Publication Date:
2019
Description:
Abstract
Two remarkable ionospheric irregularities named equatorial plasma bubble (EPB) and medium‐scale traveling ionospheric disturbance (MSTID) are verified by using multi‐instrumental observations, for example, the ground‐based GPS networks, ionosonde stations, and Swarm satellites, when the tropical cyclones Tembin and Hagibis approached Hong Kong on 26 August 2012 and 15 June 2014, respectively. The low‐latitude plasma bubble over an area of 105–120 °E in longitude was observed during 12:30–17:00 universal time (UT) on 26 August 2012. GPS observations from magnetically conjugate locations indicate that the nighttime bubble during 20:30–01:00 local time (LT = UT + 8h) on 26 August should be formed from the magnetically equatorial region rather than drifted from the west (eastward drift) or generated locally. Different from the EPB, during another cyclone on 15 June 2014, the northwest‐southeast aligned nighttime MSTID was verified in midlatitude regions at a mean horizontal velocity of 156 m/s southwestward propagation during 12:30–17:30 UT when Hagibis was near the mainland coast. By comparing the ionospheric observations during the two cyclones, differences are identified: small‐scale irregularities associated with plasma bubble cause obvious perturbations of the rate of total electron content index with the value of ~3.0 TECU/min; while the MSTID in midlatitude only cause relatively slight rate of total electron content index disturbances with the value of ~1.5 TECU/min. In addition, the magnetic conjugacy of EPB and MSTID in two hemispheres during the passage of tropical cyclones has been also discussed in this study.
Print ISSN:
2169-9380
Electronic ISSN:
2169-9402
Topics:
Geosciences
,
Physics
Permalink