May was Mercury Month a theMis! : In May 2025 took place the usual annual observation campaign of Mercury, led by researchers from the Italian National Institute of Astrophysics (INAF/IAPS in Rome) in collaboration with scientist from the French Laboratoire Atmosphères, Observations Spatiales (LATMOS/CNRS-UVSQ-SU-CNES in Paris).

In a sequence of scans of the exosphere of Mercury obtained some years ago, THEMIS could follow the hourly evolution of the reconstructed distribution of the Sodium emission. The figure displays the intensity emission (in kiloRayleigh) after preliminary reduction, including bias and sky background subtraction, as well as spectral and flux calibrations. Solid white line highlights the disk of the planet, the cross indicating the center of the disk. Mercury disk is 6.0'' wide. The Sun is located on the left. The images show the two peaks of higher intensity at high hermian latitude in the direction of the Sun. These peaks of sodium emission are roughly co-spatial with the positions of the magnetic footprints. Their evolution is due to the link of such emission with the Mercury magnetosphere and the interaction with the varying solar wind particles penetrating the magnetosphere and flowing to the surface. Adapted from Mangano et al. 2013.

A selection of THEMIS sunspot observations obtained between 2022 and 2025 with the BroadBand Imaging Camera. Observations are performed using Themis Adaptive Optics and images are processed with a Knox-Thompson image-reconstruction method.

THEMIS observations of the east sunspot group of the active region NOAA 13981 on February 6th 2025. The left image is a Knox-Thompson reconstructed from red continuum broadband camera. The right panels are intensity maps reconstructed from spectral observations by the MTR2 spectrograph observing the Hα absorption line. Theses maps are reconstructed from a scan by the telescope of the active region. While these intensity images have a lower spatial resolution, they provide a wealth of spectroscopic information. The region was observed during a flare, as can be noted by the typical ribbon-shape emission in the Hα line centre. This emission is absent from the continuum emission, indicating a chromospheric emission phenomena. Meanwhile, the red wing maps (Hα+1Å and Hα+0.5Å) display dark absorbing material above the location of the flare ribbons, signature of down-flowing dense material, a phenomena nicknamed “coronal rain”. While performing observations with THEMIS, targeting this flaring active region has been permitted thanks thanks to the high-cadence Hα surveillance permitted by the METEOSPACE/3SOLEIL service.

Observation of the main sunspot of the active region NOAA 13959 on January 15th 2025. This white light broad band image in the red continuum highlights the two “light bridges” of the sunspot. Light-bridges are lanes of bright material that divide the sunspot umbra. The image is the results from 100 acquired snapshots processed with a Knox Thompson image reconstruction method.