Solar-Flare Effect in the F2-Layer of the Ionosphere

Minnis, C. M.; Bazzard, G.H.

doi:10.1038/181690a0

Cited by 14 publications

(2 citation statements)

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“…The effect of a solar flare in the F-region was first seen by Dieminger & Geisweid (1950) in the great event of November 19, 1949, accompanied by an extraordinary increase in the intensity of cosmic rays. Subsequent analyses on the F2 layer with more events were carried out by Minnis & Bazzard (1958) proving the statistical significance of the association of these two phenomena. Dodson & Hedeman (1958) noted that Sfe tended to be associated with intense flares in the solar limb observed in the Ha line of the Balmer series.…”

Section: Discovery Of Sfementioning

confidence: 99%

Geomagnetic solar flare effects: a review

Curto

2020

J. Space Weather Space Clim.

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Solar flare effects (Sfe) are rapid variations in the Earth’s magnetic field and are related to the enhancement of the amount of radiation produced during Solar flare events. They mainly appear in the Earth’s sunlit hemisphere at the same time as the flare observation and have a crochet-like shape. Much progress has been made since Carrington’s first observations in 1859 which are considered to represent the first direct evidence of the connection between the Sun and the Earth’s environment but there is still much to discover. In this paper, we review state-of-the-art developments and the advances made in the knowledge concerning Sfe phenomena while also looking at the challenges that lie ahead. First, we offer a historical approach with a comprehensive description that allows for a better understanding of the main characteristics of Sfe. This frames specific topics like the puzzling reversed-Sfe or the nighttime Sfe. The role played by the Service of Rapid Magnetic variations (SRMV) is also assessed, followed by a discussion of the main current limiting factors in the process of detection and proposed ways to overcome challenges such as by creating an automatic detection method. The paper clarifies some aspects related to the geo-effectiveness of the solar flares producing magnetic disturbances. The importance of the global modelling studies covering critical aspects needed to understand this Sun–Earth system is assessed. Also, we provide an overview of the temporal evolution of the electric currents producing Sfe. The importance of key subjects such as the dynamic aspects of Sfe is developed in another section. Finally, estimations of the size of large flares using ionospheric and magnetic data are reviewed as well as the prospects of these large flare events putting technological systems in danger.

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Section: Discovery Of Sfementioning

confidence: 99%

Geomagnetic solar flare effects: a review

Curto

2020

J. Space Weather Space Clim.

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“…It is well known that radiation energy is released during solar flares, which, upon reaching the upper atmosphere, increases its ionization content [Dellinger, 1937;McNish, 1937;Burkard, 1938;Naismith and Beynon, 1938;Becker and Dieminger, 1950;Bibl, 1951;Findlay, 1951;Minnis and Bazzard, 1958]. If sensitive techniques are used [Watts and Davies, 1960] small changes in the instantaneous frequency, phase, and amplitude of HF waves can be traced to small ionization changes produced in the ionosphere [Fenwick and Villard, 1960;Chan, Viilard, and Dueno, 1961;Knecht and Davies, 1961;Kanellakos and Villard, 1961].…”

Section: Introductionmentioning

confidence: 99%

Ionospheric disturbances associated with the solar flare of September 28, 1961

Kanellakos¹,

Villard²

1962

J. Geophys. Res.

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Changes produced in the phase, frequency, and amplitude of stable HF waves during the solar flare of September 28, 1961, and the geomagnetic sudden commencement of September 30, 1961, are analyzed. The HF waves, of approximately 15 and 18 Mc/s, were transmitted over east-west paths 2420 and 5640 km long. Over the longer path, the phases of both signals were advanced by 1400 and 1200 cycles, respectively, whereas their respective frequencies were increased by 8.4 and 7 cps. Absorption commenced after the major portions of the phase and frequency changes had taken place. Over the shorter path, the frequencies of the 15 and 18 Mc/s signals were increased by 2.4 and 1.4 cps, respectively. Absorption data are not available over the short path. During the SC the frequency of the 18-Mc/s signal transmitted over the short path first increased by I cps and then decreased by 2.2 cps. Following the sudden frequency shift, the instantaneous received frequency oscillated with a period of about 30 sec. Since absorption commenced after the main frequency and phase advance, and since it disappeared before the phase recovery, it is suggested that the changes in the electron density were produced by UV radiation energy in the 140-to 200-km region. This hypothesis is strengthened by the circumstance that the maximum phase changes were--approximately--inversely proportional to the operating frequency. The appearance of solar X rays (•20 key) coincided with the onset of/•bsorption of the signals and the onset of a second phase of peak activity in the phase and amplitude scintillation frequency of the signals. The ionization production, as obtained from the rate of change of the phase of the incoming HF signals, does not correspond exactly with the time history of the solar X rays in the •20-kev energy. Softer X rays must be responsible for the electron production that caused the phase changes. released, URSI-IRE Meeting, Austin, Texas, October 1961; TR 45, Radioscience Laboratory, Stanford University, contract Nonr 225(33), December 4, 1961. Kanellakos, D. P., and O. G. Villard, Jr., Some relationships between frequency and azimuth angle of arrival of h-f waves propagated over long distances, USRI-IRE Meeting, Austin, Texas, October 1961; TR 43, Radioscience Laboratory, Stanford University, contract Nonr 225(33) NR 088 003, in press, 1962. Knecht, R. W., and K. Davies, Solar flare effects in the F region of the ionosphere, Nature, 190 (4778), 797-798, 1961. Kundu, M. R., Bursts of centimeter-wave emission and the region of origin of X rays from solar flares, J. Geophys. Research, 66(12), 4308-4312, 1961.

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F-region changes associated with the solar flare of 23 February 1956

Bhargava

Subrbahmanyan

1962

Journal of Atmospheric and Terrestrial Physics

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Solar-Flare Effect in the F2-Layer of the Ionosphere

Cited by 14 publications

References 1 publication

Geomagnetic solar flare effects: a review

Geomagnetic solar flare effects: a review

Ionospheric disturbances associated with the solar flare of September 28, 1961

F-region changes associated with the solar flare of 23 February 1956

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