Sometimes I complain about the earthly weather, but mostly I like to post about astronomy and space events. Hope you enjoy the articles.
By: Susie77, 5:16 PM GMT on September 30, 2009
Cosmic Rays Hit Space Age High
September 29, 2009: Planning a trip to Mars? Take plenty of shielding. According to sensors on NASA's ACE (Advanced Composition Explorer) spacecraft, galactic cosmic rays have just hit a Space Age high.
"In 2009, cosmic ray intensities have increased 19% beyond anything we've seen in the past 50 years," says Richard Mewaldt of Caltech. "The increase is significant, and it could mean we need to re-think how much radiation shielding astronauts take with them on deep-space missions."
The cause of the surge is solar minimum, a deep lull in solar activity that began around 2007 and continues today. Researchers have long known that cosmic rays go up when solar activity goes down. Right now solar activity is as weak as it has been in modern times, setting the stage for what Mewaldt calls "a perfect storm of cosmic rays."
"We're experiencing the deepest solar minimum in nearly a century," says Dean Pesnell of the Goddard Space Flight Center, "so it is no surprise that cosmic rays are at record levels for the Space Age."
Galactic cosmic rays come from outside the solar system. They are subatomic particles--mainly protons but also some heavy nuclei--accelerated to almost light speed by distant supernova explosions. Cosmic rays cause "air showers" of secondary particles when they hit Earth's atmosphere; they pose a health hazard to astronauts; and a single cosmic ray can disable a satellite if it hits an unlucky integrated circuit.
The sun's magnetic field is our first line of defense against these highly-charged, energetic particles. The entire solar system from Mercury to Pluto and beyond is surrounded by a bubble of magnetism called "the heliosphere." It springs from the sun's inner magnetic dynamo and is inflated to gargantuan proportions by the solar wind. When a cosmic ray tries to enter the solar system, it must fight through the heliosphere's outer layers; and if it makes it inside, there is a thicket of magnetic fields waiting to scatter and deflect the intruder.
"At times of low solar activity, this natural shielding is weakened, and more cosmic rays are able to reach the inner solar system," explains Pesnell.
Mewaldt lists three aspects of the current solar minimum that are combining to create the perfect storm:
1. The sun's magnetic field is weak. "There has been a sharp decline in the sun's interplanetary magnetic field down to 4 nT (nanoTesla) from typical values of 6 to 8 nT," he says. "This record-low interplanetary magnetic field undoubtedly contributes to the record-high cosmic ray fluxes." [data]
2. The solar wind is flagging. "Measurements by the Ulysses spacecraft show that solar wind pressure is at a 50-year low," he continues, "so the magnetic bubble that protects the solar system is not being inflated as much as usual." A smaller bubble gives cosmic rays a shorter-shot into the solar system. Once a cosmic ray enters the solar system, it must "swim upstream" against the solar wind. Solar wind speeds have dropped to very low levels in 2008 and 2009, making it easier than usual for a cosmic ray to proceed. [data]
3. The current sheet is flattening. Imagine the sun wearing a ballerina's skirt as wide as the entire solar system with an electrical current flowing along its wavy folds. It's real, and it's called the "heliospheric current sheet," a vast transition zone where the polarity of the sun's magnetic field changes from plus to minus. The current sheet is important because cosmic rays are guided by its folds. Lately, the current sheet has been flattening itself out, allowing cosmic rays more direct access to the inner solar system.
"If the flattening continues, we could see cosmic ray fluxes jump all the way to 30% above previous Space Age highs," predicts Mewaldt. [data]
Earth is in no great peril. Our planet's atmosphere and magnetic field provide some defense against the extra cosmic rays. Indeed, we've experienced much worse in the past. Hundreds of years ago, cosmic ray fluxes were at least 200% to 300% higher than anything measured during the Space Age. Researchers know this because when cosmic rays hit the atmosphere, they produce an isotope of beryllium, 10Be, which is preserved in polar ice. By examining ice cores, it is possible to estimate cosmic ray fluxes more than a thousand years into the past. Even with the recent surge, cosmic rays today are much weaker than they have been at times in the past millennium. [data]
"The space era has so far experienced a time of relatively low cosmic ray activity," says Mewaldt. "We may now be returning to levels typical of past centuries."
