Premium
Vertical rise velocity of equatorial plasma bubbles estimated from Equatorial Atmosphere Radar (EAR) observations and HIRB model simulations
Author(s) -
Tulasi Ram S.,
Ajith K. K.,
Yokoyama T.,
Yamamoto M.,
Niranjan K.
Publication year - 2017
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1002/2017ja024260
Subject(s) - midnight , geology , geodesy , altitude (triangle) , atmosphere (unit) , atmospheric sciences , f region , ionosphere , meteorology , geophysics , physics , astronomy , geometry , mathematics
The vertical rise velocity ( V r ) and maximum altitude ( H m ) of equatorial plasma bubbles (EPBs) were estimated using the two‐dimensional fan sector maps of 47 MHz Equatorial Atmosphere Radar (EAR), Kototabang, during May 2010 to April 2013. A total of 86 EPBs were observed out of which 68 were postsunset EPBs and remaining 18 EPBs were observed around midnight hours. The vertical rise velocities of the EPBs observed around the midnight hours are significantly smaller (~26–128 m/s) compared to those observed in postsunset hours (~45–265 m/s). Further, the vertical growth of the EPBs around midnight hours ceases at relatively lower altitudes, whereas the majority of EPBs at postsunset hours found to have grown beyond the maximum detectable altitude of the EAR. The three‐dimensional numerical high‐resolution bubble (HIRB) model with varying background conditions are employed to investigate the possible factors that control the vertical rise velocity and maximum attainable altitudes of EPBs. The estimated rise velocities from EAR observations at both postsunset and midnight hours are, in general, consistent with the nonlinear evolution of EPBs from the HIRB model. The smaller vertical rise velocities ( V r ) and lower maximum altitudes ( H m ) of EPBs during midnight hours are discussed in terms of weak polarization electric fields within the bubble due to weaker background electric fields and reduced background ion density levels.