April 2000 magnetic storm: Solar wind driver and magnetospheric response
نویسندگان
چکیده
[1] On 4 April 2000, a coronal mass ejection (CME) took place close to the western limb of the Sun. The shock front of the CME hit the Earth’s magnetosphere on 6 April. A strong interplanetary southward BZ event in the sheath region caused a magnetic storm that was the second strongest in the year 2000 if quantified by the peak of the Dst index. We have analyzed this sequence of events using observations of several spacecraft in the solar wind and at geostationary orbit as well as recordings from more than 80 magnetometer stations at latitudes higher than 40 N. In the sheath region behind the shock, the interplanetary magnetic field had an intense and long-sustained southward magnetic field orientation, and the solar wind magnetic pressure was very large, which compressed the dayside magnetopause inside geostationary orbit for a period of more than 6 hours. We conclude that it was the fluctuating but strongly southward field accompanied by the high pressure that allowed for the exceptionally strong driving of magnetospheric activity. During the main phase of the storm, the magnetosphere and ionosphere were in highly perturbed states, with several activations all around the auroral region. Detailed analysis shows that many of these activations were not substorms, in the sense that they were not associated with poleward and westward electrojet/auroral enhancement or geostationary particle injections, but were directly driven perturbations due to variations in the solar wind features. In fact, it was found that the development of the entire storm was quite independent of substorm activations and injections. Instead, the ring current development was driven by the strong convection enhancements. During the storm, the geomagnetically induced currents were strongly enhanced during several periods. While some activations were associated with substorm onsets or electrojet enhancements, others were caused by extremely localized and short-lived electrojet activations.
منابع مشابه
Magnetospheric response to the solar wind as indicated by the cross-polar potential drop and the low-latitude asymmetric disturbance field
The cross-polar potential drop 8pc and the lowlatitude asymmetric geomagnetic disturbance field, as indicated by the mid-latitude ASY-H magnetic index, are used to study the average magnetospheric response to the solar wind forcing for southward interplanetary magnetic field conditions. The state of the solar wind is monitored by the ACE spacecraft and the ionospheric convection is measured by ...
متن کاملEffect of Interplanetary Shocks on the AL and Dst Indices
[1] The question of how much interplanetary shock (IP) events contribute to the geoeffectiveness of solar wind drivers is assessed through numerical experiments using the WINDMI model, a physics-based model of the solar winddriven magnetosphere-ionosphere system. Analytic fits to solar wind input parameters (B? , usw, nsw) allowed shocks and associated shock-sheath plasma to be removed while le...
متن کاملModeling magnetospheric current response to solar wind dynamic pressure enhancements during magnetic storms: 1. Methodology and results of the 25 September 1998 peak main phase case
[1] We present a methodology for using the modular Tsyganenko storm magnetic field model (TS04) as a tool to investigate the response of magnetospheric currents to solar wind dynamic pressure enhancements during magnetic storms. We demonstrate the technique by examining the contribution of each model current to the observed dawn-dusk asymmetric ground H perturbation during a peak storm main pha...
متن کاملTerrestrial agents in the realm of space storms: Missions study oxygen ions
Observations from two recent space missions, the Active Magnetospheric Particle Tracer Explorers (AMPTE) and the Combined Release and Radiation Effects Satellite (CRRES), demonstrated that magnetospheric O + ions originating in the ionosphere are important terrestrial agents in geospace. In other words, the two missions showed that ionized oxygen escaping from the upper atmosphere, can play a c...
متن کاملThe effect of nonlinear ionospheric conductivity enhancement on magnetospheric substorms
We introduce the effect of enhanced ionospheric conductivity into a low-order, physics-based nonlinear model of the nightside magnetosphere called WINDMI. The model uses solar wind and interplanetary magnetic field (IMF) parameters from the ACE satellite located at the L1 point to predict substorm growth, onset, expansion and recovery measured by the AL index roughly 50–60 min in advance. The d...
متن کامل