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TWO WEEKS WITHOUT SUNSPOTS: The sun has been without spots for 14 straight days. To find a similar stretch of blank suns, you have to go all the way back to April of 2010 when the sun was emerging from the deepest solar minimum in a century. However, two weeks without sunspots is not a long time. At the nadir of that century-class solar minimum in 2008, the sun was blank for 52 consecutive days. Conclusion: Solar minimum is just beginning and we have a long way to go. Free: Aurora alerts.
FRIDAY THE 13TH SOLAR ECLIPSE: If you live in Tasmania, this Friday the 13th is your lucky day. The new Moon will pass in front of the sun, off center, taking a bite out of the solar disk. This video created by graphic artist Larry Koehn of ShadowandSubstance.com shows the circumstances of the partial eclipse:
The eclipse will be visible in a region stretching from the southernmost edge of Australia (2% coverage) to the northern coast of Antarctica (33% coverage). As the Moon's shadow crosses few inhabited areas, Hobart, Tasmania, arguably has the best combinaion of population (200,000) + coverage (10%). It will be interesting to see if we receive any photos of this remote event. Stay tuned!
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COSMIC RAYS IN AIRPLANES: Last month, flight attendants got some bad news. According to a new study from researchers at Harvard University, the crews of commercial airlines face an elevated risk of cancer compared to members of the general population. A likely reason: cosmic rays. High energy particles from space hitting the top of Earth's atmosphere create a spray of secondary radiation that penetrates the walls of airplanes flying above ~20,000 feet.
On June 19th, Spaceweather.com and students of Earth to Sky Calculus flew from California to New Zealand to launch a series of space weather balloons--part of our ongoing program to map cosmic rays around the globe. Naturally, we took our radiation sensors onboard the airplane. Here is what we measured:
Within minutes after takeoff from Los Angeles, radiation in the passenger compartment increased 25-fold and remained high until we landed again in Brisbane, Australia, 13 hours later. Peak dose rates were almost 40 times greater than on the ground below. In total, we absorbed a whole body dose approximately equal to a panoramic dental X-ray.
Our sensors measure three types of radiation: neutrons, X-rays and gamma-rays. Using bubble chambers, we found that about 1/3rd of our exposure came from neutrons:
Each bubble pictured above is formed by an energetic neutron (200 keV – 15 MeV) passing through the chamber. Counting bubbles yields the total dose, about 8 uGy (micro-Gray) of neutrons during the entire flight. These measurements are important because neutrons are a biologically effective form of radiation of interest to cancer researchers.
The remaining 2/3rd of our exposure came from X-rays and gamma-rays, measured using Geiger tube devices:
These are the same sensors that we have been flying to the stratosphere on space weather balloons since 2015.
Adding it all together, we detected about 24.3 uGy of neutrons + X-rays + gamma rays during the Los Angeles to Brisbane leg of our flight. For comparison, a panoramic dental X-ray yields between 14 uGy and 24 uGy.
This is just the tip of the iceberg. Cosmic rays at aviation altitudes are a cocktail of different things: e.g., neutrons, protons, pions, electrons, X-rays, and gamma rays spanning a wide range of energies. Our sensors sample only three ingredients of that cocktail (neutrons, X-rays, gamma-rays) at relatively low energies typical of medical X-rays and airport security devices. This means flight crews and passengers absorb even more radiation than we can detect. It's something to think about the next time you board a plane...
Stay tuned for updates as we continue to process our haul of data from 5 airplane flights and 3 balloon flights over New Zealand.
Reference: Tobiska, W. K., et al. (2015), Advances in Atmospheric Radiation Measurements and Modeling Needed to Improve Air Safety, Space Weather , 13 , doi:10.1002/ 2015SW001169.
Realtime Space Weather Photo Gallery
ONE RING TO RULE THE STRATOSPHERE: Two weeks ago, the students of Earth to Sky Calculus traveled to New Zealand for a launch of space weather balloons over Earth's 8th continent. To help fund their trip, they sent this ring of power to the stratosphere:
You can have it for $129.95. On the southern winter solstice, June 21st, the ring flew 109,580 feet above New Zealand's north island, passing almost directly above Hobbiton, the movie set for the Lord of the Rings. The band is made of golden-colored tungsten and inscribed with the authentic Mordor script of the One Ring. Along with the ring, you'll receive a greeting card showing the item in flight and telling the story of its journey to the edge of space.
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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 Jul. 11, 2018, the network reported 13 fireballs.
(12 sporadics, 1 Northern June Aquilid)
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 July 11, 2018 there were 1912 potentially hazardous asteroids.
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Recent & Upcoming Earth-asteroid encounters: Asteroid | Date(UT) | Miss Distance | Velocity (km/s) | Diameter (m) |
2018 NU | 2018-Jul-06 | 2.4 LD | 9.8 | 26 |
2018 NJ | 2018-Jul-07 | 2.4 LD | 6 | 9 |
2018 NV | 2018-Jul-07 | 10 LD | 6.6 | 93 |
2018 NX | 2018-Jul-07 | 0.3 LD | 4.1 | 10 |
2018 NW | 2018-Jul-08 | 0.3 LD | 21.3 | 10 |
2018 NF1 | 2018-Jul-12 | 18.1 LD | 10.8 | 38 |
2018 NM | 2018-Jul-17 | 1.4 LD | 6.7 | 19 |
2018 NQ1 | 2018-Jul-19 | 16.4 LD | 6 | 32 |
2018 NE1 | 2018-Jul-21 | 10.1 LD | 14.2 | 83 |
2018 NR1 | 2018-Jul-27 | 17.1 LD | 5.1 | 38 |
2018 LQ2 | 2018-Aug-27 | 9.4 LD | 1.5 | 39 |
2016 GK135 | 2018-Aug-28 | 16.8 LD | 2.8 | 9 |
2016 NF23 | 2018-Aug-29 | 13.3 LD | 9 | 93 |
1998 SD9 | 2018-Aug-29 | 4.2 LD | 10.7 | 51 |
2018 DE1 | 2018-Aug-30 | 15.2 LD | 6.5 | 28 |
2001 RQ17 | 2018-Sep-02 | 19.3 LD | 8.3 | 107 |
2015 FP118 | 2018-Sep-03 | 12.3 LD | 9.8 | 490 |
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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