Magneto-thermal convection in solar prominences

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Abstract

Coronal cavities are large low-density regions formed by hemispheric-scale magnetic flux ropes suspended in the Sun’s outer atmosphere1. They evolve over time, eventually erupting as the dark cores of coronal mass ejections2,3. Although coronal mass ejections are common and can significantly affect planetary magnetospheres, the mechanisms by which cavities evolve to an eruptive state remain poorly understood. Recent optical observations4 of high-latitude ‘polar crown’ prominences within coronal cavities reveal dark, low-density5 ‘bubbles’ that undergo Rayleigh–Taylor instabilities6,7 to form dark plumes rising into overlying coronal cavities. These observations offered a possible mechanism for coronal cavity evolution, although the nature of the bubbles, particularly their buoyancy, was hitherto unclear. Here we report simultaneous optical and extreme-ultraviolet observations of polar crown prominences that show that these bubbles contain plasma at temperatures in the range (2.5–12) × 105 kelvin, which is 25–120 times hotter than the overlying prominence. This identifies a source of the buoyancy, and suggests that the coronal cavity–prominence system supports a novel form of magneto-thermal convection in the solar atmosphere, challenging current hydromagnetic concepts of prominences and their relation to coronal cavities.

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Figure 1: Quiescent prominence observed on the northwest solar limb on 22 June 2010.
Figure 2: Time series of images taken during the large plume generation event in the prominence observed on 22 June 2010.
Figure 3: Emission, contrast and AIA filter ratio analysis for the bubble and plume in the 22 June 2010 quiescent prominence.
Figure 4: Quiescent prominence observed on the southeast solar limb on 2 July 2010.

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Acknowledgements

Hinode is a Japanese mission developed and launched by ISAS/JAXA, in collaboration with NAOJ as a domestic partner, and with NASA and STFC (UK) as international partners. Scientific operation of the Hinode mission is conducted by the Hinode science team organized at ISAS/JAXA. Support for the post-launch operation is provided by JAXA and NAOJ (Japan), STFC (UK), NASA, ESA and NSC (Norway). The Solar Dynamics Observatory is part of NASA’s Living with a Star programme. K.S. and A.H. are supported by the Grant-in-Aid for the Global COE Program ‘The Next Generation of Physics, Spun from Universality and Emergence’. We thank J. Martinez-Sykora for discovering the 2 July 2010 prominence bubble event in the AIA database.

Author information

T.B. was responsible for planning, coordination, data reduction and analysis of the Hinode and AIA observations, and also wrote the majority of the text. P.T. performed the AIA filter ratio temperature analysis using temperature response functions from P.B. A.H. performed numerical simulations of the Rayleigh–Taylor instability based on observational parameters established in this and earlier studies, and provided commentary on the theoretical implications of the discovery. K.S. supervised A.H. and provided theoretical interpretation of the observations and simulations. B.C.L. provided interpretation in the context of solar CMEs, the theoretical implications of the finding for coronal cavity evolution and stability, and contributed to section 3 of the Supplementary Information. C.S. leads the science section of the AIA instrument team and provided advice on the paper’s content. A.T. is the principal investigator for the AIA instrument and is the head of the Lockheed Martin solar physics group. T.T. supervised T.B. and P.B., and provided guidance on coordinating the Hinode and AIA missions.

Correspondence to Thomas Berger.

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The authors declare no competing financial interests.

Supplementary information

Supplementary Information

This file contains Supplementary Notes and Data, Supplementary Tables 1-3, Supplementary Figures 1-4 with legends, a Supplementary Discussion, additional references and legends for Supplementary Movies 1-10. (PDF 1292 kb)

41586_2011_BFnature09925_MOESM66_ESM.mov

Hinode/SOT Ca II 396.8 nm H-line filtergram movie showing the 22-June-2010 quiescent prominence above the NW solar limb-see Supplementary Information file for full legend. (MOV 6160 kb)

Supplementary Movie 1

Hinode/SOT Ca II 396.8 nm H-line filtergram movie showing the 22-June-2010 quiescent prominence above the NW solar limb-see Supplementary Information file for full legend. (MOV 6160 kb)

41586_2011_BFnature09925_MOESM67_ESM.mov

Hinode/SOT Hα 656.3 nm filtergram movie showing the 22-June-2010 quiescent prominence during the same time period as Movie 1-see Supplementary Information file for full legend. (MOV 3694 kb)

