电离层电场对磁层活动响应时延的模式研究

本文用极盖边界上电离层驱动电位φ₀随时间变化的不同模式计算了场向电流J_∥2及电离层对流电场E的演化过程。计算表明,当φ₀(t)先升后降有极大值时,J_∥2(t)和E(t)也表现出类似的趋势。但它们的极值滞后于φ_0max出现的时刻,即在一段时间内,φ₀虽已开始下降,J_∥2及高纬E却继续增大。一般说,E先于J_∥2达到极值,但相差甚小。φ₀变化形式不同时,滞后时间亦不同。当φ₀陡升缓降时,E、J_∥2的极值相对于φ_0max的时延可超过一小时。这与持续时间较长的磁暴期间所观测到的电离层场强响应时延量级是一致的。时延大小还受电离层电导率的制约。低纬电离层场强的响应与高纬不同,其升降趋势与φ₀同步。 

A Model Study of the Time Delay of the Response of the Ionospheric E-field to the Magnetospheric Activity

Several forms of the driven potential φ₀(t) on ionospheric polar boundary were used to calculate the time evolution of the region 2 field-aligned current J_∥2 and the ionospheric electric field E (t).Calculation indicates that when φ₀ increases first,and decreases then,similar tendency is shown in variation of ](2) and E in high-latitudinal ionosphere,though reach their maximum a bit later;so when the driven potential begins reducing,the J_∥2 and E,however,continue their enhancing.The time delay of J_∥2 and that of E are both related to the relaxation time of the variation of J_∥2 when φ₀(t) is a step function,but the delay of ?is a bit shorter.They also depend on the form of the φ₀(t).The retardation time can be longer than 1 hour when φ₀(t) decreases slowly after a sudden increasing.This result is coordinated by the data observed during strong magnetic storms.The response of E-field in the middle latitude ionosphere is somehow different.It increases when φ₀(t) increases,and decreases asφ₀(t) decreases.The evolution of the J_∥2 and E is also controlled by the ionospheric conductivity.