September 2017's Geoeffective Space Weather and Impacts to Caribbean Radio Communications During Hurricane Response

Abstract

Between 4 and 10 September 2017, multiple solar eruptions occurred from active region AR12673. NOAA's and NASA's well‐instrumented spacecraft observed the evolution of these geoeffective events from their solar origins, through the interplanetary medium, to their geospace impacts. The 6 September X9.3 flare was the largest to date for the nearly concluded solar cycle 24 and, in fact, the brightest recorded since an X17 flare in September 2005, which occurred during the declining phase of solar cycle 23. Rapid ionization of the sunlit upper atmosphere occurred, disrupting high‐frequency communications in the Caribbean region while emergency managers were scrambling to provide critical recovery services caused by the region's devastating hurricanes. The 10 September west limb eruption resulted in the first solar energetic particle event since 2012 with sufficient flux and energy to yield a ground level enhancement. Spacecraft at L1, including DSCOVR, sampled the associated interplanetary coronal mass ejections minutes before their collision with Earth's magnetosphere. Strong compression and erosion of the dayside magnetosphere occurred, placing geosynchronous satellites in the magnetosheath. Subsequent geomagnetic storms produced magnificent auroral displays and elevated hazards to power systems. Through the lens of NOAA's space weather R‐S‐G storm scales, this event period increased hazards for systems susceptible to elevated “radio blackout” (R3‐strong), “solar radiation storm” (S3‐strong), and “geomagnetic storm” (G4‐severe) conditions. The purpose of this paper is to provide an overview of the September 2017 space weather event, and a summary of its consequences, including forecaster, post‐event analyst, and communication operator perspectives.

Space Weather Events, Hurricanes, and Earthquakes in Mexico in September 2017

“…By the end of 6 September, an interplanetary shock wave arrived at the terrestrial space environment. This shock wave was related to a coronal mass ejection detected previously by LASCO (Large Angle and Spectrometric Coronagraph) on 4 September 2017 (Redmon et al, 2018). The shock caused a compression of the Earth's magnetosphere, provoking increments in ΔHmex index ( Figure 6c); however, the Kmex index ( Figure 6d) was not disturbed.…”

“…However, each of these effects can occur without the other. The X8.2 flare on 10 September produced a solar energetic particle event reaching a (GLE)72 category (Redmon et al, 2018). This GLE event was detected by several cosmic ray observatories on the ground located at high latitudes.…”

Time-dependent data-driven coronal simulations of AR 12673 from emergence to eruption

“…The high-energy particles accelerated by these eruptions led to several space weather effects at the Earth (e.g. Berdermann et al 2018;Redmon et al 2018;Schillings et al 2018;Yasyukevich et al 2018).…”

Developing a Nowcasting Capability for X‐Class Solar Flares Using VLF Radiowave Propagation Changes.

“…The provision of operational space weather information is a requirement for space weather centers. An example of the impact of large solar flares occurring in September 2017 on technological systems including navigation services over Europe is described by Berdermann et al (2018) and Redmon et al (2018). Solar flares are emissions of visible, ultraviolet, and X-ray energy from active regions on the surface of the Sun.…”