The recent peak of the solar cycle, while not breaking records, significantly exceeded predictions, leading to several powerful solar flares and intense geomagnetic storms on Earth. Moreover, observations suggest that solar activity in the 21st century might surpass the maximum values of the last century. In an interview, Sergei Bogachev, head of the Laboratory of Solar Astronomy at the Space Research Institute (IKI) of the Russian Academy of Sciences, discusses critical questions: from understanding the laws of solar activity and the possibility of predicting ice ages, to the impact of magnetic storms on humans, the Russian scientific community`s unique approach to projects, and the space weather forecast for the next decade.
Interview with Sergei Bogachev
Q: What does your laboratory do?
Our laboratory`s work is intrinsically linked to the broader objectives of the Space Research Institute. We specialize in studying the Sun, which is increasingly viewed as an applied science, particularly focusing on its influence on Earth – what we call solar-terrestrial connections. While we don`t operate our own telescopes, we analyze data acquired from space. Furthermore, our laboratory possesses manufacturing capabilities, allowing us to build instruments, develop electronics, and conduct equipment testing.
Q: Your website primarily publishes information on solar flares and their consequences on Earth. What proportion of your laboratory`s tasks does this work represent?
While publishing information on solar flares and their terrestrial impacts is highly sought after, it constitutes a secondary task for us. Our primary focus lies in fundamental research, often less visible to the general public, much like the submerged part of an iceberg. For instance, we are currently intensely researching small solar flares. This can be likened to the fact that the total mass of bacteria on Earth far exceeds that of all elephants. There`s a hypothesis that the large, visible flares represent only a small fraction of the Sun`s actual energy, with a vast, hidden portion remaining undetected due to insufficient instrument sensitivity. Indirect evidence supports this: the temperature of the Sun`s corona (millions of degrees) doesn`t drop even in the absence of major flares, indicating other, `invisible` heating sources. We aim to uncover these hidden processes and advocate for the launch of high-precision space telescopes to observe them. Extensive theoretical research is also underway. It appears our group is among the leading ones globally addressing these issues.
Q: The peak of solar activity, in this cycle, seems to have passed. Is this truly the case, or are there nuances?
Currently, we consider a return to last year`s activity peaks impossible. The observed decline in solar activity already surpasses all random fluctuations. For instance, in the first half of last year, over 30 X-class flares were recorded, whereas for the same period this year, there were only 10. The strongest flare last year reached X8.7, while this year`s strongest was X2, four times weaker. Other confirming signs include the appearance of numerous coronal holes (characteristic of activity minimums) and a significant decrease in sunspot numbers. For a solar physicist, these signs are as obvious as leaves turning yellow in autumn. Some suggest that solar cycles often have two peaks, and we might have only passed the first, heading towards a second. While this can happen, such deep troughs between peaks are uncommon. Moreover, two maxima occur in only about half of the cycles. We are confident that this cycle had one peak, which has passed, and we are now in a slow but steady decline phase.
Q: How did the past maximum compare to those observed previously?
The 19th solar cycle, peaking in 1958, is considered the most powerful in observational history, believed to have coincided with a secular maximum. The current cycle, projected just a few years ago to be very weak and align with a secular minimum, defied these forecasts: observed activity was approximately twice as high as predicted. This past cycle significantly surpassed the previous one by about 50%. However, it wasn`t a record-breaker, still falling short of mid-20th-century peaks by roughly the same margin. So, while the cycle was unexpectedly strong, it was not historically unprecedented. Furthermore, the most active period in the 21st century was from 2001 to 2003, when exceptionally strong flares, up to X40, were recorded. In the recently concluded cycle, there wasn`t a single flare even at the X10 level. Thus, we haven`t experienced record-breaking events, but perhaps the next cycle will surprise us.
Q: Can long-term forecasts be made based on data from past cycles now?
On one hand, predicting solar cycles appears straightforward due to their approximately 11-year period. One might simply add 11 years to the previous peak (e.g., 2014 + 11 = 2025, then 2036, and so on). However, this isn`t entirely accurate, as fluctuations exist: the next peak could occur in 9, 10, or 12 years. The main point is different. As radio enthusiasts would explain, radio transmission has a carrier frequency and modulating envelopes. The 11-year `carrier frequency` operates quite stably, but the `modulation,` which determines the cycle`s amplitude, varies considerably. Over the 25 observed cycles, these envelopes are visible, and there are indications that this envelope follows a centennial pattern. But we don`t know its nature or governing laws. Beyond the centennial, there could be millennial or even million-year envelopes. Overall, we understand that this process is at play, and if secular, ordinary, millennial, and hundred-thousand-year minima were to converge at some point, it could lead to a global activity slump, such as a new Maunder Minimum (1645-1715) and an ice age. Conversely, if all maxima align, it could trigger events similar to Carrington (the powerful geomagnetic storm of 1859) or Miyake events (increased radioactive carbon in 773 and 993 AD). Apparently, the lowest point of the secular cycle was passed in the previous cycle, and we are now moving upwards. My forecast for the next 20-30 years is that each subsequent cycle will be increasingly powerful. However, nature is unpredictable, and things could always turn out differently.
