Ionospheric effects on the F region during the sunrise for the annular solar eclipse over Taiwan on 21 May 2012

Abstract

Abstract. On 21 May 2012 (20:56, Universal Time; UT, on 20 May), an annular solar eclipse occurred, beginning at sunrise over southeast China and moving through Japan, sweeping across the northern Pacific Ocean, and completing its passage over the western United States at sunset on 20 May 2012 (02:49 UT, 21 May). We investigated the eclipse area in Taiwan, using an ionosonde and global positioning system (GPS) satellite measurements. The measurements of foF 2 , hmF 2 , bottomside scale height around the peak height (H m ), and slab thickness (B 0 ) were collected at the ionosonde station at Chung-Li Observatory. In addition, we calculated the total electron content (TEC) to study the differences inside and outside the eclipse area, using 3 receivers located at Marzhu (denoted as MATZ), Hsinchu (TNML), and Henchun (HENC). The results showed that the foF 2 values gradually decreased when the annularity began and reached a minimum level of approximately 2.0 MHz at 06:30 LT. The hmF 2 immediately decreased and then increased during the annular eclipse period. The TEC variations also appeared to deplete in the path of the eclipse and opposite the outside passing area. Further, the rate of change of the TEC values (dTEC / dt measured for 15 min) was examined to study the wave-like fluctuations. The scale height near the F 2 layer peak height (H m ) also decreased and then increased during the eclipse period. To address the effects of the annular eclipse in the topside and bottomside ionosphere, this study provides a discussion of the variations between the topside and bottomside ionospheric parameters during the eclipse period.

Ionospheric vertical plasma drift and electron density response during total solar eclipses at equatorial/low latitude

“…The data from SPIDR are automatically scaled, and the data were validated for accuracy by comparing the diurnal morphology of the derived N m F 2 data from critical frequency (f o F 2 ) obtained from some of the stations under study against local time with the electron density profile at other stations [Chuo, 2013;Nayak et al, 2012;Adeniyi et al, 2007]. The results agree well with the known electron density profile.…”

“…The decreased in electron density during eclipse window increases with time lag. However, the maximum eclipse effect did not occur during the maximum obscuration but somewhat later [e.g., Chuo, 2013]. These observed ionospheric effects may be related to the eclipse-caused dynamic.…”

“…However, the bottomside ionospheric eclipse response was associated with the change in ionospheric profile that was driven by the magnetic equatorial E × B vertical drift and redistribution. That is, the variation in F 2 layer is dominated by the vertical E × B and is affected by production and recombination [e.g., Chuo, 2013]. Then the large depression in number density of electrons in the equatorial region would reduce the plasma diffusion flux reaching the equatorial ionization anomaly (EIA) region along magnetic field line and hence affect the ionosphere [Le et al, 2009].…”

“…Most studies on ionospheric eclipse had been focused on the midlatitude ionosphere, though on different measurements and methodology. Among these are Müller-Wodarg et al [1998], Afraimovich et al [2002], Le et al [2008aLe et al [ , 2009, Tomás et al [2009], Wang et al [2010], Chuo [2013] and Adekoya and Chukwuma [2012]. Some of these studies discuss observations exclusively on the assumption that solar eclipse at midlatitude is largely controlled by plasma diffusion.…”

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

“…The major portion of solar radiation during the solar eclipses (SEs) is reduced suddenly, which produces temporal changes in the Earth's atmosphere including ionosphere [e.g., Anderson et al ., ; Antonia et al ., ; Chimonas and Hines , ; Chimonas , ; Singh et al ., ; Afraimovich et al ., ; Clilverd et al ., ; Baran et al ., ; Chandra et al ., ; Zhang et al ., ; Chuo , ; Maurya et al ., , and references therein]. Each SE is different from others in terms of their occurrence time, day and year, location of observing station, percentage of the solar disk occultation, and state of the near Earth's environment [ Baran et al ., ]; therefore, continuous investigations on SEs ionospheric effects, mainly in the lower ionosphere, are needed to better establish the SE effects and their variability.…”