Contact

Dr. Klaus Gerhard Puschmann

------------------------------------
Julius-Pfister-Ring 14d
63755 Alzenau

Bavaria

Germany

------------------------------------

Phone: +49 6023 7061001
Mobile: +49 1522 1517880

E-Mail: kgp@live.de

Dr. Klaus Gerhard Puschmann
Dr. Klaus Gerhard Puschmann

Spicules and their on-disk counterparts - The main driver for solar chromospheric heating?

@copyright - Klaus Gerhard Puschmann

Click the image "A sensational observational discovery" to see the animation and important observational discovery achieved with the GREGOR Fabry-Pérot Interferometer, confirming Spicules as the main driver for chromospheric heating of our Sun and sun-like stars.

Details

The question how the outer solar atmosphere is heated from solar photospheric temperatures of about 5800K  up to solar chromospheric and coronal temperatures of about 20.000K and millions of degrees respectively,remained with any satisfying answer for centuries.  

 

The density in the solar atmosphere drops fast in the photosphere, where the opacity reduces so much that the solar plasma becomes transparent to radiation. Therefore it seems to be impossible to transfer energy to the outer solar atmosphere by radiation.  Different energy transport mechanisms are apparently required.

 

Spicules are highly dynamic jet-like structures best observed at and beyond the solar limb in chromospheric  lines such as Hα (6563 Å), Ca II H (3968.5 Å) and Ca II IR (8542 Å).

 

Provided that spicules possess on-disk counter parts, they could be one of the main drivers for the solar chromospheric heating. Type I spicules might be the result of photospheric acoustic p-mode leakage between granular cells, providing significant energy to the chromosphere. Type II spicules might by the result of magnetic reconnection at photopheric level and be related to Alfvén waves (MHD waves).

@copyright - Klaus Gerhard Puschmann

Movie 1a: The standard picture of solar spicules: elongated highly dynamic jet-like features best seen beyond the solar limb in emission. Temporal evolution (15min) of Hα Line parameters for solar limb spicules. From left to right and top to bottom: Full-width at half-maximum (standard estimate, Gaussian Fit), line-wing intensity, line-core intensity, height distribution. For a detailed description of the data-set represented  here see the text below.

On 04 May 2005, I recorded several  time series of Hα line scans with the GREGOR Fabry-Perot Interferometer (GFPI, Puschmann et al. 2006, A&A 451, 1151), still deployed at the German Vacuum Tower Telescope (VTT). For different solar limb and on-disc positions, as well as for solar disk center, the Hα line was sampled in 21 steps of 11 pm width with a cadence of about 22 s. The total duration of each time series was up to 15 min.  

 

Applying the Multi-Object Multi-Frame Blind Deconvolution technique (MOMFBD,van Noort, M., Rouppe van der Voort, L., & Löfdahl, M. G. 2005, Sol. Phys., 228, 191) as part of  the GREGOR Fabry-Perot Interferometer Data Pipeline iSPOR-DP (imaging Spectropolarimetric Parallel Organized Reconstruction Data Pipeline, Puschmann, K. G. & Beck, C. 2011, A&A, 533, A21), I subsequently improved the spatial resolution of the spectra substantially far beyond the real-time correction of Adaptive Optics.

 

The resulting time series of Hα line parameters presented below reveal the entire and detailed complexity as well as the overwhelming dynamics of spicules apparently covering the entire solar disk, thus confirming spicules as the potential driver of chromospheric heating.

 

While spicules by definition should appear exclusively in emission beyond the solar limb, the intensity maps resulting from the spectral scans of the Hα line performed with the GREGOR Fabry-Pérot Interferometer reveal spicular counterparts also on solar disk, apparent in absorption at certain line wing wavelengths of the Hα line.

Fig. 1: Example of a typical Hα Line Scan of solar off-limb spicules (in emission) and on-disk counterparts (in absorption) – Reconstructed Hα narrowband images at relevant spectral positions around the Hα line core.

GREGOR Fabry-Perot Interferometer @ German Vacuum Tower Telescope (VTT) - Hα Line Scan of solar off-limb spicules and on-disc counterparts

@copyright - Klaus Gerhard Puschmann

Movie 1: Example of a typical Hα Line Scan of solar off-limb spicules (in emission) and on-disk counterparts (in absorption) – Reconstructed Hα narrowband images at consecutive spectral positions around the Hα line core.

Apparently and as demonstrated in the following figures and movies below, spicular counterparts and
their overwhelming dynamics are not only detected in areas closed to the solar limb, but also
in active regions harboring sunspots or pores and even in quiet sun at solar disk center.

Fig. 2: Still image of time series I, showing Hα line-wing intensities of solar off-limb spicules (in emission) and on-disk counterparts (in absorption) close to the solar north-west limb.

@copyright - Klaus Gerhard Puschmann

Movie 2: Time series I (15 min): Hα line-wing intensity maps of solar off-limb spicules (in emission)

and on-disk counterparts (in absorption) at a temporal cadence of 22 s close the solar north-west
limb.

Fig. 3: Still image of time series II, showing Hα line-wing intensities of solar off-limb spicules (in emission) and on-disk counterparts (in absorption) close the solar north-east limb.