Q: Will solar activity reach the levels of 2001-2003 or even the records of the mid-last century?
It`s possible that activity will even exceed the values of 2001-2003 or the records of the mid-last century, as we don`t know what global envelopes are influencing this process. Perhaps the secular maxima, which have their own envelope, are also currently increasing. It`s quite plausible that the secular maximum of the mid-21st century will be higher than that of the last century. However, here we venture into territory where we lack sufficient data. The problem is also that solar flares do not leave lasting traces. For example, a meteorite crater persists for millions of years, but a solar flare from a million years ago would leave absolutely nothing on Earth. Even all the radioactivity it produced would completely dissipate. Therefore, we have no information about solar activity older than 10,000 years, which makes our predictions quite uncertain.
Q: Where, then, do scientists get data on solar activity older than 10,000 years?
Scientists obtain data on solar activity older than 10,000 years primarily from the radioactive carbon isotope C-14. This element is produced from nitrogen, and its creation is stimulated by solar activity. Carbon, being the basis of all life, is easily absorbed by plants or accumulates in Antarctic ice. Miyake events, for example, were discovered by tree rings: a cross-section reveals a peak of incredible intensity in a specific year. This is how we learned that the Sun can produce flares hundreds or thousands of times more powerful than the Carrington event. The Carrington flare (whose exact date is known) left no trace in tree rings, whereas the event of 773 AD left such radioactivity that its trace is still visible more than a thousand years later.
Q: Is there a chance to get closer to understanding the modulating envelopes?
Progress in any science is only possible after establishing an adequate physical model. While gathering data haphazardly, you will, of course, learn something, but this knowledge is akin to a blind person feeling an object. Once you grasp the physics of the process, the picture becomes much clearer. It is now understood that a mechanism called the dynamo mechanism operates within solar physics. However, the parameters governing it remain unknown. Perhaps planets, through their gravity, cause the Sun to oscillate, or perhaps it`s due to internal oscillations of the Sun`s core. One can only speculate, as there isn`t a single reasonable hypothesis.
Q: The next peak will be in 9-10 years. Will the Sun be calm all that time?
An analogy with regular climate is appropriate here. We know that temperatures generally rise from winter to summer, but this doesn`t preclude snow in May or an unexpected September heatwave amidst general autumn cooling. Roughly the same applies to the solar cycle. Activity will slowly decline for about four years. During this period, unexpected, very powerful events – strong flares and storms – are possible. In the previous two cycles, record-breaking events occurred not at the peak but 2-3 years afterward. The strongest flare of the 21st century (X40) happened in 2003, while the maximum was in 2001. The strongest flare of the subsequent cycle occurred in 2017, three years after its peak. Truly `dead` periods usually last only two or three years. In the previous cycle, this was 2018-2020; in the current one, it will be approximately 2029-2030, possibly extending partly into 2031.
Q: Can we learn to predict ice ages if we understand how this mechanism works?
This is a rather speculative topic. It`s important to understand that the Sun, as a source of heat and light, has shone quite stably for millions of years, and its global luminosity does not affect Earth`s climate. Greenhouse gases are considered the main factor regulating Earth`s temperature. They allow solar light to reach Earth but trap its heat from escaping, thereby raising the temperature. In our modern era, Earth`s average temperature should be around -15 degrees Celsius, but it`s +15, meaning it`s about 30 degrees higher due to greenhouse gases. These gases (mainly water vapor, CO2, O3) are found at high altitudes where they interact actively with solar radiation, making them very sensitive to solar activity. Since changes in solar activity can influence greenhouse gases, the hypothesis that flares can regulate Earth`s climate is plausible and widely accepted. It`s difficult to confirm, as, fortunately, we haven`t personally experienced ice ages. However, there were so-called mini ice ages – climatic depressions in the Middle Ages, confirmed by contemporary accounts of snow in June and crop failures. At least one such depression, occurring when the Sun was already being actively studied, coincided with a period of low solar activity. Thus, by understanding solar activity, it might be possible to predict ice ages, but we currently, unfortunately, do not fully understand it. This is precisely what we are working on.
Q: Many people believe that flares and magnetic storms affect well-being, mostly negatively. What is your view on this?
Indeed, the polarization of opinions on this matter is striking, sometimes escalating into aggressive debates. As a scientist, I dislike extreme viewpoints and would like to correct both. To those who claim it`s all nonsense, saying `you`re not afraid to ride a tram, but you fear storms,` we usually remind them of official sanitary regulations (SanPiN). This state document explicitly states that variable magnetic fields are harmful to humans. Moreover, it includes protection standards – of course, not directly against magnetic storms, but against variable magnetic fields in general. There`s also the other extreme: people who try to attribute every malaise to external factors. This is also incorrect, especially if it leads to self-medication. Physics identifies mechanisms through which magnetic storms influence humans. Variable magnetic fields generate eddy currents not only in technology but also within the human body. At the technological level, this influence has been experimentally recorded, reliably confirmed, and measurable. You can`t connect an ammeter to a person, so confirming this influence for humans is much harder. Cardiologists professionally study this topic. In my opinion, this is correct because if I, as a physicist, were to consider the impact on humans, eddy currents would primarily affect the circulatory system – where there are many ions, blood plasma. However, I am not prepared to give specific recommendations, for example, at what storm level one should seek shelter, or at what level one can live calmly.
