• Beyond the aurorae: How solar flares spill out across the Solar System

    From Leroy N. Soetoro@21:1/5 to All on Sat Jul 20 01:30:07 2024
    XPost: talk.politics.guns, alt.astronomy.solar, alt.politics.republicans
    XPost: alt.fan.rush-limbaugh, sac.politics

    https://www.bbc.com/future/article/20240702-beyond-the-northern-lights- how-solar-flares-spill-out-across-the-solar-system

    The Sun is extremely active right now, blasting the Earth with the biggest solar storms in 20 years. This is what it is doing to the rest of the
    Solar System.

    If you happened to look skywards on a few nights in May 2024, there was a
    good chance of seeing something spectacular. For those at relatively low latitudes, there was a rare chance to see the flickering red, pink, green
    glow of our planet's aurorae.

    A powerful solar storm had sent bursts of charged particles barrelling
    towards Earth and, as they bounced around in our planet's atmosphere, they unleashed spectacular displays of the Northern and Southern Lights. The dazzling displays of aurora borealis were visible far further south than
    they might normally be – and far further north in the case of aurora
    australis thanks to the power of the geomagnetic storm, the strongest in
    two decades.

    Although some people experienced only a faint, eerie glow, others were
    treated to a myriad of colour as far south as London in the UK and Ohio in
    the US. Reports even came in from just to the north of San Francisco, California.

    But while this spike in activity from the Sun left many on Earth
    transfixed by the light display it produced, it has also had a profound
    effect elsewhere in the Solar System. As most of us wondered at the
    colours dancing across the night's sky, astronomers have been peering far beyond to see the strange ways such intense bursts of particles affect
    other planets and the space between them.

    "The Sun can fire material outwards in any direction like a garden
    sprinkler," says Jim Wild, a professor of space physics at Lancaster
    University in the UK. "The effects are felt throughout the Solar System."

    Our Sun is currently heading towards, or has already reached, its solar
    maximum – the point in an 11-year cycle where it is most active. This
    means the Sun produces more bursts of radiation and particles from solar
    flares and events known as coronal mass ejections (CMEs). If these are
    sprayed in our direction, they can supercharge the Earth's magnetic field, causing magnificent aurorae but also posing problems for satellites and
    power grids.

    "Things really seem to be picking up right now," says Mathew Owens, a
    space physicist at the University of Reading in the UK. "I think we're
    about at solar maximum now, so we may see more of these kinds of storms in
    the next couple of years."

    Around the Sun, multiple spacecraft are observing this increase in
    activity up close. One of those, the European Space Agency's (Esa) Solar Orbiter, has been studying the Sun since 2020 on an orbit that takes it
    within the path of Mercury. Currently the spacecraft is "on the far side
    of the Sun as seen from Earth", says Daniel Müller, project scientist for
    the Solar Orbiter mission at Esa in the Netherlands. "So we see everything
    that Earth doesn't see."

    The storm that hit Earth in May originated from an active region of solar flares and sunspots, bursts of plasma and twisting magnetic fields on the
    Sun's surface, known as its photosphere. Solar Orbiter was able to see
    "several of the flares from this monster active region that rotated out of Earth's view", says Müller, bright flashes of light and darkened regions
    called sunspots on the Sun's surface.

    One of the goals of Solar Orbiter is "to connect what's happening on the
    Sun to what's happening in the heliosphere," says Müller. The heliosphere
    is a vast bubble of plasma that envelops the Sun and the planets of the
    Solar System as it travels through interstellar space. What Müller and his colleagues hope to learn more about is where the solar wind – the constant stream of particles spilling out from the Sun across the Solar System –
    "blows into the interstellar medium", he says. "So we are particularly interested in anything energetic on the Sun that we can find back in the turbulence of the solar wind."

    This particular cycle, cycle 25, appears to be "significantly more active
    than what people predicted", says Müller, with the relative sunspot number
    – an index used to measure the activity across the visible surface of the
    Sun – eclipsing what was seen as the peak of the previous solar cycle. The National Oceanic and Atmospheric Administration (Noaa) in the US had
    predicted a maximum monthly average of 124 sunspots a day in May, but the actual number was 170 on average, with one day exceeding 240, according to Müller.

    But the exact cause of the Sun's 11-year-long cycle and its variabilities remains a bit of a mystery.

    More like this:

    • Alien aurora: The strange displays that light up other worlds

    • Why Einstein was wrong about black holes

    • The Moon is slipping away from the Earth – and our days are getting
    longer

    The effects of these changes in solar activity, however, extend far across
    the Solar System. Earth is not the only planet to be hit by solar storms
    as they billow across interplanetary space. Mercury, the closest planet to
    the Sun, has a much weaker magnetic field than Earth – about 100 times
    less – and lacks a substantial atmosphere. But solar activity can cause
    the surface of the planet to glow with X-rays as solar wind rains down.

    Venus also lacks a substantial magnetic field, but the planet does still
    create auroras as the solar wind interacts with the planet's ionosphere.

