Laboratory for Atmospheric and Space Physics

Abstract Recent three-dimensional flare models suggest that flare ribbon substructure is linked to the fragmentation of the reconnecting current sheet in the corona. Flare ribbon substructure can therefore potentially serve as a unique diagnostic tool for physical processes in the flare current sheet. In this paper, we describe a new method to quantify the evolution of ribbon substructure that first extracts the ribbon’s bright leading edge and then quantifies its morphology using the box-counting dimension and correlation dimension mapping (CDM). We first test our method using synthetic observations. We then apply it to an M6.5-class solar flare on 2015 June 22 observed by the Interface Region Imaging Spectrograph (IRIS) 1330 Å slit-jaw imager. We find that when the flare ribbon boundary has more multiple-spatial-scale features (a higher box-counting dimension), hard X-ray emission and magnetic reconnection rates are the strongest. We also find that the flare ribbon complexity characterized by CDM has a moderate correlation with the IRIS Si IV 1402.77 Å nonthermal velocity (in the negative polarity ribbon) and reconnection flux rates (in ribbons of both magnetic polarities). We conclude that the buildup of the spatial complexity of the ribbons at multiple spatial scales can serve as an observational proxy for current-sheet fragmentation in the corona.

We use the REPT (relativistic Electron Proton Telescope) data onboard the Van Allen Probes mission to examine the penetration of solar energeetic Helium into the magnetosphere. Specidfically we the pulse height analyzed data (PHA) in the REPT solid state detector stack for each individual particle measured. we identify SEP-He is by using active periods with identified SEP events. We will specifically focus on the large SEP events that occurede during the September of 2017. Using PHA data we derive the incident spectrum nd its evolution during the event. From a space weather perspective It is important note that He ions deposit energy through rapid ionization resulting in single event upsets (SEU) whereas protons do that via nuclear interactions.

Plasma Observatory (PO) is one of the three candidate ESA M7-class missions currently in Phase A. Its primary goal is to investigate the fundamental multi-scale processes that govern plasma energization and energy transport within Earth's magnetospheric system. To address these objectives, PO will deploy a constellation of seven spacecraft in a double-nested tetrahedral configuration with a common vertex, enabling simultaneous measurements at both fluid and ion scales and, crucially, their coupling.Compared to previous multi-spacecraft missions such as Cluster and MMS, PO's expanded constellation introduces unprecedented opportunities to resolve multi-scale dynamics in space plasmas. However, these opportunities come with significant challenges. Realizing PO's full scientific potential requires the development and application of novel multi-point and advanced data analysis methodologies capable of exploiting measurements from more than four spacecraft.The Multi-Point and Advanced Data Analysis Methods Working Group has been established to support the mission's Science Study Team (SST) in evaluating how PO's science goals can be achieved through its unique configuration. The Working Group brings together expertise in multi-spacecraft diagnostics and the analysis of in situ plasma observations. We present the composition and ongoing activities of the Working Group, highlight the represented analysis methods (both established and under active development), and outline ongoing efforts to assess and enhance the scientific capabilities of the PO mission.

The developments rapidly (and alarmingly) playing out in low-Earth orbit (LEO) are significantly affecting aspects of radio astronomy, nighttime ground-based astronomy, space weather remote sensing, space physics, solar observing, and access to space itself. It is suggested that space-involved organizations should step in to promote actions to regulate the nearly $400 billion space industry that presently is operating in a Wild West , essentially unregulated, fashion due to the inadequacy of current licensing and launch practices. Many forums have provided compelling evidence from scientists and engineers about the interference that communications spacecraft are having on research programs. When the added—and extremely concerning—consequences of exponentiating orbital debris associated with satellite launches and collisions are folded in, we are seeing the equivalent of Garrett Hardin’s “Tragedy of the Commons” in near-Earth space (Science, 1968). It is enticing to citizens world-wide to have low-priced, essentially global, and unfettered communications. However, this is coming at a significant cost to science in our cosmic “backyard”. If satellites continue to increase in number and attendant debris continues to fill bands around Earth, it will soon be nearly impossible to observe the universe beyond our planet with ground-based telescopes or even safely launch and operate scientific satellites in LEO. What is quite clear is that the uncontrolled and unregulated flooding of LEO now is encouraging further players to do the same as what the U.S. is doing. This will not ‘self-regulate’ for economic reasons: an earlier 2021 NSF-funded study by the JASON committee, titled “The Impacts of Large Constellations of Satellites”, found that the perceived and persistent positive economic payoff return vs. investment cost would not limit the rapid deployment trend even beyond 100,000 satellites. Until the problems and dangers of the populating LEO are better understood and until mitigation is possible, research bodies should be insisting that governments (as well as non-government players) be constrained from carrying out more massive launches. It would be hoped that this presentation will allow an examination of the issues and will lead to productive discussion of policy approached that can help address the growing problem including:Regulatory Framework and GovernanceSustainability of Satellite OperationsAstronomical ObscurationRadio Astronomy InterferenceSatellite Collisions and Orbital DebrisInternational Cooperation and Coordination

