Search Publications
A Critical Assessment of Nonlinear Force-Free Field Modeling of the Solar Corona for Active Region 10953
Leka, K. D.; Cheung, Mark C. M.; Lites, Bruce W. +16 more
Nonlinear force-free field (NLFFF) models are thought to be viable tools for investigating the structure, dynamics, and evolution of the coronae of solar active regions. In a series of NLFFF modeling studies, we have found that NLFFF models are successful in application to analytic test cases, and relatively successful when applied to numerically …
Observing the Roots of Solar Coronal Heating—in the Chromosphere
De Pontieu, Bart; McIntosh, Scott W.; Hansteen, Viggo H. +1 more
The Sun's corona is millions of degrees hotter than its 5000 K photosphere. This heating enigma is typically addressed by invoking the deposition at coronal heights of nonthermal energy generated by the interplay between convection and magnetic field near the photosphere. However, it remains unclear how and where coronal heating occurs and how the…
Velocity Characteristics of Evaporated Plasma Using Hinode/EUV Imaging Spectrometer
Milligan, Ryan O.; Dennis, Brian R.
This paper presents a detailed study of chromospheric evaporation using the EUV Imaging Spectrometer (EIS) onboard Hinode in conjunction with hard X-ray (HXR) observations from Reuven Ramaty High-Energy Solar Spectroscopic Imager (RHESSI). The advanced capabilities of EIS were used to measure Doppler shifts in 15 emission lines covering the temper…
Emergence of Small-scale Magnetic Loops Through the Quiet Solar Atmosphere
Bellot Rubio, L. R.; Martínez González, M. J.
We investigate the emergence of magnetic flux in the quiet Sun at very small spatial scales, focusing on the magnetic connection between the photosphere and chromosphere. The observational data consist of spectropolarimetric measurements and filtergrams taken with the Hinode satellite and the Dutch Open Telescope. We find that a significant fracti…
A Power-Law Distribution of Solar Magnetic Fields Over More Than Five Decades in Flux
Lamb, D. A.; DeForest, C. E.; Hagenaar, H. J. +3 more
Solar flares, coronal mass ejections, and indeed phenomena on all scales observed on the Sun, are inextricably linked with the Sun's magnetic field. The solar surface is covered with magnetic features observed on many spatial scales, which evolve on differing timescales: the largest features, sunspots, follow an 11-year cycle; the smallest seem to…
Fan-Spine Topology Formation Through Two-Step Reconnection Driven by Twisted Flux Emergence
Golub, L.; Aulanier, G.; Schmieder, B. +2 more
We address the formation of three-dimensional nullpoint topologies in the solar corona by combining Hinode/X-ray Telescope (XRT) observations of a small dynamic limb event, which occurred beside a non-erupting prominence cavity, with a three-dimensional (3D) zero-β magnetohydrodynamics (MHD) simulation. To this end, we model the boundary-driven "k…
Active Region Loops: Hinode/Extreme-Ultraviolet Imaging Spectrometer Observations
Young, Peter R.; Dwivedi, Bhola N.; Tripathi, Durgesh +2 more
We have carried out a study of active region loops using observations from the Extreme-ultraviolet Imaging Spectrometer (EIS) on board Hinode using 1'' raster data for an active region observed on 2007 May 19. We find that active region structures which are clearly discernible in cooler lines (≈1 MK) become "fuzzy" at higher temperatures (≈2 MK). …
Magnetic Reconnection along Quasi-separatrix Layers as a Driver of Ubiquitous Active Region Outflows
Mandrini, C. H.; van Driel-Gesztelyi, L.; Démoulin, P. +2 more
Hinode's EUV Imaging Spectrometer (EIS) has discovered ubiquitous outflows of a few to 50 km s-1 from active regions (ARs). These outflows are most prominent at the AR boundary and appear over monopolar magnetic areas. They are linked to strong non-thermal line broadening and are stronger in hotter EUV lines. The outflows persist for at…
Properties of Magnetohydrodynamic Waves in the Solar Photosphere Obtained with Hinode
Tsuneta, S.; Fujimura, D.
We report the observations of the magnetohydrodynamic (MHD) waves propagating along magnetic flux tubes in the solar photosphere. We identified 20 isolated strong peaks (8 peaks for pores and 12 peaks for intergranular magnetic structure) in the power spectra of the line-of-sight (LOS) magnetic flux, the LOS velocity, and the intensity for 14 diff…
Active Region Transition Region Loop Populations and Their Relationship to the Corona
Warren, Harry P.; Ugarte-Urra, Ignacio; Brooks, David H.
The relationships among coronal loop structures at different temperatures are not settled. Previous studies have suggested that coronal loops in the core of an active region (AR) are not seen cooling through lower temperatures and therefore are steadily heated. If loops were cooling, the transition region would be an ideal temperature regime to lo…