NASA spacecraft will continue to monitor the situation as solar minimum unfolds. Stay tuned for updates.
By: Susie77, 7:24 PM GMT on September 28, 2009
What beautiful weather we are having today here in STL. Hope wherever you are, the sun is shining and the temps are delicious. :-)
By: Susie77, 12:29 AM GMT on September 25, 2009
By: Susie77, 12:44 AM GMT on September 23, 2009
Space Weather News for Sept. 22, 2009
NEW SUNSPOTS: In a year when the sun has been utterly blank 80% of the time, the sudden emergence of two large sunspots in a single day is a noteworthy event. Today is such a day. NASA satellites and amateur astronomers are monitoring a pair of growing sunspots, both apparently members of long-overdue Solar Cycle 24. The emergence of these active regions is not enough to end the deepest solar minimum in nearly a hundred years, but they do represent a significant uptick in solar activity. Check http://spaceweather.com for images and updates.
SEPT. EQUINOX: Today, Sept. 22nd at 2118 UT (5:18 pm EDT), the sun crosses the celestial equator. This event marks the beginning of autumn in the northern hemisphere and spring in the southern hemisphere. It's also the beginning of aurora season around the poles. Happy equinox!
By: Susie77, 12:35 AM GMT on September 22, 2009
CASSINI REVEALS NEW RING QUIRKS, SHADOWS DURING SATURN EQUINOX
PASADENA, Calif. -- NASA scientists are marveling over the extent of
ruffles and dust clouds revealed in the rings of Saturn during the
planet's equinox last month. Scientists once thought the rings were
almost completely flat, but new images reveal the heights of some
newly discovered bumps in the rings are as high as the Rocky
Mountains. NASA released the images Monday.
"It's like putting on 3-D glasses and seeing the third dimension for
the first time," said Bob Pappalardo, Cassini project scientist at
NASA's Jet Propulsion Laboratory in Pasadena, Calif. "This is among
the most important events Cassini has shown us."
On Aug. 11, sunlight hit Saturn's rings exactly edge-on, performing a
celestial magic trick that made them all but disappear. The spectacle
occurs twice during each orbit Saturn makes around the sun, which
takes approximately 10,759 Earth days, or about 29.7 Earth years.
Earth experiences a similar equinox phenomenon twice a year; the
autumnal equinox will occur Sept. 22, when the sun will shine
directly over Earth's equator.
For about a week, scientists used the Cassini orbiter to look at puffy
parts of Saturn's rings caught in white glare from the low-angle
lighting. Scientists have known about vertical clumps sticking out of
the rings in a handful of places, but they could not directly measure
the height and breadth of the undulations and ridges until Saturn's
equinox revealed their shadows.
"The biggest surprise was to see so many places of vertical relief
above and below the otherwise paper-thin rings," said Linda Spilker,
deputy project scientist at JPL. "To understand what we are seeing
will take more time, but the images and data will help develop a more
complete understanding of how old the rings might be and how they are
The chunks of ice that make up the main rings spread out 85,000 miles
from the center of Saturn, but they had been thought to be only
around 30 feet thick in the main rings, known as A, B, C, and D.
In the new images, particles seemed to pile up in vertical formations
in each of the rings. Rippling corrugations -- previously seen by
Cassini to extend approximately 500 miles in the innermost D ring --
appear to undulate out to a total of 11,000 miles through the
neighboring C ring to the B ring.
The heights of some of the newly discovered bumps are comparable to
the elevations of the Rocky Mountains. One ridge of icy ring
particles, whipped up by the gravitational pull of Saturn's moon
Daphnis as it travels through the plane of the rings, looms as high
as 2.5 miles. It is the tallest vertical wall seen within the rings.
"We thought the plane of the rings was no taller than two stories of a
modern-day building and instead we've come across walls more than two
miles high," said Carolyn Porco, Cassini imaging team leader at the
Space Science Institute in Boulder, Colo. "Isn't that the most
outrageous thing you could imagine? It truly is like something out of
Scientists also were intrigued by bright streaks in two different
rings that appear to be clouds of dust kicked up in collisions
between small space debris and ring particles. Understanding the rate
and locations of impacts will help build better models of
contamination and erosion in the rings and refine estimates of their
age. The collision clouds were easier to see under the low-lighting
conditions of equinox than under normal lighting conditions.
