@InProceedings{CuevaRoPaTsGrRa:2015:SpEcVa,
author = "Cueva, R. Y. C. and Rodrigues, F. S. and Paula, Eurico Rodrigues
de and Tsunoda, R. T. and Groves, K. M. and Raulin, J. P.",
affiliation = "{Universidade Presbiteriana Mackenzie} and {University of Texas}
and {Instituto Nacional de Pesquisas Espaciais (INPE)} and {SRI
International} and {Boston College} and {Universidade
Presbiteriana Mackenzie}",
title = "Spread F echoes variability along solar flux and seasonality
conditions over the 50- MHz radar on Christmas Island",
year = "2015",
organization = "International Congress of the Brazilian Geophysical Society, 14.",
abstract = "Perturbations in the amplitude (or phase) of radio signals are
caused by irregularities in the ionospheric electron density.
Ionospheric structures can disrupt the propagation of radio waves,
and are commonly observed, for instance, by ionospheric vertical
radio sounders (ionosondes). For historical reasons, the
signatures of ionospheric irregularities in different types
observations (optical, radio, in-stu) are referred to as
equatorial spread F (ESF). Previous studies show that the
occurrence rate can be greatly affected by solar and magnetic
conditions. Observations during the period of 2003 to 2012 of
nighttime echoes made from the 50-MHz radar on Christmas Island
(2.0o N, 157.4o W) have revealed time and altitude pattern
distribution along the descending phase of solar cycle 23 and the
recent extended solar minimum phase. We present the study of
spread F echoes as a function of solar flux conditions and
seasonality in order to quantify their variability. Under higher
solar flux conditions, echoes reach higher altitudes but decay
earlier. Only during solar minimum conditions the echoes exist
throughout the whole night, since the post\‐ reversal
anti\‐ zonal background electric field is weaker. Thus,
irregularities during solar maximum will be dominated by dynamics
near the time of the PRE. Since the population of irregularities
during solar minimum exists throughout the whole night,
post\‐ reversal ionospheric conditions may play a role in
the morphology of plasma irregularities, especially with the
coincidentally weaker PRE during solar minimum. Peak time
occurrence of echoes along the current period show a well defined
pattern, meanwhile the peak altitude occurrence of echoes show a
slight regular pattern.",
conference-location = "Rio de Janeiro, RJ",
conference-year = "3-6 Aug.",
urlaccessdate = "29 mar. 2024"
}