Solar Energetic Particles and their Effects on the Terrestrial Environment

Reid, George C.

doi:10.1007/978-94-009-5255-3_7

Cited by 15 publications

(12 citation statements)

References 119 publications

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“…156 The early modeling work of Madden and Thompson (1965) set the stage for understanding 157 cavity response to ionizing radiation on short timescales by first identifying two key Fig. 1 Vertical profiles of ionization rate associated with the vertical entry of (a) mono-energetic protons adapted from Reid (1986) and (b) mono-energetic electrons adapted from Rees (1989) into the Earth's atmosphere. Magnetic shielding is assumed to be zero in both cases…”

Section: 21 Short Timescalementioning

confidence: 99%

Effects of Energetic Solar Emissions on the Earth–Ionosphere Cavity of Schumann Resonances

et al. 2016

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Section: 21 Short Timescalementioning

confidence: 99%

Effects of Energetic Solar Emissions on the Earth–Ionosphere Cavity of Schumann Resonances

et al. 2016

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“…In each slab the incremental absorption is related to the square root of the production rate by the "combined coefficient", c (equal to the specific absorption divided by the square root of the effective recombination coefficient). The production rates are computed from geosynchronoussatellite measurements of the proton fluxes by the method of Reid (Reid, 1986;Reid et al, 1991). The scheme of computation is based on laboratory measurements of ionization by protons in air.…”

Section: A New Approachmentioning

confidence: 99%

A new method of studying the relation between ionization rates and radio-wave absorption in polar-cap absorption events

Hargreaves

2005

Ann. Geophys.

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Abstract. During polar-cap absorption events, which are caused by the incidence of energetic solar protons, the highlatitude ionospheric D region is extended down to relatively low altitudes. While the incoming proton fluxes may be monitored by satellite-borne detectors, and the resulting radiowave absorption with a ground-based riometer, the enhancement of electron density at a given altitude is less easily determined. Direct measurements by incoherent-scatter radar are infrequent and they tend to lack the necessary sensitivity at the lower levels. Computations of the electron density from the observed particle fluxes are handicapped by uncertainties in the height profile of the effective recombination coefficient. This paper describes a new approach based on finding the best-fit solution to an over-determined set of equations. The D region is treated as a set of slabs, each contributing to the total radio absorption, and the method relies on the fact that the proton spectrum varies during the event. The analysis produces a set of coefficients relating the absorption increment in the slab to the square root of the production rate, as a function of height. Values of effective recombination coefficient are also deduced over a range of heights, and these agree with previous estimates (Gledhill, 1986) to within a factor of 2. However, whereas the latter do not generally go below 60 km altitude the new determination extends the values down to 40 km.The new method provides a measurement of the height profile of the absorption in PCA events. It is shown that the slabs centred from 45 to 65 km typically account for 80% of the total daytime absorption, and that less than 1% of the total arises above 80 km or below 30 km. At night most of the absorption comes from the slabs at 75 and 80 km, with no significant contribution from slabs below 75 or above 85 km. These results would not differ significantly from estimates based on the Gledhill profiles if extrapolated downward.Correspondence to: J. K. Hargreaves (j.hargreaves@lancaster.ac.uk) Predictions based on the coefficients generated by the procedure are compared with the polar-cap absorption observed during some recent events. Typical electron-density values are derived, and the study provides an independent confirmation that the electron density and the production rate are related by a square-root law.

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“…Schueberl and Strobel (1978) used a zonally averaged quasi-geostrophic numerica• model to study the effects of solar particle events (e.g., August 1972) on general circulation. They concluded that the global effect would be negligible, largely due to the relatively sm•ll surface area of the earth affected by solar particles (see •lso Reid 1986). On the other hand, Geller and Alpert (1980) concluded that planetary wave coupling on a global physica• and long temporal scale was a plausible mechanism to give a tropospheric response to solar activity.…”

Section: Some Global Considerationsmentioning

confidence: 99%

Highly relativistic magnetospheric electrons: A role in coupling to the middle atmosphere?

Baker

Blake

Gorney

et al. 1987

Geophysical Research Letters

115

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Long‐term (1979‐present) observations of relativistic electrons (2–15 MeV) at geostationary orbit show a strong solar cycle dependence. Such electrons were largely absent near the last solar maximum (1979–80), while they were prominent during the approach to solar minimum (1983–85). This population now is dwindling as solar minimum has been reached. The strong magnetospheric presence of this population closely parallels the presence of high‐speed solar wind streams which results from solar coronal hole structures during the approach to solar activity (sunspot) minimum. We clearly observe 27‐day periodic enhancements of the relativistic electrons in association with concurrently measured solar wind streams (VSW ≳ 600 km/s). We have used a numerical transport code to study the coupling of these high‐energy electrons to earth's upper and middle atmosphere. We calculate using the observed energy spectra of the electrons that, when precipitated, these electrons show a large (maximum of ∼100 keV/cm³‐s) energy deposition at 40–60 km altitude, which is 3–4 orders of magnitude greater than the galactic cosmic ray or solar EUV energy deposition at these altitudes. We also find that the global energy deposition in the mid‐latitudes totals nearly 1021 ergs for a typical 2–3 day event period. We conclude that this previously unrecognized electron population could play an important role in coupling solar wind and magnetospheric variability (on 27‐day and 11‐year cycles) to the middle atmosphere through a modulating effect on lower D‐region ionization and, possibly, on upper level ozone chemistry. These electrons also may contribute to the recent Antarctic polar ozone depletion phenomenon.

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Solar Energetic Particles and their Effects on the Terrestrial Environment

Cited by 15 publications

References 119 publications

Effects of Energetic Solar Emissions on the Earth–Ionosphere Cavity of Schumann Resonances

Effects of Energetic Solar Emissions on the Earth–Ionosphere Cavity of Schumann Resonances

A new method of studying the relation between ionization rates and radio-wave absorption in polar-cap absorption events

Highly relativistic magnetospheric electrons: A role in coupling to the middle atmosphere?

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