Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “high-latitudes”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 991 records · Page 55
All sourcesNASA NTRSDOE OSTI
NASA NTRS2022

Economic incentives modify agricultural impacts of nuclear war

A nuclear war using less than 1% of the current global nuclear arsenal, which would inject 5 Tg of soot into the stratosphere, could produce climate change unprecedented in recorded human history and significant impacts on agricultural productivity and the economy. These effects would be most severe for the first five years after the nuclear war and may last for more than a decade. This paper calculates how food availability would change by employing the Environmental Impact and Sustainability Applied General Equilibrium model. Under a robust world trading system, global food availability would drop by a few percentage points. If the war would destabilize trade, it would magnify by several times the negative ramifications of land productivity shocks on food availability. If exporting countries redirect production to domestic consumption at the expense of importing countries, it would lead to the destabilization of international trade. The analysis suggests that economic models aiming to inform policymakers require both economic behavior analysis and biophysical drivers. Policy lessons derived from a crop model can be significantly nuanced when coupled with economic feedback derived from economic models. Through the impact on yield, farmers could shift production among crops and reallocate land use to maximize profits, showing the importance of general equilibrium effects such as product and input substitution and international trade. Although the global impact on corn and soybean production would be significant when just considering crop production, it could be considerably smaller under the economic model. However, this would be at the expense of other sectors, including livestock. In addition, the costs borne from disruptions to climate would vary significantly across regions, with significant adverse effects in high latitude regions. The severity of the shocks in the high-latitude areas would marginalize the farmers' product and input substitution ability.

Nuclear war↗
NASA NTRS2022

Imaging the End-to-End Dynamics of the Global Solar Wind-Magnetosphere Interaction

Much of what we know about the solar wind’s interaction with the Earth’s magnetosphere has been gained from isolated in situ measurements by single or multiple spacecraft. Based on their observations, we know that reconnection, whether on the dayside magnetopause or deep within the Earth’s magnetotail, controls the flow of solar wind energy into and through the global system. We know that nightside activity provides the energized particles that power geomagnetic storms. But by their very nature these isolated in situ measurements cannot provide an instantaneous global view of the entire system or its cross-scale dynamics. As a result, we don’t know which mode of reconnection prevails on the dayside magnetopause or within the magnetotail as a function of solar wind and geomagnetic conditions. We don’t know which mode or modes of nightside activity supply the most energized particles to the ring current. Nor do we know the dominant loss mode for ring current decay: precipitation, magnetopause outflow, or charge exchange with neutrals. Nor do we know how processes deep within the magnetosphere provide feedback to those happening in the outer magnetosphere. The answers to these questions could have an impact far beyond magnetospheric physics, since magnetic reconnection, particle acceleration, and charge-exchange are fundamental plasma processes that operate at other planets and throughout the universe. Comprehensive end-to-end global imaging of the key micro, meso-, and macro-scale plasma structures that comprise the magnetosphere will provide the answers to these questions via observations with a spatial resolution that exceeds anything possible with in situ measurements. Each proposed interaction mechanism generates a diagnostic plasma structure or boundary signature. Global, end-to-end, imaging provides the pathway to understanding the system as a whole, its constituent parts, and its cross-scale processes on a continuous basis, as needed to quantify the flow of solar wind energy through the global magnetospheric system. The significance of each mechanism is the product of its amplitude and occurrence rate. This white paper describes how a comprehensively-instrumented single spacecraft in a high-latitude circular polar orbit can provide the essential observations needed to track and quantify the flow of solar wind energy through the magnetosphere, including the solar wind plasma and magnetic field input, the magnetopause location in soft X-rays, the auroral oval in far ultraviolet, the ring current in energetic neutrals, the plasmasphere in extreme ultraviolet, the exosphere in Lyman-, the microstructure of the nightside auroral oval in ground-based all sky cameras, and the magnetic perturbations of ionospheric current patterns seen by ground-based magnetometers.

