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SOLAR SECTOR BOUNDARY CROSSING: High-latitude auroras are possible on April 25th when Earth crosses through a fold in the heliospheric current sheet. This is called a "solar sector boundary crossing," and NOAA forecasters estimate a 30% chance of polar geomagnetic storms when it occurs. Aurora alerts: text, voice.
VOLCANIC BULLS-EYE: When Chile's Calbuco volcano erupted on April 22nd, plumes of ash and volcanic gas shot more than 50,000 ft above Earth's surface. Orbiting overhead in the darkness of space, the NOAA/NASA Suomi NPP satellite observed the ripple effect of the blast. Night had fallen over the volcano during the early hours of April 23rd when a low-light camera on the satellite photographed a "bulls-eye" pattern of waves centered on the rising plume:
Ripples like these have been observed before, high above powerful thunderstorms. They are called "gravity waves"--essentially, waves of pressure and temperature excited by the upward motion of air. (Gravity does not vary inside the waves; the waves get their name from the fact that gravity acts as a vertical restoring force that tries to restore equilibrium to up-and-down moving air.)
The waves are visible because they glow. Readers of spaceweather.com have seen the phenomenon before--it's called "airglow." Airglow is caused by an assortment of chemical reactions in the upper atmosphere driven mainly by solar ultraviolet radiation. Gravity waves rippling away from the central axis of a thunderstorm or, in this case, a volcano, cause temperature and density perturbations in the upper atmosphere. Those perturbations alter the chemical reaction rates of airglow, leading to more-bright or less-bright bands depending on whether the rates are boosted or diminished, respectively.
Airglow occurs about 100 km above Earth's surface alongside meteors, noctilucent clouds and even some auroras. This makes airglow--and the bullseye above Calbuco--a true space weather phenomenon.
Realtime Space Weather Photo Gallery
MAGNETIC FILAMENT: For the 4th day in a row, amateur astronomers around the world are monitoring a filament of magnetism snaking over the sun's northeastern limb. This morning, Bill Hrudey photographed the structure from his observatory in the Cayman Islands:
Filled with hot-glowing plasma, the magnetic filament is more than 5 times taller than Earth and 25 times as long. These dimensions make it an easy target for backyard optics. "I used a Lunt solar telescope to take this picture," says Hrudey.
Bushy solar filaments like this one often become unstable and erupt. Debris falling to the sun's surface can produce secondary explosions called Hyder flares--a type of flare that happens without an underlying sunspot. Monitoring is encouraged.
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SPACE YEAST MAKES SPACE BREAD: Thought experiment: Suppose you flew a packet of baker's yeast high above Earth's surface, to the edge of space itself, and exposed the microbes to a blast of cosmic rays. Then you made some bread. How would it taste? "Delicious," reports Eileen Weingram of Highland Lakes, New Jersey, who actually did the experiment:
On March 17th, during the strongest geomagnetic storm of the current solar cycle, the students of Earth to Sky Calculus flew a Space Weather Buoy to the stratosphere. Along with radiation detectors and other sensors, the payload carried packets of brewer's and baker's yeast. En route to the stratosphere, the microbes experienced temperatures as low as -63 C and cosmic ray doses 40x Earth-normal.
To support the students' research, Eileen Weingram bought a packet of the baker's yeast. "It made a huge loaf of bread," she says. "Very yummy."
If this story whets your appetite, you can bake some "space bread" of your own. Packets of yeast are still available for only $49.95. Contact Dr. Tony Phillips to place your order--and let the baking begin! All sales support high altitude balloon flights to measure the effect of solar storms on Earth's atmosphere.
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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 Apr. 25, 2015, the network reported 9 fireballs.
(7 sporadics, 2 April Lyrids)
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 25, 2015 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.
| ||The official U.S. government space weather bureau |
| ||The first place to look for information about sundogs, pillars, rainbows and related phenomena. |
| ||Researchers call it a "Hubble for the sun." SDO is the most advanced solar observatory ever. |
| ||3D views of the sun from NASA's Solar and Terrestrial Relations Observatory |
| ||Realtime and archival images of the Sun from SOHO. |
| ||from the NOAA Space Environment Center |
| ||the underlying science of space weather |