Modeling the geomagnetic effects caused by the solar eclipse of 11 August 1999

Curto, J. J.; Heilig, B.; Piñol, M.

doi:10.1029/2005ja011499

Cited by 33 publications

(37 citation statements)

References 20 publications

(22 reference statements)

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“…They found a gradual decrease in D region electron density and an increase in reflection height following the eclipse conditions at Allahabad and Nainital. The eclipse creates nighttime like situation due to blockage of Lyman-α radiation, but still electron density is higher than nighttime due to some of the ionization produced by the soft X-ray and EUV radiations originating from the limb solar corona [Curto et al, 2006;Singh et al, 2011]. The overall effect of SE is to increase the D region VLF reflection height and create discontinuity in the total eclipse region of TRGCPs and hence changes in the VLF propagation conditions that result in the increase/decrease in the received VLF signal amplitude at the receiver.…”

Section: Experimental Setup and Datamentioning

confidence: 99%

Low‐mid latitude D region ionospheric perturbations associated with 22 July 2009 total solar eclipse: Wave‐like signatures inferred from VLF observations

Maurya¹,

Phanikumar

Singh³

et al. 2014

JGR Space Physics

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We present first report on the periodic wave-like signatures (WLS) in the D region ionosphere during 22 July 2009 total solar eclipse using JJI, Japan, very low frequency (VLF) navigational transmitter signal (22.2 kHz) observations at stations, Allahabad, Varanasi and Nainital in Indian Sector, Busan in Korea, and Suva in Fiji. The signal amplitude increased on 22 July by about 6 and 7 dB at Allahabad and Varanasi and decreased by about 2.7, 3.5, and 0.5 dB at Nainital, Busan, and Suva, respectively, as compared to 24 July 2009 (normal day). The increase/decrease in the amplitude can be understood in terms of modal interference at the sites of modes converted at the discontinuity created by the eclipse intercepting the different transmitter-receiver great circle paths. The wavelet analysis shows the presence of WLS of period~16-40 min at stations under total eclipse and of period~30-80 min at stations under partial eclipse (~85-54% totality) with delay times between~50 and 100 min at different stations. The intensity of WLS was maximum for paths in the partially eclipsed region and minimum in the fully eclipsed region. The features of WLS on eclipse day seem almost similar to WLS observed in the nighttime of normal days (e.g., 24 July 2009). The WLS could be generated by sudden cutoff of the photo-ionization creating nighttime like conditions in the D region ionosphere and solar eclipse induced gravity waves coming to ionosphere from below and above. The present observations shed additional light on the current understanding of gravity waves induced D region ionospheric perturbations.

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Section: Experimental Setup and Datamentioning

confidence: 99%

Low‐mid latitude D region ionospheric perturbations associated with 22 July 2009 total solar eclipse: Wave‐like signatures inferred from VLF observations

Maurya¹,

Phanikumar

Singh³

et al. 2014

JGR Space Physics

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“…So we calculate the obscuration at the time near totality when foE or foF1 is available. Following a similar approach as Davis et al (2000) and Curto et al (2006), we calculated the relative changes in the peak electron density of the E layer and F1 layer, NmE E /NmE C and NmF1 E /NmF1 C , as a function of the fraction of the Sun's photosphere area unmasked by the Moon, SP E /SP C as seen at the height of 200 km, where NmE E and NmF1 E are the peak electron densities of the E layer and F1 layer on the eclipse day, NmE C and NmF1 C are the peak electron densities of the E layer and F1 layer on the control day, SP E is the Sun's photosphere area unmasked by the Moon during the eclipse, SP C is the Sun's photosphere area before and after the eclipse. The values of SP E /SP C can be obtained by astronomical calculation.…”

Section: Data Sourcementioning

confidence: 99%

“…The values of SP E /SP C can be obtained by astronomical calculation. According to the algorithm of Curto et al (2006), the unmasked fraction of the total solar ionizing radiation drops to a minimum of about 22% of the value before eclipse at totality (SP E /SP C =0),i.e. the relative unmasked flux fraction of solar ionizing radiation is always larger than the unmasked area fraction of the Sun's corona over the photosphere (SP E /SP C ), because some of the radiations come from the Sun's coronal layer.…”

