arXiv subjects

Lot Ram

Publications and source records attributed to Lot Ram.

5 recordsLinked to original sources

arXiv2026

Impact of May 2024 ICME Event on Martian UV Dayglow Emissions using MAVEN/IUVS and EMM/EMUS Observations

We present first near-simultaneous observations of large-scale spatial response of the Martian H Lyman-{\alpha} and atomic oxygen dayglow emissions (O(3S) 130.4 nm and O(5S) 135.6 nm) during May 2024 interplanetary coronal mass ejection (ICME). Using coordinated near-simultaneous observations from MAVEN/Imaging Ultraviolet Spectrograph (IUVS) and the EMM/Emirates Mars Ultraviolet Spectrometer (EMUS), we have identified pronounced enhancements in all three emissions relative to quiet-time conditions. Interestingly, coordinated IUVS limb and EMUS disk observations reveal that ICME-driven response extends vertically through the thermosphere and horizontally across broad ranges of latitude, longitude, local-time, and solar zenith angle. Concurrent enhancement of hydrogen and oxygen emissions indicates the simultaneous contribution of proton and electron-driven excitation mechanisms during ICME. These findings reveal a novel planetary-scale response of the Martian dayglow. By highlighting the critical role of energetic-particle precipitation in amplifying this global response, our work carries crucial implications for understanding Martian thermospheric response during intense solar transients.

physics.space-ph↗

arXiv2025

Climatology of Mars Topside Ionosphere during Solar Cycles 24 and 25 using MAVEN Dataset of 2015-2024

The Mars ambient space environment evolves with the varying solar activity. Understanding the Martian space environment, particularly the topside ionosphere across different phases of Solar Cycles (SC) 24 \& 25 remains a key research gap in planetary ionospheric science. In this study, we utilized the NASA Mars Atmosphere and Volatile EvolutioN (MAVEN) mission data (150-500 km) from Martian years 32-38 (2015-2024) during solar quiet-time. This study investigated the behavior of topside ionosphere (e-, CO2+, O2+, NO+, OH+, O+, N+ \& C+) across different phases of SC over the northern hemisphere. A significant variation in ionosphere is observed over low-latitude (0-30{\deg}N) with higher densities compared to mid-latitude (31-60{\deg}N) across SC. Additionally, we found that the Martian northern ionospheric densities were highest during solar maximum phase on both dayside and nightside compared to low active phases. The dayside densities were approximately 1-2 orders higher compared to those on the nightside. The electron and molecular ions densities increased by factors of 1-5 and 1-13, respectively. While O+ ion density was enhanced by nearly 2-2.5 times, along with an upliftment of 40-50 km in the peak height. The enhanced dayside densities are attributed to the elevated solar irradiance (1.4-2 times) and varying solar wind flux. Furthermore, the enhanced day-to-night plasma transport and elevated solar electron flux during maxima, higher by 33-66\% than during low-activity, can contribute to the increased nightside ionization. This work, for the first time, uses long-term MAVEN datasets across the descending-to-maxima phases of SC to reveal climatology of Martian topside ionosphere.

physics.space-ph↗

arXiv2025

Investigation of Martian UV Dayglow Emissions in the Southern Hemisphere during Solar Quiet-time Conditions: Insights from Multi-year MAVEN/IUVS Observations

The southern hemisphere of Mars possesses concentrated region of strong crustal magnetic fields (CMF), which generate localized magnetic anomalies that can influence atmospheric dynamics and energy deposition in the Martian thermospheric-ionospheric system. Although their effects on the atmosphere (>200 km) in the southern hemisphere are well documented, however their role in modulating the behavior of atmospheric plasma and neutrals below 200 km are poorly understood. The atmosphere at these altitudes can be comprehended by studying the variation of dayglow emissions. We have investigated few dayglow emissions over the CMF and non-CMF regions using the MAVEN remote-sensing measurements from Martian Years 33-37. Particularly, the CO Cameron bands, CO2+ ultraviolet doublet, and atomic oxygen emissions at 297.2 nm, 130.4 nm, and 135.6 nm have been studied below 200 km during solar quiet-time conditions. The results show strong seasonal variations in all the emissions peak altitudes and intensities in the dayside and near-terminator regions. The variation in the peak altitude of molecular and atomic emissions are nearly 20 km and 30 km, respectively. On the dayside, the emissions show minimal variation across CMF and non-CMF regions, indicating a minimal effect of the CMF at these altitudes, suggesting a key role of plasma demagnetization and photochemical processes. In addition, an insignificant variation in the dayglow emissions is likely masked by compensating mechanisms such as energy-dependent electron shielding and thermospheric expansion. This work presents the first focused investigation on the dayglow emissions over CMF and non-CMF regions across different seasons and solar zenith angles.

physics.space-ph↗

arXiv2024

A case study on the impact of interplanetary coronal mass ejection on the Martian O(1S) 557.7 nm dayglow emission using ExoMars TGO/NOMAD-UVIS observations: First Results

We report, for the first time, the impact of an interplanetary coronal mass ejection (ICME) on the recently discovered O($^1$S) 557.7 nm dayglow emission in the Martian atmosphere. Although there are only a few studies on the seasonal variation are available in the literature, the impact of ICME on 557.7 nm dayglow emission has not been investigated so far. Using the instruments aboard ExoMars-TGO and MAVEN spacecrafts, we show that the primary emission peak (75-80 km) remains unaffected during the ICME event compared to quiet-times. However, a noticeable enhancement has been observed in the brightness of secondary emission peak (110-120 km) and the upper altitude region (140-180 km). The enhancement is attributed to the increased solar electrons and X-ray fluxes, augmenting the electron-impact process and causing the enhancement in the brightness. These analyses have an implication to comprehend the role of intense solar transients like ICME on the Martian dayglow emissions.

physics.space-ph↗

arXiv2022

A comparison of the impacts of CMEs and CIRs on the Martian dayside and nightside ionospheric species

Measurements from the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft, orbiting Mars are used for investigating the impact of coronal mass ejections (CMEs) and corotating interaction regions (CIRs) on Martian ionospheric species. We have chosen 15 CME and 15 CIR events (2015-2020) at Mars from the existing catalogs. We have extensively analyzed the Martian dayside and nightside profiles of ionospheric species during each of the CME and CIR events. We have selected those orbit plasma density profiles which showed significant differences from the mean quiet-time profile during each event. The primary focus of this paper is to provide a comparative average scenario of the variation of Martian ionospheric species during CMEs and CIRs events. A significant difference can be observed in the profiles of the Martian dayside and nightside ionospheric species (O+, O2+, CO2+, NO+, C+, N+, & OH+) during CMEs and CIRs in comparison to mean quiet-time profile. The difference is more prominent on the nightside compared to the dayside ionosphere. During CIRs, the nightside ion density is nearly one order of magnitude less (above 250 km) in comparison to CMEs. The mean peak altitude and density of the lighter ions (O+, C+, N+, & OH+) were at lower altitudes during the CIRs compared to CMEs. Therefore, this study suggests that during the declining phase of solar cycle (SC 24), the impact of CIRs on the Martian ionospheric species is more prominent compared to CMEs.

physics.space-ph↗