OBSERVING THE ROOTS OF SOLAR CORONAL HEATING—IN THE CHROMOSPHERE

By B. de Pontieu, S. McIntosh, V. Hansteen, C. Schrijver. 2009

232 citations recorded by the source corpus.

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 corona is filled with hot plasma. We show that energy deposition at coronal heights cannot be the only source of coronal heating by revealing a significant coronal mass supply mechanism that is driven from below, in the chromosphere. We quantify the asymmetry of spectral lines observed with Hinode and SOHO and identify faint but ubiquitous upflows with velocities that are similar (50–100 km s−1) across a wide range of magnetic field configurations and for temperatures from 100,000 to several million degrees. These upflows are spatiotemporally correlated with and have similar upward velocities as recently discovered, cool (10,000 K) chromospheric jets or (type II) spicules. We find these upflows to be pervasive and universal. Order of magnitude estimates constrained by conservation of mass and observed emission measures indicate that the mass supplied by these spicules can play a significant role in supplying the corona with hot plasma. The properties of these events are incompatible with coronal loop models that include only nanoflares at coronal heights. Our results suggest that a significant part of the heating and energizing of the corona occurs at chromospheric heights, in association with chromospheric jets.

Subfields: Astronomy and Astrophysics, Geophysics

View Paper: https://www.semanticscholar.org/paper/e0632109dcf15e607146607f13193f771ef74623

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In Astronomy and Astrophysics

In Geophysics

C. Schrijver

Citations in the corpus

HEATING OF THE SOLAR CHROMOSPHERE AND CORONA BY ALFVÉN WAVE TURBULENCE (2011, background): “This has led some authors to suggest that the heating of active region loops is localized in the low corona and involves energization processes that operate in the chromosphere and transition region (Aschwanden 2001; Aschwanden et al. 2007; De Pontieu et al. 2009).”
Origins of the Ambient Solar Wind: Implications for Space Weather (2017, background): “Some have suggested that much of the corona’s mass and energy may be injected directly from these structures (Pneuman 1986; Loucif 1994; De Pontieu et al. 2009; Moore et al. 2011; Tian et al. 2014; Raouafi et al. 2016).”
Slow Solar Wind: Observations and Modeling (2016, unknown): “De Pontieu et al. (2009) found a correlation between the emission line asymmetries in the corona and the dynamics in type II spicules in the chromosphere.”
Solar Orbiter (2012, background): “Such spicules also support waves, possibly with sufficient energy to accelerate fast wind streams in coronal holes (De Pontieu et al. 2009, 2011).”
ON-DISK COUNTERPARTS OF TYPE II SPICULES IN THE Ca ii 854.2 nm AND Hα LINES (2009, background): “…of RBEs on the solar disk also provides an exciting way of establishing the connection of these jets to the recently discovered upflows that are seen as faint asymmetric profiles of EUV and UV emission lines which are formed at transition region and coronal temperatures (De Pontieu et al. 2009).”
The Interface Region Imaging Spectrograph (IRIS) (2012, background): “…may occur primarily in the chromosphere and transition region, as evidenced, e.g., by chromospheric jets such as spicules (De Pontieu et al., 2011), and their faint coronal counterparts, visible only as slight enhancements in the blue wing of coronal spectral lines (De Pontieu et al., 2009).”