Properties of Flapping Current Sheet of the Martian Magnetotail

Abstract

Knowing the properties of the Martian magnetotail flapping waves is critical to understand the dynamics of the Martian induced magnetosphere. Based on the measurements by Mars Atmosphere and Volatile EvolutioN and a newly developed method, we provide the first quantitative study of Martian magnetotail flapping waves in comparison with Earth's magnetotail flapping waves. We found that the period of Martian magnetotail flapping waves ranges from ∼50 to ∼250 s. The estimated average wave amplitude is ∼380 km, and the wavelength is ∼1,100 km. The estimated propagation speed ranges from ∼3 to ∼30 km/s, which is about a third of that of Earth's magnetotail flapping waves, and the speed declines with the increase of the current sheet thickness. Intriguingly, we found that the flapping waves with shorter periods, or lower wavelengths, can propagate faster, showing similar dispersive signatures as that found in the Earth's magnetotail. Our results demonstrate that the fluctuated field energy carried by flapping waves within unit time along unit magnetotail length is one order higher than that of Earth's flapping waves, as normalized by the magnetic energy of planetary magnetotail. Thus, in comparison with Earth's magnetotail, the flapping waves of Martian induced magnetotail would play a more important role in affecting the magnetotail dynamics.

The Energetic Oxygen Ion Beams in the Martian Magnetotail Current Sheets: Hints From the Comparisons Between Two Types of Current Sheets

“…The CS are initially identified by a significant and rapid reversal in B x . Specifically, we define the magnetic field characteristic of the CS as a change in the polarity of B x , accompanied by a variation in its magnitude exceeding 5 nT within a 60‐s period (Zhang, Rong, et al., 2023). Additionally, we visually check each CS, to eliminate the pseudo‐crossings in the external magnetosheath, which exhibits a continuous spectrum of solar wind ions with energies typically above 800 eV and a highly fluctuating magnetic field.…”

“…This study employs two Cartesian coordinate systems. The first is the Mars Solar Orbital (MSO) coordinates, where $${\overrightarrow{X}}_{MSO}$$ points from Mars to the Sun, $${\overrightarrow{Y}}_{MSO}$$ points opposite to the component of the orbital velocity perpendicular to $${\overrightarrow{X}}_{MSO}$$, and $${\overrightarrow{Z}}_{MSO}$$ completes the right‐handed system (e.g., Li et al., 2023; Zhang, Rong, et al, 2023). The second is the Mars Solar Electric coordinates (MSE), where $${\overrightarrow{X}}_{MSE}$$ points antiparallel to the upstream solar wind flow, $${\overrightarrow{Y}}_{MSE}$$ points along the cross‐flow magnetic field component of the upstream IMF, and $${\overrightarrow{Z}}_{MSE}$$ points along the direction of the convection electric field in the solar wind.…”

“…To guarantee the accuracy of the moment data, we only consider data when both the Sun and tail directions are within STATIC's FOV, and its energy range spans from below 10 eV to above 1,000 eV. The CS are initially identified by a significant and rapid reversal in B x . Specifically, we define the magnetic field characteristic of the CS as a change in the polarity of B x , accompanied by a variation in its magnitude exceeding 5 nT within a 60‐s period (Zhang, Rong, et al., 2023). Additionally, we visually check each CS, to eliminate the pseudo‐crossings in the external magnetosheath, which exhibits a continuous spectrum of solar wind ions with energies typically above 800 eV and a highly fluctuating magnetic field. Since the CS identification is only reliable in non‐crustal fields region (Halekas & Brain, 2010; Harada et al., 2020), we only choose the CS that fulfill the criterion $$\vert $$ B obs $$\vert $$ ≥ 10$$\vert $$ B model $$\vert $$.…”

“…In the magnetotail, the two lobes exhibit stretched magnetic field lines that are antiparallel to each other. This configuration leads to the formation of a magnetotail current sheet (CS), which is centrally situated between these lobes (Dubinin et al., 1993; Zhang, Futaana, et al., 2022; Zhang, Rong, et al., 2022, 2023). Previous observations shown that, near the CS, the oxygen ions could be accelerated to over 1 keV and often show a narrow beam pattern in the energy spectrum (e.g., Carlsson et al., 2008; Dubinin et al., 1993; Fedorov et al., 2006, 2008; Nilsson et al., 2006, 2012; Verigin et al., 1991).…”

Discovery of Intrinsic Magnetospheric Ion Behavior at Mars

“…coordinates 48 , where 𝑋 𝑀𝑆𝑂 points from Mars to the Sun, 𝑌 ⃗ 𝑀𝑆𝑂 points opposite to the component of the orbital velocity perpendicular to 𝑋 𝑀𝑆𝑂 , and 𝑍 𝑀𝑆𝑂 completes the right-handed system. For the open-to-day type, the field line has one of the foot points that ends in the dayside ionosphere, which can be identified by the precipitation of solar wind electrons and an outflow of photoelectrons.…”