TY - JOUR
T1 - Postmidnight equatorial plasma irregularities on the June solstice during low solar activity - A case study
AU - Candido, Claudia M.N.
AU - Shi, Jiankui
AU - Batista, Inez S.
AU - Becker-Guedes, Fabio
AU - Correia, Emília
AU - Abdu, Mangalathayil A.
AU - Makela, Jonathan
AU - Balan, Nanan
AU - Chapagain, Narayan
AU - Wang, Chi
AU - Liu, Zhengkuan
N1 - Funding Information:
This research has been supported by the China-Brazil Joint Laboratory for Space Weather (CBJLSW) and a Brazilian funding agency (CNPq, grant no. 64537/2015-5). Jiankui Shi was supported by the National Natural Science Foundation of China (NSSC, grant nos. 41474137 and 1674145). Work at the University of Illinois at Urbana-Champaign was supported by National Science Foundation CEDAR (grant no. AGS 09-40253). Claudia M. N. Candido thanks the China- Brazil Joint Laboratory for Space Weather, CBJLSW, for the postdoctoral fellowship program. The authors thank the EMBRACE/ INPE/MCTIC program for providing ionospheric data for this work. We are grateful to the Universidade Federal de Campina Grande and Ricardo A. Buriti for support regarding the imaging systems installed at Cajazeiras. Narayan Chapagain thanks the NASA Living with a Star Heliophysics Postdoctoral Fellowship Program, administered by the University Corporation for Atmospheric Research (UCAR). Work at the University of Illinois at Urbana- Champaign was performed in collaboration with John Meriwether at Clemson University.
Funding Information:
Acknowledgements. Claudia M. N. Candido thanks the China– Brazil Joint Laboratory for Space Weather, CBJLSW, for the postdoctoral fellowship program. The authors thank the EMBRACE/INPE/MCTIC program for providing ionospheric data for this work. We are grateful to the Universidade Federal de Campina Grande and Ricardo A. Buriti for support regarding the imaging systems installed at Cajazeiras. Narayan Chapagain thanks the NASA Living with a Star Heliophysics Postdoctoral Fellowship Program, administered by the University Corporation for Atmospheric Research (UCAR). Work at the University of Illinois at Urbana– Champaign was performed in collaboration with John Meriwether at Clemson University.
Funding Information:
Financial support. This research has been supported by the China–
Publisher Copyright:
© 2019 Author(s).
PY - 2019/7/30
Y1 - 2019/7/30
N2 - 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=10-22Wm-2 s-1) have characteristics different from typical post-sunset equatorial spread F. The spread-F traces first appeared at or above the Flayer 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.
AB - 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=10-22Wm-2 s-1) have characteristics different from typical post-sunset equatorial spread F. The spread-F traces first appeared at or above the Flayer 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.
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U2 - 10.5194/angeo-37-657-2019
DO - 10.5194/angeo-37-657-2019
M3 - Article
AN - SCOPUS:85070217054
SN - 0992-7689
VL - 37
SP - 657
EP - 672
JO - Annales Geophysicae
JF - Annales Geophysicae
IS - 4
ER -