Geoeffectiveness of interplanetary shocks controlled by impact angles: past research, recent advancements, and future work

Abstract

Interplanetary shocks are disturbances commonly observed in the solar wind. IP shock impacts can cause a myriad of space weather effects in the Earth’s magnetopause, inner magnetosphere, ionosphere, thermosphere, and ground magnetic field. The shock impact angle, measured as the angle the shock normal vector performs with the Sun-Earth line, has been shown to be a very important parameter that controls shock geoeffectivess. An extensive review provided by Oliveira and Samsonov (2018) summarized all the work known at the time with respect to shock impact angles and geomagnetic activity; however, this topic has had some progress since Oliveira and Samsonov (2018) and the main goal of this mini review is to summarize all achievements to date in the topic to the knowledge of the author. Finally, this mini review also brings a few suggestions and ideas for future research in the area of IP shock impact angle geoeffectiveness.

Substorm‐Time Ground dB/dt Variations Controlled by Interplanetary Shock Impact Angles: A Statistical Study

“…As shown in Figure 10, the enhancements in absolute area coverages are larger and sharper in the shock inclination categories with smaller shock impact angles, which agrees with previous observations described above. These results agree with ground magnetic field response to shocks with different inclinations since more frontal shocks compress the magnetosphere more symmetrically and enhances magnetospheric and ionospheric currents more effectively in comparison to inclined shocks (Oliveira, 2023a;Oliveira & Samsonov, 2018).…”

“…More specifically, forecasters should predict and track impacts of nearly frontal shocks on the Earth's magnetosphere. Additionally, as pointed out by Oliveira (2023a), it is strongly recommended modelers simulate the impacts of shocks with different normal orientations on the magnetosphere to investigate, in particular, the subsequent GIC enhancements during asymmetric magnetospheric compressions. As reported by Welling et al (2021), ground dB/dt variations were highly intensified and reached low equatorial latitudes as a result of the impact of a perfect coronal mass ejection with purely frontal normal orientation, which is a very particular case.…”

“…Assumptions of energy and momentum conservation, represented by the Rankine‐Hugoniot jump conditions (Jeffrey & Taniuti, 1964; Oliveira, 2017; Priest, 1981), are used in the calculations of shock‐related parameters including the shock normal vector n . Figure 1 of Oliveira (2023a) brings schematic representations of a purely frontal shock and a highly inclined shock.…”

“…Weygand (2021) also showed similar dB/dt variations during isolated substorms without discrimination of the substorm triggering mechanism. As a result, as pointed out by Oliveira (2023a), space weather forecasting tools should focus on tracking IP shocks that are predicted to impact the magnetosphere nearly head-on for predicting high-risk dB/dt variations at magnetic latitudes lower than 70°. In addition, a visual inspection of Figure 8 and the curves in Figures 9, 10, and 12 show that, based on dB/dt responses, a typical solar wind shock normal vector has moderate inclination with ∼20°-40°deviations with respect to the Sun-Earth line, which are more frequently observed at 1 AU (Echer et al, 2023;Kilpua et al, 2015;Oh et al, 2007;Oliveira, 2023a;Oliveira & Raeder, 2015;Rudd et al, 2019).…”

“…(2021) concluded that d B / d t variations occurred faster, were stronger, and covered larger geographic areas in the frontal case when compared to the inclined case. The general conclusion of the works mentioned above is that nearly frontal impacts compress the magnetosphere almost symmetrically setting the stage with favorable conditions for effective energy release by the magnetotail, which does not clearly occur with inclined shock impacts (Oliveira, 2023a; Oliveira & Samsonov, 2018).…”