Mohammad Barani

and 4 more

Ionospheric heavy ions in the distant tail of the Earth’s magnetosphere at lunar distances are observed using the ARTEMIS mission. These heavy ions are originally produced in the terrestrial ionosphere. Using the ElectroStatic Analyzers (ESA) onboard the two probes orbiting the Moon, these heavy ions are observed as cold populations with distinct energies higher than the baseline energy of protons, with the energy-per-charge values for the heavy populations highly correlated with the proton energies. We conducted a full solar cycle survey of these heavy ion observations, including the flux, location, and drift energy, as well as the correlations with the solar wind and geomagnetic indices. The likelihood of finding these heavy ions in the preferred regions of observation called “loaded” quadrants of the terrestrial magnetotail is ~90%, regardless of the z orientation of the IMF. We characterize the ratio of the heavy ion energy to the proton energy, as well as the velocity ratio of these two populations, for events from 2010 to mid-2023. This study shows that the “common velocity” assumption for the proton and heavy ion particles, as suggested in previous work through the velocity filter effect, is not necessarily valid in this case. Challenges in the identification of the mass of the heavy ions due to the ESA’s lack of ion composition discrimination are addressed. It is proposed that at the lunar distances the heavy ion population mainly consists of atomic oxygen ions (O+) with velocities ~25% more than the velocity of the co-located proton population.

Andrea C. G. Hughes

and 14 more

We compare observations of hydrogen (H) and protons associated with Martian proton aurora activity, co-evaluating remote sensing and in situ measurements during these events. Following the currently understood relationship between penetrating protons and H energetic neutral atoms (ENAs) in the formation of proton aurora, we observe an expected correlation between the H Lyman-alpha (Ly-α) emission enhancement (used herein as a proxy for H-ENAs) and penetrating proton flux. However, we observe a notable spread in the trend between these two datasets. We find that this spread is contemporaneous with one of two major impacting events: high dust activity or extreme solar activity. Proton aurora events exhibiting a relative excess in penetrating proton flux compared to Ly-α enhancement tend to correspond with periods of high dust activity. Conversely, proton aurora events exhibiting a relative deficit of penetrating proton flux compared to Ly-α enhancement are qualitatively associated with periods of extreme solar activity. Moreover, we find that the largest proton aurora events occur during concurrent dust storm and solar events, primarily due to the compounding intensified increase in H column density above the bow shock. Finally, we present a simplified empirical estimate for Ly-α emission enhancement during proton aurora events based on observed penetrating proton flux and a knowledge of local dust/solar activity at the time, providing a straightforward method for predicting auroral activity when direct observations are not available. The results of this study advance our understanding of the interconnected relationship between H and protons during Martian proton aurora activity.

Andrea C. G. Hughes

and 16 more

Proton aurora are the most commonly observed yet least studied type of aurora at Mars. In order to better understand the physics and driving processes of Martian proton aurora, we undertake a multi-model comparison campaign. We compare results from four different proton/hydrogen precipitation models with unique abilities to represent Martian proton aurora: Jolitz model (3-D Monte Carlo), Kallio model (3-D Monte Carlo), Bisikalo/Shematovich et al. model (1-D kinetic Monte Carlo), and Gronoff et al. model (1-D kinetic). This campaign is divided into two steps: an inter-model comparison and a data-model comparison. The inter-model comparison entails modeling five different representative cases using similar constraints in order to better understand the capabilities and limitations of each of the models. Through this step we find that the two primary variables affecting proton aurora are the incident solar wind particle flux and velocity. In the data-model comparison, we assess the robustness of each model based on its ability to reproduce a MAVEN/IUVS proton aurora observation. All models are able to effectively simulate the data. Variations in modeled intensity and peak altitude can be attributed to differences in model capabilities/solving techniques and input assumptions (e.g., cross sections, 3-D versus 1-D solvers, and implementation of the relevant physics and processes). The good match between the observations and multiple models gives a measure of confidence that the appropriate physical processes and their associated parameters have been correctly identified, and provides insight into the key physics that should be incorporated in future models.

