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CHANCE OF STORMS THIS WEEK: NOAA forecasters estimate a 35% chance of polar geomagnetic storms on Oct. 25-26 when Earth enters a stream of high-speed solar wind flowing from a coronal hole on the sun. Analysts say storm levels could reach category G2, which means bright auroras are likely around the Arctic Circle. The glow might even be visible from northern-tier US states such as Minnesota and Michigan. Free: Aurora Alerts.
This image from NASA's Solar Dynamics Observatory shows the outlines of the coronal hole on Oct. 24th:
Coronal holes are, essentially, gaps the sun's atmosphere where the magnetic field opens up and allows solar wind to escape. They typically appear once or twice a month. This coronal hole is, however, larger than usual, and the emerging stream of solar wind is broad. Earth could be inside it for 3 days or more. Stay tuned for updates as the solar wind approaches.
AURORAS AND COMET DUST: On October 23rd, Nina Rajani witnessed a display of bright auroras over Tromso, Norway ... and it was sprinkled with comet dust.
"What started out as a quiet night of aurora watching with three friends on a Tromso beach very quickly developed into a spectacular display of intense and vibrant auroras," says Rajani. "They danced above and ahead in every direction as far as the eye could see. And then some late-arriving Orionid meteors blazed across the sky trying to steal the show. It was a case of not knowing where to look and we were completely awestruck! I was very fortunate to capture this magical moment."
Realtime Aurora Photo Gallery
SINUSOIDAL GROUND CURRENTS IN NORWAY: Not all space weather occurs high overhead. Sometimes it happens in the soil beneath our feet. Example: On Oct. 23rd in the Lofoten Islands of Norway, electrical currents began to flow through the ground, back and forth with a sinusoidal period of 74 seconds. Rob Stammes recorded the phenomenon at his geomagnetic observatory:
"Just after midnight UTC and around 02.36 local time, my ground current instruments picked up these very stable pulsations," says Stammes.
What's happening here? Ground currents are a sign of changing magnetic fields. Earth's magnetic field around the Lofoten Islands was swinging back and forth, inducing a sinusoidal amperage in the soil beneath Stamme's observatory.
These are natural ultra-low frequency oscillations known to researchers as "pulsations continuous" (Pc). The physics is familiar to anyone who has studied bells or resonant cavities. Earth's magnetic field extends out into space and carves out a cavity in the surrounding solar wind. Pressure fluctuations in the solar wind can excite wave modes in the cavity--usually in a noisy cacophany of many frequencies, but sometimes with almost-monochromatic purity. In such cases, Earth's magnetic field "rings like a bell" with slow tones that reach all the way down to the ground. That's what happened on Oct. 23rd. References: #1, #2, #3.
Realtime Space Weather Photo Gallery
Realtime Airglow Photo Gallery
Realtime Sprite Photo Gallery
| ||Cosmic Rays in the Atmosphere |
Updated: Sept. 29 2016 // Next Flight: Oct. 1, 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 Oct. 24, 2016, the network reported 30 fireballs.
(18 sporadics, 11 Orionids, 1 Leonis Minorid)
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 October 24, 2016 there were 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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