Spotless Days Current Stretch: 0 days 2018 total: 80 days (52%) 2017 total: 104 days (28%) 2016 total: 32 days (9%) 2015 total: 0 days (0%) 2014 total: 1 day (<1%) 2013 total: 0 days (0%) 2012 total: 0 days (0%) 2011 total: 2 days (<1%) 2010 total: 51 days (14%) 2009 total: 260 days (71%) Updated 04 Jun 2018
Geomagnetic Storms: Probabilities for significant disturbances in Earth's magnetic field are given for three activity levels: active, minor storm, severe storm
Updated at: 2018 Jun 04 2200 UTC
Monday, Jun. 4, 2018
What's up in space
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EXITING THE SOLAR WIND STREAM: Earth is exiting a stream of solar wind that sparked G1-class geomagnetic storms and apparitions of STEVE during the weekend. NOAA forecasters have reduced the chance of additional storms on June 4th to 25% as the solar wind speed subsides. Free:Aurora Alerts.
SMALL ASTEROID HITS EARTH: On Saturday, June 2nd, astronomers working with the Catalina Sky Survey in Arizona discovered a small asteroid (2018 LA) near the orbit of the Moon. Hours later, it hit Earth. The boulder-sized space rock entered the atmosphere traveling 38,000 mph (17 km/s) and exploded over Botswana at 6:44 p.m. local time. A video camera at a farm near Ottosda, South Africa, recorded the explosion. It was impressively bright even at a distance:
The explosion sent waves of low-frequency sound (infrasound) rippling through the atmosphere, and it was detected by an infrasound monitor in South Africa, deployed as part of the International Monitoring System of the Comprehensive Nuclear-Test-Ban Treaty. Meteor expert Peter Brown of the University of Western Ontario analyzed the signals and came to these conclusions about the explosion:
"The yield was in the range 0.3 to 0.5 kilotons of TNT," he says. "That corresponds to a 2 meter diameter asteroid."
As asteroids go, that's very small. It posed no significant danger to objects on the ground as it disintegrated almost wholly in the atmosphere. Fragments may yet be found on the ground and recovered for sale or scientific study.
The real significance of this event is that it highlights the growing capability of modern sky surveys to discover asteroids targeting Earth. Even small faint space rocks are being caught in the net. Boulder-sized impactors have been discovered hurtling toward Earth three times in the past 10 years: 2008 TC3 exploded over northern Sudan on Oct. 7, 2008; 2014 AA burned up above the Atlantic Ocean on Jan. 1, 2014; and now 2018 LA. In each case, the warning was less than a day. Larger asteroids may be seen at a greater distance, however, allowing for more lead time. Learn more about the latest impact from NASA.
A CRYSTAL BALL IN THE STRATOSPHERE: Father's Day is less than two weeks away. To get ready, the students of Earth to Sky Calculus launched a crystal ball to the stratosphere. Watch the video as the crystal orb travels onboard a giant helium balloon 93,000 feet above Earth's surface, stretching, focusing, and inverting the incredible landscape of the Sierra Nevada mountains behind it:
The students are selling these crystal balls as a fundraiser, and you can have one for $229. The 800 gram sphere contains an embedded model of the Solar System, including the sun, eight planets and their moons. It makes an incredible gift for anyone interested in space. Dad-satisfaction guaranteed.
Each crystal ball comes with a unique gift card showing the item at the edge of space and telling the story of its flight. All proceeds support Earth to Sky Calculus and hands-on STEM research.
NOCTILUCENT CLOUDS INTENSIFY OVER EUROPE: NASA's AIM spacecraft is seeing electric-blue noctilucent clouds (NLCs) spread across the Arctic Circle. Observers on the ground are beginning to see them, too. Over the weekend we received reports of sightings from England, Scotland, Norway, Northern Ireland--and this incredible shot from Denmark:
"The noctilucent clouds were intense over Northern Jutland on June 3rd," says photographer Ruslan Merzlyakov. "I was totally amazed, how bright they were compared to their first appearance just 3 days earlier."
What are NLCs? You can think of them as frosted meteoroids. Noctilucent clouds form when summertime wisps of water vapor waft up to the top of Earth's atmosphere and crystallize around specks of meteor smoke. The resulting swarms of tiny ice crystals glow electric blue when struck by high altitude sunlight.
These displays should increase in the nights ahead. Previous data from AIM have shown that NLCs are like a great "geophysical light bulb." They turn on every year in late spring, reaching almost full intensity over a period of 5 to 10 days. Soon the ripples people are seeing in Northern Europe should intensify and spread, forming electric-blue waves that glow deep into the night.
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 Jun. 4, 2018, the network reported 12 fireballs. (11 sporadics, 1 Daytime Arietid)
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]
Near Earth Asteroids
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 June 4, 2018 there were 1912 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.
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.