Effect of magnetic activity on plasma bubbles over equatorial and low-latitude regions in East Asia

G. Li,L. Liu,B. Ning,W. Wan,J. Y. Liu

doi:10.5194/angeo-27-303-2009

Abstract

Abstract. The dependence of plasma bubble occurrence in the eveningside ionosphere, with magnetic activity during the period years 2001–2004, is studied here based on the TEC observations gathered by ground-based GPS receivers which are located in the equatorial and low-latitude regions in East Asia. The observed plasma bubbles consist of the plasma-bubble events in the equatorial (stations GUAM, PIMO and KAYT), and low-latitude regions (stations WUHN, DAEJ and SHAO). It is shown that most equatorial plasma-bubble events commence at 20:00 LT, and may last for >60 min. The magnetic activity appears to suppress the generation of equatorial plasma bubbles with a time delay of more than 3 h (4–9 h). While in the low-latitude regions, most plasma-bubble events commence at about 23:00 LT and last for <45 min. The best correlation between Kp and low-latitude plasma-bubble occurrence is found with an 8–9 h delay, a weak correlation exists for time delays of 6–7 h. This probably indicates that over 3 h delayed disturbance dynamo electric fields obviously inhibit the development of plasma bubbles in the pre-midnight sector.

Highlights

Plasma bubbles are plasma density depletions and accompanying plumes of irregularities that rise in altitude to extend to a wide band in latitude
We investigate the effect of magnetic activity on plasma bubbles by utilizing measurements of ground-based GPS receivers in years 2001–2004
Weak correlation is observed with time delays 6–7 h, whereas for time delays 0– 5 h, the magnetic activity does not affect the probability of observing plasma bubbles. This is consistent with equatorial observational results since there is a time delay about 3 h between the first occurrence of equatorial and low-latitude plasma bubbles

Summary

Introduction

Plasma bubbles are plasma density depletions and accompanying plumes of irregularities that rise in altitude to extend to a wide band in latitude. The enhancement or suppression of pre-midnight equatorial spreadF depends on the relative contributions from the prompt penetration and ionospheric disturbance dynamo induced electric field disturbances with respect to local time effects during the geomagnetic storms (Martinis et al, 2005; Basu et al, 2007). Based on the Dynamics Explorer (DE) 2 satellite observations from August 1981 to February 1983, Palmroth et al (2000) investigated the occurrence of equatorial plasma bubbles and found that magnetic activity appears to suppress the generation of eveningside plasma bubbles with a delay of 2–3 h. Besides space-based satellite observations, the groundbased GPS receivers provide a new observational technique for investigating the effect of magnetic activity on plasma bubbles They measure total electron content (TEC) continuously with little lack of data. Exact time delays of Kp index, inhibiting the generation of plasma bubbles have been obtained

Data selection and processing

Example of plasma-bubble events

Conclusions