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AURORAS LOVE EQUINOXES: At this time of year, even a gentle gust of solar wind can spark auroras. NOAA forecasters say that such a gust is coming on Sept. 25th when a stream of solar wind flowing from a coronal hole is expected to reach Earth. High-latitude sky watchers should be alert for Northern Lights. Free: Space Weather Alerts
A BEAUTIFUL COINCIDENCE: What are the odds? Catching a lunar rainbow beneath a ribbon of green auroras is rare. Yet it happened twice this week in Iceland. Here is the first time. And here is the second:
"Big rain clouds had been rolling over the whole day with good gaps in between," says photographer Sigurdur William Brynjarsson, who took the picture on Sept. 20th from Reykjanes, Iceland. "The Moon was almost full and aurora activity was picking up. I knew conditions were perfect to capture a lunar rainbow with the Northern Lights together."
"I've never witnessed a lunar rainbow and lady Aurora dancing hand in hand before," he adds. "What a night... =) "
Now that autumn has arrived, rainclouds are mixing with auroras around the Arctic Circle on a regular basis. Those raindrops will turn into snowflakes as winter approaches. Until then, keep an eye on the photo gallery for more moonbows in the Arctic night.
Realtime Aurora Photo Gallery
WATCH OUT FOR THE EVENING STAR: Sky watchers, keep an eye on the sunset. Venus is emerging from the glare of the sun, climbing higher in the evening sky as September comes to an end. Frank A. Rodriguez sends this picture from Gran Canaria in the Canary Islands:
"I caught Venus shining next to Roque Nublo, an enormous basalt monolith of 80 meters located in the center of the island," says Rodriguez. "In the distance we can see the Teide volcano on the island of Tenerife, about 106 km away. It is the highest point in Spain."
Graphic artist Larry Koehn has created an excellent animation showing how Venus will become even more visible in the weeks and months ahead. A date of special interest is Oct. 3rd when Venus poses next to the slender crescent Moon: sky map. Mark your calendar and enjoy the show.
Realtime Space Weather Photo Gallery
NEW! RADS ON A PLANE: Spaceweather.com is now reporting data you won't find anywhere else: Regular measurements of cosmic rays at aviation altitudes. Approximately once a week, we launch high-altitude balloons equipped with X-ray/gamma-ray sensors. En route to the stratosphere over California the payload passes through aviation altitudes. Here are 18 months' worth of data at 25,000 ft and 40,000 ft:
In this plot, dose rates are expressed as multiples of sea level. For instance, we see that boarding a plane that flies at 25,000 feet exposes passengers to dose rates ~10x higher than sea level. At 40,000 feet, the multiplier is closer to 50x.
Cosmic rays and solar activity have a yin-yang relationship. When the sun grows quiet (as it has been doing), cosmic rays increase. We have already observed this effect in the stratosphere, where radiation levels have increased by more than 12% since 2015. Will these increases eventually trickle down to aviation altitudes? Our monitoring program will answer that question as the solar cycle continues to ebb.
To view the latest data, scroll down from here to the section entitled "Cosmic Rays in the Atmosphere."
Realtime Sprite Photo Gallery
| ||Cosmic Rays in the Atmosphere |
Updated: Sept. 20, 2016 // Next Flight: Sept. 27, 2016
Sept. 20, 2016: Readers, thank you for your patience while we continue to develop this new section of Spaceweather.com. We've been working to streamline our data reduction, allowing us to post results from balloon flights much more rapidly, and we have developed a new data product, shown here:
This plot displays radiation measurements not only in the stratosphere, but also at aviation altitudes. Dose rates are expessed as multiples of sea level. For instance, we see that boarding a plane that flies at 25,000 feet exposes passengers to dose rates ~10x higher than sea level. At 40,000 feet, the multiplier is closer to 50x. These measurements are made by our usual cosmic ray payload as it passes through aviation altitudes en route to the stratosphere over California.
What is this all about? Approximately once a week, Spaceweather.com and the students of Earth to Sky Calculus fly space weather balloons to the stratosphere over California. These balloons are equipped with radiation sensors that detect cosmic rays, a surprisingly "down to Earth" form of space weather. Cosmic rays can seed clouds, trigger lightning, and penetrate commercial airplanes. Furthermore, there are studies ( #1, #2, #3, #4) linking cosmic rays with cardiac arrhythmias and sudden cardiac death in the general population. Our latest measurements show that cosmic rays are intensifying, with an increase of more than 12% since 2015:
Why are cosmic rays intensifying? The main reason is the sun. Solar storm clouds such as coronal mass ejections (CMEs) sweep aside cosmic rays when they pass by Earth. During Solar Maximum, CMEs are abundant and cosmic rays are held at bay. Now, however, the solar cycle is swinging toward Solar Minimum, allowing cosmic rays to return. Another reason could be the weakening of Earth's magnetic field, which helps protect us from deep-space radiation.
The radiation sensors onboard our helium balloons detect X-rays and gamma-rays in the energy range 10 keV to 20 MeV. These energies span the range of medical X-ray machines and airport security scanners.
The data points in the graph above correspond to the peak of the Reneger-Pfotzer maximum, which lies about 67,000 feet above central California. When cosmic rays crash into Earth's atmosphere, they produce a spray of secondary particles that is most intense at the entrance to the stratosphere. Physicists Eric Reneger and Georg Pfotzer discovered the maximum using balloons in the 1930s and it is what we are measuring today.
Every night, a network of NASA all-sky cameras
scans the skies above the United States for meteoritic fireballs. Automated software maintained by NASA's Meteoroid Environment Office calculates their orbits, velocity, penetration depth in Earth's atmosphere and many other characteristics. Daily results are presented here on Spaceweather.com.
On Sep. 23, 2016, the network reported 16 fireballs.
In this diagram of the inner solar system, all of the fireball orbits intersect at a single point--Earth. The orbits are color-coded by velocity, from slow (red) to fast (blue). [Larger image] [movies]
Potentially Hazardous Asteroids (PHAs
) are space rocks larger than approximately 100m that can come closer to Earth than 0.05 AU. None of the known PHAs is on a collision course with our planet, although astronomers are finding new ones
all the time.
On September 23, 2016 there were 1730 potentially hazardous asteroids. Notes: LD means "Lunar Distance." 1 LD = 384,401 km, the distance between Earth and the Moon. 1 LD also equals 0.00256 AU. MAG is the visual magnitude of the asteroid on the date of closest approach.
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