Preliminary Study Of Gravity Wave Triggering Plasma Bubble In Low Latitudes And Equatorial Regions

Plasma bubbles will disturb the radio waves passing through it,severely affecting satellite communication and navigation.Under the action of Rayleigh-Taylor instability in equatorial and low-latitude regions,gravity wave is an important disturbance source to trigger plasma bubbles.Therefore,the study of the effect of gravity wave on the development of plasma bubbles is of great significance not only in theory,but also in the field of artificial influence ionosphere.Firstly,in this paper,the the correlation between the rate of TEC index?ROTI?and S₄/?_?was studied with data collected from the GPS scintillation monitoring receiver installed at Hainan province.The variations of satellite elevation angle,rate of TEC?ROT?,S₄ and?_?with local time were analyzed by using data in two days with different scintillation intensity.The correlation coefficients of ₄S and ROTI,?_?and ROTI for each GPS satellite,calculated with the data of these two days,were 0.6 and0.4 respectively.Using data during 2015 to 2017,the correlation coefficients of ROTI and S₄ of all satellites per day were calculated and compared with the number of evens of S₄>0.2 per day.Results showed that the variations of ROT and S₄ and?_?with time were consistent;the stronger the scintillation activity,the stronger the correlation between ROTI and scintillation index,and the correlation between ROTI and S₄ is greater than that between ROTI and?_?.This means that the activity level of plasma bubbles can be represented by the S₄ index.Then,the correlations between S₄ of Vanimo station?geographic coordinates:2.7°S,141.3°E?and Outgoing Long-wave Radian?OLR?data during 2002 to 2003were analyzed to study the correlations between plasma bubble and gravity wave.The S₄ data of Vanimo station and OLR data of different longitude were analyzed by linear correlation and Fourier.A weak negative linear correlation was found between S₄ and OLR.The correlation coefficient is about-0.3.The correlation between Vanimo station S₄ and OLR on the west side was stronger than that on the east side.The peak of power spectral density of S₄ index is in the range of short cycle?2-6 days?and long cycle?10-15 days?,and the OLR power spectral density is low at the peak.These further verify that gravity wave is the seed factor of plasma bubble.Finally,according to Rayleigh-Taylor's instability criterion,the variation of the minimum?_min with the initial disturbance wave number is analyzed,and the critical wave number?_c at?_min=1 is calculated by using dichotomy method,and the variation of?_c with longitude,latitude,solar activity level,season,local time and horizontal eastward electric field intensity is analyzed.It was found that the variation rule of?_c was basically consistent with the variation rule of plasma bubble and scintillation activity with longitude,latitude,season,solar activity and local time.Also,the smaller the?_c,the easier plasma bubbles are produced.What's more,the enhancement of horizontal eastward electric field facilitates the formation of plasma bubbles.The value of?_c is of great significance for selecting optimal disturbance conditions when artificially affecting ionosphere.