The Entomological Society of America (ESA) was founded in 1889 and today has more than 7,000 members, including educators, extension personnel, consultants, students, researchers, and scientists from agricultural departments, health agencies, private industries, colleges and universities, and state and federal governments. It serves the professional and scientific needs of entomologists and people in related disciplines. To facilitate communication among members, the ESA is divided into four sections based on entomological interests, and six branches, based on geographic proximity. The national office is located in Annapolis, Maryland.
The EU and ESA plan to launch a dual-frequency Ku- and Ka-band polar-orbiting synthetic aperture radar (SAR) altimeter, the Copernicus Polar Ice and Snow Topography Altimeter (CRISTAL), by 2027 to monitor polar sea ice thickness (SIT) and its overlying snow depth, among other applications. However, the interactions of Ku- and Ka-band radar waves with snow and sea ice are not fully understood, demanding further research effort before we can take full advantage of the CRISTAL observations. Here, we use three ongoing altimetry missions to mimic the sensing configuration of CRISTAL over Arctic sea ice and investigate the derived snow depth estimates obtained from dual-frequency altimetry. We apply a physical model for the backscattered radar altimeter echo over sea ice to CryoSat-2's (CS2's) Ku-band altimeter in SAR mode and to the SARAL mission's AltiKa (AK) Ka-band altimeter in low-resolution mode (LRM), and then we compare it to reference laser altimetry observations from ICESat-2 (IS2). ICESat-2 snow freeboards (snow + sea ice) are representative of the air–snow interface, whereas the radar freeboards of AltiKa are expected to represent a height at or close to the air–snow interface, and CryoSat-2 radar freeboards are expected to represent a height at or close to the snow–ice interface. The freeboards from AltiKa and ICESat-2 show similar patterns and distributions; however, the AltiKa freeboards do not thicken at the same rate over winter, implying that Ka-band height estimates can be biased low by 10 cm relative to the snow surface due to uncertain penetration over first-year ice in spring. Previously observed mismatches between radar freeboards and independent airborne reference data have frequently been attributed to radar penetration biases, but they can be significantly reduced by accounting for surface topography when retracking the radar waveforms. Waveform simulations of CRISTAL in its expected sea ice mode reveal that the heights of the detected snow and ice interfaces are more sensitive to multi-scale surface roughness than to snow properties. For late-winter conditions, the simulations suggest that the CRISTAL Ku-band radar retrievals will track a median elevation 3 % of the snow depth above the snow–ice interface because the radar return is dominated by surface scattering from the snow–ice interface which has a consistently smoother footprint-scale slope distribution than the air–snow interface. Significantly more backscatter is simulated to return from the air–snow interface and snow volume at Ka band, with the radar retrievals tracking a median elevation 10 % of the snow depth below the air–snow interface. These model results generally agree with the derived satellite radar freeboards, which are consistently thicker for AltiKa than CryoSat-2, across all measured snow and sea ice conditions.
During the 21-22 January 2005 magnetic storm, the FAST satellite observed warm (< few keV) ions in discrete energy bands on the dayside at similar to 3,000 km altitude for more than 6.5 hr. We suggest that the ionospheric energy-banded ions represent the low-altitude edge of the warm plasma cloak observed simultaneously by magnetospheric satellites. This is a clear example of the multi-species ion energy bands (10 eV to several keV) observed during strong magnetic storms by the FAST satellite, stretching from the diffuse auroral region to the plasmapause with lifetimes up to 12 hr. The close association of these energy-banded ions with magnetic storms, their broad latitudinal extent, and the presence of multiple ion species in the same energy band, rather than at the same velocity, indicate that this is a distinct phenomenon from other types of energy-banded ions. During the 21-22 January 2005 magnetic storm, the dayside ion energy band structures, centered at 10 eV (H+), 40 eV (H+ and He+), and 160 eV (H+, He+, and O+), were consistent with a "time-of-flight and velocity filter" formation process acting on a near-cusp, impulsive outflow of a <200 eV multi-species ion-source population, poleward and in the same hemisphere as FAST. Understanding the sources and dynamics of warm energy-banded ions and their linkage to the warm plasma cloak is important because during superstorms these ions are transported to L values as low as L similar to 1.2 in the dawn sector, significantly altering the energetics of the mid-latitude ionosphere.
Satellite-based automatic dependent surveillance-broadcast (ADS-B) enables global-scale aircraft tracking, but introduces significant challenges in packet detection due to the severe signal attenuation experienced along the propagation path. This paper investigates detection strategies for satellite ADS-B receivers based on the generalized likelihood ratio test (GLRT), providing a statistically sound alternative to existing heuristic solutions. To enhance robustness against residual frequency offsets, we exploit the modulus of the received samples, which is invariant to phase distortions. Additionally, we extend the observation window beyond the packet preamble to improve detection performance. To reduce the computational cost of an exact GLRT implementation, we explore several alternatives, including an asymptotic approximation of the Rician distribution and a Gaussian model for the observation data. Simulation results show that the proposed schemes achieve reliable detection even at low signal-to-noise ratios, and outperform existing methods by leveraging both the preamble and part of the data payload.
Measurements by the dual Langmuir Probe (LAP) on board Rosetta in the inner coma of comet 67P/Churyumov-Gerasimenko revealed an unexpected similar to 50% level of attenuation of the impinging solar extreme-ultraviolet (EUV) radiation while the comet was near perihelion. It was argued that this possibly could be a sign of upstream grain fragmentation. Here the effect of grain fragmentation on the EUV transmission fraction in a cometary coma is looked at through two simple analytical models: a continuous fragmentation model and an abrupt fragmentation model. We assume in both models radially expanding grains that readily reach their respective size-dependent terminal velocity. Without specifying driving mechanisms, we assume in the continuous fragmentation model that any grain splits into the same number of equal-sized fragments at a fixed size- and position-independent rate, Gamma , as long as said grain has not yet reached a prescribed minimal size from which point it cannot fragment further. In the abrupt fragmentation model, we instead assume that grains undergo complete fragmentation into minimal-sized subunits at a fixed cometocentric distance. In order for the models to produce transmission fraction profiles compatible with the aforementioned LAP observations, specific conditions appear necessary. A particularly puzzling aspect is the apparent requirement that a significant fraction of the dayside dust population disintegrate gradually or abruptly down to sizes of several tens of nanometers already by a distance of several 1000 km.
We show that Lasso and Bayesian Lasso are very close when the sparsity is large and the noise is small. We propose to solve Bayesian Lasso using multivalued stochastic differential equation. We derive four discretization algorithms, and present highly efficient multilevel Monte Carlo (MLMC) simulations. Additionally, we perform a numerical comparison of the Monte Carlo (MC), MLMC and proximal Markov chain Monte Carlo algorithm (PMALA).