D G Sibeck↗
NASA NTRS2022

The Puzzling Structure of Solar Convection: Window into the Dynamo

The operation of the solar dynamo, with all of its remarkable spatio-temporal ordering, remains an outstanding problem of modern solar physics. A number of mechanisms that might plausibly contribute to its operation have been proposed, but the relative role played by each remains unclear. This uncertainty stems from continuing questions concerning the speed and structure of deep-seated convective flows. Those flows are in-turn thought to sustain both the Sun’s turbulent EMF and the large-scale flows of differential rotation and meridional circulation suspected of influencing the dynamo’s organization and timing. Ultimately, the convective and large-scale flow structure derive from the Coriolis force. When the Coriolis effect is weak (rapid convective flow), convection exhibits little organization in its spatial structure, and the meridional flow is expected to assume a single-celled profile within each hemisphere. Convection subject to strong Coriolis forces instead organizes into compact, spiraling columnar structures and sustains meridional flows that possess multiple cells in latitude and radius. The implications for the dynamo in these two regimes are substantial, impacting the flux-transport properties of any assumed meridional flow and the convectively-driven EMF. Continued progress in this area is complicated by (i) inconsistencies between helioseismic measurements of convective and meridional flow made with different techniques and instruments, and (ii) a lack of high-latitude data for convection, differential rotation, and meridional flow. We suggest that the path forward to resolving these difficulties is twofold. First, the acquisition of long-term helioseismic and emissivity measurements obtained from a polar vantage point is vital to complete our picture of the Sun’s outer convection zone. Second, sustained and expanded investment in theory-oriented and combined theory/observational research initiatives will be crucial to fully exploit these new observations and to resolve inconsistencies between existing measurements.

SMD↗
NASA NTRS2022

The Impact of Winds on AMOC in a Fully-Coupled Climate Model

Here we investigate the role of the atmospheric circulation in AMOC by comparing a fully-coupled large ensemble, a forced-ocean simulation, and new experiments using a fully-coupled global climate model where winds above the boundary layer are nudged towards reanalysis. When winds are nudged north of 45°N, agreement with RAPID array observations of AMOC at 26.5°N improves across several metrics. The phasing of interannual variability is well-captured due to the response of the local Ekman component in both wind-nudging and forced-ocean simulations, however the variance remains underestimated. The mean AMOC strength is substantially reduced relative to the fully-coupled model large ensemble, which is biased high, due to the impact of winds on surface buoyancy fluxes over the subpolar gyre. Nudging winds towards observations also reduces the 1979-2016 trend in AMOC, suggesting that improvement in the representation of the high-latitude atmosphere is important for projecting long-term AMOC changes.

AMOC↗
NASA NTRSDate not supplied

NAIRAS Model Nowcasting and Forecasting of the Aviation Radiation Environment

The Nowcast of Aerospace Ionizing RAdiation System (NAIRAS) predicts dosimetric quantities for quantifying human radiation exposure and differential/integral flux/fluence quantities for assessing single event effects (SEE) in avionic systems from galactic cosmic rays (GCR), trapped inner belt protons, and solar energetic particle (SEP) events from the Earth’s surface to the space environment. Real-time predictions of the aviation radiation environment are available at NASA Goddard Space Flight Center’s Community Coordinated Modeling Center (CCMC) integrated Space Weather Analysis (iSWA) data feeds and cygnets, and a run-on-request (RoR) capability has also been deployed at CCMC. Recent model improvements include a more accurate atmospheric ionizing radiation transport methodology and more robust and reliable SEP nowcast dose predictions. In addition, preliminary results of SEP dose forecasts are shown by coupling the University of Malaga Solar Energetic Particle (UMASEP) model of integral proton flux forecasts with the NAIRAS model. These model updates and improvements are presented, and results are shown for aircraft, high-latitude balloon, and low-Earth orbit flights during quiescent and solar-geomagnetic disturbed conditions. Model comparisons with flight measurements are also shown.