David Blewett

and 18 more

NASA designated Reiner Gamma (RG) as the landing site for the first Payloads and Research Investigations on the Surface of the Moon (PRISM) delivery (dubbed PRISM-1a). Reiner Gamma is home to a magnetic anomaly, a region of magnetized crustal rocks. The RG magnetic anomaly is co-located with the type example of a class of irregular high-reflectance markings known as lunar swirls. RG is an ideal location to study how local magnetic fields change the interaction of an airless body with the solar wind, producing stand-off regions that are described as mini-magnetospheres. The Lunar Vertex mission, selected by NASA for PRISM-1a, has the following major goals: 1) Investigate the origin of lunar magnetic anomalies; 2) Determine the structure of the mini-magnetosphere that forms over the RG magnetic anomaly; 3) Investigate the origin of lunar swirls; and 4) Evaluate the importance of micrometeoroid bombardment vs. ion/electron exposure in the space weathering of silicate regolith. The mission goals will be accomplished by the following payload elements. The lander suite includes: The Vertex Camera Array (VCA), a set of fixed-mounted cameras. VCA images will be used to (a) survey landing site geology, and (b) perform photometric modeling to yield information on regolith characteristics. The Vector Magnetometer-Lander (VML) is a fluxgate magnetometer. VML will operate during descent and once on the surface to measure the in-situ magnetic field. Sophisticated gradiometry allows for separation of the natural field from that of the lander. The Magnetic Anomaly Plasma Spectrometer (MAPS) is a plasma analyzer that measures the energy, flux, and direction of ions and electrons. The lander will deploy a rover that conducts a traverse reaching ≥500 m distance, obtaining spatially distributed measurements at locations outside the zone disturbed by the lander rocket exhaust. The rover will carry two instruments: The Vector Magnetometer-Rover (VMR) is an array of miniature COTS magnetometers to measure the surface field. The Rover Multispectral Microscope (RMM) will collect images in the wavelength range ~0.34–1.0 um. RMM will reveal the composition, texture, and particle-size distribution of the regolith.

Cynthia Cattell

and 8 more

The role of waves in the propagation, scattering and energization of electrons in the solar wind has long been a topic of interest. Conversely, understanding the excitation of waves by energetic electrons can provide us with a diagnostic for the processes that accelerate the electrons. We will discuss two different processes: (1) the interaction of narrowband whistler-mode waves with solar wind electrons, and (2) how periodic Type III radio bursts yield clues to small-scale acceleration of energetic electrons in the solar corona. Waveform captures in the solar wind at 1 AU obtained by the STEREO revealed the existence of narrowband large amplitude whistler mode waves, propagating at highly oblique angles to the magnetic field. Similar waves are less commonly seen inside .2 AU by Parker Solar Probe. The differences provide clues for understanding electron propagation, scattering and energization. Type III radio bursts have long been used as remote probes of electron acceleration in the solar corona. The occurrence of periodic behavior in Type III bursts observed by Parker Solar Probe, Wind and STEREO when there are no observable flares provides a unique opportunity to diagnose small-scale acceleration of electrons in the corona. Periodicities of ~ 5 minutes in the Solar Dynamics Observatory Atmospheric Imaging Assembly (AIA) Extreme Ultraviolet data in several areas of an active region are well correlated with the repetition rate of the Type III radio bursts. Similar periods occur in the Helioseismic and Magnetic Imager (HMI )data. These results provide evidence for acceleration by wave-modulated reconnection or small-scale size waves, such as kinetic Alfven waves, even during intervals with no observable flares. The possible connections between these two phenomena will be addressed.

Zachary Girazian

and 10 more

Discrete aurora at Mars, characterized by their small spatial scale and tendency to form near strong crustal magnetic fields, are emissions produced by particle precipitation into the Martian upper atmosphere. Since 2014, Mars Atmosphere and Volatile EvolutioN’s (MAVEN’s) Imaging Ultraviolet Spectrograph (IUVS) has obtained a large collection of nightside UV discrete aurora observations. Initial analysis of these observations has shown that, near the strong crustal field region (SCFR) in the southern hemisphere, the aurora detection frequency is highly sensitive to the interplanetary magnetic field (IMF) clock angle. However, the role of other solar wind properties in controlling the aurora detection frequency has not yet been determined. In this work, we use IUVS discrete aurora observations, and MAVEN solar wind observations, to determine how the discrete aurora detection frequency varies with solar wind dynamic pressure, IMF strength, and IMF cone angle. We find that, outside of the SCFR, the detection frequency is relatively insensitive to the IMF orientation, but significantly increases with solar wind dynamic pressure and moderately increases with IMF strength. Interestingly, the auroral emission brightness outside the SCFR is insensitive to the dynamic pressure. Inside the SCFR, the detection frequency is moderately dependent on the dynamic pressure and is much more sensitive to the IMF clock and cone angles. In the SCFR, aurora are unlikely to occur when the IMF points near the radial or anti-radial directions. Together, these results provide the first comprehensive characterization of how upstream solar wind conditions affect the formation of discrete aurora at Mars.