Keypoints:

The last time the sunspot number was higher than it is now, SpaceX was a 6-month-old company, Rocket Lab was still 4 years from being founded, and the first standardized CubeSats were still one year from being launched. This was September 2002, when the monthly sunspot number was 188. Less than 100 spacecraft were launched in that year and Nokia was still the most popular cellphone brand. Space Weather was in the process of being launched after the success of the 2001 AGU Monograph on Space Weather (doi:10.1002/9781118668351).

The monthly mean sunspot number has been 163 and 159 for the last two months (2023 June-July). This is larger than the double peak of solar cycle 24 (146 in February 2014 and 139 in November 2011) and brings us back to the sunspot level of solar cycle 23.

In 2022, there were close to 200 rockets that launched into orbit, with more than 60 from SpaceX. There are now about 8700 active satellites, including over 4000 (and counting) active Starlink satellites.

The first Starlink launch occurred in 2019 during the last solar minimum. From 2016 to 2021, the sunspot number was below 60, representing weak to very weak solar activity. New space companies have almost exclusively operated during weak geomagnetic conditions, with unusually low thermospheric densities, very rare extreme solar energetic particle events and extreme X-ray flares. The development and usability of very low Earth orbits (VLEO) below 400 km, where the atmospheric drag is significantly higher and atomic oxygen is a key element, are strongly affected by changes in atmospheric densities. Governmental space agencies and private companies have made lunar missions a priority over the coming years. This will result in a dramatic increase in technology and human presence in cislunar space – a region that largely lies outside of the Earth’s magnetosphere’s protection from solar and cosmic ray radiation. So far, while the sunspot number of solar cycle 25 is matching up to that in the ascending phase of solar cycle 23 and the thermospheric temperature is reaching a 20-year high, the number of large flares, energetic particle events and large geomagnetic storms are still lagging behind. If this were to continue, the disconnect between the sunspot number and solar eruptive events would have to be investigated by the scientific community, but this might provide a respite to space companies. If large flares, eruptions and energetic particle events increase significantly, an even closer attention to space weather by new space companies might be warranted. We note, however that (i) not all extreme events occur during large solar cycles (e.g., see Reyes et al., 2021, 10.1029/2021SW002766), (ii) not all extreme or large events occur during the maximum of solar cycle (e.g., see the Sep 2017 geomagnetic storm at a time when sunspot number was below 50), (iii) space weather impact do not correlate one-on-one with extreme drivers, it varies depending on the impact (radiation, geomagnetically induced currents, etc.) and is still an active area of research.

The consequences of increased solar activity are well known and well documented: e.g., increased thermospheric temperature and density (and therefore atmospheric drag), first due to the higher solar EUV fluxes but also due to flares and geomagnetic storms, higher probability of large radiation events, etc. It appears, however, that many space companies, operating in LEO, have been caught unaware of the recent increase in solar activity. While the 2022 February SpaceX event is an often-cited example (Hapgood et al., 2022), the long-term effects of enhanced drag on LEO constellations, the need for either higher initial altitudes, more adaptive mission planning or better performing propulsion systems for these constellations, could have more important economical consequences. This return to a more “normal” level of solar activity is also likely to impact other industries similarly used to more benign conditions. Space Weather was founded to serve as a journal, not only for scientific researchers but also for space and operations engineers while reaching out to policy makers (Lanzerotti, 2003; doi.org/10.1029/2003SW000024). We hope that the journal is able to fulfill this role as the number of companies potentially affected by space weather grows.