Decompression sickness in space-cabin atmospheres after only two hours of 'ground level denitrogenation'
Ground level denitrogenation duration effects on decompression sickness occurrence in space cabin atmospheres
Allen, T. H.↗
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The Potential Impact of Satellite-Retrieved Cloud Parameters on Ground-Level PM2.5 Mass and Composition
Satellite-retrieved aerosol optical properties have been extensively used to estimate ground-level fine particulate matter (PM2.5) concentrations in support of air pollution health effects research and air quality assessment at the urban to global scales. However, a large proportion, approximately 70%, of satellite observations of aerosols are missing as a result of cloud-cover, surface brightness, and snow-cover. The resulting PM2.5 estimates could therefore be biased due to this non-random data missingness. Cloud-cover in particular has the potential to impact ground-level PM2.5 concentrations through complex chemical and physical processes. We developed a series of statistical models using the Multi-Angle Implementation of Atmospheric Correction (MAIAC) aerosol product at 1 km resolution with information from the MODIS cloud product and meteorological information to investigate the extent to which cloud parameters and associated meteorological conditions impact ground-level aerosols at two urban sites in the US: Atlanta and San Francisco. We find that changes in temperature, wind speed, relative humidity, planetary boundary layer height, convective available potential energy, precipitation, cloud effective radius, cloud optical depth, and cloud emissivity are associated with changes in PM2.5 concentration and composition, and the changes differ by overpass time and cloud phase as well as between the San Francisco and Atlanta sites. A case-study at the San Francisco site confirmed that accounting for cloud-cover and associated meteorological conditions could substantially alter the spatial distribution of monthly ground-level PM2.5 concentrations.
MAIAC AO↗
Southeast Michigan Health & Air Quality: Identifying Trends of Ground-level Ozone Precursors in Southeast Michigan and Northern Ohio
Pollutants resulting from industrial activity can react with sunlight to create ground-level ozone, a harmful pollutant that can exacerbate respiratory health issues such as asthma. Due to a history of heavy industrialization, residents of southeast Michigan and northern Ohio are especially susceptible to ground-level ozone. NASA DEVELOP, in partnership with the Michigan Department of Environment, Great Lakes, and Energy’s (EGLE) Air Quality Division and the Lake Michigan Air Directors Consortium (LADCO), investigated the effectiveness of Earth observations (EO) in monitoring pollutants that contribute to ground-level ozone. The team used the European Space Agency’s TROPOspheric Monitoring Instrument (TROPOMI) aboard Sentinel-5P, and NASA’s Ozone Monitoring Instrument (OMI) aboard Aura, to measure nitrogen dioxide (NO2), formaldehyde (HCHO), and methane (CH4) from 2019 to 2021 (May-September). The team oversampled the EO data on monthly, yearly, and 3-year time scales where possible to enhance more localized pollutant trends. Specifically, TROPOMI effectively monitored NO2 from space, indicating sub-city distributions on a monthly timescale. Contrastingly, the measurements of HCHO were predominately noisy, and therefore failed to show any distribution trends. Lastly, CH4 trends were identifiable yet coarse, hinting that EO monitoring in the case of CH4 is not beneficial for our partners. The end products provide the partners with insight on the utility of EO in measuring certain ozone precursors and can be used to guide ground-level ozone reduction strategies throughout the region.
Mariam Moeen↗
Ground-Level Digital Terrain Model (DTM) Construction from Tandem-X InSAR Data and Worldview Stereo-Photogrammetric Images
The ground-level digital elevation model (DEM) or digital terrain model (DTM) information are invaluable for environmental modeling, such as water dynamics in forests, canopy height, forest biomass, carbon estimation, etc. We propose to extract the DTM over forested areas from the combination of interferometric complex coherence from single-pass TanDEM-X (TDX) data at HH polarization and Digital Surface Model (DSM) derived from high-resolution WorldView (WV) image pair by means of random volume over ground (RVoG) model. The RVoG model is a widely and successfully used model for polarimetric SAR interferometry (Pol-InSAR) technique for vertical forest structure parameter retrieval [1][2][3][4]. The ground-level DEM have been obtained by complex volume decorrelation in the RVoG model with the DSM using stereo-photogrammetric technique. Finally, the airborne lidar data were used to validate the ground-level DEM and forest canopy height results.
