Earth's orbit around the sun isn't a perfect circle, it's an ellipse. One side is closer to the sun (147.5 million km) than the other (152.6 million km). This weekend (Jan. 2nd), we're at the closest point, known to astronomers as perihelion. When Earth is at perihelion, the sun looks a little bigger than usual, as shown in this composite image from Khosro Jafarizadeh of Karaj, Alborz, Iran:
Jafarizadeh took the two pictures from opposite ends of Earth's orbit: perihelion and aphelion. Sunlight falling on Earth at perihelion is 3.5% stronger than the year-long average. Northern snow doesn't melt, however, because seasons are shaped primarily by the tilt of Earth's spin axis, not the eccentricity of its orbit.
In Iceland, the New Year began with a very special sunrise. "Just before the sun appeared on Jan. 1st, a pink shaft of light sprung up from the eastern horizon," says Wioleta Gorecka, who sends this picture from the port of Hafnarfjordur: "What a beautiful way to greet 2021," she says.
This is a sun pillar, caused by plate-shaped ice crystals fluttering like leaves in distant cirrus clouds. The crystals intercept sunbeams, bending and reflecting them into a tall column of light. Look for pillars around sunrise and sunset; they are especially easy to find in cold places like Iceland where icy clouds bookend the short days of winter.
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New Moon Hypothesis Need: https://news.unm.edu/news/new-researc...
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Geomag Max in Mesopotamia: https://www.sciencedirect.com/science...
Amazon to Disappear? https://www.bangor.ac.uk/news/researc... …
Probably not: https://earthobservatory.nasa.gov/ima...
A sunspot is emerging in the sun's northern hemisphere. Its magnetic polarity identifies it as a probable member of new Solar Cycle 25. This is the second Solar Cycle 25 sunspot we've seen this month, continuing a trend of low but intensifying Cycle 25 activity. The next solar cycle is coming, after all.
Solar Minimum is having a calming effect on Earth's magnetic field. The deepening quiet is shown in these geomagnetic data, taken by Stuart Green of Preston, Lancashire, UK, during each of the past 3 summers:
"I've plotted the changing levels of geomagnetic activity for the months of May, June and July (between the equinoxes) for the years 2017, 2018 and 2019," explains Green, who operates a research-grade magnetometer buried in his backyard. "The trend is clearly downward, with less frequent and intense storms in 2019, as the sun continues deeper into Solar Minimum."
His data show why minor G1-class geomagnetic storms, which would rarely be mentioned during Solar Maximum, are suddenly noteworthy. Any magnetic storm is news at this point in the solar cycle.
The quiet won't last forever, though. A panel led by experts from NOAA and NASA predict that the solar cycle will bottom out in late 2019 with a bounce back to higher levels of activity beginning sometime in 2020. Meanwhile, G1 is a significant magnetic storm.
A minor interplanetary shock wave hit Earth on May 26th at approximately 22:00 UT. The CME-like disturbance was unexpected. It caused the density of the solar wind around Earth to abruptly quadruple, while the interplanetary magnetic field doubled in strength. Minor geomagnetic storms are possible on May 27th as our planet passes through the shock wave's wake.
Ski resorts are one of the best places to see sun halos--rings of light that surround the sun when ice crystals fill the air. Spaceweather.com reader Julie Morris was skiing at the Snowbasin Resort in Huntsville, Utah, on Nov. 25th when she witnessed this incredible specimen:
"I had never seen anything like it," says Morris. "It lasted for more than 15 minutes, and other skiers stopped to photograph it as well. I was so glad that my iPhone photo turned out because my hands were numb and I also couldn't see that well because I had stared at the brightness for so long!"
Ordinary sun halos are caused by ice crystals floating high above Earth's surface in cirrus clouds. "Ski halos," on the other hand, are formed by ice crystals near the ground, kicked into the air by the action of skis and snow-making machines.
"There were snow-making machines in operation at the time," says Morris. That's important because snow-making machines produce a very special type of ice. Crystals called "diamond dust" grow slowly downwind of ski-slope snow blowers. These man-made crystals tend to be more optically perfect than natural crystals in clouds, producing extra-bright, extra-sharp halos.
Morris's quick iPhone photo captured a rare variety of forms: a 22-degree halo, sundogs, sub-sundogs, a sub-sun, a lower sun pillar, an upper tangent arc, a supralateral arc, a Parry arc, a 46-degree halo, a circumzenithal arc, and a parhelic circle--all sculpted from sunlight by floating diamond dust.
