Search results for "Solar physics"
showing 10 items of 25 documents
Acoustic Wave Properties in Footpoints of Coronal Loops in 3D MHD Simulations
2021
Acoustic waves excited in the photosphere and below might play an integral part in the heating of the solar chromosphere and corona. However, it is yet not fully clear how much of the initially acoustic wave flux reaches the corona and in what form. We investigate the wave propagation, damping, transmission, and conversion in the lower layers of the solar atmosphere using 3D numerical MHD simulations. A model of a gravitationally stratified expanding straight coronal loop, stretching from photosphere to photosphere, is perturbed at one footpoint by an acoustic driver with a period of 370 seconds. For this period acoustic cutoff regions are present below the transition region (TR). About 2% …
Non-local heat transport in static solar coronal loops
1991
We investigate the limits of applicability of the Spitzer-Harm thermal conductivity in solar coronal loops and show that the ratio λ0/LTof electron mean-free path to temperature scale height in large-scale structures can approach the limits of the Spitzer-Harm theory. We use a non-local formulation of heat transport to compute a grid of loop models: the effects of non-local transport on the distribution of differential emission measure are particularly important in the coronal part of loops longer than the pressure scale height sp.We derive a scaling law for λ0/LTin the corona, showing that it grows exponentially with L/sp, and discuss effects of non-local heat transport in the transition r…
2015
Advanced Astronomy for Heliophysics Plus (ADAHELI+) is a project concept for a small solar and space weather mission with a budget compatible with an European Space Agency (ESA) S-class mission, including launch, and a fast development cycle. ADAHELI+ was submitted to the European Space Agency by a European-wide consortium of solar physics research institutes in response to the "Call for a small mission opportunity for a launch in 2017," of March 9, 2012. The ADAHELI+ project builds on the heritage of the former ADAHELI mission, which had successfully completed its phase-A study under the Italian Space Agency 2007 Small Mission Programme, thus proving the soundness and feasibility of its in…
Thermal conduction and modeling of static stellar coronal loops
1993
We have modeled stellar coronal loops in static conditions for a wide range of loop length, plasma pressure at the base of the loop and stellar surface gravity, so as to describe physical conditions that can occur in coronae of stars ranging from low mass dwarfs to giants as well as on a significant fraction of the Main-Sequence stars.
Penumbral oscillations in Na D lines
1990
Penumbral oscillations were measured in two opposite parts in the penumbra of a spot, using photographic spectra of Na D lines. Power spectra of velocities show the presence of the 5-min oscillation with lowv rms. Coherence and phase analyses between the velocity fluctuations of the lines are also studied. The results seem to show that the 5-min oscillation is still surviving as a standing or evanescent wave at the height of formation of Na D lines.
Transverse component of the magnetic field in the solar photosphere observed by Sunrise
2010
We present the first observations of the transverse component of photospheric magnetic field acquired by the imaging magnetograph Sunrise/IMaX. Using an automated detection method, we obtain statistical properties of 4536 features with significant linear polarization signal. Their rate of occurrence is 1-2 orders of magnitude larger than values reported by previous studies. We show that these features have no characteristic size or lifetime. They appear preferentially at granule boundaries with most of them being caught in downflow lanes at some point in their evolution. Only a small percentage are entirely and constantly embedded in upflows (16%) or downflows (8%).
Influencia del movimiento de vórtices de plasma en concentraciones magnéticas finas en la fotósfera solar
2016
High-resolution observations from ground-based (Solar Swedish Telescope) and space-borne (Hinode) solar telescopes acquired data with various filters, obtaining images of a quiet Sun region populated with small-scale magnetic elements. The region is also characterized by the presence of photospheric swirl convective plasma structures. This work abridges the results of different analysis applied over time series of images to follow the evolution of magnetic features aiming to establish the influence of the plasma vortices on their motions. Observaciones solares en alta resolución desde telescopios en tierra (SST) y en el espacio (Hinode) registraron datos con diferentes filtros, obteniendo i…
Fine structure and dynamic heating from temporal and spatial analysis of a solar active region observed with Solar Dynamics Observatory (SDO)
An outstanding issue in current solar and astrophysical research is that of the heating of the solar corona. How is the corona heated to temperatures of greater than 1 MK when the photosphere below is only 6000 K? One observational approach to addressing this important question is to focus on particular areas in the corona such as active regions (ARs). In a scenario that heating is impulsive and the cross-field spatial scale of the heating is so small, under the resolution of the current instruments, we attempted to narrow the question further to discrete bright magnetic flux tubes, the coronal loops, inside active regions. We investigate the emission variability, heating and substructure o…
Plasma Diagnostics and Magnetic Complexity of a Post-Flare Active Region with Hinode/XRT: Spatial and Temporal Evolution
2012
Flares are localized phenomena in active regions, but the magnetic and plasma responses may propagate to a larger area. In this work we investigate the temporal evolution of a flare in an active region with particular attention to the morphological details, and to the temperature and emission measure diagnostics allowed by Hinode/XRT.