NAIRAS↗
NASA NTRSDate not supplied

Cubespark: A New Satellite-Based 3d Lightning Observing Concept

Legacy and current space-based optical lightning detectors are insensitive to small and dim pulses that make up much of the lightning activity produced by severe storms. Moreover, lightning flashes produced at low altitudes within optically thick clouds are severely under-detected by current optical detectors. Lastly, there is currently no capability to characterize the 3D structure of lightning both day and night at the global scale, yet this information is critical for identifying lightning produced in updraft regions, including lightning occurring in overshooting tops, which is a distinctive signature of severe weather. Global 3D lightning information is also critical for understanding the vertical distribution of NOx production and identifying anomalously electrified storms. Furthermore, the vertical distribution of lightning has implications for how microphysical (e.g., ice-based) and thermodynamical (e.g., latent heat release) processes vary regionally, as well as seasonally – e.g., winter lightning typically occurs at lower altitudes than summer lightning and is often associated with tall, man-made structures. Finally, global-scale 3D lightning observations would directly provide flash type (i.e., CG or IC) information that is very useful in all of the studies mentioned in this paragraph and is fundamental in identifying/documenting deleterious CG-caused impacts (e.g., wildfires, power-outages, crop and property damage, and associated insurance claims). A new, satellite mission concept called CubeSpark is being designed to address these shortcomings and fill this measurement gap by providing novel 3D observations of total lightning activity. CubeSpark will utilize a constellation of low-Earth orbiting small satellites that make radio frequency (RF) and bi-spectral optical measurements of lightning. Two options for combining these measurements to retrieve the 3D location of lightning are considered with corresponding measurement simulators built to understand the level of detail and viability of each approach. Although the level of detail varies for each combined measurement approach, results indicate that a 3D location accuracy of < 1-2 km in each dimension is feasible across 300-500 km wide swaths, which suggests that CubeSpark can resolve the charge structure of thunderclouds from the tropics to the mid- and high-latitudes.

lightning↗
NASA NTRS2023

Global Climate Impacts of Greenland and Antarctic Meltwater: A Comparative Study

Both the Greenland and Antarctic ice sheets have been melting at an accelerating rate over recent decades. Meltwater from Greenland might be expected to initiate a climate response which is distinct, and perhaps different from, that associated with Antarctic meltwater. Which one might elicit a greater climate response, and what mechanisms are involved? To explore these questions, we apply “Climate Response Functions (CRFs)” to guide a series of meltwater perturbation experiments using a fully-coupled climate model. In both hemispheres, meltwater drives atmospheric cooling, sea-ice expansion, and strengthened Hadley and Ferrel cells. Greenland meltwater induces a slowdown of the Atlantic Meridional Overturning Circulation (AMOC) and a cooling of the subsurface ocean in the northern high-latitudes. Antarctic meltwater, instead, induces a slowdown of the Antarctic Bottom Water formation and a warming of the subsurface ocean around Antarctica. For melt-rates up to 2000 Gt yr −1 , the climate response is rather linear. However, as melt-rates increase to 5000 Gt yr −1 , the climate response becomes non-linear. Due to a collapsed AMOC, the climate response is super-linear at high Greenland melt-rates. Instead, the climate response is sub-linear at high Antarctic melt-rates, due to the halting of the northward expansion of Antarctic sea ice by warm surface waters. Finally, in the linear limit, we use CRFs and linear convolution theory to make projections of important climate parameters in response to meltwater scenarios, which suggest that Antarctic meltwater will become a major driver of climate change, dominating that of Greenland meltwater, as the current century proceeds.

Greenland ice sheet↗
NASA NTRS2023

Global and Zonal-Mean Hydrological Response to Early Eocene Warmth

Earth's hydrological cycle is expected to intensify in response to global warming, with a “wet-gets-wetter, dry-gets-drier” response anticipated over the ocean. Subtropical regions (∼15°–30°N/S) are predicted to become drier, yet proxy evidence from past warm climates suggests these regions may be characterized by wetter conditions. Here we use an integrated data-modeling approach to reconstruct global and zonal-mean rainfall patterns during the early Eocene (∼56–48 million years ago). The Deep-Time Model Intercomparison Project (DeepMIP) model ensemble indicates that the mid- (30°–60°N/S) and high-latitudes (>60°N/S) are characterized by a thermodynamically dominated hydrological response to warming and overall wetter conditions. The tropical band (0°–15°N/S) is also characterized by wetter conditions, with several DeepMIP models simulating narrowing of the Inter-Tropical Convergence Zone. However, the latter is not evident from the proxy data. The subtropics are characterized by negative precipitation-evaporation anomalies (i.e., drier conditions) in the DeepMIP models, but there is surprisingly large inter-model variability in mean annual precipitation (MAP). Intriguingly, we find that models with weaker meridional temperature gradients (e.g., CESM, GFDL) are characterized by a reduction in subtropical moisture divergence, leading to an increase in MAP. These model simulations agree more closely with our new proxy-derived precipitation reconstructions and other key climate metrics and imply that the early Eocene was characterized by reduced subtropical moisture divergence. If the meridional temperature gradient was even weaker than suggested by those DeepMIP models, circulation-induced changes may have outcompeted thermodynamic changes, leading to wetter subtropics. This highlights the importance of accurately reconstructing zonal temperature gradients when reconstructing past rainfall patterns.