Over the weekend, a small sunspot materialized in the sun's northern hemisphere, then, hours later, vanished again. Such an occurrence is hardly unusual during solar minimum when sunspots are naturally small and short-lived. However, this ephemeral spot was noteworthy because its magnetic field was reversed--marking it as a member of the next solar cycle.
Shown above is a magnetic map of the sun from NASA's Solar Dynamics Observatory on Nov. 17th. Two sunspot groups visible at 21:00 UT are inset.
Note sunspot AR2727 just north of the sun's equator. It is a member of decaying Solar Cycle 24, the cycle that peaked back in 2012-2014. Next, compare its magnetic polarity to that of the other, unnumbered sunspot high above it. They are opposite. According to Hale's Law, this means the two sunspots belong to different solar cycles. The high latitude sunspot appears to be a harbinger of Solar Cycle 25.
Solar cycles always mix together at their boundaries. Indeed, ephemeral sunspots possibly belonging to Solar Cycle 25 have already been reported on Dec. 20, 2016, and April 8, 2018. Now we can add Nov. 17, 2018, to list. The slow transition between Solar Cycle 24 and Solar Cycle 25 appears to be underway.
What does this mean? First, it suggests that the solar cycle is still operative. This contradicts widespread internet buzz that a Grand Minimum is in the offing, with no new sunspots expected for decades as the solar cycle grinds to a halt. Second, if patterns of previous solar cycles hold, Solar Minimum is not finished. It will probably continue to deepen in the year or so ahead even as new Solar Cycle 25 sunspots occasionally pop up, promising an ultimate end to the lassitude.
Last weekend, Nov. 10th, a stream of fast-moving solar wind hit Earth's magnetic field, igniting a ring of auroras around the South Pole. Minoru Yoneto saw the red-purple glow all the way from Queenstown, New Zealand:
"We were lucky to catch another Southern Lights display during my stargazing tour," says Yoneta. "Our guests were excited to photograph them using their own cameras."
Queenstown is at 45 degrees south latitude--a considerable distance from the South Pole. That's why the auroras looked red. Auroras circling the South Pole must reach very high above Earth's surface to be visible half a hemisphere away. At altitudes greater than ~200 km, auroras turn red. The ruby glow occurs when high energy particles from space hit oxygen atoms at the top of the atmosphere. Ionized molecular nitrogen adds a dash of purple to the high-altitude palette.
More red Southern Lights are possible on Nov. 18th or 19th when a new stream of solar wind is expected to arrive. The gaseous material is flowing from a relatively small hole in the sun's atmosphere. Queenstown stargazers, charge your cameras!
The Parker Solar Probe has just radioed NASA with good news. The spacecraft survived its close approach to the sun on Nov. 5th. Because the sun is a giant natural source of broadband radio noise, Parker cannot transmit complicated data streams through the interference. Images and data won't arrive until early December when the probe has reached a sufficient distance from the sun again. For now, mission controllers are happy to have received a simple beacon saying the spacecraft is okay.
First Perihelion: Into the Unknown - Parker Solar Probe
JHU Applied Physics Laboratory
Published on Nov 2, 2018
Earlier this week, Parker screamed around the sun at 213,200 mph only 15 million miles from the stellar surface--shattering old records for both speed and distance. Intense sunlight raised the temperature of the probe's heat shield to about 820 degrees Fahrenheit. All the while, instruments and systems behind the shield kept cool in the mid-80s F.
Mission controllers at the Johns Hopkins University Applied Physics Lab received the status beacon at 4:46 p.m. EST on Nov. 7, 2018. It indicated, simply, "A" — the best of all four possible status signals, meaning that the probe is operating well with all instruments running and collecting science data and, if there were any minor issues, they were resolved autonomously by the spacecraft. Stay tuned for "first light" science results about one month from now.
NASA's Parker Solar Probe is now closer to the sun than any other spacecraft in history, shattering the previous record of 26.6 million miles set by the Helios 2 spacecraft in 1976. The probe is now well inside the orbit of Mercury."It's a proud moment for our team," says Project Manager Andy Driesman of the Johns Hopkins Applied Physics Laboratory.
Count to 3. Parker just broke the record again. The spacecraft is accelerating sunward for the mission's first perihelion on Nov. 5th. At closest approach, the solar disk will seem 6 times wider than it does on Earth as the probe is hit by "brutal heat and radiation" (NASA's words). Parker's carbon-composite heat shield is expected to heat up to a sizzling 2000 deg. F.
Parker's prime mission is to investigate the origin of the solar wind--a project best done uncomfortably close to the star. Parker will trace the solar wind back to its source and find out how it escapes the sun's gravity and magnetic confinement.
