Effects of pre-reversal enhancements and gravity wave activity on the characteristics of equatorial plasma bubbles

The characteristics of equatorial plasma bubbles, which occur during the nighttime and along the course of the geomagnetic equator in the F-region of the ionosphere, are investigated using space-based GPS radio occultation measurements from the FormoSat-3/COSMIC mission. These observations provide unique altitudinal resolution on a global scale. On the other hand, the influence of pre-reversal enhancement (PRE) and gravity wave activity on the plasma bubble characteristics are studied on a long-term basis using the International Reference Ionosphere (IRI) model and TIMED/SABER measurements, respectively.

The occurrence and altitudinal characteristics of plasma bubbles are investigated in four regions, i.e., America, Africa, Asia, and the Pacific. Both the attributes of plasma bubbles are compared with the PRE and gravity waves to understand the preconditioning as well as the uplift of plasma bubbles. A brief statistical study indicated a strong positive correlation between the occurrence rate of plasma bubbles and PRE, mainly in the American sector, followed by the African, Asian, and Pacific sectors. In addition, a positive correlation was detected between the PRE and plasma bubble altitudes during the solar maximum period. However, a negative correlation was observed during the solar minimum period. Furthermore, gravity wave activity was investigated to understand the influence on plasma bubble altitudes during the solar minimum period. Interestingly, the gravity wave activity seemed to have a significant influence on plasma bubble altitudes during the solar minimum years, while, the PRE controlled them during solar maximum years across different regions during different seasons.