The photospheric Poynting flux and coronal heating
TLDR
In this article, the upward transport of magnetic energy across the photosphere in a plage region was investigated using high-resolution observations of plage magnetic fields made with the Solar Optical Telescope aboard the Hinode satellite.Abstract:
Some models of coronal heating suppose that convective motions at the photosphere shuffle the footpoints of coronal magnetic fields and thereby inject sufficient magnetic energy upward to account for observed coronal and chromospheric energy losses in active regions. Using high-resolution observations of plage magnetic fields made with the Solar Optical Telescope aboard the Hinode satellite, we investigate this idea by estimating the upward transport of magnetic energy --- the vertical Poynting flux, S_z --- across the photosphere in a plage region. To do so, we combine: (i) estimates of photospheric horizontal velocities, v_h, determined by local correlation tracking applied to a sequence of line-of-sight magnetic field maps from the Narrowband Filter Imager, with (ii) a vector magnetic field measurement from the SpectroPolarimeter. Plage fields are ideal observational targets for estimating energy injection by convection, because they are: (i) strong enough to be measured with relatively small uncertainties; (ii) not so strong that convection is heavily suppressed (as within umbrae); and (iii) unipolar, so S_z in plage is not influenced by mixed-polarity processes (e.g., flux emergence) unrelated to heating in stable, active-region fields. In this plage region, we found that the average S_z varied in space, but was positive (upward) and sufficient to explain coronal heating, with values near (5 +/- 1) x 10^7 erg/cm^2/s. We find the energy input per unit magnetic flux to be on the order of 10^5 erg/s/Mx. A comparison of intensity in a Ca II image co-registered with the this plage shows stronger spatial correlations with both total field, B, and unsigned vertical field, |B_z|, than either S_z or horizontal field, B_h. The observed Ca II brightness enhancement, however, probably contains a strong contribution from a near-photosphere hot-wall effect unrelated to atmospheric heating.read more
Citations
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Journal ArticleDOI
Numerical Simulations of Coronal Heating through Footpoint Braiding
TL;DR: In this paper, the authors analyzed the heating at both large and small scales and found that heating is episodic and highly structured in space, but occurs along loop shaped structures, and moves along with the magnetic field.
Journal ArticleDOI
Solar Coronal Loops Associated with Small-scale Mixed Polarity Surface Magnetic Fields
Lakshmi Pradeep Chitta,Hardi Peter,Sami K. Solanki,Peter Barthol,Achim Gandorfer,Laurent Gizon,Johann Hirzberger,Tino L. Riethmüller,M. van Noort,J. Blanco Rodríguez,J. C. del Toro Iniesta,D. Orozco Suárez,Wolfgang Schmidt,V. Martínez Pillet,Michael Knölker +14 more
TL;DR: In this paper, the authors used high-resolution line-of-sight magnetic field data from the Imaging Magnetograph eXperiment instrument on the Sunrise balloon-borne observatory and coronal observations from the Atmospheric Imaging Assembly onboard the Solar Dynamics Observatory of an emerging active region.
Journal ArticleDOI
Numerical Simulations of Coronal Heating through Footpoint Braiding
TL;DR: In this paper, the authors analyzed the heating at both large and small scales and found that heating is episodic and highly structured in space, but occurs along loop shaped structures, and moves along with the magnetic field.
Journal ArticleDOI
Solar Coronal Loops Associated with Small-scale Mixed Polarity Surface Magnetic Fields
Lakshmi Pradeep Chitta,Hardi Peter,Sami K. Solanki,Peter Barthol,Achim Gandorfer,Laurent Gizon,Johann Hirzberger,T. L. Riethmueller,M. van Noort,J. Blanco Rodríguez,J. C. del Toro Iniesta,D. Orozco Suárez,Wolfgang Schmidt,V. Martínez Pillet,M. Knoelker +14 more
TL;DR: In this article, the authors used high-resolution line-of-sight magnetic field data from the Imaging Magnetograph eXperiment instrument on the SUNRISE balloon-borne observatory and coronal observations from the Atmospheric Imaging Assembly onboard the Solar Dynamics Observatory of an emerging active region.
Journal ArticleDOI
The Role of Magnetic Helicity in Coronal Heating
TL;DR: In this article, the authors showed that the heat generated by the reconnection responsible for the helicity condensation process is sufficient to account for the observed coronal heating, and they also found that the heating rate is only weakly dependent on the net helicity preference of the photospheric driving.
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TL;DR: The Interface Region Imaging Spectrograph (IRIS) as mentioned in this paper provides simultaneous spectra and images of the photosphere, chromosphere, transition region, and corona with 0.33 arcsec and up.