Europlanet Science Congress 2020
Virtual meeting
21 September – 9 October 2020
Europlanet Science Congress 2020
Virtual meeting
21 September – 9 October 2020
EPSC Abstracts
Vol. 14, EPSC2020-220, 2020, updated on 14 May 2024
https://doi.org/10.5194/epsc2020-220
Europlanet Science Congress 2020
© Author(s) 2024. This work is distributed under
the Creative Commons Attribution 4.0 License.

Exospheric Na distributions along the Mercury orbit with the THEMIS telescope

Anna Milillo1, Valeria Mangano1, Stefano Massetti1, Alessandro Mura1, Christina Plainaki2, Tommaso Alberti1, Alessandro Aronica1, Elisabetta De Angelis1, Alessandro Ippolito2, Adrian Kazakov1, Raffaella Noschese1, Stefano Orsini1, Rosanna Rispoli1, Roberto Sordini1, and Nello Vertolli1
Anna Milillo et al.
  • 1National Institute of Astrophysics, Institute for Space Astrophysics and Planetology, Rome, Italy (anna.milillo@inaf.it)
  • 2Italian Space Agency (ASI), Rome, Italy

The variability of Na exosphere of Mercury shows time scales from less than one hour to seasonal variations. While the faster variations, accounting of about 10-20% of fluctuations are probably linked to the planetary response to solar wind and Interplanetary Magnetic Field variability, the seasonal variations (up to about 80%) should be explained by complex mechanisms involving different surface release processes, loss, source and migrations of the exospheric Na atoms. Eventually, a Na annual cycle can be identified. In the past, ground-based observations and equatorial density from MESSENGER data have been analysed. In this study, for a better investigation of the exospheric Na features, we have studied the local time and latitudinal distributions of the exospheric Na column density as a function of the True Anomaly Angle (TAA) of Mercury by means of the extended dataset of images, collected from 2009 to 2013, by the THEMIS solar telescope. Our results show that the THEMIS images, in agreement with previous results, registered a strong general increase at aphelion and a dawn ward emission predominance with respect to dusk ward and subsolar region between 90° and 150° TAA. Unlikely other analyses, ours evidences a predominance of subsolar column density along the rest of Mercury’s orbit. An unexpected relationship between Northward or Southward peak emission and both TAA and local time is also evidenced by our analysis. This result seems to contradict previous results obtained from different data sets and it is not easily explained, thus it requires further investigations.

How to cite: Milillo, A., Mangano, V., Massetti, S., Mura, A., Plainaki, C., Alberti, T., Aronica, A., De Angelis, E., Ippolito, A., Kazakov, A., Noschese, R., Orsini, S., Rispoli, R., Sordini, R., and Vertolli, N.: Exospheric Na distributions along the Mercury orbit with the THEMIS telescope, Europlanet Science Congress 2020, online, 21 Sep–9 Oct 2020, EPSC2020-220, https://doi.org/10.5194/epsc2020-220, 2020.