Margot J. Cramwinckel↗
NASA NTRSDate not supplied

Temporal and Spatial Dynamics of Nitric Oxide Production at High Latitudes During an ICME-driven Storm on Dec. 14, 2006

During geomagnetic storms driven by interplanetary coronal mass ejections (ICMEs), Earth’s upper atmosphere neutral mass density is directly driven by the geomagnetic storm cycle from intense driving and subsequent recovery. The neutral density heating and cooling times are shorter for stronger storms and longer for weaker storms. The influx of energy (Joule Heating and precipitation) into Earth’s upper atmosphere during the storm main phase allows for the enhanced production of nitric oxide (NO) at high latitudes, which in turn cools the thermosphere by radiating away excess energy. As a result, greater NO production results in quicker thermospheric cooling. Yet while the production of NO on a global scale has been examined in detail, the space and time evolution of NO is not well-known. In this study, we investigate the effects of a particular ICME-driven storm, which occurred on Dec. 14th, 2006, on the production of NO at high latitudes. We compare NO measurements from the Thermosphere, Ionosphere, Mesosphere Dynamics (TIMED) spacecraft to neutral mass density measurements from the Challenging Minisatellite Payload (CHAMP) spacecraft and find that the impact of the shock prior to the storm, not just the onset of the storm itself, is responsible for an increase in NO production. We also observe a dawn-dusk asymmetry in high-latitude NO production and discuss how the geometry of the solar wind driver may play a role in creating this asymmetry. Finally, we discuss how the improved hemispheric and local time coverage provided by the GDC and DYNAMIC missions will enable more robust studies of the spatiotemporal evolution of NO during storms. Since NO is an important factor in regulating the neutral density of the thermosphere, such studies will be relevant for more accurate orbital drag calculations.

Kevin Delano↗
NASA NTRS2023

Summer Atmospheric Circulation Over Greenland in Response to Arctic Amplification and Diminished Spring Snow Cover

The exceptional atmospheric conditions that have accelerated Greenland Ice Sheet mass loss in recent decades have been repeatedly recognized as a possible dynamical response to Arctic amplification. Here, we present evidence of two potentially synergistic mechanisms linking high-latitude warming to the observed increase in Greenland blocking. Consistent with a prominent hypothesis associating Arctic amplification and persistent weather extremes, we show that the summer atmospheric circulation over the North Atlantic has become wavier and link this wavier flow to more prevalent Greenland blocking. While a concomitant decline in terrestrial snow cover has likely contributed to this mechanism by further amplifying warming at high latitudes, we also show that there is a direct stationary Rossby wave response to low spring North American snow cover that enforces an anomalous anticyclone over Greenland, thus helping to anchor the ridge over Greenland in this wavier atmospheric state.

Atmospheric dynamics↗
NASA NTRS2021

On the Settling Depth of Meltwater Escaping From Beneath Antarctic Ice Shelves

Antarctic glacial meltwater is thought to play an important role in determining large-scale Southern Ocean climate trends, yet recent modeling efforts have proceeded without a good understanding of how its vertical distribution in the water column is set. To rectify this, here we conduct new large-eddy simulations of the ascent of a buoyant meltwater plume after its escape from beneath an Antarctic ice shelf. We find that the meltwater’s settling depth is primarily a function of the buoyancy forcing per unit width of the source and the ambient stratification, consistent with the classical theory of turbulent buoyant plumes and in contrast to previous work that suggested an important role for centrifugal instability. Our results further highlight the significant role played by localized variability in stratification; this helps explain observed interannual variability in the vertical meltwater distribution near Pine Island Glacier. Because of the vast heterogeneity in mass loss rates and ambient conditions at different Antarctic ice shelves, a dynamic parameterization of meltwater settling depth may be crucial for accurately simulating high-latitude climate in a warming world; we discuss how this may be developed following this work, and where the remaining challenges lie.

