Guest essay by Eric Worrall
Before you ask, it’s not because of all the climate satellites that NASA plans to launch in the next few years.
What if space debris and climate change become the same problem?
Changes in the atmosphere caused by carbon dioxide emissions can increase the amount of debris remaining in orbit.
By Jonathan O’Callaghan May 12, 2021 at 12:38 p.m. ET
It’s easy to compare the space debris problem to climate change. Human activity leaves too many dead satellites and machine fragments in orbit. If this option is not activated, space debris can pose significant problems for future generations and make access to space increasingly difficult or, in the worst case, impossible.
Nevertheless, the two can be linked together. Our planet’s atmosphere naturally pulls circling debris down and burns it up in the thicker lower atmosphere. However, increasing levels of carbon dioxide decrease the density of the upper atmosphere, which can reduce this effect. A study presented at the European Conference on Space Debris last month said the problem was underestimated and that in the worst case scenario, the amount of space debris in orbit could increase 50-fold by 2100.
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The research is “very important work,” said John Emmert, an atmospheric scientist at the US Naval Research Laboratory in Washington, DC who studied the loss of atmospheric density. Dr. However, Emmert says more research is needed to understand the severity of the problem – with The influence of the sun’s solar cycle is also known as a Main factor in atmospheric density changes.
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Read more: https://www.nytimes.com/2021/05/12/science/space-junk-climate-change.html
Some scientists seem to prefer solar activity as the main driver, with low solar activity associated with periods of decreased drag experienced by near-Earth satellites and space debris.
Record low thermospheric density during the solar minimum in 2008
JT EmmertJ. L. LeanJ. M. Picone
We use the global average total thermospheric mass density, which results from the drag effect on the orbits of many space objects, to study the behavior of the thermosphere during the prolonged minimum of solar activity between cycles 23 and 24. A reference altitude of 400 km was the lowest in the 43 Year database and was unusually low at 10–30% compared to the climatologically expected values. The density anomalies appear to have started before 2006, well before the minimum of cycle 23/24, and are larger than expected when thermospheric cooling is improved by increasing CO2 concentrations. The altitude dependence of the mass density anomalies suggests that they are due to a combination of lower than expected exospheric temperature (-14 K) and a decrease in the numerical density of atomic oxygen (-12%) and other species (-3%) near the Base of the diffusive part of the thermosphere.
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In the thermosphere of the earth The density at a fixed geometric height is very sensitive to changes in solar radiation at extreme ultraviolet (EUV) wavelengths (0–120 nm).. EUV and far ultraviolet (FUV) photons are the primary heat source of the thermosphere [Roble, 1995], which expands and contracts in response to changes in temperature. The solar EUV irradiance increases from the minimum to the maximum of the 11-year solar activity cycle by a factor of 2 or more [Lean, 1997], Increase in total mass density by 400 orders of magnitude near 400 km [e.g., Emmert and Picone, 2010]. Cycle 23 (1996.4–2008.8, 12.4 years) was unusually long compared to previous cycles 22 (9.7 years) and 21 (10.3 years). The 23/24 cycle minimum had the most days with no sunspots since the 1933 minimum [Livingston and Penn, 2009]. The thermosphere is expected to be unusually cool and contracted during this period in response to the appropriately sustained low solar radiation from EUV. Measurements of ion temperatures [Heelis et al., 2009] provide indirect evidence of this.
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Read more: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2010GL043671
Another paper from 2018;
EUV irradiance inputs for models with thermospheric density: Open problems and the way forward
A. Vourlidas S. Bruinsma
First published: January 16, 2018
One of the goals of the NASA Living With a Star Institute on “Nowcasting Air Resistance for Low Earth Orbit Spacecraft (LEO)” was to investigate whether and how the accuracy of air resistance models can be increased by improving the quality of solar radiation inputs, namely information about the extreme ultraviolet (EUV) irradiance. In this focused review, we examine the status and issues with EUV measurements and proxies, discuss the latest promising developments, and suggest a number of ways to improve the reliability, availability, and forecasting accuracy of EUV measurements in the next solar cycle.
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Solar variability affects human society in many ways, from long-term climate change to telecommunications to the longevity of spacecraft. Of particular importance here are the effects of solar variability on the thermosphere (90–600 km altitude) in which many spaceships, including the International Space Station, are located. The most important solar thermal drivers are (1) the extreme ultraviolet (EUV) radiation flux per unit area (irradiance) at wavelengths below ~ 200 nm and (2) intermittent solar wind inputs from coronal mass ejections (CMEs) and high-speed currents (HSS) (Chen et al., 2012; McGranaghan et al., 2014).
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In view of the fact that we seem to experience unusually low solar activity over a longer period of time, a fluctuation in the thermosphere is more due to a change in solar EUV emissions than to anthropogenic CO2. The EUV component of solar emissions is far more variable than total solar radiation, so that even a small change in solar activity can have a profound impact on the energy balance of layers of the atmosphere that are particularly sensitive to the EUV flow.
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