Postmidnight equatorial plasma irregularities on the June solstice during low solar activity – a case study
-
Published:2019-07-30
Issue:4
Volume:37
Page:657-672
-
ISSN:1432-0576
-
Container-title:Annales Geophysicae
-
language:en
-
Short-container-title:Ann. Geophys.
Author:
Candido Claudia M. N., Shi Jiankui, Batista Inez S.ORCID, Becker-Guedes Fabio, Correia Emília, Abdu Mangalathayil A., Makela Jonathan, Balan Nanan, Chapagain NarayanORCID, Wang Chi, Liu Zhengkuan
Abstract
Abstract. We present a case study of unusual spread-F structures observed by
ionosondes at two equatorial and low-latitude Brazilian stations – São Luís
(SL: 44.2∘ W, 2.33∘ S; dip angle: −6.9∘)
and Fortaleza (FZ: 38.45∘ W, 3.9∘ S; dip angle:
−16∘). The irregularity structures observed from midnight to
postmidnight hours of moderate solar activity (F10.7 < 97 sfu,
where 1 sfu = 10−22 W m−2 s−1) have characteristics different
from typical post-sunset equatorial spread F. The spread-F traces first
appeared at or above the F-layer peak and gradually became well-formed mixed
spread F. They also appeared as plasma depletions in the 630.0 nm airglow
emissions made by a wide-angle imager located at the nearby low-latitude station
Cajazeiras (CZ: 38.56∘ W, 6.87∘ S; dip angle:
−21.4∘). The irregularities appeared first over FZ and later over
SL, giving evidence of an unusual westward propagation or a horizontal
plasma advection. The drift-mode operation available in one of the
ionosondes (a digital portable sounder, DPS-4) has enabled us to analyze the
horizontal drift velocities and directions of the irregularity movement. We
also analyzed the neutral wind velocity measured by a Fabry–Pérot
interferometer (FPI) installed at CZ and discuss its possible role in the
development of the irregularities.
Publisher
Copernicus GmbH
Subject
Space and Planetary Science,Earth and Planetary Sciences (miscellaneous),Atmospheric Science,Geology,Astronomy and Astrophysics
Reference47 articles.
1. Abalde, J. R., Sahai, Y., Fagundes, P. R., Becker-Guedes, F., Bittencourt,
J. A., Pillat, V. G., Lima, W. L. C., Candido, C. M. N., and de Freitas, T. F.:
Day-to-day variability in the development of plasma bubbles associated with
geomagnetic disturbances, J. Geophys. Res., 114, A04304,
https://doi.org/10.1029/2008JA013788, 2009. 2. Abdu, M. A., Bittencourt, J. A., and Batista, I. S.: Magnetic declination
control of the equatorial F region dynamo field development and spread F, J.
Geophys. Res., 86, 11443–11446, 1981a. 3. Abdu, M. A., Batista, I. S., and Bittencourt, J. A.: Some characteristics of
spread F at the magnetic equatorial station Fortaleza, J. Geophys. Res., 86,
6836–6842, 1981b. 4. Abdu, M. A., Sobral, J. H. A., Batista, I. S., Rios, V. H., and Medina, C.:
Equatorial spread F occurrence statistics in the American longitudes:
Diurnal, seasonal and solar cycle variations, Adv. Space Res., 22, 851–854, 1998. 5. Abdu, M. A., Batista, I. S., Reinisch, B. W., de Souza, J. R., Sobral, J. H.
A., Pedersen, T. R., Medeiros, A. F., Schuch, N. J., de Paula, E. R., and
Groves, K. M., Conjugate Point Equatorial Experiment (COPEX) campaign in
Brazil: Electrodynamics highlights on spread F development conditions and
day-to-day variability, J. Geophys. Res., 114, A04308,
https://doi.org/10.1029/2008JA013749, 2009.
Cited by
3 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献
|
|