Study of intensive solar flares in the rise phase of solar cycle 23 and 24 and other activities

Using data from the GPS and GLONASS navigation satellite systems, we analyze the responses of the mid-latitude ionosphere to the extreme solar flares that occurred at the maximum of solar cycle 23 (October 28, 2003) and at the minimum of solar cycle 24 (September 6, 2017) during the same season at close solar zenith angles. To obtain the response, we use the rate of change of the total electronic content, which is practically independent of characteristics of equipment and is determined only by parameters of a propagation medium (the ionosphere in our case). The ionospheric response is shown to be almost independent of the total duration of the flare. In both cases, the duration of the main response at a level of 0.5 is about 1.5–2 min, whereas the total duration of the response is about 10 min and fairly independent of solar flare importance.

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Low-latitude geomagnetic signatures during major solar energetic particle events of solar cycle-23

Annales Geophysicae ◽

10.5194/angeo-24-3569-2006 ◽

2006 ◽

Vol 24 (12) ◽

pp. 3569-3583 ◽

Cited By ~ 7

Author(s):

R. Rawat ◽

S. Alex ◽

G. S. Lakhina

Keyword(s):

Magnetic Field ◽

Solar Cycle ◽

Coronal Mass Ejections ◽

Solar Flares ◽

Energetic Particle ◽

Solar Energetic Particle ◽

Proton Flux ◽

Main Phase ◽

Low Latitude ◽

Solar Cycle 23

Abstract. The frequency of occurrence of disruptive transient processes in the Sun is enhanced during the high solar activity periods. Solar cycle-23 evidenced major geomagnetic storm events and intense solar energetic particle (SEP) events. The SEP events are the energetic outbursts as a result of acceleration of heliospheric particles by solar flares and coronal mass ejections (CMEs). The present work focuses on the geomagnetic variations at equatorial and low-latitude stations during the four major SEP events of 14 July 2000, 8 November 2000, 24 September 2001 and 4 November 2001. These events have been reported to be of discernible magnitude following intense X-ray flares and halo coronal mass ejections. Low-latitude geomagnetic records evidenced an intense main phase development subsequent to the shock impact on the Earth's magnetosphere. Satellite observations show proton-flux enhancements associated with solar flares for all events. Correlation analysis is also carried out to bring out the correspondence between the polar cap magnetic field perturbations, AE index and the variations of low-latitude magnetic field. The results presented in the current study elucidate the varying storm development processes, and the geomagnetic field response to the plasma and interplanetary magnetic field conditions for the energetic events. An important inference drawn from the current study is the close correspondence between the persistence of a high level of proton flux after the shock in some events and the ensuing intense magnetic storm. Another interesting result is the role of the pre-shock southward IMF Bz duration in generating a strong main phase.

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Investigation of the ionospheric absorption response to flare events during the solar cycle 23 as seen by European and South African ionosondes

10.5194/angeo-2019-14 ◽

2019 ◽

Author(s):

Veronika Barta ◽

Gabriella Sátori ◽

Kitti Alexandra Berényi ◽

Árpád Kis ◽

Earle Williams

Keyword(s):

Solar Cycle ◽

South African ◽

Zenith Angle ◽

Solar Flares ◽

Solar Zenith Angle ◽

Systematic Analysis ◽

Low Latitudes ◽

Solar Cycle 23 ◽

Radio Wave Absorption ◽

Qualitative Measure

Abstract. Systematic analysis of ionosopheric parameters measured at mid- and low-latitudes was performed to study the ionospheric response to solar flares. The lowest recorded ionosonde echo, the mimimum frequency (fmin, a qualitative proxy for the nondeviative radio wave absorption occurring in the D-layer), furthermore the dfmin parameter (difference between the value of the fmin and the mean fmin for reference days) have been investigated. The time series of the fmin and dfmin parameters recorded at meridionally-distributed ionosonde stations in Europe and South Africa were analyzed during eight X and M class solar flares during solar cycle 23. The solar zenith angles of the observation sites at the time of the selected flares have been also taken into account. Total and partial radio fade-out was experienced at every ionospheric stations during intense solar flares (> M6). The duration of the total radio fade-out varied between 15 and 150 min and it was highly dependent on the solar zenith angle of the ionospheric stations. Furthermore, a solar zenith angle-dependent enhancement of the fmin (2–9 MHz) and dfmin (1–8 MHz) parameters was observed at almost every stations. The fmin and dfmin parameters show an increasing trend with the enhancement of the X-ray flux. Based on the results, the dfmin parameter is a good qualitative measure for the relative variation of the nondeviative absorption especially in the case of the less intense solar flares which do not cause total radio fade-out in the ionosphere (class

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Ionospheric effects of two solar flares in the maximum of solar cycle 23 and in the minimum of solar cycle 24

Solnechno-Zemnaya Fizika ◽

10.12737/szf-52201911 ◽

2019 ◽

Vol 5 (2) ◽

pp. 82-88

Author(s):

Владимир Смирнов ◽

Vladimir Smirnov ◽

Елена Смирнова ◽

Elena Smirnova

Keyword(s):

Solar Cycle ◽

Solar Flares ◽

Total Duration ◽

Rate Of Change ◽

Satellite Systems ◽

Solar Cycle 23 ◽

Solar Cycle 24 ◽

Cycle 24 ◽

Using Data ◽

Total Electronic Content

Using data from the GPS and GLONASS navigation satellite systems, we analyze the responses of the mid-latitude ionosphere to the extreme solar flares that occurred at the maximum of solar cycle 23 (October 28, 2003) and at the minimum of solar cycle 24 (September 6, 2017) during the same season at close solar zenith angles. To obtain the response, we use the rate of change of the total electronic content, which is practically independent of characteristics of equipment and is determined only by parameters of a propagation medium (the ionosphere in our case). The ionospheric response is shown to be almost independent of the total duration of the flare. In both cases, the duration of the main response at a level of 0.5 is about 1.5–2 min, whereas the total duration of the response is about 10 min and fairly independent of solar flare importance.

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