Why Is The Sun's Atmosphere So Hot?

A schematic diagram of the cycle of mass in the solar atmosphere. High speed upflows seen in the magnetic upper chromosphere as Type-II spicules, get thrust into the corona; this material is visible at a wide range of temperatures, and some of it becomes entrained in the coronal magnetic field. Later, this material falls out along the same magnetic field lines, most likely as a phenomena called "coronal rain."

From Live Science:

The 2006 launch of the multinational Hinode satellite changed the picture of the Sun for astrophysicists. For two astrophysicists in particular, the resulting imagery offered a voyage of discovery and the thrill of unraveling a long-held solar mystery.

Earth's atmosphere can obscure the view of unaided ground-based telescopes, but, unimpeded by this problem, the high-resolution telescope flying on Hinode captures images of the Sun in unparalleled detail.

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Solar Flares Back, But Oddly Small

Sun activity rises and falls in an 11-year-long cycle, such as this cycle from top left taken in early 1997 to bottom right, taken in early 2000. Credit: NASA

From Cosmos:

SYDNEY: After a long silence, the Sun erupted in an unusual pattern of small solar flares, said an Australian astrophysicist, which may provide a unique opportunity to predict when bigger solar flares will erupt.

Solar flares are explosions in the Sun's atmosphere marked by a burst of X-rays. They increase or decrease in a roughly 11-year cycle — larger flares can reach tens of millions of degrees Celsius and interfere with communications satellites and affect astronauts' health.

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Solar Activity Intensifies After Long Period Of Calm

From The BBC:

New photographs taken by space telescopes show activity on the surface of the sun has intensified in recent weeks.

Scientists say solar flares and regions of powerful magnetic fields known as sun-spots have increased markedly after a period of the lowest activity for almost a century.

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Do Not Adjust Your Sets: Solar Storms Could Cause Blackouts At Olympics

Solar flares erupting from the surface of the Sun fling billions of tonnes of electrically-charged matter towards the Earth in a solar storm. ESA/ASA

From The Independent:

With terrorist threats, dire transport links and overspent budgets you'd be forgiven for thinking that the 2012 London Olympics had enough problems to worry about. But another nightmare scenario has just been added to the Olympic dream – a communications blackout caused by solar storms.

After a period of unprecedented calm within the massive nuclear furnace that powers the Sun, scientists have detected the signs of a fresh cycle of sunspots that could peak in 2012, just in time for the arrival of the Olympic torch in London.

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Nasa Mission To Unravel Sun’s Threat To Earth

Scientists have designed a space probe to peer deep beneath the solar surface
and observe how sunlight is generated

From Times Online:

A new probe could help scientists predict the solar storms that cause chaos for us.

NASA is to embark on one of its most ambitious missions in an attempt to unlock the secrets of the sun.

Following its launch in nine days’ time, the US space agency’s Solar Dynamics Observatory (SDO) will spend five years in orbit trying to discover the causes of extreme solar activity, such as sun spots and solar winds and flares.

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Sun May Soon Send Magnetic Storms Toward Earth

From US News And World Report/AP:

BOULDER, Colo.—The sun may finally be awakening from its longest quiet period in about a century and powering up to solar maximum, when it could fling disruptive electromagnetic storms toward Earth.
Click here to find out more!

But once the sun does ramp up, it could be a relatively quiet solar maximum, with a below-average number of eruptions, scientists say.

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The Intricate Beauty Of The Solar Corona

(Click Image to Enlarge)

From Discovery News:

The solar corona is the magnetically dominated atmosphere of the sun, reaching millions of miles into space. Paradoxically, the corona is many times hotter than the solar 'surface' (the photosphere) and solar physicists are currently trying to understand why this is the case.

The photosphere has an average temperature of approximately 6000 degrees Celsius, whereas the corona can be millions of degrees Celsius. This is analogous to the air surrounding a hot light bulb being hotter than the bulb itself; in reality, the air surrounding the bulb is cooler than the bulb's glass surface, and it gets cooler the further you move your hand away.

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2009’s Sleepy Sun Finally Woke Up In December

From Wired Science:

2009 will go down as the sun’s third quietest year on record, under-shone only by 1913 and 2008.

Two hundred-sixty of the year’s 365 days (71 percent) were sunspotless. Last year saw 266 sunspotless days, while the sun had no spots on 311 of the days in 1913. It was only a very active December that kept 2009 from falling below last year’s mark.

Sunspot activity waxes and wanes in a roughly 11-year cycle, so hitting solar minima isn’t surprising. But what the numbers underscore is that we spent much of the year still in the midst of the deepest, longest solar minimum in a long time.

