Forecasting Periods of Strong Southward Magnetic Field Following Interplanetary Shocks

Abstract

Long periods of strong southward magnetic fields are known to be the primary cause of intense geomagnetic storms. The majority of such events are caused by the passage over Earth of a magnetic ejecta. Irrespective of the interplanetary cause, fast-forward shocks often precede such strong southward B${}_z$ periods. Here, we first look at all long periods of strong southward magnetic fields as well as fast-forward shocks measured by the \textit{Wind} spacecraft in a 22.4-year span. We find that 76{\%} of strong southward B${}_z$ periods are preceded within 48 hours by at least a fast-forward shock but only about 23{\%} of all shocks are followed within 48 hours by strong southward B${}_z$ periods. Then, we devise a threshold-based probabilistic forecasting method based on the shock properties and the pre-shock near-Earth solar wind plasma and interplanetary magnetic field characteristics adopting a `superposed epoch analysis'-like approach. Our analysis shows that the solar wind conditions in the 30 minutes interval around the arrival of fast-forward shocks have a significant contribution to the prediction of long-duration southward B${}_z$ periods. This probabilistic model may provide on average a 14-hour warning time for an intense and long-duration southward B${}_z$ period. Evaluating the forecast capability of the model through a statistical and skill score-based approach reveals that it outperforms a coin-flipping forecast. By using the information provided by the arrival of a fast-forward shock at L1, this model represents a marked improvement over similar forecasting methods. We outline a number of future potential improvements.

published in Space Weather, 22 Nov 2018

References in corpus (5)

• Connecting speeds, directions and arrival times of 22 coronal mass ejections from the Sun to 1 AU
• Determining the Intrinsic CME Flux Rope Type Using Remote-sensing Solar Disk Observations
• Predicting the magnetic vectors within coronal mass ejections arriving at Earth: 1. Initial Architecture
• Factors Affecting the Geo-effectiveness of Shocks and Sheaths at 1 AU
• Importance of CME Radial Expansion on the Ability of Slow CMEs to Drive Shocks

Cited by in corpus (4)

• MHD study of planetary magnetospheric response during extreme solar wind conditions: Earth and exoplanet magnetospheres applications
• MHD study of extreme space weather conditions for exoplanets with Earth-like magnetospheres: On habitability conditions and radio-emission
• On Earth's habitability over the Sun's main-sequence history: joint influence of space weather and Earth's magnetic field evolution
• Earth-affecting Solar Transients: A Review of Progresses in Solar Cycle 24