    At Mars, the effect of solar activity is more obvious. Here, a Nasa
    spacecraft called Maven (Mars Atmosphere and Volatile Evolution) has been studying the planet's atmosphere from orbit since 2014. "We were on the declining side of solar cycle 24 [then]," says Shannon Curry, a planetary scientist at the University of Colorado, Boulder in the US and the lead on
    the mission. "We are now coming up on the peak of cycle 25, and this
    latest series of active regions has produced the strongest activity Maven
    has ever seen."

    Between 14 and 20 May the spacecraft detected exceptionally powerful solar activity reaching Mars, including an X8.7 – solar flares are ranked B, C,
    M, and X in order from weakest to strongest. Results from the event have
    yet to be studied, but Curry noted that a previous X8.2 flare had resulted
    in "a dozen papers" published in scientific journals. Another flare on 20
    May, later estimated to be an even bigger X12, hurled X-rays and gamma
    rays towards Mars before a subsequent coronal mass ejection launched a
    barrage of charged particles in the same direction.

    Images beamed back from Nasa's Curiosity Rover on Mars revealed just now
    much energy struck the Martian surface. Streaks and dots caused by charged particles hitting the camera's sensors caused the images to "dance with
    snow", according to a press release from Nasa. Maven, meanwhile, captured glowing aurora as the particles hit the Mars' atmosphere, engulfing the
    entire planet in an ultraviolet glow.

    The entire atmosphere expands dozens of kilometres – exciting for
    scientists but detrimental for spacecraft

    The flares can cause the temperature of the Martian atmosphere to
    "dramatically increase," says Curry. "It can even double in the upper atmosphere. The atmosphere itself inflates. The entire atmosphere expands dozens of kilometres – exciting for scientists but detrimental for
    spacecraft, because when the atmosphere expands there's more drag on the spacecraft."

    The expanding atmosphere can also cause degradation of the solar panels on spacecraft orbiting Mars from the increase in radiation. "The last two
    flares caused more degradation than what a third of a year would typically
    do," says Curry.

    Mars, while it has lost most of its magnetic field, still has "crustal
    remnant magnetic fields, little bubbles all over the southern hemisphere",
    says Curry. During a solar event, charged particles can light those up and excite particles. "The entire day side lights up in what we call a diffuse aurora," says Curry. "The entire sky glows. This would most likely be
    visible to astronauts on the surface."

    By the time solar storms reach further out into the solar system, they
    tend to have dissipated but can still have an impact on the planets they encounter. Jupiter, Saturn, Uranus, and Neptune all have aurorae that are
    in part driven by charged particles from the Sun interacting with their magnetic fields.

    But one of the key effects of solar activity on interplanetary space that astronomers are eager to study is something called "slow solar wind", a
    more sluggish, but denser stream of charged particles and plasma from the
    Sun. Steph Yardley, a solar astronomer at Northumbria University in the
    UK, says solar wind is "generally classed about 500km/s (310 miles/s)",
    but slow wind falls below this. It also has a lower temperature and tends
    to be more volatile.

    Recent work by Yardley and her colleagues, using data from Solar Orbiter, suggests that the Sun's atmosphere, its corona, plays a role in the speed
    of the solar wind. Regions where the magnetic field lines, the direction
    of the field and charged particles are "open" – stretching out into space without looping back – provide a highway for solar wind to reach high
    speeds. Closed loops over some active regions – where the magnetic field
    lines have no beginning and end – can occasionally snap, producing slow
    solar wind. The variability in the slow solar wind seems to be driven by
    the unpredictable flow of plasma inside the Sun, which makes the magnetic
    field particularly chaotic.

    The X-class flares and coronal mass ejections seen in May transformed the interplanetary medium as they flung out material across the solar system.
    Solar Orbiter detected a huge spike in ions moving at thousands of
    kilometres per second immediately after the 20 May flare. Computers on
    board other spacecraft – the BepiColombo probe, which is currently on a seven-year journey to Mercury, and Mars Express, in orbit around the Red
    Planet – both saw a dramatic increase in the number of memory errors
    caused by the high energy solar particles hitting the memory cells.

    The day after the coronal mass ejection, magnetometers on board the Solar Orbiter also saw large swings in the magnetic field around the spacecraft
    as a huge bubble of plasma made up of charged particles thrown out from by
    the event washed past it at 1,400km/s (870 miles/s).

    Increased solar activity is a boon for scientists. "If you track the
    number of papers produced by solar physicists, you can almost see an 11-
    year cycle in there," says Owens. "We are all more scientifically
    productive when there's a lot of activity to study."

    As the Sun continues into solar maximum, the Solar System will see more
    and more activity streaming from its surface. Yet while all the planets
    witness at least some of the activity, our planet bears the brunt more
    than most. "Earth is slightly unique in that space weather can have
    interesting effects on human technologies," says Wild. "There's an extra dimension here on Earth."

    Perhaps one day those anthropogenic effects might be felt elsewhere, too.
    "If you're going to fly to Mars and you have a six-month flight through
    the interplanetary environment, you're going to potentially suck up a lot
    of space weather events," says Wild. "How you protect your astronauts is
    an interplanetary issue that we need to get our heads around."


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