Antarctic glacial meltwater↗
NASA NTRSDate not supplied

Climate change signal in global agriculture emerges earlier in new generation of climate and crop models

Potential climate-related impacts on future crop yield are a major societal concern first surveyed in a harmonized multi-model effort in 2014. We report here on new 21st-century projections using ensembles of latest-generation crop and climate models. Results suggest markedly more pessimistic yield responses for maize, soybean, and rice compared to the original ensemble. Mean end-of-century maize productivity is shifted from +5 to -6% (SSP126) and +1 to -24% (SSP585) — explained by warmer climate projections and improved crop model sensitivities. In contrast, wheat shows stronger gains (+9 shifted to +18%, SSP585), linked to higher CO2 concentrations and expanded high-latitude gains. The ‘emergence’ of climate impacts — when the change signal emerges from the noise — consistently occurs earlier in the new projections for several main producing regions before 2040. While future yield estimates remain uncertain, these results suggest that major breadbasket regions will face distinct anthropogenic climatic risks sooner than previously anticipated.

climate change↗
NASA NTRSDate not supplied

NASA’s Geospace Dynamics Constellation—Providing the first Systematic Measurements of Global Magnetospheric Energy Inputs and Ionosphere-Thermosphere Responses

The Geospace Dynamics Constellation (GDC) is NASA's next strategic Living With a Star mission. GDC's goals are: 1) Understand how the high-latitude ionosphere-thermosphere system responds to variable solar wind/magnetosphere forcing; and 2) Understand how internal processes in the global ionosphere-thermosphere system redistribute mass, momentum, and energy. Planned for launch by the end of the decade, GDC will use six identical observatories, each identically instrumented to fully characterize the magnetospheric drivers of the I-T system as well as the global response of the ionized and neutral gases. GDC will do this with a series of orbital configurations that will enable it to study the widest range of spatial and temporal scales to date, ranging from hundreds of kilometers and several seconds to tens of minutes, and extending through the regional to the global scale. This talk presents GDC's current status, measurement capabilities, sampling scheme, and model development efforts and show how GDC will fit into the larger Heliophysics ecosystem, by 1) obtaining critically needed scientific observations; 2) providing a source for real-time space weather and situational awareness, as well as retrospective studies to further the science of space weather; 3) serving as a "strategic hub" for other space-based and ground-based efforts that want to leverage GDC to perform complementary science. To get the most benefit from GDC’s observations, it will be critical to identify partnerships with other research efforts in the ITM and Geospace arenas, including those utilizing space-based, ground-based, or theoretical investigations. We particularly would like to discuss with groups who are planning or considering observational campaigns during the GDC era, to find ways to leverage GDC observations to do synergistic science that could not be done otherwise.

Douglas E Rowland↗
NASA NTRS2022

A Regional Classification of Time Spectral Amplitudes in Total Electron Content: Southeastern United States During Solar Cycle 24

To investigate the meso-scale structure (100 s of km) of the ionosphere at mid-latitudes, the spectral properties in calculated total electron content (TEC) at a cluster of GPS receivers in and around Florida are analyzed. The ionosphere does not respond exactly the same to periodic solar driving at different locations around the planet, due to the complex electrodynamic interactions of the coupled magnetosphere-ionosphere system. Therefore, at each GPS receiver in the cluster we compare spatio-temporal variations of the spectral amplitudes for diurnal, solar rotation, and seasonal oscillations. The amplitudes for these dominant oscillations are organized with respect to magnetic latitude of the receiver. A low-latitude and high-latitude station are also included to put the mid-latitude ionospheric response into a global context. The amplitudes of diurnal, seasonal, and solar rotation signals are well ordered by magnetic latitude, superposed with meso-scale deviations between stations separated by ~100s of km. The results suggest that spatio-temporal variations of spectral amplitudes in the mid-latitude ionosphere are not dominated by a single process. This conclusion is based on our finding that at high latitude, the shape of the diurnal signal varies significantly less with solar activity compared to low- and mid-latitudes, and additionally, that the ratio of annual to semi-annual amplitudes fluctuates around 1 with time and from station-to-station only at mid-latitudes.

ionosphere↗
NASA NTRSDate not supplied

Oceanic Validation of IMERG Version 7 with the GPM Validation Network

- To validate Version 7 of the Integrated Multi-satellitE Retrievals for the Global Precipitation Measurement (GPM) mission (IMERG) over tropical and high-latitude oceans using the GPM Validation Network (VN). - To trace errors from the Level-3 IMERG V07 product back through to the input Level-2 Goddard Profiling Algorithm (GPROF) V07 product for the GPM Microwave Imager (GMI).

