Low‐latitude daytime F region irregularities observed in two geomagnetically quiet days by the Hainan coherent scatter phased array radar (HCOPAR)

Hainan coherent scatter phased array radar (HCOPAR) located at low latitude of China has recorded the extremely rare daytime F region irregularities at noon of 22 July 2013 and 23 May 2016. The two field‐aligned irregularities (FAIs) appeared in the topside F2 layer and presented small Doppler veloc...

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Bibliographic Details
Published in:Journal of geophysical research. Space physics 2017-02, Vol.122 (2), p.2645-2654
Main Authors: Chen, Gang, Jin, Han, Yan, Jingye, Zhang, Shaodong, Li, Guozhu, Yokoyama, Tatsuhiro, Yang, Guotao, Yan, Chunxiao, Wu, Chen, Wang, Jin, Zhong, Dingkun, Li, Yaxian, Wang, Zhihua
Format: Article
Language:English
Subjects:
Bubbles
coherent scatter radar
Coherent scattering
Daytime
Doppler effect
F 2 region
F region
field‐aligned irregularities
Geomagnetism
Geophysics
Ionosphere
Irregularities
Latitude
low latitude
Magnetic fields
Night
Noon
Photoionization
Plasma bubbles
Radar
Scattering
Sunrise
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Summary:Hainan coherent scatter phased array radar (HCOPAR) located at low latitude of China has recorded the extremely rare daytime F region irregularities at noon of 22 July 2013 and 23 May 2016. The two field‐aligned irregularities (FAIs) appeared in the topside F2 layer and presented small Doppler velocities and narrow spectral widths. The fan sector maps show that the FAIs moved northward with almost no zonal speed. The irregularities emerged in the geomagnetically quiet condition and were irrelevant to the storm‐induced eastward electric field as other daytime cases. More than 2 h after the emergency of the daytime irregularities over Hainan, the Shaoyang digisonde situated ~870 km north to the HCOPAR recorded the spread‐F in ionospheric F1 layer. According to the echo altitudes, the spread‐F may connect the daytime bubbles via magnetic field line. The strong photoionization after sunrise made it difficult to generate the plasma bubbles in the sunlit ionosphere. Consequently, the two midday FAIs over Hainan may drift along the magnetic field lines from higher altitudes in the south and are most likely the remnant of previous night's bubbles. Key Points The HCOPAR has recorded two cases of midday F region irregularities in geomagnetically quiet condition at low latitude The irregularities were observed with small Doppler velocities, narrow spectral widths, and northward drifting tendency The daytime irregularities were fossil structures and most likely the remnant of previous night's bubbles
ISSN:2169-9380
2169-9402
DOI:10.1002/2016JA023628