I have just released the latest episode of the Space Weather Facts & Forecast podcast, talking about the history of space weather observation and forecasting! Check it out via the Podbean feed on the blog sidebar. Here is the episode transcript with images inserted (minus the intro and outro) if you prefer to read:
Forecast:
The sun has really been upping the ante lately! Many large active regions and flares have been appearing in the last couple weeks. Two sunspot groups, ARs 3363 and 3372, currently dominate the sun, although there are 5 other smaller ones as well. If you have a pair of eclipse glasses, take a look! The two groups should both be barely visible to the unaided eye.
AR3363, classified as beta-delta, is in the southwest quadrant of the solar disk, and is beginning to turn away from Earth. While it is large and fairly complex, it has been inexplicably quiet during its transit across the sun. However, it seems to have quite recently gained complexity and begun to flare, of course only once it left the Earth strike zone! AR3372, in the northeast quadrant, is just entering the Earth strike zone. This AR rotated over the East limb a few days ago with a bang, producing an M6.97 flare, as well as other smaller M-flares, none of which were Earth-directed at all.
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| M6.79 flare from AR3372 (July 12th) |
It is still crackling with low level M-class flares, although it has not yet triggered an Earth-facing CME. The other active regions on the disk are currently small and not complex, and do not pose a flare threat. All in all, there is a good chance that we will continue to see low-level M-flares over the next few days to a week, and stronger (greater than M5) flares, even into the X range, would not be shocking. All of these flares would have a good chance of being Earth-facing.
The current geomagnetic conditions are quiet. We are at a Kp 1, with moderately weak solar wind data. No storming for now! There was a forecast for a G1 storm (Kp 5) July 14th, due to a CME from a filament eruption on the 11th. While we did see a CME arrive on the 14th, it was much weaker than expected and only resulted in a brief Kp 4. There are no known storms on their way to Earth at this moment, and so the geomagnetic forecast remains quiet. It is very possible, though, that AR3372 could produce an Earth-facing eruption, which would then cause storm conditions here at Earth. We will simply have to watch and wait!
History of Space Weather:
In this episode I’ll be looking at somewhat of a different topic from normal: the history of space weather! Now, of course, space weather has been around for as long as the sun has, so I won’t be talking about the history of it itself, but more the history of our observations and forecasting of it.
One of the first to kickstart the field of space weather was German naturalist Alexander von Humbolt. In 1808 he observed magnetic compass needles being deflected from reading North, and realized that that deflection was happening at the same time as he saw aurora. He published a paper reporting his findings, calling it a “magnetic storm”.
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| Alexander von Humbolt |
Other English observations of magnetic telegraph needle movements at the same time as aurora confirmed this connection.
Heinrich Schwabe discovered the solar cycle when he observed sunspots almost daily from 1825 to 1843. He realized that they followed a close to 10 year pattern of increase and decrease. Next in the field, Edward Sabine spent much time analyzing geomagnetic disturbances. In 1852 he realized that these disturbances, as well as auroral displays and sunspots, all followed the same roughly 10-year cycle. Sabine is often credited as the first to discover this solar-terrestrial relationship.
The next major figure in the space weather field was Richard Carrington. In 1859, Carrington was observing a large sunspot group when he saw a white band or arch forming across the spots. He correctly interpreted this as a white light flare.
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| Carrington's drawing of the sunspot group, showing the flare as white arches connecting spots |
A white light solar flare occurs when a flare is strong enough that some of its energy is emitted in the visible spectrum, as well as the usual x-rays. About 18 hours after Carrington saw the solar flare, an intense geomagnetic storm arrived at Earth. The storm is now known as the Carrington Event, and it reportedly created currents in the telegraph system that set telegraph paper on fire, as well as gave operators shocks, while aurora was seen in Hawaii, Mexico, southern Japan and China, and even possibly as far south as Colombia. This was the first time that an observation of solar activity was directly correlated with geomagnetic activity.
The first published space weather prediction was made by Royal Observatory at Greenwich member William Ellis in 1879. He had observed several solar cycles and understood the relationship between sunspot activity and magnetic storms at Earth. He also knew that strong enough magnetic storms could induce currents in the telegraph system (as demonstrated in the Carrington Event). And so he made a prediction warning telegraph operators that the next solar maximum would be in 1882, and that they should begin taking appropriate precautions. His forecast turned out to be off by two years, as the real max occurred in 1884, however, it was still quite an accomplishment for his time.
1928 saw the first space weather radio forecast. It had been known for some time that space weather had an effect on radio propagation, and so, in 1928, in order to aid radio operators around the world, the Union Radio Scientifique International (or URSI), started sending out daily bulletins concerning space weather and radio conditions. Americans realized the value of these messages and began to send out their own in 1929, not simply rebroadcasting the URSI bulletins, but using their own data.
The next development in space weather forecasting came in 1939 from the Australian Ronald Gordon Giovanelli. He created a simple formula to determine the probability of a specific sunspot group producing a solar flare, based on the complexity, size, and rate of growth of the group. His formula was based on observations of nearly 1400 solar flares occurring over two years, and proved very useful.
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| Ronald Gordon Giovanelli |
The radio aspect of space weather saw more advances during World War II. Countries realized the importance of long-distance communications between bases and troops, and so radio scientists and solar astronomers were hired by many countries to make predictions of the best frequencies to use at any given time. With this knowledge, communications could continue on other frequencies even when the usual ones were experiencing a blackout. This type of forecasting is still in use today, mainly targeted towards pilots, ship captains, and other navigators that rely on HF radio.
Today, we know more than ever about space weather. But while we have come a long way in understanding and forecasting it, there is still much more to learn. For example, we can not yet predict the occurrence of solar flares, we can only give a probability of them occurring. Or again, we can’t accurately forecast solar cycles, including the timing and strength of the maxes and mins. Being able to forecast these and other space weather events would give affected groups, such as navigators and technology companies, much more time to prepare in case of a strong solar storm, and the technological impacts of the storm would be greatly diminished.
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