Lee, Seung-Kuk↗
Why Are Most Ground Level Events Associated with High Fe/O Ratios?
In a seminal paper about Ground Level Events (GLEs), Dietrich and Lopate (1999) reported on 24 GLEs from April, 1973 to May, 1998. They noted that alt but one of these GLEs, June 15, 1991, were associated with a Solar Energetic Particle (SEP) event with an enhanced Fe/O ratio. The Fe/O ratio observed for the June 15, 1991 event was only 0.03, well below the nominal coronal abundance of Fe/O = 0.134. For the remaining events, Fe/O ranged from 0.27 to over 3, welt over the nominal coronal value. During Solar Cycle 23, 14 more GLEs were observed, only one of which had very low Fe/O. This was the event of January 20, 2005, the largest ground-level neutron monitor event in 49 years. We will report on our efforts to find out whether the events of June 15, 1991 and January 20, 2005 have features in common, besides high Fe/O, that distinguish them from all other GLE events and may help determine the cause of elevated Fe/O in almost all GLE events. We will use energetic particle, magnetic field, and solar wind plasma data from NASA's IMP-8 Wind, and ACE spacecraft.
von Rosenvinge, Tycho T.↗
Ground-level detection of low- and medium-frequency auroral radio emissions
Natural radio emissions in the frequency range of several hundred kHz were detected at ground level in the auroral region during a ground-level observing program conducted near Fairbanks, Alaska in the spring of 1986 in an attempt to detect auroral cyclotron-maser-generated whistler modes. Most of the strongest emissions were observed in a small time interval around midnight magnetic local time, suggesting a close tie-in with auroral processes. The results support earlier reports of radio noise from the aurora at frequencies of about 100 kHz and indicate the importance of extending the upper frequency of ground-based high-latitude VLF stations to the vicinity of 1 MHz.
Benson, Robert F.↗
A suggested standardized format for cosmic ray ground-level event data
A standardized format is suggested for the archival storage and exchange of neutron monitor data obtained during solar flare initiated ground level cosmic ray events. Using the data for the 7 May 1978 ground level event, a format has been developed that incorporates hourly data preceding and following the event and small time interval data immediately before and during the event. Provision has been made for the inclusion of uncorrected and corrected data as well as the atmospheric pressure. The cosmic ray intensity data are then reduced to a standard counting rate of counts per second facilitating the graphing and comparison of these data for various analyses.
Shea, M. A.↗
The effectiveness of ground level post-flight 100 percent oxygen breathing as therapy for pain-only altitude Decompression Sickness (DCS)
In both the aviation and space environments, decompression sickness (DCS) is an operational limitation. Hyperbaric recompression is the most efficacious treatment for altitude DCS. However, the inherent recompression of descent to ground level while breathing oxygen is in itself therapy for altitude DCS. If pain-only DCS occurs during a hypobaric exposure, and the symptoms resolver during descent, ground level post-flight breathing of 100% O2 for 2 hours (GLO2) is considered sufficient treatment by USAF Regulation 161-21. The effectiveness of the GLO2 treatment protocol is defined.
Demboski, John T.↗
Calculated maximum Hl ground-level concentrations downwind from launch pad aborts of the space shuttle and Titan 3 C vehicles at Kennedy Space Center
A quantitative assessment is described of the potential environmental hazard posed by the atmospheric release of HCl resulting from the burning of solid propellant during two hypothetical on-pad aborts of the Titan 3 C and space shuttle vehicles at Kennedy Space Center. In one pad-abort situation, it is assumed that the cases of the two solid-propellant engines are ruptured and the burning propellant falls to the ground in the immediate vicinity of the launch pad where it continues to burn for 5 minutes. In the other pad-abort situation considered, one of the two solid engines on each vehicle is assumed to ignite and burn at the normal rate while the vehicle remains on the launch pad. Calculations of maximum HCl ground-level concentration for the above on-pad abort situations were made using the computerized NASA/MSFC multilayer diffusion models in conjunction with appropriate meteorological and source inputs. Three meteorological regimes are considered-fall, spring, and afternoon sea-breeze. Source inputs for the hazard calculations were developed. The principal result of the calculations is that maximum ground-level HCl concentrations at distances greater than 1 kilometer from the launch pad are less than 3 parts per million in all cases considered.