Q: How have solar observation tools changed from the beginning of the space age to today?
The main change since the dawn of the space age is the very possibility of deploying instruments in space. Earth`s atmosphere, fortunately, effectively protects us from harmful radiation, and hard wavelengths. However, for astronomy, this protection is too effective; almost nothing is visible from Earth. To observe solar flares in all their diversity, including their harmful aspects, instruments must operate in space. Naturally, progress in electronics is crucial. Everyone using mobile phones observes the increasing megapixel count in cameras. In a sense, a space telescope is a large camera. And to a significant extent, the amazing images and high precision with which solar images can now be obtained are due to advancements in detectors, data processing, and storage. The optics of the telescope itself – the tube, mirrors, lenses – surprisingly, have barely changed in the last 100 years. Moreover, many observatories on Earth use telescopes with century-old optics, which have simply been updated with modern detectors and perform excellently for astronomical tasks. And, of course, progress in computers. For example, the SDO solar telescope, currently the most renowned, transmits two terabytes of solar images daily. It`s impossible to view and interpret these manually. Without computational processing tools, studying almost anything would be impossible.
Q: What capabilities does Russia have in satellite solar monitoring? What data do you use?
Russia`s last dedicated solar observatory, `Coronas-Photon,` ceased operations on November 30, 2009. Since then, the primary source of data has been open foreign sources. I would like to commend Roshydromet, which is attempting to rectify this situation by installing solar instruments on its meteorological satellites. However, these are very basic, second-tier instruments that can only supplement data from larger telescopes and are not capable of independently forming a complete space weather forecast.
Q: You mentioned promoting the idea that a dedicated telescope is needed. Is that what you`re referring to?
Yes, precisely. The urgent need for our own solar observation satellite emerged in 2009, after the `Coronas-Photon` mission concluded. At that time, proposals were made to replicate that apparatus at a higher technical level. However, a different concept was chosen: to create something entirely new, `revolutionary` – the `Interhelioprobe` project, which envisioned a satellite flying towards the Sun, shielding itself with a thermal barrier, and then exiting the ecliptic plane using Venus`s gravity. Unfortunately, in our mindset, it`s often believed that for a project to gain traction, it must be somewhat revolutionary and breathtaking. In many ways, this approach proved detrimental: the project progressed with difficulty and has been practically stalled in recent years, straining under its own weight. In recent discussions regarding the Russian Academy of Sciences` fundamental space research program, `Interhelioprobe` is no longer mentioned. Even if the project is indeed terminated, I believe the accumulated groundwork (instruments, mock-ups) should be preserved and transferred to a new project to avoid starting from scratch. Our country needs its own solar observatory regardless, and the timing of its development is crucial. As an example of a different concept, consider the leading foreign solar observatory SDO. Its main instrument, AIA, consists of just four, albeit very high-quality, telescopes. In our system, such a project, unfortunately, would likely not receive support, as it would be deemed not to address fundamentally new tasks. Looking ahead, we need a relatively simple but high-quality monitoring satellite equipped with modern solar telescopes, photometers, particle detectors, and solar wind monitors. It should likely be launched to the L1 Lagrange point, where the gravitational influences of the Sun and Earth balance out. The scientific community supports this concept and orbit. We are capable of manufacturing all necessary instruments, and for those we cannot, we know where to procure them turnkey. As a temporary solution, we are actively developing nanosatellites. However, the instruments we can place on them are very simple, providing only a minimal level of research. For full-scale research, a large satellite is undoubtedly required.
Q: What capabilities does your laboratory have in the field of instrument manufacturing?
Our work in instrument manufacturing is primarily conducted under state orders. Unfortunately, currently, there are no large-scale `hardware` projects in solar physics; it`s mostly conceptual design and research. Our country has been influenced by the global trend towards small satellites, or `CubeSats.` We manufacture instruments for them. In 2023, there was a major launch where five of our instruments were deployed, two of which are still operational and transmitting data. We are currently developing new instruments for CubeSats, but their launch is almost certainly not expected before 2027.
Q: Can private space companies order instruments from you?
Scientific organizations are permitted to engage in contractual commercial activities in addition to state assignments. We also participate in such activities. There have been instances where we manufactured something not for ourselves, but for other organizations. We possess unique expertise in detectors and optics that not everyone has. Such work is undertaken, but primarily for financial support and team retention. Unfortunately, this external activity does not directly advance the solar physics research that is our main focus.
