Our star, the sun, is by far the most massive body in our solar system, encompassing more than 99.8 per cent of all the mass in the system. While sunlight sustains photosynthetic life forms on our planet, our star is dynamical in appearance, activity and radiation output. It experiences changes in activity, driven by its magnetic field, following an approximately 11-year cycle, with solar maximum referring to a period where the sun exhibits an increased number of sunspots, coinciding solar flares and coronal mass ejections (CMEs).
The sun is currently approaching solar maximum for the current solar cycle, with maximum expected sometime between now and mid-2025.
Sunspots on the solar surface are regions of increased magnetic activity, which activity partially blocks energy from the sun’s core from reaching the surface. This results in a slight lowering of surface temperature in these regions, with the sun’s surface at these locations going ‘darker’ with respect to the rest of the solar surface.
During periods of higher solar activity, sunspots tend to be located approximately 30 degrees north or south of the solar equator, tending more towards the equator during periods of lower solar activity. Magnetic field lines in such sunspot regions tend to ‘get tangled up’ and reorganise, resulting in solar flares and sometimes also leading to CMEs.
While Earth’s magnetic field is effective in shielding our planet from the typical influx of solar wind from the sun, it can get overloaded during such energetic events, redirecting some of the incoming solar particles towards the magnetic poles.
Build-up of high-energy electrons which penetrate spacecraft shielding can result in a sudden discharge of such electrons, damaging on-board electronics, perhaps irreversibly
This causes interaction with Earth’s upper atmosphere, resulting in fantastic light displays, called aurorae, as nitrogen and oxygen molecules are excited and fall back to their ground state, typically releasing reddish and greenish hues respectively. Apart from the pretty Northern and Southern Lights, this also results in geomagnetic storms, high up in Earth’s atmosphere, which can cause spacecraft and satellite damage.
Build-up of high-energy electrons which penetrate spacecraft shielding can result in a sudden discharge of such electrons, damaging on-board electronics, perhaps irreversibly.
Radio wave communications are also heavily influenced by changes in the ionosphere, brought about by geomagnetic storms, impacting the ability of spacecraft to communicate effectively, introducing a dynamic calibration challenge based on current space weather conditions. This can be a significant problem in ground systems requiring GPS signals for high-accuracy positioning, such as the aviation industry.
While spacecraft employ shielding to counter such effects, they can still be overwhelmed during high-level geomagnetic storms. During such events, putting sensitive electronics into safe mode, or shutting them down completely until the geomagnetic storm subsides, is essential in protecting them from critical errors or damage. Prediction of space weather via the assessment of solar activity is thus crucial.
The Carrington event in 1859 was the strongest recorded geomagnetic storm to date, strong enough to cause electrical surges in telegraph lines at the time, in some cases spawning fires in some telegraph machines.
An event of the same magnitude today could result in extensive damage to spacecraft and power grid lines, with an estimated damage cost numbering in the trillions of dollars.
Josef Borg completed a PhD in astronomy at the Institute of Space Sciences and Astronomy, University of Malta, and is currently a post-doctoral researcher at the Faculty of Health Sciences at the University of Malta. He is also Malta’s representative on the European Astrobiology Network Association (EANA) council.
Sound Bites
• Will sunspot AR3664 return? The sun’s rotation period varies depending on the solar latitude in question, taking approximately 25 days at the latitude for the massive sunspot AR3664. The latter sunspot has now rotated out of view from Earth, but there is a chance that it shall still be visible on the solar surface in about two weeks’ time, when that region of the solar surface rotates back into view. Typically, large sunspot clusters persist for two or three weeks before decaying significantly in size and intensity.
For more soundbites, listen to Radio Mocha every Saturday at 7.30pm on Radju Malta and the following Monday at 9pm on Radju Malta 2 https://www.fb.com/RadioMochaMalta/.
DID YOU KNOW?
• You should NEVER look at the sun though a telescope without adequate filters in place. Perhaps the most important precaution that anyone using a telescope should take is to ensure to never point the telescope at the sun without appropriate filters in place. The main aim of a telescope is to increase light collection capacity, making faint things brighter. The sun, itself already too bright to observe with the naked eye, would cause irreversible eye damage if observed through a telescope without a solar filter covering the aperture of the telescope, and thus extreme caution is a must.
• The largest solar flare ever recorded was classified as an X28 flare. Flares are typically classified in three broad categories, with increasing levels of intensity from C-class to M-class to X-class (weaker than C-class solar flares are also classified into further sub-categories, A-class and B-class flares). While C-class flares are typically too low in intensity to have notable effects on Earth, M-class and X-class events can trigger regional or global radio blackouts. The strongest solar flare ever recorded in history occurred on November 4, 2003.
For more trivia, see: www.um.edu.mt/think.