The first coordinated observations of mid-latitude &amp;lt;i&amp;gt;E&amp;lt;/i&amp;gt;-region quasi-periodic radar echoes and lower thermospheric 557.7-nm airglow

Ogawa, T.; Otsuka, Yuichi; Onoma, F.; Shiokawa, K.; Yamamoto, M.

doi:10.5194/angeo-23-2391-2005

Cited by 11 publications

(12 citation statements)

References 44 publications

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“…Larsen [] found that the gravity wave‐based mechanism has problems and put forward a shear instability seed mechanism. However, the comparison between the airglow images and the VHF radar echoes still suggested that the gravity waves play a very important role in generating the FAIs in E region plasma [ Ogawa et al ., ; Onoma et al ., ]. The new observations of the Gadanki radar in low latitude suggested the gravity waves as a potential source in forming the FAIs [ Venkateswara Rao et al ., ].…”

Section: Discussionmentioning

confidence: 98%

Daytime E region field‐aligned irregularities observed during a solar eclipse

Chen

Zhao

et al. 2014

JGR Space Physics

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The driving mechanism of the midlatitude field-aligned irregularities (FAIs) has been in dispute for many years. The experimental observations were carried out during the solar eclipse of 22 July 2009 in Wuhan, China, to study the possibility of the wave-driven irregularities. A high-frequency coherent scatter radar was used to detect the E region irregularities. An ionosonde was applied to record the trace of gravity waves in ionosphere. The E region FAIs occurred at the end of the solar eclipse with fluctuant Doppler. At the same time, the oscillations on the fE s (maximum reflecting frequency of E s ) curve and in the Doppler velocity of the echoes from the E s layer were also recorded. The data analysis and comparison show that the gravity waves and the FAIs occurred at the same time with the in-phase variations in amplitude and phase. Thus, the solar eclipse and the gravity waves may play important roles in the occurrence of the irregularities. A schematic diagram of one-period gravity wave is used to explain the possible gravity wave-driven mechanism and the Doppler fluctuation in the irregularities. The daytime FAI in midlatitude is a rare phenomenon, even in the condition of solar eclipse. There are only four cases of the E region FAIs observed during a solar eclipse, including our observations. The unique feature of our observations is the synchronized oscillations in the irregularities and in the E s layer, which will help address the outstanding question of the source of the midlatitude E region FAIs.

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Section: Discussionmentioning

confidence: 98%

Daytime E region field‐aligned irregularities observed during a solar eclipse

Chen

Zhao

et al. 2014

JGR Space Physics

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“…Therefore, the amplitude of the AGW in the QP echo region will be very likely large enough to modulate the FAI. A clear evidence of gravity wave modulation was presented by Ogawa et al (2005). They reported that during the QP echo event, the echo altitudes clearly went up (down) in harmony with an airglow enhancement (subsidence).…”

Section: Conjecture On Qp Echoesmentioning

confidence: 92%

“…This result suggests that the interaction between AGW and E-region plasma plays an important role in generating FAI. Ogawa et al (2005) compared the data of the QP echoes (as the height of QP echoes was low) and the air glow at the same altitude, and found a positive correlation between the height variation of FAI echoes and airglow intensity. Also, conducted simultaneous observations of FAIs and neutral wind with interferometry measurements, and found that QP echoes propagated northwestward when the rockets were launched.…”

mentioning

confidence: 99%

Phase and group velocity tracing analysis of projected wave packet motion along oblique radar beams – qualitative analysis of QP echoes

2007

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Abstract. The wave packets of atmospheric gravity waves were numerically generated, with a given characteristic wave period, horizontal wave length and projection mean wind along the horizontal wave vector. Their projection phase and group velocities along the oblique radar beam (v pr and v gr ), with different zenith angle θ and azimuth angle φ, were analyzed by the method of phase-and group-velocity tracing. The results were consistent with the theoretical calculations derived by the dispersion relation, reconfirming the accuracy of the method of analysis. The RTI plot of the numerical wave packets were similar to the striation patterns of the QP echoes from the FAI irregularity region. We propose that the striation range rate of the QP echo is equal to the radial phase velocity v pr , and the slope of the energy line across the neighboring striations is equal to the radial group velocity v gr of the wave packet; the horizontal distance between two neighboring striations is equal to the characteristic wave period τ . Then, one can inversely calculate all the properties of the gravity wave responsible for the appearance of the QP echoes. We found that the possibility of some QP echoes being generated by the gravity waves originated from lower altitudes cannot be ruled out.

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“…The striated QP echoes scattered from the midlatitude E region FAIs appear to represent a very simple phenomenon, although the cause of the striation and its tilt remains unclear. Some authors have attributed it to the propagation of gravity waves, while others have considered that the tilt is caused by background winds [ Ogawa et al , ; Larsen , ]. The Hainan VHF radar and the Hainan Digisonde in Fuke were used to observe E region irregularities and the plasma blob drift, respectively.…”

Section: Introductionmentioning

confidence: 99%

Strong correlation between quasiperiodic echoes and plasma drift in the E region

et al. 2015

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Simultaneous observations of quasiperiodic (QP) echoes and plasma drift in the ionospheric E region were conducted in Fuke (19.5°N, 109.1°E), Hainan province, China, to investigate the QP striation tilts under varying plasma drift conditions. The E region field‐aligned irregularities (FAIs), observed using the Hainan VHF radar, and the drift velocities of the plasma blobs in the Es layer, recorded by the Hainan Digisonde operating in drift mode, are reported. The QP echoes and drift data recorded during the entire year of 2013 were analyzed and compared. A surprising consistency between the striation tilt of the QP echoes and the drift direction of the plasma blobs was discovered. A negative echo striation of the QP FAIs was recorded when the measured drift direction of the plasma blobs was southward, whereas a positive echo striation was observed during the northward drift. Furthermore, the echo trace was continuous, whereas the QP striation changed from negative to positive, and vice versa. Thus, it can be concluded that the morphology of the QP echoes may be controlled by the background wind fields in the E region. The northward/southward‐drifting striated FAIs in the observation region of a coherent scatter radar might induce the positive/negative QP echo striation in the range‐time‐intensity plots.

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The first coordinated observations of mid-latitude <i>E</i>-region quasi-periodic radar echoes and lower thermospheric 557.7-nm airglow

Cited by 11 publications

References 44 publications

Daytime E region field‐aligned irregularities observed during a solar eclipse

Daytime E region field‐aligned irregularities observed during a solar eclipse

Phase and group velocity tracing analysis of projected wave packet motion along oblique radar beams – qualitative analysis of QP echoes

Strong correlation between quasiperiodic echoes and plasma drift in the E region

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