Occurrence of the blanketing sporadic E layer during the recovery phase of the October 2003 superstorm

Abstract

We have routinely monitored the total frequency (ftEs) and the blanketing frequency (fbEs) of sporadic E layers with the digital sounder under the magnetic equator in the Brazilian sector. Sporadic layers appear in the equatorial region (Es q ) at heights between 90 and 130 km, mainly due to irregularities in the equatorial electrojet current. However, during the recovery phase of the October 2003 superstorm, an anomalous intensification of the ionospheric density that exceeded the normal ambient background values for local time and location was observed. The parameter fbEs rose to almost 7.5 MHz during this event, due to a type "c" blanketing sporadic layer (Es c ), which is driven by wind shear. This result is discussed in terms of the atmosphere dynamics based on magnetic signature of the equatorial electrojet current using magnetometer data. Also, using data measured by sensors onboard the Geostationary Operational Environmental Satellite (GOES) 10 we analyze the possible influence of the solar flare-associated X-ray flux as an additional source of ionization.

Effects of solar flares on the ionosphere as shown by the dynamics of ionograms recorded in Europe and South Africa

“…The results related to different flares from high to lower intensities are shown from panels (a) to (h), respectively. hancements of f min during solar flares are in good agreement with the results reported by Sharma et al (2010) and with the values measured in South America during X-class flares (Nogueira et al, 2015;Denardini et al, 2016). The analysis of the f min and df min values measured at the peak time of the flares or just after the fade-out shows a solar zenith angle dependence as well.…”

“…They suggested that the reason for the amplified VLF signals could be enhanced D-region ionization due to solar flares which could also cause the increased absorption of HF radio waves observed in the ionograms. Partial radio fade-out and a blanketing-type sporadic E-layer were also detected in ionograms measured close to the Equator in the Brazilian sector (Denardini et al, 2016). They determined a 42 %-146 % enhancement in the electron density of the E-layer after X-class solar flares with the observation of peaks in the fbEs (blanketing frequency of the sporadic E-layer) parameter.…”

Quiet and Disturbed Time Characteristics of Blanketing Es (Esb) During Solar Cycle 23

“…Thus, we propose that the enhanced meteoric input during local summer can help in sustaining higher electron densities, resulting in higher blanketing frequencies. On disturbed days, presence of higher fbEs during a geomagnetic storm has been reported for a station close to dip equator in the Brazilian sector (Denardini et al, ). E region tidal winds and electric fields play key roles in the formation of Esb (Resende et al, , ), even at latitudes closer to the dip equator.…”

“…Information on the type of Esb (for example, f , l , c , and h type (Wakai et al, )) is equally important, as it may give some clue about the generation process of Esb. These Esb types are associated with wind shear (Abdu et al, ; Denardini et al, ). Some studies have demonstrated that Esb occurring close to evening hours at low latitudes can play important role in the generation and dynamics of postsunset equatorial spread F (ESF) irregularities (Joshi, ; Patra et al, ; Prakash, ).…”

The Embrace Magnetometer Network for South America: First Scientific Results

“…Therefore, the additional radiation from this X2.8 solar flare certainly increased the D region density. Consequently, it would lead to an increase in its opacity to shorter wavelength electromagnetic (EM) signals propagating upward (Denardini, Resende, et al, ). Such opacity will appear in the ionograms as a blackout of the sounding waves having shorter wavelengths (few megahertz).…”