The observation and simulation of ionospheric response to CIR/high‐speed streams‐induced geomagnetic activity on 4 April 2005

Abstract

The ionospheric response to corotating interaction region (CIR)-induced geomagnetic activity on 4 April 2005 has been studied using in situ electron density measurements, ground GPS-total electron content (TEC) observations, and numerical simulations of the National Center for Atmospheric Research Thermosphere-Ionosphere-Electrodynamics General Circulation Model (TIE-GCM). The case study resulted that the ionospheric positive response occurred from high to low latitudes. The positive effect at low latitudes could continue for 4 days, whereas at middle to high latitudes the disturbance mainly lasted only for 1 day. The modeled Ne and TEC from TIE-GCM had a good agreement with those from observations. The simulation results showed that penetration electric fields were responsible for the daytime positive response during the initial and main phases of the geomagnetic storm, while neutral winds were responsible for the presunset positive effects. The long-lasting positive storm effect during the storm recovery time at low latitudes was related to the thermospheric composition (O/N 2 ) changes during the storm event.

High‐Speed Solar Wind Imprints on the Ionosphere During the Recovery Phase of the August 2018 Geomagnetic Storm

“…Note that the varying IMF Bz itself, especially for the weakly negative Bz, can also modulate the terrestrial ionosphere. Additionally, the HSS can lead to the enhancement of the ratio of atomic oxygen to molecular nitrogen number densities (O/N 2 ) by modulating the thermospheric circulation, and thus slightly contribute to the TEC increase of electron density at lower latitude, which is consistent with the study of Chen et al (2016). Overall, the maximum increase of TEC during the recovery phase of the August 2018 storm was about 2 TECU in the TIEGCM as shown in Figure 8b, which was significantly lower than the observation results (more than 10 TECU) at the EIA region.…”

Diagnostic Analysis of the Physical Processes Underlying the Long‐Duration O/N2 Depletion During the Recovery Phase of the 8 June 2019 Geomagnetic Storm

“…It should be noted that during the recovery phase of the storms studied by Chen et al. (2016), there exist geomagnetic disturbances during the storm recovery phase (AE = ∼500 nT), resulting in a longer recovery of the thermosphere than in our study.…”

“…Using GUVI observations and TIEGCM simulations, Chen et al. (2016) showed that the storm‐induced decrease in O/N 2 at ∼300 km lasted for about 2 days during the storm recovery phase. In contrast, the O/N 2 increases at low latitudes could last for 4 days.…”

“…During the 8 June 2019 geomagnetic storm, the recovery process of the middle latitude composition perturbations lasted for about 31 hr Fuller-Rowell et al (1996) used a Thermosphere Ionosphere General Circulation Model to show that the global composition disturbance persisted for 1-2 days after the end of the main phase of a geomagnetic storm. Using GUVI observations and TIEGCM simulations, Chen et al (2016) showed that the storm-induced decrease in O/N 2 at ∼300 km lasted for about 2 days during the storm recovery phase. In contrast, the O/N 2 increases at low latitudes could last for 4 days.…”