Dumbauld, R. K.↗
Wideband noise observed at ground level in the auroral region
A sideband noise event was detected at ground level from the Andoya Rocket Range in Norway in January 1989. The signals were observed on four commercial communication receivers (tuned to 159, 515, 905, and 1200 kHz), an ionosonde (200-kHz to 3.5-MHz interference-free observations) and a riometer (32.5 MHz). The event, which occurred during a period of magnetic disturbance near magnetic midnight, was the only one observed during nearly 3 weeks of operations. This low frequency-of-occurrence is attributed partly to high local noise levels. The ease with which this event was identified on the ionograms produced by the local ionosonde suggests that routine ionosonde recordings should be inspected in search for such events. Such an effort would enhance existing research directed toward developing techniques for identifying quiet communication channels and help to identify the origin and frequency-of-occurrence of high-latitude wideband noise events.
Benson, Robert F.↗
Ground Level Enhancement in the 2014 January 6 Solar Energetic Particle Event
We present a study of the 2014 January 6 solar energetic particle event which produced a small ground level enhancement (GLE), making it the second GLE of this unusual solar cycle 24. This event was primarily observed by the South Pole neutron monitors (increase of approximately 2.5 percent) while a few other neutron monitors recorded smaller increases. The associated coronal mass ejection (CME) originated behind the western limb and had a speed of 1960 kilometers per second. The height of the CME at the start of the associated metric type II radio burst, which indicates the formation of a strong shock, was measured to be 1.61 solar radii using a direct image from STEREO-A/EUVI. The CME height at the time of the GLE particle release (determined using the South Pole neutron monitor data) was directly measured as 2.96 solar radii based on STEREO-A/COR1 white-light observations. These CME heights are consistent with those obtained for GLE71, the only other GLE of the current cycle, as well as cycle-23 GLEs derived using back-extrapolation. GLE72 is of special interest because it is one of only two GLEs of cycle 24, one of two behind-the-limb GLEs, and one of the two smallest GLEs of cycles 23 and 24.
ground level enhancement↗
Road Vehicle Functional Safety in Ground-Level Radiation Environments
This presentation gives an overview of the natural space radiation environment, the ground-level radiation environment, and single-event effects (SEEs). We then discuss the impact of SEEs for road vehicle functional safety and issues with commercial electronic components in these high-reliability systems. Finally, we introduce some forward-looking concepts that the radiation effects and automotive electronics communities will have to address as aggressive technology insertion continues.
Pellish, Jonathan↗
Mars Ground Level Enhancements in the Context of the Solar Energetic Particle Clock
In this work we discuss the growing ensemble of solar particle events registered on the Martian surface, including their temporal appearance and solar sources. Solar energetic particle events from the surface of Mars have been observed starting soon after the August 2012 landing of the Radiation Assessment Detector onboard Curiosity. The Martian atmosphere prevents protons and heavy ions of up to 180 MeV/n kinetic energy from directly reaching the Martian surface. This cut-off is high enough to limit the number of solar energetic particle events measured on the surface to only 15 in ~12 ½ years. Yet we find in this analysis that Mars ground level enhancements follow the distinct SEP clock pattern as proton events observed at lower energies as reported in Posner, Richardson and Strauss (2024). Proton acceleration occurs predominantly near the solar surface, while transport to Mars incurs a delay in onset, and, as we show here, peak, that is a function of the longitudinal magnetic connection distance. between the foot point of solar wind magnetic field lines that intersect the Mars environment with the source longitude of the solar magnetic eruption. A distinct clustering of relative solar source locations at or near the Mars foot points at the Sun’s western limb is apparent, indicating lower flux thresholds from such preferred locations. Our findings have implications for astronaut safety at Mars.