Section: Data Sourcementioning

confidence: 99%

“…However, they only considered the occultation of the photosphere being shielded by the Moon for variations in solar radiation during a solar eclipse. According to their method, the solar radiation should be zero when the photosphere is totally obscured, which would introduce some errors, especially in the low altitudes, because even at totality there are still some radiations from the unmasked part of solar corona (Rishbeth, 1968;Davis et al, 2000;Curto et al, 2006). In this paper, according to the astronomical model of Curto et al (2006), we construct a revised eclipse factor to describe the variation of solar radiation during a solar eclipse.…”

Section: Introductionmentioning

confidence: 99%

“…According to their method, the solar radiation should be zero when the photosphere is totally obscured, which would introduce some errors, especially in the low altitudes, because even at totality there are still some radiations from the unmasked part of solar corona (Rishbeth, 1968;Davis et al, 2000;Curto et al, 2006). In this paper, according to the astronomical model of Curto et al (2006), we construct a revised eclipse factor to describe the variation of solar radiation during a solar eclipse. Unlike earlier studies mentioned above, in addition to the response of the ionosphere in the Northern Hemisphere during the eclipse, we also find the ionospheric disturbance in the conjugate hemisphere.…”

Section: Introductionmentioning

confidence: 99%

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The ionospheric responses to the 11 August 1999 solar eclipse: observations and modeling

Liu

Yue

et al. 2008

Ann. Geophys.

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Abstract.A total eclipse occurred on 11 August 1999 with its path of totality passing over central Europe in the latitude range 40 • -50 • N. The ionospheric responses to this eclipse were measured by a wide ionosonde network. On the basis of the measurements of foE, foF1, and foF2 at sixteen ionosonde stations in Europe, we statistically analyze the variations of these parameters with a function of eclipse magnitude. To model the eclipse effects more accurately, a revised eclipse factor, F R , is constructed to describe the variations of solar radiation during the solar eclipse. Then we simulate the effect of this eclipse on the ionosphere with a mid-and low-latitude ionosphere theoretical model by using the revised eclipse factor during this eclipse. Simulations are highly consistent with the observations for the response in the E-region and F1-region. Both of them show that the maximum response of the mid-latitude ionosphere to the eclipse is found in the F1-region. Except the obvious ionospheric response at low altitudes below 500 km, calculations show that there is also a small response at high altitudes up to about 2000 km. In addition, calculations show that when the eclipse takes place in the Northern Hemisphere, a small ionospheric disturbance also appeared in the conjugate hemisphere.

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Changes in the D region associated with three recent solar eclipses in the South Pacific region

Kumar

Maurya

et al. 2016

JGR Space Physics

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We estimate D region changes due to 22 July 2009 total solar eclipse (SE), 13–14 November 2012 total SE, and 9–10 May 2013 annular SE, using VLF navigational transmitters signal observations at Suva, Fiji. The North West Cape (NWC) signal (19.8 kHz) showed an amplitude and phase decrease of 0.70 dB and 23° during November SE and 2.0 dB and 90° during May SE. The modeling using Long Wave Propagation Capability code for NWC‐Suva path during November and May SEs showed an increase in average D region reflection height (H′) and sharpness factor (β) by 0.6 and 0.5 km and 0.012 and 0.015 km−1, respectively. The July total SE for JJI‐Suva path showed an increase in H′ of 1.5 km and a decrease in β of 0.055 km−1. The decrease in the electron density calculated using SE time H′ and β is maximum for July total SE and minimum for May annular SE. The effective recombination coefficient estimated from the decay and recovery of signal phase associated with May annular SE was higher (27%) than normal daytime value 5.0 × 10−7 cm−3 s−1 and varied between 1.47 × 10−6 and 1.15 × 10−7 cm−3 s−1 in the altitude 70 to 80 km. Morlet wavelet analysis of signals amplitude shows strong wave‐like signatures (WLS) associated with three SEs with period ranging 24–66 min, but the intensity and duration of WLS show no clear dependence on SE magnitude and type. Apart from the cooling spot, the eclipse shadow can also generate WLS associated with atmospheric gravity waves.

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Modeling the geomagnetic effects caused by the solar eclipse of 11 August 1999

Cited by 33 publications

References 20 publications

Low‐mid latitude D region ionospheric perturbations associated with 22 July 2009 total solar eclipse: Wave‐like signatures inferred from VLF observations

Low‐mid latitude D region ionospheric perturbations associated with 22 July 2009 total solar eclipse: Wave‐like signatures inferred from VLF observations

The ionospheric responses to the 11 August 1999 solar eclipse: observations and modeling

Changes in the D region associated with three recent solar eclipses in the South Pacific region

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