Supplementary Movie 2

Hinode/SOT Hα 656.3 nm filtergram movie showing the 22-June-2010 quiescent prominence during the same time period as Movie 1-see Supplementary Information file for full legend. (MOV 3694 kb)

41586_2011_BFnature09925_MOESM68_ESM.mov

Hinode/SOT Hα dopplergram movie showing the 22-June-2010 quiescent prominence during the same time period as Movie 1-see Supplementary Information file for full legend. (MOV 3243 kb)

Supplementary Movie 3

Hinode/SOT Hα dopplergram movie showing the 22-June-2010 quiescent prominence during the same time period as Movie 1-see Supplementary Information file for full legend. (MOV 3243 kb)

41586_2011_BFnature09925_MOESM69_ESM.mov

SDO/AIA 304 channel movie showing the 22-June-2010 quiescent prominence during the same time period as Movie 1-see Supplementary Information file for full legend. (MOV 9718 kb)

Supplementary Movie 4

SDO/AIA 304 channel movie showing the 22-June-2010 quiescent prominence during the same time period as Movie 1-see Supplementary Information file for full legend. (MOV 9718 kb)

41586_2011_BFnature09925_MOESM70_ESM.mov

SDO/AIA 171 channel movie showing the 22-June-2010 quiescent prominence during the same time period as Movie 1-see Supplementary Information file for full legend. (MOV 5718 kb)

Supplementary Movie 5

SDO/AIA 171 channel movie showing the 22-June-2010 quiescent prominence during the same time period as Movie 1-see Supplementary Information file for full legend. (MOV 5718 kb)

41586_2011_BFnature09925_MOESM71_ESM.mov

SDO/AIA 193 channel movie showing the 22-June-2010 quiescent prominence during the same time period as Movie 1-see Supplementary Information file for full legend. (MOV 5561 kb)

Supplementary Movie 6

SDO/AIA 193 channel movie showing the 22-June-2010 quiescent prominence during the same time period as Movie 1-see Supplementary Information file for full legend. (MOV 5561 kb)

41586_2011_BFnature09925_MOESM72_ESM.mov

SDO/AIA 211 channel movie showing the 22-June-2010 quiescent prominence during the same time period as Movie 1-see Supplementary Information file for full legend. (MOV 9111 kb)

Supplementary Movie 7

SDO/AIA 211 channel movie showing the 22-June-2010 quiescent prominence during the same time period as Movie 1-see Supplementary Information file for full legend. (MOV 9111 kb)

41586_2011_BFnature09925_MOESM73_ESM.mov

SDO/AIA 131 channel movie showing the 22-June-2010 quiescent prominence during the same time period as Movie 1-see Supplementary Information file for full legend. (MOV 8043 kb)

Supplementary Movie 8

SDO/AIA 131 channel movie showing the 22-June-2010 quiescent prominence during the same time period as Movie 1-see Supplementary Information file for full legend. (MOV 8043 kb)

41586_2011_BFnature09925_MOESM74_ESM.mov

Composite movie showing a close-up of the large plume in the 22-June-2010 quiescent prominence in three wavelengths: Hinode/SOT Ca H-line, SDO/AIA 171 and SDO/AIA 211 channels-see Supplementary Information file for full legend. (MOV 882 kb)

Supplementary Movie 9

Composite movie showing a close-up of the large plume in the 22-June-2010 quiescent prominence in three wavelengths: Hinode/SOT Ca H-line, SDO/AIA 171 and SDO/AIA 211 channels-see Supplementary Information file for full legend. (MOV 882 kb)

41586_2011_BFnature09925_MOESM75_ESM.mov

SDO/AIA 304 and 171 channel movies showing the 02-July-2010 quiescent prominence above the SE limb of the Sun-see Supplementary Information file for full legend. (MOV 5861 kb)

Supplementary Movie 10

SDO/AIA 304 and 171 channel movies showing the 02-July-2010 quiescent prominence above the SE limb of the Sun-see Supplementary Information file for full legend. (MOV 5861 kb)

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Berger, T., Testa, P., Hillier, A. et al. Magneto-thermal convection in solar prominences. Nature 472, 197–200 (2011). https://doi.org/10.1038/nature09925

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