CME front and severe space weather

Abstract

Thanks to the work of a number of scientists who made it known that severe space weather can cause extensive social and economic disruptions in the modern high-technology society. It is therefore important to understand what determines the severity of space weather and whether it can be predicted. We present results obtained from the analysis of coronal mass ejections (CMEs), solar energetic particle (SEP) events, interplanetary magnetic field (IMF), CME-magnetosphere coupling, and geomagnetic storms associated with the major space weather events since 1998 by combining data from the ACE and GOES satellites with geomagnetic parameters and the Carrington event of 1859, the Quebec event of 1989, and an event in 1958. The results seem to indicate that (1) it is the impulsive energy mainly due to the impulsive velocity and orientation of IMF B z at the leading edge of the CMEs (or CME front) that determine the severity of space weather. (2) CMEs having high impulsive velocity (sudden nonfluctuating increase by over 275 km s À1 over the background) caused severe space weather (SvSW) in the heliosphere (failure of the solar wind ion mode of Solar Wind Electron Proton Alpha Monitor in ACE) probably by suddenly accelerating the high-energy particles in the SEPs ahead directly or through the shocks. (3) The impact of such CMEs which also show the IMF B z southward from the leading edge caused SvSW at the Earth including extreme geomagnetic storms of mean Dst MP < À250 nT during main phases, and the known electric power outages happened during some of these SvSW events. (4) The higher the impulsive velocity, the more severe the space weather, like faster weather fronts and tsunami fronts causing more severe damage through impulsive action. (5) The CMEs having IMF B z northward at the leading edge do not seem to cause SvSW on Earth, although, later when the IMF B z turns southward, they can lead to super geomagnetic storms of intensity (Dst min ) less than even À400 nT.

The density compression ratio of shock fronts associated with coronal mass ejections

“…While particle acceleration by flares (see Reames, 1999) is expected to occur in a limited volume (i.e., magnetic reconnection site), fastmode coronal shocks are able to directly inject SEPs over a broad range in heliolongitudes (e.g., Cliver et al, 1995Cliver et al, , 2005. SEPs are an important component of space weather as the cause of radiation hazards to astronauts and satellites, orbital degradation of satellites, communication disruptions, and electrical blackouts (e.g., Balan et al, 2014, and references therein). To better understand how coronal shocks accelerate particles over a wide range of heliolongitudes and hence improve our ability to predict their intensity, duration and energy spectrum, it is important to understand the properties of coronal shocks associated with CMEs and their temporal and spatial relationship with the SEPs measured in interplanetary space (IP).…”

Plasma Physical Parameters Along Cme-Driven Shocks. Ii. Observation–simulation Comparison

“…Moreover, shocks propagating into the interplanetary space toward the Earth can carry a significant southward component of the magnetic field that can eventually reconnect with the Earth magnetosphere triggering electromagnetic disturbances at the ground (the so-called geomagnetic storms). For these reasons and because of the severe consequences on human technologies and the terrestrial environment, these phenomena can possibly lead to (e.g., Balan et al 2014), deepening our understanding of the origin, propagation and physical properties of CME-driven shocks is fundamental in the perspective of space weather forecasting applications.…”

Automatic selection of Dst storms and their seasonal variations in two versions of Dst in 50 years

“…Since energy input takes place during MP, the mean value of Dst during MP is calculated as ⟨Dst MP ⟩ = (−1/T MP )∫ TMP |Dst|dt. It represents the impulsive strength (or strength in short) of Dst storms while DstMin represents their intensity (Balan et al 2014). It (⟨Dst MP ⟩) has been shown to be a unique parameter that can indicate the severity of space weather while the conventional parameter DstMin is insufficient (Balan et al 2016).…”