Mars Ground Level Enhancements↗
Solar Source and CME Properties of Solar Cycle 23 Ground Level Enhancement Events
Solar cycle 23 witnessed the most complete set of observations of coronal mass ejections (CMEs) associated with the Ground Level Enhancement (GLE) events. GLE events are extreme cases of solar energetic particle (SEP) events in that the energetic particles penetrate Earth's neutral atmosphere to be detected by neutron monitors. In this paper we present the CME and their source properties that seem to be equally extreme. These observations are consistent with the idea that the GLE particles are accelerated in the same way as the regular SEP events by CME-driven shocks. While we cannot rule out the possibility of the presence of a flare component during GLE events, we can definitely say that a shock component is present in all the GLE events. We provide additional information on the GLE-associated type II radio bursts, complex type III radio bursts, and soft X-ray flares, which are not very different from those associated with large SEP events. Finally we compare the properties of GLEassociated CMEs in cycle 23 with those in cycle 22.
Gopalswamy, Nat↗
The First Ground Level Enhancement Event of Solar Cycle 24: Direct Observation of Shock Formation and Particle Release Heights
We report on the 2012 May 17 ground level enhancement (GLE) event, which is the first of its kind in solar cycle 24. This is the first GLE event to be fully observed close to the surface by the Solar Terrestrial Relations Observatory (STEREO) mission.We determine the coronal mass ejection (CME) height at the start of the associated metric type II radio burst (i.e., shock formation height) as 1.38 Rs (from the Sun center). The CME height at the time of GLE particle release was directly measured from a STEREO image as 2.32 Rs, which agrees well with the estimation from CME kinematics. These heights are consistent with those obtained for cycle-23 GLEs using back-extrapolation. By contrasting the 2012 May 17 GLE with six other non-GLE eruptions from well-connected regions with similar or larger flare sizes and CME speeds, we find that the latitudinal distance from the ecliptic is rather large for the non-GLE events due to a combination of non-radial CME motion and unfavorable solar B0 angle, making the connectivity to Earth poorer. We also find that the coronal environment may play a role in deciding the shock strength.
CMEs↗
Search for tachyons associated with extensive air showers in the ground level cosmic radiation
Events detected in a shielded plastic scintillation counter occurring in the 26 microsec preceding the arrival of an extensive air shower at ground level with local electron density or = 20 m to the -2 power and the 240 microsec after its arrival have been studied. No significant excess of events (tachyons) arriving in the early time domain have been observed in a sample of 11,585 air shower triggers.
Masjed, H. F.↗
Ground-Level Solar Cosmic Ray Data from Solar Cycle 19
The purpose of this grant was to locate, catalog, and assemble, in standard computer format, ground-level solar cosmic ray data acquired by cosmic ray detectors for selected events in the 19th solar cycle. The events for which we initially proposed to obtain these data were for the events of 23 February 1956,4 May 1960, 12 and 15 November 1960 and 18 and 20 July 1961. These were the largest events of the 19th solar cycle. However, a severe (more than 50%) reduction in the requested funding, required the work effort be limited to neutron monitor data for the 23 February 1956 event and the three major events in 1960.
Shea, M. A.↗
Spectral Analyses and Radiation Exposures from Several Ground-Level Enhancement (GLE) Solar Proton Events: A Comparison of Methodologies
Several methods for analyzing the particle spectra from extremely large solar proton events, called Ground-Level Enhancements (GLEs), have been developed and utilized by the scientific community to describe the solar proton energy spectra and have been further applied to ascertain the radiation exposures to humans and radio-sensitive systems, namely electronics. In this paper 12 GLEs dating back to 1956 are discussed, and the three methods for describing the solar proton energy spectra are reviewed. The three spectral fitting methodologies are EXP [an exponential in proton rigidity (R)], WEIB [Weibull fit: an exponential in proton energy], and the Band function (BAND) [a double power law in proton rigidity]. The EXP and WEIB methods use low energy (MeV) GLE solar proton data and make extrapolations out to approx.1 GeV. On the other hand, the BAND method utilizes low- and medium-energy satellite solar proton data combined with high-energy solar proton data deduced from high-latitude neutron monitoring stations. Thus, the BAND method completely describes the entire proton energy spectrum based on actual solar proton observations out to ~10 GeV. Using the differential spectra produced from each of the 12 selected GLEs for each of the three methods, radiation exposures are presented and discussed in detail. These radiation exposures are then compared with the current 30-day and annual crew exposure limits and the radiation effects to electronics.
Atwell, William↗