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'Solar Tsunamis' Tower On Surface Of The Sun

A solar tsunami can be seen as a dark wave spreading across the surface of the Sun (small sphere on left). The greyed-out band has been enhanced for contrast. The green shows the solar flare or CME that has caused the tsunami. Credit: NASA

From Cosmos:

SYDNEY: Observations from NASA's STEREO space probes have confirmed that vast 'solar tsunamis', taller than the Earth itself, ripple across the Sun for millions of kilometres.

The technical name is 'fast-mode magneto -hydrodynamical wave (MHD)'. The one the STEREO probes recorded reared up to 100,000 km in height, and raced outward at 900 km/h packing as much energy as 2,400 megatons of TNT.

The findings are reported in the Astrophysical Journal Letters. See a video here of a solar tsunami as seen from different angles by the STEREO spacecraft.

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Solar Winds Triggered By Magnetic Fields

XRT Full Sun (Synoptic). (Credit: Images courtesy of JAXA, NAOJ, PPARC and NASA.)

From Science Daily:

Science Daily (Nov. 22, 2009) — Solar wind generated by the sun is probably driven by a process involving powerful magnetic fields, according to a new study led by UCL (University College London) researchers based on the latest observations from the Hinode satellite.

Scientists have long speculated on the source of solar winds. The Extreme Ultraviolet Imaging Spectrometer (EIS), on board the Japanese-UK-US Hinode satellite, is now generating unprecedented observations enabling scientists to provide a new perspective on the 50-year old question of how solar wind is driven. The collaborative study, published in this month's issue of Astrophysical Journal, suggests that a process called slipping reconnection may drive these winds.

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Great Ball Of Fire! Video Reveals Explosive Magnetic Power Of The Sun

The solar prominence is viewed in profile from Stereo Ahead (which did not photograph the whole star), while the filament is shown as a dark patch from Stereo Behind

From The Daily Mail:

Dramatic eruptions on the Sun have been captured in rare footage by two Nasa spacecraft.

Filmed over two days, the images show large glowing clouds of gas bursting from the Sun's surface and held aloft by the star's twisted magnetic fields.

These huge solar prominences are several times larger than the Earth and are caused by the solar activity cycle. It is one of the most spectacular events that the twin STEREO (Solar TErrestrial RElations Observatory) craft have observed.

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Plumes Of Fire And Gas Erupting From The Sun Have Been Captured By Nasa Spacecraft

From The Telegraph:

Great balls of gas erupting from the Sun have been captured in rare footage by two Nasa spacecraft.

Filmed over two days, the images show huge plumes of gas bursting from the Sun's surface and held aloft by its magnetic field.

These gas bursts - known as solar prominences - are several times larger than the Earth and travel at enormous speed.

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Solar Superstorm

An ultraviolet-wavelength picture of the sun taken by the ESA/NASA Solar and Heliospheric Observatory (SOHO) on Oct. 23, 2003.

From NASA:

October 23, 2003: Newly uncovered scientific data of recorded history's most massive space storm is helping a NASA scientist investigate its intensity and the probability that what occurred on Earth and in the heavens almost a century-and-a-half ago could happen again.

In scientific circles where solar flares, magnetic storms and other unique solar events are discussed, the occurrences of September 1-2, 1859, are the star stuff of legend. Even 144 years ago, many of Earth's inhabitants realized something momentous had just occurred. Within hours, telegraph wires in both the United States and Europe spontaneously shorted out, causing numerous fires, while the Northern Lights, solar-induced phenomena more closely associated with regions near Earth's North Pole, were documented as far south as Rome, Havana and Hawaii, with similar effects at the South Pole.

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Global Warming And The Sun -- A Commentary

From L.A. Times:

Recent studies seem to show that there's more to climate change than we know.

Assuming there are no sunspots today, a 96-year record will have been broken: 53 days without any solar blemishes, giant magnetic disruptions on the sun's surface that cause solar flares. That would be the fourth-longest stretch of stellar solar complexion since 1849. Wait, it gets even more exciting.

During what scientist call the Maunder Minimum -- a period of solar inactivity from 1645 to 1715 -- the world experienced the worst of the cold streak dubbed the Little Ice Age. At Christmastime, Londoners ice skated on the Thames, and New Yorkers (then New Amsterdamers) sometimes walked over the Hudson from Manhattan to Staten Island.

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Is the Sun Missing Its Spots?

