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. 2022 Jun 28;49(12):e2022GL098007.
doi: 10.1029/2022GL098007. Epub 2022 Jun 16.

A Statistical Investigation of Factors Influencing the Magnetotail Twist at Mars

Gina A DiBraccio  1 , Norberto Romanelli  1   2 , Charles F Bowers  3 , Jacob R Gruesbeck  1 , Jasper S Halekas  4 , Suranga Ruhunusiri  4 , Tristan Weber  1   5 , Jared R Espley  1 , Shaosui Xu  6 , Janet G Luhmann  6 , Yuki Harada  7 , Eduard Dubinin  8 , Gang Kai Poh  1   9 , David A Brain  10 , Shannon M Curry  6
Affiliations

A Statistical Investigation of Factors Influencing the Magnetotail Twist at Mars

Gina A DiBraccio et al. Geophys Res Lett. .

Abstract

The Martian magnetotail exhibits a highly twisted configuration, shifting in response to changes in polarity of the interplanetary magnetic field's (IMF) dawn-dusk (B Y) component. Here, we analyze ∼6000 MAVEN orbits to quantify the degree of magnetotail twisting (θ Twist) and assess variations as a function of (a) strong planetary crustal field location, (b) Mars season, and (c) downtail distance. The results demonstrate that θ Twist is larger for a duskward (+B Y) IMF orientation a majority of the time. This preference is likely due to the local orientation of crustal magnetic fields across the surface of Mars, where a +B Y IMF orientation presents ideal conditions for magnetic reconnection to occur. Additionally, we observe an increase in θ Twist with downtail distance, similar to Earth's magnetotail. These findings suggest that coupling between the IMF and moderate-to-weak crustal field regions may play a major role in determining the magnetospheric structure at Mars.

Keywords: Mars; magnetic reconnection; magnetosphere; magnetotail.

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Figures

Figure 1
Figure 1
Magnetic maps of the normalized, average B X component in the Martian magnetotail, separated +B Y IMF (left column) and −B Y IMF (right column) cases. The maps are projections in the Y MSO−Z MSO plane, as viewed from the magnetotail looking towards Mars. Red sectors, +B X/B, represent the sunward tail lobes, while blue sectors, −B X/B, represent the antisunward tail lobes. The black circle represents Mars. (a) and (b) show the original results and coverage from DiBraccio et al. (2018), while (c) and (d) display the updated maps from this present study.
Figure 2
Figure 2
An example of magnetic maps generated with a 1.50‐R M radius spatial constraint (outer black circle) for (a) +B Y and (b) −B Y IMF. Green dots represent the centers of each lobe. The lobe vector (green vector) identifies the actual tail lobe location compared with the expected draped lobe location based on IMF draping (black vector). θ Twist is highlighted as the thick black arc between the vectors. Colored concentric circles and dots represent the spatial constraints and resulting lobe centers, respectively, that were tested for (c) +B Y and (d) −B Y IMF using radii of 1.00 R M (black), 1.25 R M (red), 1.50 R M (blue), and ∼1.96 R M (yellow).
Figure 3
Figure 3
Histograms demonstrating the sampling frequency of the MAVEN orbits included in this study based on (a) strong crustal field location, (b) northern hemisphere season, and (c) downtail distance for +B Y (yellow) and −B Y (gray stripe) IMF. Scatterplots reveal changes in calculated θ Twist values as a function of (d) strong crustal field location, (e) northern hemisphere season, and (f) downtail distance for +B Y (yellow circles) and −B Y (gray squares) IMF.
See this image and copyright information in PMC

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