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INCOMING SOLAR WIND STREAM: A stream of solar wind is approaching Earth and it could graze our planet's magnetic field on April 26th or 27th. The gaseous material is flowing from a northern hole in the sun's atmosphere. The stream won't hit our planet head on, but sometimes grazing impacts produce interesting effects--for instance, making Earth's magnetosphere ring like a bell. Free: Aurora Alerts
NORTH KOREA AND AVIATION RADIATION: For the past 4 years, Spaceweather.com and Earth to Sky Calculus have been flying radiation sensors onboard airplanes to map the distribution of cosmic rays around our planet. Our database currently contains more than 17,000 GPS-tagged radiation measurements spanning 5 continents and 43,000 feet of altitude. Yesterday, we realized we could use this database to investigate a current event--namely, the possibility of a radiation leak from North Korea.
Above: Earth to Sky Calculus X-ray/gamma radiation sensors onboard a plane flying near N. Korea.
North Korea recently surprised observers by announcing a suspension of its underground nuclear testing program. Geologists in China quickly offered an explanation: Mount Mantap, which sits atop of the test site, had collapsed. The mountain crumbled in Sept. 2017 minutes after the North Korean regime exploded a 100 kiloton prototype weapon. According to the South China Morning Post, the China Earthquake Administration believes the collapse may have created a "chimney" that allows the escape of radioactive materials.
Is there any sign of radioactivity in the air space around North Korea? Our database contains four flights near the Korean Peninsula--two in March 2016 (before the collapse), and two more in Feb. 2018 (after the collapse). These are shown in the map, below, where orange circles of 350 miles and 700 miles radius are centered on nuclear test site. During each flight we sampled X-rays and gamma-rays in the energy range 10 keV to 20 MeV at one minute intervals, accumulating more than 600 data points. Low energy X-rays have been used in the past to trace radioactive fallout from atomic tests, so our measurements may have some bearing on the question.
Above: In this map, red dots show where we have collected radiation data in airspace near N. Korea.
And the answer is .... no. We found no significant difference in radiation levels before and after the mountain's collapse. For instance, radiation dose rates in March 2016 at 31,500 feet were 0.9 uGy/hr (18 times the natural rate at sea level). Radiation dose rates in February 2018 at the same altitude were 1.0 uGy/hr (20 times sea level), a slight increase within the uncertainty of our measurements. If radiation is indeed leaking from the collapsed mountain site, we could not find it in our flights over neighboring countries.
FAR-OUT MOTHER'S DAY GIFT: Mother's Day is less than 3 weeks away. To get ready, the students of Earth to Sky Calculus launched an array of cosmic ray sensors to the stratosphere onboard a helium balloon. This Mother's Day pendant went along for the ride:
You can have it for $99.95. The students are selling these pendants as a fund-raiser for their cosmic ray monitoring program--and they make great Mother's Day gifts. All proceeds support atmospheric radiation measurements and hands-on STEM education.
Each pendant comes with a greeting card showing the jewelry in flight and telling the story of its journey to the stratosphere and back again. Mom-satisfaction guaranteed.
Far Out Gifts: Earth to Sky Store
All proceeds support hands-on STEM education
WHAT LIES INSIDE A RAINBOW: The next time you see a rainbow, look carefully at the colors. There's red on the outside, followed by orange, yellow, green and, finally, on the inside, blue. That's how a rainbow stops--on blue. Except this rainbow, photographed on April 25th by Honor Wheeler of Kent, UK, kept going. Blue, green, blue, green, blue, green:
"Crazy weather in Kent produced these rainbows," says Wheeler. "The colors were gorgeous."
Atmospheric optics expert Les Cowley explains: "The extra bows just inside the primary rainbow are called supernumeraries. They were so named because 17th century theories of the rainbow could not explain them -- they were thought of as extras and not supposed to exist. Now we know supernumeraries are produced by the interference between light waves when raindrops are unusually small."
Realtime Space Weather Photo Gallery
Realtime Aurora Photo Gallery
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 Apr. 26, 2018, the network reported 7 fireballs.
(7 sporadics)
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 April 26, 2018 there were 1907 potentially hazardous asteroids.
|
Recent & Upcoming Earth-asteroid encounters: Asteroid | Date(UT) | Miss Distance | Velocity (km/s) | Diameter (m) |
2018 HT | 2018-Apr-21 | 7.1 LD | 7.6 | 15 |
2018 HL1 | 2018-Apr-21 | 4.7 LD | 14.4 | 57 |
2018 GR1 | 2018-Apr-21 | 18.3 LD | 16.4 | 52 |
2018 HN | 2018-Apr-21 | 8 LD | 9.8 | 37 |
2018 HW1 | 2018-Apr-21 | 0.9 LD | 5 | 23 |
2018 HX1 | 2018-Apr-22 | 2.7 LD | 25 | 45 |
2018 HV | 2018-Apr-22 | 0.4 LD | 16 | 6 |
2018 GG4 | 2018-Apr-23 | 9.7 LD | 14.9 | 20 |
2018 HY1 | 2018-Apr-23 | 9.5 LD | 7.6 | 31 |
2012 XL16 | 2018-Apr-23 | 15.8 LD | 6.1 | 28 |
2018 GH | 2018-Apr-25 | 14.6 LD | 10.7 | 89 |
2018 HP | 2018-Apr-26 | 11.6 LD | 10.3 | 20 |
2018 GH5 | 2018-Apr-27 | 12.2 LD | 12.7 | 32 |
2018 GB2 | 2018-Apr-27 | 17.1 LD | 14.6 | 92 |
2013 US3 | 2018-Apr-29 | 10.1 LD | 7.7 | 214 |
2018 GO4 | 2018-Apr-29 | 11.8 LD | 8.6 | 40 |
2018 GY1 | 2018-Apr-29 | 13.2 LD | 16.7 | 139 |
2018 FV4 | 2018-Apr-29 | 17.7 LD | 6.5 | 59 |
2002 JR100 | 2018-Apr-29 | 10.8 LD | 7.7 | 49 |
2018 HF2 | 2018-Apr-30 | 18.6 LD | 6.8 | 20 |
2018 HB1 | 2018-May-02 | 10.1 LD | 9.2 | 39 |
2018 HR1 | 2018-May-04 | 17.3 LD | 16.3 | 48 |
1999 FN19 | 2018-May-07 | 9.7 LD | 5.7 | 118 |
2016 JQ5 | 2018-May-08 | 6.3 LD | 10.4 | 9 |
388945 | 2018-May-09 | 6.5 LD | 9 | 295 |
2018 GR2 | 2018-May-11 | 13.4 LD | 9.8 | 109 |
1999 LK1 | 2018-May-15 | 13.3 LD | 10 | 141 |
2018 GL1 | 2018-May-18 | 14.3 LD | 5.2 | 66 |
68347 | 2018-May-29 | 9.5 LD | 13.3 | 389 |
2013 LE7 | 2018-May-31 | 17.8 LD | 1.7 | 12 |
2018 EJ4 | 2018-Jun-10 | 5.6 LD | 6.2 | 195 |
2015 DP155 | 2018-Jun-11 | 9 LD | 4.4 | 170 |
2017 YE5 | 2018-Jun-21 | 15.6 LD | 15.5 | 513 |
467309 | 2018-Jun-23 | 17.9 LD | 14 | 355 |
441987 | 2018-Jun-24 | 7.3 LD | 12.6 | 178 |
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. | Cosmic Rays in the Atmosphere |
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 13% 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.
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