An Introduction to the Ionosphere and Magnetosphere

Ratcliffe, J.A.; Holzer, T. E.

doi:10.1119/1.1987378

Cited by 65 publications

(99 citation statements)

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“…The 11 yr (Schwabe) solar cycle variations are apparent. A further long-duration data series is that of the 10.7 cm solar radio flux, which is widely used as a proxy for solar brightness, and solar UV emissions (Ratcliffe 1972). Figure 1b shows a subset of the daily 10.7 cm solar radio flux data, covering the same period as figure 1a.…”

Section: Spectral Investigations Of Cr Solar and Cloud Parametersmentioning

confidence: 99%

Discrimination between cosmic ray and solar irradiance effects on clouds, and evidence for geophysical modulation of cloud thickness

Harrison

2008

Proc. R. Soc. A.

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Solar activity and galactic cosmic rays (CRs) are closely inversely correlated. In studies of cloud changes associated with solar changes, the close solar activity-CR relationship can cause ambiguity in attributing the cloud changes to one factor or the other. A method for discriminating between cloud effects from these causes is described, using the 1.68 yr periodicity present in surface-based measurements of CRs but absent in radio flux measurements of solar activity. The periodicity is present in CRs and other heliospheric parameters during, at least, solar cycle 21. Daily surface radiation measurements sensitive to cloud during a similar period (1978)(1979)(1980)(1981)(1982)(1983)(1984)(1985)(1986)(1987)(1988)(1989)(1990) at Jersey and Lerwick exhibit 1.68 yr periodicities, indicating a CR, rather than solar irradiance, cloud effect. In the Jersey data, it is not possible to discriminate between 'near-cloud' (droplet charging) and 'clearair' (ion nucleation) effects, but further study of the Lerwick cloud data shows that the periodicity is present only during thick overcast cloud conditions. Bandpass filtering the cloud and CR data (passband 1.55-1.81 years) shows that the cloud thickness responds in phase with the CR flux. This modulation suggests the near-cloud effect through geophysical modulation of the air-Earth current density. Cloud thickness modulation by the air-Earth current density can occur by the charge-enhanced activation (electroactivation) of cloud droplets on the upper and lower boundaries of stratiform cloud.

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Section: Spectral Investigations Of Cr Solar and Cloud Parametersmentioning

confidence: 99%

Discrimination between cosmic ray and solar irradiance effects on clouds, and evidence for geophysical modulation of cloud thickness

Harrison

2008

Proc. R. Soc. A.

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“…Equation (3) is obtained by applying Ampere's law to the horizontal ionospheric current. In dividing by P to obtain E the tilt of the magnetic field is ignored, an approximation that is accurate to better than 3% poleward of 60 • MLAT, where the average deviation between the true magnetic field vector and the radial direction is <10 • in a dipolar field (Ratcliffe, 1972). The sources for ionospheric conductivity are solar illumination, particle precipitation, and background radiation (e.g., Reiff, 1983).…”

Section: Electric Fieldmentioning

confidence: 99%

High-latitude electromagnetic and particle energy flux during an event with sustained strongly northward IMF

et al. 2005

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Abstract. We present a case study of a prolonged interval of strongly northward orientation of the interplanetary magnetic field on 16 July 2000, 16:00-19:00 UT to characterize the energy exchange between the magnetosphere and ionosphere for conditions associated with minimum solar windmagnetosphere coupling. With reconnection occurring tailward of the cusp under northward IMF conditions, the reconnection dynamo should be separated from the viscous dynamo, presumably driven by the Kelvin-Helmholtz (KH) instability. Thus, these conditions are also ideal for evaluating the contribution of a viscous interaction to the coupling process. We derive the two-dimensional distribution of the Poynting vector radial component in the northern sunlit polar ionosphere from magnetic field observations by the constellation of Iridium satellites together with drift meter and magnetometer observations from the Defense Meteorological Satellite Program (DMSP) F13 and F15 satellites. The electromagnetic energy flux is then compared with the particle energy flux obtained from auroral images taken by the far-ultraviolet (FUV) instrument on the Imager for Magnetopause to Aurora Global Exploration (IMAGE) spacecraft. The electromagnetic energy input to the ionosphere of 51 GW calculated from the Iridium/DMSP observations is eight times larger than the 6 GW due to particle precipitation all poleward of 78 • MLAT. This result indicates that the energy transport is significant, particularly as it is concentrated in a small region near the magnetic pole, even under conditions traditionally considered to be quiet and is dominated by the electromagnetic flux. We estimate the contributions of the high and mid-latitude dynamos to both the Birkeland currents and electric potentials finding that highlatitude reconnection accounts for 0.8 MA and 45 kV while we attribute <0.2 MA and ∼5 kV to an interaction at lower latitudes having the sense of a viscous interaction. Given that these conditions are ideal for the occurrence of the KH instability at the magnetopause and hence the viscous interaction, Correspondence to: H. Korth (haje.korth@jhuapl.edu) this result suggests that the viscous interaction is a small contributor to coupling solar wind energy to the magnetosphereionosphere system.

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“…In our attempt to use the reconstructed emission pro®les for estimating the ionospheric conductivities, we had to consider the relative motion of the ®eld-aligned currents with reference to the ground-based observer. Furthermore, during the night without ionization by solar UV radiation, the electron densities in the E and F layers rapidly decrease until the new equilibrium of ionization by cosmic radiation and high-energetic solar particles is reached (Ratclie, 1972). Precipitating auroral electrons are an additional ionization source in the polar ionosphere, but after the disappearance of ®eld-aligned currents in a certain area the electron density decreases according to the continuity relation dn e dt q À an 2 e À bn e 14 with the ionization q, the recombination a, and attachment b coecients, respectively.…”

Section: Reconstruction Of Real Observationsmentioning

confidence: 99%

Optical tomography of the aurora and EISCAT

Frey

Lanchester

et al. 1998

Ann Geophysicae

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Abstract. Tomographic reconstruction of the threedimensional auroral arc emission is used to obtain vertical and horizontal distributions of the optical auroral emission. Under the given experimental conditions with a very limited angular range and a small number of observers, algebraic reconstruction methods generally yield better results than transform techniques. Dierent algebraic reconstruction methods are tested with an auroral arc model and the best results are obtained with an iterative least-square method adapted from emission-computed tomography. The observation geometry used during a campaign in Norway in 1995 is tested with the arc model and root-mean-square errors, to be expected under the given geometrical conditions, are calculated. Although optimum geometry was not used, root-mean-square errors of less than 27 for the images and of the order of 307 for the distribution could be obtained. The method is applied to images from real observations. The correspondence of original pictures and projections of the reconstructed volume is discussed, and emission pro®les along magnetic ®eld lines through the three-dimensionally reconstructed arc are calibrated into electron density pro®les with additional EISCAT measurements. Including a background pro®le and the temporal changes of the electron density due to recombination, good agreement can be obtained between measured pro®les and the time-sequence of calculated pro®les. These pro®les are used to estimate the conductivity distribution in the vicinity of the EISCAT site. While the radar can only probe the ionosphere along the radar beam, the three-dimensional tomography enables conductivity estimates in a large area around the radar site.

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An Introduction to the Ionosphere and Magnetosphere

Cited by 65 publications

References 0 publications

Discrimination between cosmic ray and solar irradiance effects on clouds, and evidence for geophysical modulation of cloud thickness

Discrimination between cosmic ray and solar irradiance effects on clouds, and evidence for geophysical modulation of cloud thickness

High-latitude electromagnetic and particle energy flux during an event with sustained strongly northward IMF

Optical tomography of the aurora and EISCAT

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