@copyright - Klaus Gerhard Puschmann

Movie 3: Time series II (4 min): Hα Line wing-intensity maps of solar off-limb spicules (in emission) and on-disk counterparts (in absorption) at a temporal cadence of 22 s close the solar north-east limb.

Fig. 4: Still image of time series III, showing Hα line-wing intensities of solar off-limb spicules (in emission) and on-disk counterparts (in absorption) close the solar south-west limb.

@copyright - Klaus Gerhard Puschmann

Movie 4: Time series III (7 min): Hα line-wing intensity maps of solar off-limb spicules (in emission) and on-disk counterparts (in absorption) at a temporal cadence of 22 s close the solar south-west limb.

Fig. 5: Still image of time series IV, showing Hα line-wing intensities of spicular on-disk counterparts (in absoprtion) in a typical active region harboring a sunspot.

@copyright - Klaus Gerhard Puschmann

Movie 5: Time series IV (6 min):  Hα line-wing intensities of spicular on-disk counterparts (in absorption) in a typical active region harboring a sunspot at a temporal cadence of 22 s.

Fig. 6: Still image of time series V, showing Hα line-wing intensities of spicular on-disk counterparts (in absorption) in a typical active region harboring a solar pore.

@copyright - Klaus Gerhard Puschmann

Movie 6: Time series V (7 min): Hα line-wing intensities of spicular on-disk counterparts (in absorption) in a typical active region harboring a solar pore at a temporal cadence of 22 s.

Fig. 7: Still image of time series VI, showing Hα line-wing intensities of a quiet sun region at solar disk center. Remarkable - on-disk projection of spicules (in absorption).

@copyright - Klaus Gerhard Puschmann

Movie 7: Time series VI (14 min), showing Hα Line wing-intensities of a quiet sun region at solar disk center. Remarkable - on-disk projection of spicules (in absoprtion) at a temporal cadence of 22 s.

Spicules - not only observed in emission beyond the solar limb but also observed in absorption on the solar disk - in areas close to the solar limb, in active solar regions, and now even in quiet solar regions at solar disk center - a simple but maybe canonical proof that "spicules" cover the entire solar disk and therefore should be considered as the main driver of chromospheric heating for both the Sun and solar-like stars, with an expected mass flux larger than 100 times that of the solar wind. The main findings presented here shed light on a key question in Solar Physics that remained without a really satisfying answer for centuries.

 

The high resolution time series and animations furthermore reveal that spicules seem to be the result of the interaction of the highly dynamic photospheric small scale magnetic field (brightening in both Hα line wing intensity maps and broadband white light intensity maps @ 656nm), which is dominated by convective processes and is predominantly located in intergranular lanes and at meso- and supergranular scales.

 

Movie 8 reveals the interaction of small-scale quiet-sun magnetic field at solar disk center, driven by the surrounding convection. Spicules are observed in consequence. Movie 9 reveals the enlargement of the rectangular area indicated in Movie 8. 

 

@copyright - Klaus Gerhard Puschmann

Movie 8: Time series VI (14 min). Left panel - reconstructed white-light intensity maps @ 656nm. Right panel - Hα Line Wing intensities presented in Fig. 7 and Movie 7. The indicated rectangular area is  magnified and displayed in Movie 9. Remarkable feature - interaction of small-scale quiet-sun magnetic field at solar disk center, driven by the surrounding convection. Spicules are observed in consequence. Temporal cadence: 22 s.

@copyright - Klaus Gerhard Puschmann

Movie 9: Magnifiation of the rectangular area indicated in Movie 8. Left panel - reconstructed white-light intensity-maps @ 656nm. Right panel - Hα Line Wing intensities. Remarkable feature - interaction of small-scale quiet-sun magnetic field at solar disk center, driven by the surrounding convection (image center). Spicules are observed in consequence. Temporal cadence: 22 s.

The spicular endings seem to feed the carpet of gas observable at high chromospheric layers (at spectral positions towards and at the Hα line core). As deduced from the present investigation of spicular on-disk counterparts, there seems to exist a certain height, spicules can reach at all. Above this height, on-disk spicules seem to bend horizontally (see e.g. Fig.2 and Movie 2). A fact that might have to be reconsidered also in the case of previous analyses and interpretations of spicules published in literature, mainly addressing off-limb spicules in emission. Also remarkable, the highly dynamic meso-granular pattern, best visible in the Hα line wing intensity maps of the quiet solar region observed at disk center (see Fig.7 and Movie 7), i.e. a cell like brightening with extremely fast moving fine structure in horizontal direction.

 

Finally, I would like to point to a statistical analysis of spicules, which has been recently provided on arXiv by J. Shetye et al. 2016.

 

I myself and collaborators are currently investigating all available data sets reflected in the figures (above) or animations (provided by links) presented here. Processes and dynamics of off-limb spicules and their on-disk counterparts revealed in the individual time series of Hα line parameters are simply overwhelming. I encourage experts in chromospheric heating to contribute in the data analysis and interpretation/publication of the results. Any response by E-Mail will be highly appreciated. 

 

 

All above findings and descriptions are published within the article provided below:

 

******************************************

 

Spicules and their on-disk counterparts, the main driver for solar chromospheric heating?

 

Klaus Gerhard Puschmann

 

 

                                                     2016arXiv160205185P

 

                                                      ******************************************

Druckversion Druckversion | Sitemap
© Dr. Klaus Gerhard Puschmann