Observations and Impacts of the 10 September 2017 Solar Events at Mars: An Overview and Synthesis of the Initial Results

Abstract

On 10 September 2017, some of the strongest solar activity occurred in association with active region 12673 (AR2673), including an X‐class solar flare and a fast coronal mass ejection. Although AR2673 was not centrally facing Mars, the activity impacted the local space weather conditions at Mars. We give an overview of observations obtained from the Mars Atmosphere and Volatile EvolutioN, Mars Science Laboratory, and Mars Express missions. Numerical results from the Wang‐Sheeley‐Arge (WSA)‐Enlil‐cone model together with Earth/L1 and STEREO‐A observations are also presented to provide some heliospheric context. We discuss the initial results on the space weather impacts at Mars, which include heating of the upper atmosphere by solar flare emissions, flare‐related enhancements of ion and neutral densities, solar energetic particles impacting the atmosphere and surface, bright emissions of a diffuse (global) aurora, deeply penetrating interplanetary magnetic fields over the Martian dayside, and enhanced atmospheric escape rates.

Variability of Precipitating Ion Fluxes During the September 2017 Event at Mars

“…This period corresponds very probably to the encounter of Mars with a CIR or a SIR. This CIR/SIR induced an increase of the dynamic pressure and an increase of the energetic particles (Lee et al, , ), which can be seen in Figures f and g, a phenomenon also observed in several other CIR/SIR encounters (Hara et al, ; Lee et al, ). The measured increase of the SEP ions seems to be associated with the arrival of this solar wind perturbation, and therefore, most probably energetic picked up ions are accelerated by the intense convective electric field (see Figure e).…”

“…On 13 September 2017, the most intense solar event observed by MAVEN propagated past Mars (Lee et al, ). Such an encounter was a unique opportunity to study the influence of various potential solar drivers on the heavy ion precipitation.…”

“…Moreover, the early Sun is also expected to have been much more active, with generally more intense solar energetic events interacting with Mars much more frequently than today. In this context, the series of solar events that took place in September 2017 (Guo et al, ; Lee et al, ; Ma et al, ; Romanelli et al, ; Xu et al, ) is a unique opportunity to observe the effects on the heavy precipitating ion flux of an unusually high EUV flux (during the strong flare event on the 11 September as an example), but also of an Interplanetary Coronal Mass Ejection (ICME; during the 13 September encounter) and of a Corotating Interaction Region (CIR) or of a Stream Interaction Region (SIR; during the 21 September encounter).…”

Magnetic Topology Response to the 2003 Halloween ICME Event at Mars

“…To place the 2003 Halloween ICME event in the context of Mars, we compare the maximum dynamic pressure of this event with several ICME events that occurred within the last decade. The maximum dynamic pressure for the 2003 Halloween event is 33.4 nPa (Crider et al, ), much larger than the peak dynamic pressure of the March 2015 ICME (∼13 nPa; e.g., Jakosky et al, ) and the September 2017 ICME (∼5 nPa from Lee et al, , or ∼20 nPa from ; Ma et al, ) observed by MAVEN. For the latter event, MAVEN did not have direct upstream observations so that these two different dynamic pressure values come from different proxies based on the methodology described in Halekas et al () and Ma et al (), respectively.…”

“…Different ICME events might have different effects on the Mars plasma environment depending on specific upstream drivers. We use the recent 2017 September space weather event observed at Mars, including an X‐class solar flare and an ICME, to describe typical effects as the impact was investigated in a great breadth and depth with observations from multiple Mars missions, including MAVEN, MEX, Mars Science Laboratory, Mars Odyssey, and Trace Gas Orbiter, as well as numerical simulations (Lee et al, , and references therein). The impacts of this space weather event include atmospheric heating due to the flare, the ion, and neutral density enhancement during the flare event, bright emissions of a widespread diffuse aurora, and a ground‐level radiation enhancement event caused by increased Solar Energetic Particle (SEP) fluxes, a deep penetration of interplanetary magnetic fields (IMFs) due to the ICME, and an enhanced atmospheric loss rate.…”