Response of ionospheric and field-aligned currents to geomagnetic storms driven by solar wind high-speed streams and coronal mass ejections
Thesis event information
Date and time of the thesis defence
Place of the thesis defence
Auditorium L6, Linnanmaa, Oulu
Topic of the dissertation
Response of ionospheric and field-aligned currents to geomagnetic storms driven by solar wind high-speed streams and coronal mass ejections
Doctoral candidate
Master of Science Marcus Pedersen
Faculty and unit
University of Oulu Graduate School, Faculty of Science, Space Physics and Astronomy Research Unit
Subject of study
Physics
Opponent
Professor Lasse Clausen, University of Oslo
Custos
Docent Heikki Vanhamäki, University of Oulu
Electric currents in the auroral ionosphere during geomagnetic storms
Geomagnetic storms are large disturbances in the Earth’s magnetosphere. Their main causes are solar wind high speed streams and associated stream interaction regions (HSS/SIR), sheaths ahead of interplanetary coronal mass ejections, and magnetic clouds (MCs). During geomagnetic storms large electrical currents flow in the auroral ionosphere, yet their evolution is still poorly understood. In this thesis we study the development and evolution of the high-latitude ionospheric and field-aligned currents during different types of geomagnetic storms using superposed epoch and cross-correlation analyses.
It is found that HSS/SIR, sheaths and MCs storms cause very different developments in the auroral currents. During HSS/SIR and sheath storms the currents develop rapidly at the beginning of the storm and maximize within the first hour after the storm main phase onset. The currents remain larger for a longer time for sheath than HSS/SIR storms, but in the recovery phase the situation reverses and sheath storms are the first to diminish while some activity are still seen for HSS/SIRs. In contrast, during MC-driven storms the currents develop gradually when the storm begins and maximize 11 hours after the onset, close to the end of the storm main phase. The response time of the currents to the solar wind driving is also different for the different storms. For HSS/SIR and sheath storms the auroral currents lag the solar wind that is hitting the magnetopause by 40 min, while the lag is 60 min for MC-driven storms.
A good understanding of auroral currents during storms is important to predict and mitigate hazardous space weather events, such as enhanced atmospheric drag slowing down satellites or geomagnetically induced currents which can damage transformers, power grids and pipeline systems. The results of this thesis show that it is important to consider the driver of the geomagnetic storm to accurately predict the auroral currents and their impact on geospace and Earth.
It is found that HSS/SIR, sheaths and MCs storms cause very different developments in the auroral currents. During HSS/SIR and sheath storms the currents develop rapidly at the beginning of the storm and maximize within the first hour after the storm main phase onset. The currents remain larger for a longer time for sheath than HSS/SIR storms, but in the recovery phase the situation reverses and sheath storms are the first to diminish while some activity are still seen for HSS/SIRs. In contrast, during MC-driven storms the currents develop gradually when the storm begins and maximize 11 hours after the onset, close to the end of the storm main phase. The response time of the currents to the solar wind driving is also different for the different storms. For HSS/SIR and sheath storms the auroral currents lag the solar wind that is hitting the magnetopause by 40 min, while the lag is 60 min for MC-driven storms.
A good understanding of auroral currents during storms is important to predict and mitigate hazardous space weather events, such as enhanced atmospheric drag slowing down satellites or geomagnetically induced currents which can damage transformers, power grids and pipeline systems. The results of this thesis show that it is important to consider the driver of the geomagnetic storm to accurately predict the auroral currents and their impact on geospace and Earth.
Last updated: 23.1.2024