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Bagwell, C.

Publications and source records attributed to Bagwell, C..

5 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Properties of Cosmic Deuterons Measured by the Alpha Magnetic Spectrometer

Precision measurements by the Alpha Magnetic Spectrometer (AMS) on the International Space Station of the deuteron (𝐷) flux are presented. The measurements are based on 21 × 10 6 𝐷 nuclei in the rigidity range from 1.9 to 21 GV collected from May 2011 to April 2021. We observe that over the entire rigidity range the 𝐷 flux exhibits nearly identical time variations with the 𝑝, 3 He, and 4 He fluxes. Above 4.5 GV, the 𝐷/ 4 He flux ratio is time independent and its rigidity dependence is well described by a single power law ∝𝑅 Δ with Δ 𝐷/ 4 He = −0.108 ± 0.005. This is in contrast with the 3 He/ 4 He flux ratio for which we find Δ 3 He/ 4 He = −0.289 ± 0.003. Above ∼13 GV we find a nearly identical rigidity dependence of the 𝐷 and 𝑝 fluxes with a 𝐷/𝑝 flux ratio of 0.027 ± 0.001. These unexpected observations indicate that cosmic deuterons have a sizable primarylike component. With a method independent of cosmic ray propagation, we obtain the primary component of the 𝐷 flux equal to 9.4 ± 0.5% of the 4 He flux and the secondary component of the 𝐷 flux equal to 58 ± 5% of the 3 He flux.

cosmic ray acceleration↗
DOE OSTI2023

Temporal Structures in Positron Spectra and Charge-Sign Effects in Galactic Cosmic Rays

We present the precision measurements of 11 years of daily cosmic positron fluxes in the rigidity range from 1.00 to 41.9 GV based on 3.4 × 10 6 positrons collected with the Alpha Magnetic Spectrometer (AMS) aboard the International Space Station. The positron fluxes show distinctly different time variations from the electron fluxes at short and long timescales. A hysteresis between the electron fluxes and the positron fluxes is observed with a significance greater than 5⁢𝜎 at rigidities below 8.5 GV. On the contrary, the positron fluxes and the proton fluxes show similar time variation. Remarkably, we found that positron fluxes are modulated more than proton fluxes with a significance greater than 5⁢𝜎 for rigidities below 7 GV. These continuous daily positron fluxes, together with AMS daily electron, proton, and helium fluxes over an 11-year solar cycle, provide unique input to the understanding of both the charge-sign and mass dependencies of cosmic rays in the heliosphere.

astroparticles↗
NASA NTRS1977

A procedure used for a ground truth study of a land use map of North Alabama generated from LANDSAT data

A land use map of a five county area in North Alabama was generated from LANDSAT data using a supervised classification algorithm. There was good overall agreement between the land use designated and known conditions, but there were also obvious discrepancies. In ground checking the map, two types of errors were encountered - shift and misclassification - and a method was developed to eliminate or greatly reduce the errors. Randomly selected study areas containing 2,525 pixels were analyzed. Overall, 76.3 percent of the pixels were correctly classified. A contingency coefficient of correlation was calculated to be 0.7 which is significant at the alpha = 0.01 level. The land use maps generated by computers from LANDSAT data are useful for overall land use by regional agencies. However, care must be used when making detailed analysis of small areas. The procedure used for conducting the ground truth study together with data from representative study areas is presented.

Downs, S. W., Jr.↗