Ionospheric Plasma Depletions at Mars Observed by the MAVEN Spacecraft

Steep electron density depletions in the Martian ionosphere are important, especially because they could be regions of significant plasma escape. Local electron density profiles of the Martian ionosphere obtained from the radar sounder onboard the Mars Express spacecraft often show large fluctuations. In some cases, these fluctuations are observed as deep depletions in the electron density. Investigation over the past 12 years of Mars Advanced Radar for Subsurface and Ionospheric Sounding data have revealed over 200 cases of density depletions where the lowest density is less than one fifth of the density in the surrounding regions. These density dips occur both on the dayside and the nightside, with an abundance between solar zenith angles of 50–70° and 100–120°. They occur at all altitudes in the ionosphere. Many of the depletions occur in the southern hemisphere where the crustal magnetic field is stronger and there are more regions where the crustal magnetic field is mostly vertical. In more than half of the cases, the depletion in the local electron density corresponds to a decrease in the electron flux measured with the Analyzer of Space Plasmas and Energetic Atoms electron spectrometer. Several different mechanisms could be responsible for the formation of the depletions, including regions of localized electric fields or magnetic fields creating areas of increased field pressure, escape of the plasma along magnetic field lines depleting density locally, and the density decrease around the photoelectron boundary followed by an increase in the plasma density due to plasma clouds.

Section: Discussionmentioning

confidence: 87%

Section: Discussionmentioning

confidence: 97%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Local Electron Density Depletions in the Martian Upper Ionosphere Obtained From MARSIS: Comparison With ASPERA‐3, and MAVEN, and the Connection With Crustal Magnetic Fields

Duru,

Frahm,

Hughes

et al. 2023

Climatology of Martian Ionospheric Disturbances Deduced From MAVEN Data in 2014–2023

Park

2024

We investigate the climatology of Martian ionospheric disturbances using Mars Atmosphere and Volatile Evolution missioN (MAVEN) data in 2014–2023. The disturbance strength is estimated by calculating residuals of in situ density from its large‐scale (filter window size ∼560 km) background and normalizing the residual with the background, as has been commonly used in terrestrial aeronomy. The disturbances are statistically stronger (a) in the local winter hemisphere than in summer and (b) on the nightside than on the dayside, with stark contrast across the terminator. The disturbances are more intense over the regions with strong radial magnetic fields (i.e., Martian crustal anomaly) than at unmagnetized regions, especially during the nighttime. Day‐to‐day variability of the Martian ionospheric disturbances does not exhibit a strong correlation with those of thermospheric CO2 disturbances or solar wind electron density/temperature at Mars.

An Automatic Method for Detection and Naive Classification of the Martian Ionospheric Irregularities

Wan,

Zhong,

Hao

et al. 2024

The abundant observations and research established a detailed category of the terrestrial ionospheric irregularities, which significantly advanced our understanding of how the Earth system's complicated physical and chemical process generates the intermediate‐scale structures of the charged particles. Motivated by a future attempt at categorizing the Martian ionospheric irregularity, this study designs a method for naive classification of the plasma density depletion, enhancement, and oscillation based on the in situ measurements of the Martian ionosphere. The technique consists of several procedures: trend estimation, detrending and candidate extraction, and parameterization. The classification is achieved through a machine‐learning‐like process using some testing artificial density profiles. A preliminary credence test shows a good performance in separating the terrestrial low‐latitude Equatorial Plasma bubble (depletion) and mid‐latitude Median‐scale Traveling Ionospheric Disturbance (oscillation). Another detection experiment of the Martian plasma depletion events (collected by Basuvaraj et al. (2022a, https://doi.org/10.1029/2022je007302)) showed a recall rate (i.e., true positive) of 38% but with a high precision of 67.8%. Therefore, we believe the proposed method could convincingly extract different Martian ionospheric irregularities and help uncover the climatological characteristics in the future.