflaring corona.Comment: Published in Science on October 17:
http://www.sciencemag.org/content/346/6207/1255724 . 26 pages, 10 figures.
Movies are available at: http://www.lmsal.com/~ptesta/iris_science_mov
Time-dependent suppression of oscillatory power in evolving solar magnetic fields
Oscillation amplitudes are generally smaller within magnetically active regions like sunspots and plage when compared to their surroundings. Such magnetic features, when viewed in spatially resolved power maps, appear as regions of suppressed power due to reductions in the oscillation amplitudes. Employing high spatial- and temporal-resolution observations from the Dunn Solar Telescope (DST) in New Mexico, we study the power suppression in a region of evolving magnetic fields adjacent to a pore. By utilizing wavelet analysis, we study for the first time how the oscillatory properties in this region change as the magnetic field evolves with time. Image sequences taken in the blue continuum, G-band, Ca ii K, and Hα filters were used in this study. It is observed that the suppression found in the chromosphere occupies a relatively larger area, confirming previous findings. Also, the suppression is extended to structures directly connected to the magnetic region, and is found to get enhanced as the magnetic field strength increased with time. The dependence of the suppression on the magnetic field strength is greater at longer periods and higher formation heights. Furthermore, the dominant periodicity in the chromosphere was found to be anti-correlated with increases in the magnetic field strength