GPM↗
NASA NTRSDate not supplied

Maintaining the Continuity of the Global Climate Data Record of Lightning from Space

Lightning is a natural hazard, an indicator of changes in convective storm behavior across multiple spatial and temporal scales, and a major influence on climate-affecting chemicals such as ozone and methane. Lightning also has substantial impacts on the near-space environment. As such, the World Meteorological Organization (WMO) has designated lightning as an Essential Climate Variable (ECV); that is, a measurement that is really important for understanding Earth’s climate. Spaceborne lightning observations are the gold standard for measuring global lightning, as the detection efficiency is more spatially uniform compared to ground-based lightning measurements. In addition, spaceborne is the only practical method for measuring total lightning (i.e., both intracloud and cloud-to-ground) at the global scale, as ground-based networks have limited ability to detect intracloud lightning at long distances (e.g., over oceans, far from land-based sensors). Since 1995, with only a two-year gap (2015-2017), lightning has been observed globally using a combination of Optical Transient Detector (OTD) and Lightning Imaging Sensor (LIS) instruments. However, the year 2023 is the planned end for the International Space Station (ISS) LIS mission, and there is no designated low-Earth orbit (LEO) successor yet identified. Since 2017, geostationary (GEO) observations of lightning have become increasingly available. These include the U.S. Geostationary Lightning Mappers (GLMs), China’s Lightning Mapping Imager (LMI), and Europe’s Lightning Imager (LI). While GEO provides continuous, quasi-hemispheric coverage of lightning and thunderstorms, there are current gaps preventing global coverage, particularly in portions of Asia and the western Pacific, as well as high-latitude regions. Moreover, integration of the GEO constellation into a Climate Data Record (CDR) of lightning is a major challenge only recently begun to be addressed by the WMO. Furthermore, recent work has demonstrated some deficiencies in the global record of lightning from space. For example, small lightning flashes are very common in severe weather, but are difficult to observe using the present set of spaceborne lightning imagers. Moreover, some types of lightning are best observed using frequencies other than the commonly used near-infrared (777-nm), including ultraviolet and the radio spectrum. Finally, it is not possible to assess the vertical distribution of lightning globally, even though this measurement is highly relevant to thunderstorm behavior as well as lightning’s effects on greenhouse gases and the near-space environment. This presentation will provide a current assessment of lightning measurements from space, will identify significant current and future gaps in these observations, and will evaluate potential solutions for improving the overall CDR of global lightning.

Timothy Lang↗
NASA NTRS2023

Fast Plasma Drifts in the High Latitude Lonosphere

We have identified over 200 fast plasma drift events (>5 km/s) in the high-latitude ionosphere, as measured by the electric field double probe on the Dynamics Explorer-2 satellite during its 18 months lifetime from August 1981 to February 1983. Although these drifts can appear at all local time sectors, they are most common on the dawnside and in the pre-midnight sector. The fast plasma drifts generally occur between 64° and 82° inv.lat. although they sometimes appear below 55° inv.lat. in the pre-midnight sector, in which case they appear associated with a phenomenon often referred to as sub-auroral ion drifts. For increasing Auroral Electrojet index, their occurrence rate increases and their latitudinal locations move equatorward. The observed events last between 0.1 and 60 s, corresponding to (north-south) widths of 1–500 km along the satellite trajectory. The observations show a seasonal dependence such that the faster drifts tend to occur over the dark (winter) hemisphere.

Harri Laakso↗
NASA NTRSDate not supplied

Dynamics of Solar Energetic Particles in Geospace

Solar energetic particles (SEPs) penetrate deep into the geospace and the Earth's atmosphere, initiating nuclear and chemical reactions. These reactions produce secondary hadrons, leptons, and photons, posing radiation hazards at commercial aviation altitudes, particularly during high-latitude flights. During solar particle events, protons with energies above 10 MeV can reach below 100 km altitude, causing ionization that disrupts HF communication and navigation in polar regions. Galactic Cosmic Rays (GCRs) and Solar Energetic Particles (SEPs) pose radiation risks to satellites, astronauts, and ground infrastructure. High-energy particles can lead to single-event effects in spacecraft electronics, such as upsets, latch-ups, and burnouts. These particles also interact with the Earth's atmosphere, generating ionization and secondary particles like hadrons, leptons, and photons, creating hazards for astronauts, especially during extravehicular activities. The work presented in the paper is focused on characterizing the SEP population in geospace in the altitude range starting from that of LEO through MEO and GEO, and up to the magnetopause accounting for the realistic geomagnetic field. The dynamics of SEPs are studied during quiet and geomagnetically active times using Monte Carlo simulations. The paper discusses the variability of the SEP population in geospace in response to geomagnetic activity. The former manifests in the temporal trapping of SEPs in geospace and the suppression of rigidity cutoff during geomagnetic storms.

Valeriy Tenishev↗