| Both sides previous revisionPrevious revisionNext revision | Previous revision |
| themis [2025/07/04 16:03] – etienne | themis [2025/08/12 16:13] (current) – etienne |
|---|
| |
| |
| == THEMIS image of the month: June 2025 == | == THEMIS image of the month: July 2025 == |
| |
| <columns 80% l > | <columns 100% l 40%> |
| |
| <html> <a href="https://www.themis.iac.es/lib/exe/fetch.php?media=science:gallery:protu:solarfilament_meteospace_2025june05.jpg"> <img src="https://www.themis.iac.es/lib/exe/fetch.php?media=science:gallery:protu:solarfilament_meteospace_2025june05.jpg" alt="Solar filament observations on June 5th 2025." style="width: 100%; height: auto;"></a></html> \\ | <html> <a href="https://www.themis.iac.es/lib/exe/fetch.php?media=science:gallery:instrumentation:spectro_with_light.png"> <img src="https://www.themis.iac.es/lib/exe/fetch.php?media=science:gallery:instrumentation:spectro_with_light.png" alt="A peek inside THEMIS MTR2 spectrograph" style="width: 100%; height: auto;"></a></html> \\ |
| |
| In June, during an observation campaign lead by researchers from the Paris Observatory (France) and the University of Wroclaw (Poland), THEMIS observed solar filaments. Solar filaments are large magnetised structure of the solar corona confining cold chromospheric-like plasma. Thanks to its specific magnetic structure, solar filaments plasma, of a temperature of about 10 000°K, "hangs" thermally isolated from the million °K solar corona. As this dense and cool plasma absorbs the light emitted from the lower solar layer, the filament appears dark relatively to the background.\\ | |
| |
| The THEMIS observation presented here results from two reconstructed images obtained from two adjacent scans over the solar filament with the THEMIS spectrograph slit. The two scans, which have a 80" range with a 0.5" spatial step, are then stitched together to obtain a larger field of view of about 110" x 90". Only the reconstructed image in the core of Hα line is displayed here, but THEMIS data allow to sample the full range of the Hα line with a spectral resolution of 4mÅ.\\ | <newcolumn 60%> |
| | If one could sneak inside [[technical:mtr2 | MTR2 spectrograph]] while THEMIS is observing, this is what one would see looking down. The picture shows the beautiful work of decomposing the white solar light into small ranges of electromagnetic spectrum that are of interest for researchers to study the physical properties of the Sun. \\ |
| THEMIS high-resolution observations are very complementary to the observations of the [[https://www.oca.eu/fr/lag-physol-projects?option=com_content&view=category&layout=blog&id=295&Itemid=908 | Meteospace/3SOLEIL]] solar surveillance service of OCA/CNRS-INSU, which provide full-Sun high cadence (every 10s) Hα observations, presented on the right panel. \\ | |
| |
| Thanks to its high-resolution, as illustrated in the left panel, THEMIS permits to analyse the filamentary structure of the solar filament and understand its magnetic field thanks to THEMIS polarised measurements. In particular, the magnetic properties of the "barbs" of the filament, the features which extend away from the "spine" (the filament axis), remains ill understood and an active topic of research. | The white light beam coming from the THEMIS telescope (white light on the left) is first decomposed in a low resolution spectrum (rainbow on the middle left). A rigid mask placed on the light path, enables to select several bands within the solar spectrum that will be analysed (overlapping orange and red patch on the middle right). Finally, an echelle grating enables to strongly increase the dispersion (spacing) of the spectral domains of interest (separated and extended red and orange patch on the right). There spectral cameras are placed to record the high resolution spectrum. |
| | |
| | With its a spectral resolving power, R, of about 200 000-300 000, THEMIS MTR2 spectrograph has one of the world's best resolving power in astrophysics. MTR2 has the ability to distinguish between two wavelengths separated by a small amount. THEMIS theoretical can produce simultaneously up to eight high resolution spectrograms (although most cases, only 2-4 are requested). The choice of wavelength domains is not pre-imposed to the visiting research scientist observing with THEMIS. The choice is left to the investigators, giving them a high level of freedom to study [[https://www.themis.iac.es/doku.php?id=science:objectives | diverse topics in solar physics]]. |
| | \\ |
| </columns> | </columns> |
| |