SUN GAZING These photos show sunspots near solar maximum on July 19, 2000, and near solar minimum on March 18, 2009. Some global warming skeptics speculate that the Sun may be on the verge of an extended slumber. NASA

From The New York Times:

The Sun is still blank (mostly).

Ever since Samuel Heinrich Schwabe, a German astronomer, first noted in 1843 that sunspots burgeon and wane over a roughly 11-year cycle, scientists have carefully watched the Sun’s activity. In the latest lull, the Sun should have reached its calmest, least pockmarked state last fall.

Indeed, last year marked the blankest year of the Sun in the last half-century — 266 days with not a single sunspot visible from Earth. Then, in the first four months of 2009, the Sun became even more blank, the pace of sunspots slowing more.

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Sun Leaves Earth Wide Open To cCsmic Rays

The sun protects the earth from cosmic rays and dust from the solar system but squeezing of various stars could leave us unprotected (Image: NASA/HST collection)

From New Scientist:

THE sun provides ideal conditions for life to thrive, right? In fact, it periodically leaves Earth open to assaults from interstellar nasties in a way that most stars do not.

The sun protects us from cosmic rays and dust from beyond the solar system by enveloping us in the heliosphere - a bubble of solar wind that extends past Pluto. These cosmic rays would damage the ozone layer, and interstellar dust could dim sunlight and trigger an ice age. However, when the solar system passes through very dense gas and dust clouds, the heliosphere can shrink until its edge is inside Earth's orbit.

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Light Goes Out On Solar Mission

From The BBC:

After more than 18 years studying the Sun, the plug is finally being pulled on the ailing spacecraft Ulysses.

Final communication with the joint European-US satellite will take place on 30 June.

The long-serving craft, launched in October 1990, has already served four times its expected design life.

The Esa-Nasa mission was the first to survey the environment in space above and below the poles of the Sun.

Data from the craft, published last year, also suggested that the solar wind - the stream of charged particles billowing away from the Sun - is at its weakest for 50 years.

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Sunspots Revealed In Striking Detail By Supercomputers

The interface between a sunspot's umbra (dark center) and penumbra (lighter outer region) shows a complex structure with narrow, almost horizontal (lighter to white) filaments embedded in a background having a more vertical (darker to black) magnetic field. (Credit: Copyright UCAR, image courtesy Matthias Rempel, NCAR)

From Science Daily:

ScienceDaily (June 21, 2009) — In a breakthrough that will help scientists unlock mysteries of the Sun and its impacts on Earth, an international team of scientists led by the National Center for Atmospheric Research (NCAR) has created the first-ever comprehensive computer model of sunspots. The resulting visuals capture both scientific detail and remarkable beauty.

The high-resolution simulations of sunspot pairs open the way for researchers to learn more about the vast mysterious dark patches on the Sun's surface. Sunspots are associated with massive ejections of charged plasma that can cause geomagnetic storms and disrupt communications and navigational systems. They also contribute to variations in overall solar output, which can affect weather on Earth and exert a subtle influence on climate patterns.

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Solar Sleuths Tackle Mystery Of Quiet Sun

Scientists have found that slow, eastward-moving "jet streams" (depicted in yellow) move about 7000 kilometres below the sun's surface. As this plot shows, over time they migrate from near the sun's poles toward its equator. The ones corresponding to Cycle 24 took their time reaching 22° in latitude, matching the prolonged solar minimum seen in recent years. (Illustration: Frank Hill and Rachel Howe/NSO)

From New Scientist:

For the past couple of years, our sun has been at the minimum of its 11-year activity cycle. Its face has been virtually spotless for months on end, and there've been no dire alerts of titanic solar storms about to slam into Earth.

The problem is that this "quiet sun" has continued far too long – two years ago, a special task force predicted that the transition from the just-ended Cycle 23 to the upcoming Cycle 24 would come around March 2008. It didn't. (To be fair, there was sharp disagreement within the group at that time.)

Much fanfare accompanied the appearance of a tiny high-latitude sunspot in early 2008, supposedly heralding Cycle 24's arrival. Yet for months and months afterward the sun's face remained spotless.

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Sun Cycle 'Lowest Since 1928'

From NASA:

May 29, 2009: An international panel of experts led by NOAA and sponsored by NASA has released a new prediction for the next solar cycle. Solar Cycle 24 will peak, they say, in May 2013 with a below-average number of sunspots.

"If our prediction is correct, Solar Cycle 24 will have a peak sunspot number of 90, the lowest of any cycle since 1928 when Solar Cycle 16 peaked at 78," says panel chairman Doug Biesecker of the NOAA Space Weather Prediction Center.

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