Russell Howard of the Naval Research Laboratory expects to learn a lot from this encounter. "We might detect magnetic islands in the solar wind, which have been theoretically predicted. And if a CME (solar explosion) happens or a comet passes through the sun's atmosphere while we are so nearby, it could be spectacular."
Howard is the principal investigator for WISPR, the probe's wide-field camera system. WISPR can actually see the solar wind, allowing it to image clouds and shock waves as they approach and pass the spacecraft. Other sensors on the spacecraft will sample the structures that WISPR sees, making measurements of particles and fields that researchers can use to test competing theories.
"We lose communication with the spacecraft during the perihelion period which begins next week," notes Howard. "This is because there isn't sufficient power to drive both the instruments and the transmitter. The first dump of data will occur in early December." Stay tuned for that.
Parker will plunge toward the sun 24 more times in the next 8 years, breaking many records en route. Here's the timeline.
On Oct. 26th, Venus will pass almost directly between Earth and the sun--an event astronomers call "inferior solar conjunction." As Venus approaches the sun, the planet is turning its night side toward Earth, reducing its luminous glow to a thin sliver. Shahrin Ahmad of Kuala Lumpur, Malaysia, took this picture on Oct. 20th:
"I took this picture in broad daylight," says Ahmad. "Venus was really big in the eyepiece of my telescope--almost a full arcminute in diameter. And the crescent shape easily visible in the 8x50 finder scope."
In the days ahead, the crescent of Venus will become increasingly thin and circular. The horns of the crescent might actually touch when the Venus-sun angle is least (~6 degrees) on Oct. 26th. This is arguably the most beautiful time to observe Venus, but also the most perilous. The glare of the nearby sun magnified by a telescope can damage the eyes of anyone looking through the eyepiece.
Anthony J. Cook of the Griffith Observatory has some advice for observers: "I have observed Venus at conjunction, but only from within the shadow of a building, or by adding a mask to the front end of the telescope to fully shadow the optics from direct sunlight. This is tricky with a refractor or a catadioptric, because the optics start at the front end of the tube. Here at Griffith Observatory, I rotate the telescope dome to make sure the lens of the telescope is shaded from direct sunlight, even through it means that the lens will be partially blocked when aimed at Venus. With our Newtonian telescope, I add a curved cardboard mask at the front end of the tube to shadow the primary mirror."
For the rest of this week Venus can still be observed without elaborate precautions in deep twilight after sunset. Every evening the crescent grows and narrows. Scan the realtime photo gallery for updates.
The sun is entering a deep Solar Minimum, and Earth's upper atmosphere is responding. Data from NASA's TIMED satellite show that the thermosphere (the uppermost layer of air around our planet) is cooling and shrinking, literally decreasing the radius of the atmosphere. If current trends continue, the thermosphere could set a Space Age record for cold in the months ahead: Full story.
The northern autumnal equinox is only a week away (23 September). That means one thing: Cracks are opening in Earth's magnetic field. Researchers have long known that during weeks around equinoxes, fissures form in Earth's magnetosphere. Solar wind pours through the gaps to fuel bright displays of Northern Lights. It happened just last night in Rovaniemi, Finland:
"The auroras were totally awesome," says photographer Alexander Kuznetsov. "We weren't expecting a huge storm, yet this was the best display of the new season."
This is called the "Russell-McPherron effect," named after the researchers who first explained it. The cracks are opened by the solar wind itself. South-pointing magnetic fields inside the solar wind oppose Earth's north-pointing magnetic field. North and South partially cancel one another, opening a crack. This cancellation can happen at any time of year, but it happens with greatest effect around the equinoxes. Indeed, a 75-year study shows that September is one of the most geomagnetically active months of the year–a direct result of "equinox cracks."
NASA and European spacecraft have been detecting these cracks for years. Small ones are about the size of California, and many are wider than the entire planet. There's no danger to people on Earth. Our planet's atmosphere intercepts the rush of incoming particles with no harm done and a beautiful afterglow. Stay tuned for more Arctic lights as autumn approaches.
The Moon is about to take a bite out of the sun. On Saturday, August 11th, there will be a partial solar eclipse visible from locations around the Arctic Circle and across much of Asia. During the 3+ hour event, as much as 73% of the solar disk will be covered. Selected cities in the eclipse zone include Moscow (2.1% coverage), Oslo (4.8%), Raykjavik (20%), Tromso (29%), and Seoul (35%). www.spaceweather.com
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