Abstract The effect of supernovae (SNe) on star formation in the interstellar medium (ISM) depends sensitively on where SNe explode with respect to ISM clouds. Observationally, SN ISM environments characterized by spatially resolved gas maps can empirically guide the placement of SNe in subgrid models, but unfortunately such measurements remain scarce, as SNe are rare and often distant. Here we demonstrate a new approach—mapping the ISM around evolved massive stars that are soon to explode. These provide a substantially larger sample of “explosion sites” (than just historical SNe) in nearby galaxies that have high-resolution atomic and molecular ISM maps from the Jansky Very Large Array and Atacama Large Millimeter/submillimeter Array. We demonstrate this technique in the well-resolved Local Group spiral M33 by analyzing the 50 pc scale projected ISM densities around red supergiants (RSGs; 8–30 M ⊙ stars) Wolf–Rayet stars (W-Rs; >30 M ⊙ stars), and supernova remnants. We find a mass-dependent correlation between stars and gas clouds, with at least 45% of W-Rs and up to 77% of RSGs having no detectable H 2 at their pixel locations. In the sample with H 2 detections, we find that more-massive younger progenitors are coincident with denser gas. We show that the density distributions for stars >15 M ⊙ are statistically distinct from random alignment of stars and gas in M33. Our work provides the first observationally derived estimate of the fraction of the SN-producing stellar population correlated with ISM density peaks. We demonstrate how this can be compared with galaxy simulations, and advocate similar comparisons to the community for constraining subgrid models.

Abstract Clouds are the largest source of uncertainty in climate simulations. For exoplanets, cloud simulation is particularly challenging because of the lack of observational data to tune parameterized cloud models. Here we apply Community Aerosol and Radiation Model for Atmospheres ( CARMA ), a size-resolved bin cloud microphysics model, to the atmospheric global climate model Community Atmosphere Model (CAM6) and simulate exoplanets with a range of planetary rotation rates. CARMA produces fewer liquid clouds than the native CAM6 parameterized cloud microphysics scheme (Morrison–Gettelman two-moment microphysics, MG), more ice clouds, and a significantly different ice cloud size distribution. Overall, this leads to a decrease in the magnitude of the net CRE by 4–10 W m −2 , which is unlikely to change the determination of habitability from a climate perspective in most cases. The difference in ice cloud size distribution is likely to strongly affect transmission spectral retrievals. Our work confirms that the MG parameterized cloud microphysics scheme can produce reasonable climate simulation when extrapolated to some exoplanet contexts and highlights the value of resolved cloud microphysics for evaluating parameterized schemes and for interpreting observations.

Abstract A key early discovery of the Mars Exploration Rover Opportunity on Meridiani Planum was the hematite spherules that are a ubiquitous component of the Burns formation sandstones at the rover's landing site (colloquially known as “blueberries”). The Meridiani spherules possess a suite of characteristics that are collectively very rare in terrestrial settings, including their gray color, a thermal spectral signature that indicates preferential exposure of the c crystal axis, a spherical shape that is evidently attributable to radially oriented crystallite growth, and high chemical and mineralogical purity. The origin of the Meridiani “blueberries” has remained a matter of considerable debate, but one leading hypothesis is that they formed through the decomposition of iron‐rich sulfate minerals from the alunite group, specifically jarosite. To date, however, there has been no described terrestrial analog where the formation of hematite spherules is shown to be directly linked to jarosite decomposition. Here, we report the discovery of hematite spherules in Aztec Sandstone that possess many of the same characteristics as the martian “blueberries,” albeit with substantially smaller size. The spherules occur primarily in narrow gray bands within mineralized fractures where the pore spaces are predominantly occupied by jarosite‐alunite solid solutions (JASS). The spherules formed through partial decomposition and release of Fe 3+ from adjacent JASS, supporting the possibility that analogous processes may have been responsible for the formation of hematite spherules during diagenesis of the sulfate‐rich Burns sandstones on Mars. Continued study of the Aztec Sandstone spherules may provide new constraints on near‐surface environmental conditions on early Mars.

Abstract The Magnetospheric Multiscale (MMS) mission's extended phase introduced an “unbiased campaign” that provided the first high‐resolution data set of the terrestrial magnetosheath obtained without human selection, across complete crossings from the bow shock to the magnetopause. This is achieved by collecting 3 min of burst‐mode data every 9 min. Leveraging this novel data set, we report average plasma parameters and observe the emergence of a range in the magnetic field power spectrum. A distinct ordering of both bulk and turbulence quantities is demonstrated when the Alfvénic Mach number is used as a proxy for the distance from the bow shock. This ordering enables us to obtain clear insights into the occurrence of small‐scale current sheets throughout the magnetosheath by evaluating magnetic field kurtosis. Furthermore, the evolution of the correlation time is opposite to that of kurtosis and aligns with the principle of turbulence relaxation. This information is dispersed when quantities are sorted by geocentric distance. Crucially, striking differences emerge in turbulence‐related quantities when comparing unsupervised and supervised data sets. These findings provide valuable insights into magnetospheric turbulence, establishing the campaign as a critical resource for unbiased statistical analysis of this environment.

Abstract Magnetic reconnection occurs continuously along long X‐lines at the Earth's magnetopause. The maximum magnetic shear model predicts the locations of these long X‐lines for a wide range of upstream solar wind conditions. One of the more perplexing observational results is that these X‐lines appear to be stationary, even in the presence of significant magnetosheath plasma bulk flow. A scenario is developed whereby an X‐line forms at the location predicted by the maximum magnetic shear model, but then immediately propagates with the magnetosheath plasma bulk flow away from this location. Before this X‐line can travel far, a new X‐line forms at the location of the original X‐line. If the X‐line reformation cadence is high enough, then these multiple, propagating X‐lines could appear as a single, quasi‐stationary X‐line. One observational test of this scenario is that a spacecraft crossing the magnetopause poleward of the original X‐line location would always observe multiple X‐lines. Magnetospheric Multiscale observations are used to perform this observational test. Results show that there are multiple X‐lines near the predicted location of the X‐line and therefore, this scenario may have merit.