Review of the August 1972 and March 1989 Space Weather Events: Can We Learn Anything New From Them?

TL;DR

This paper updates and compares major historical space weather events, analyzing their features, energy distribution, and mechanisms, to understand potential lessons and the variability of space weather impacts.

Contribution

It provides a detailed comparison of the 1972 and 1989 events with the 1859 Carrington event, highlighting differences in energy release and mechanisms, and discusses implications for extreme space weather scenarios.

Findings

Solar active regions release energy in various forms, not in a one-to-one relationship.

Fermi acceleration at quasi-parallel shocks is weak; electric fields at quasi-perpendicular shocks produce harder spectra.

Under certain conditions, extreme SEP events similar to Miyake et al. (2012) could occur.

Abstract

Updated summaries of the August 1972 and March 1989 space weather events have been constructed. The features of these two events are compared to the Carrington 1859 event and a few other major space weather events. It is concluded that solar active regions release energy in a variety of forms (X-rays, EUV photons, visible light, coronal mass ejection (CME) plasmas and fields) and they in turn can produce other energetic effects (solar energetic particles (SEPs), magnetic storms) in a variety of ways. It is clear that there is no strong one-to-one relationship between these various energy sinks. The energy is often distributed differently from one space weather event to the next. Concerning SEPs accelerated at interplanetary CME (ICME) shocks, it is concluded that the Fermi mechanism associated with quasi-parallel shocks is relatively weak and that the gradient drift mechanism (electric fields) at quasi-perpendicular shocks will produce harder spectra and higher fluxes. If the 4 Augusut 1972 intrinsic magnetic cloud condition (southward interplanetary magnetic field instead of northward) and the interplanetary Sun to 1 au conditions were different, a 4 August 1972 magnetic storm and magnetospheric dawn-to-dusk electric fields substantially larger than the Carrington event would have occurred. Under these special interplanetary conditions, a Miyake et al. (2012)-like extreme SEP event may have been formed. The long duration complex 1989 storm was probably greater than the Carrington storm in the sense that the total ring current particle energy was larger.