Europlanet Science Congress 2021
Virtual meeting
13 – 24 September 2021
Europlanet Science Congress 2021
Virtual meeting
13 September – 24 September 2021
EPSC Abstracts
Vol. 15, EPSC2021-64, 2021, updated on 14 May 2024
https://doi.org/10.5194/epsc2021-64
Europlanet Science Congress 2021
© Author(s) 2024. This work is distributed under
the Creative Commons Attribution 4.0 License.

Investigating exospheric Na distributions at different spatial scales to disentangle between single and double peaked global patterns

Tommaso Alberti1, Martina Moroni1, Anna Milillo1, Valeria Mangano1, Alessandro Mura1, Stefano Massetti1, Stefano Orsini1, Christina Plainaki2, Alessandro Aronica1, Elisabetta De Angelis1, Adrian Kazakov1, Raffaella Noschese1, Rosanna Rispoli1, Roberto Sordini1, and Nello Vertolli1
Tommaso Alberti et al.
  • 1Istituto Nazionale di Astrofisica, Istituto di Astrofisica e Planetologia Spaziali, Roma, Italy
  • 2Italian Space Agency, Rome, Italy

Since mid ‘80s the Na exosphere of Mercury has been investigated by means of both ground-based observations and spacecraft measurements, showing a wide range of variability from tens of minutes up to seasonal variations along the planetary orbit. It has been shown that the most common Na distribution is characterized by a high latitude double peak probably related to solar wind ion precipitation through the polar cusps. However, the existence of a single peaked equatorial Na emission has been frequently observed too. Generally, it is not straightforward to recognize the contributions due to different surface release processes that produces the observed Na exospheric global image.

Here we apply the Multivariate Empirical Mode Decomposition (MEMD) to a dataset of images of the exospheric Na emission collected by the THEMIS ground-based telescope with the goal to disentangle the different contributions operating at different scales that are expected to be responsible of the occurrence of single vs. double peaked emissions or exospheric asymmetries. In particular, we found the existence of a wide range of scales characterizing both type of spatial patterns, ranging from small scales (less than 0.5 Mercury radii) up to large scales (about 1-2 Mercury radii). These scale-dependent patterns can be linked to different source mechanisms as the variability of solar wind magnetic field, different surface release mechanisms (thermal desorption, photon-stimulated desorption, micrometeoroid impact vaporization and ion-sputtering), as well as, to the whole Na exosphere surrounding the Hermean environment. Our conclusions are double checked by applying the MEMD both on Na exospheric measurements and on simulations of the Na exosphere as created by the different source mechanisms. The positive results show the great potential of the MEMD technique to study the complex environment of planetary exospheres and recognize the different components/processes that create it.

How to cite: Alberti, T., Moroni, M., Milillo, A., Mangano, V., Mura, A., Massetti, S., Orsini, S., Plainaki, C., Aronica, A., De Angelis, E., Kazakov, A., Noschese, R., Rispoli, R., Sordini, R., and Vertolli, N.: Investigating exospheric Na distributions at different spatial scales to disentangle between single and double peaked global patterns, Europlanet Science Congress 2021, online, 13–24 Sep 2021, EPSC2021-64, https://doi.org/10.5194/epsc2021-64, 2021.