At the same time Cassini was snapping visible-light photographs of
Saturn's rings, the Composite Infrared Spectrometer instrument was
taking the rings' temperatures. During equinox, the rings cooled to
the lowest temperature ever recorded. The A ring dropped down to a
frosty 382 degrees below zero Fahrenheit. Studying ring temperatures
at equinox will help scientists better understand the sizes and other
characteristics of the ring particles.
The Cassini spacecraft has been observing Saturn, its moons and rings
since it entered the planet's orbit in 2004. The spacecraft's
instruments have discovered new rings and moons and have improved our
understanding of Saturn's ring system.
The Cassini-Huygens mission is a cooperative project of NASA and the
European and Italian Space Agencies. JPL manages the mission for the
Science Mission Directorate at NASA Headquarters in Washington. JPL
also designed, developed and assembled the Cassini orbiter and its
two onboard cameras. The imaging team is based at the Space Science
Institute. The Composite Infrared Spectrometer team is based at
NASA's Goddard Space Flight Center in Greenbelt, Md.
To view Cassini images of the equinox and for more information about
the mission, visit:
By: Susie77, 2:18 AM GMT on September 18, 2009
Hey you guys, please go check out Auburn's blog here on WU and give Zoie a prayer and a hand if you can. Thanks. Love you all.
By: Susie77, 10:55 PM GMT on September 08, 2009
Well, I tried using that WU multiple-photo-upload thingie but it sucks. So here, in no particular order, are some pix of our vacation/wedding....
Later I'll put the best of the best on some web pages sorted by date/area so that they make more sense.
By: Susie77, 4:25 AM GMT on September 02, 2009
Hey, WU friends.... we got 'er done. :) Using friend's puter up here in Fairbanks so can't access my domain to upload any photos, but did add one to my photo section here at WU.
And tonight -- the aurora!
Party on, and have one for us, would you please? :)
By: Susie77, 2:27 AM GMT on September 01, 2009
Honey, I Blew up the Tokamak
August 31, 2009: Magnetic reconnection could be the Universe's favorite way to make things explode. It operates anywhere magnetic fields pervade space--which is to say almost everywhere. On the sun magnetic reconnection causes solar flares as powerful as a billion atomic bombs. In Earth's atmosphere, it fuels magnetic storms and auroras. In laboratories, it can cause big problems in fusion reactors. It's ubiquitous.
The problem is, researchers can't explain it.
The basics are clear enough. Magnetic lines of force cross, cancel, reconnect and—Bang! Magnetic energy is unleashed in the form of heat and charged-particle kinetic energy.
But how? How does the simple act of crisscrossing magnetic field lines trigger such a ferocious explosion?
"Something very interesting and fundamental is going on that we don't really understand -- not from laboratory experiments or from simulations," says Melvyn Goldstein, chief of the Geospace Physics Laboratory at NASA's Goddard Space Flight Center.
NASA is going to launch a mission to get to the bottom of the mystery. It's called MMS, short for Magnetospheric Multiscale Mission, and it consists of four spacecraft which will fly through Earth's magnetosphere to study reconnection in action. The mission passed its preliminary design review in May 2009 and was approved for implementation in June 2009. Engineers can now start building the spacecraft.
"Earth's magnetosphere is a wonderful natural laboratory for studying reconnection," says mission scientist Jim Burch of the Southwest Research Institute. "It is big, roomy, and reconnection is taking place there almost non-stop."
In the outer layers of the magnetosphere, where Earth's magnetic field meets the solar wind, reconnection events create temporary magnetic "portals" connecting Earth to the sun. Inside the magnetosphere, in a long drawn-out structure called "the magnetotail," reconnection propels high-energy plasma clouds toward Earth, triggering Northern Lights when they hit. There are many other examples, and MMS will explore them all.
The four spacecraft will be built at the Goddard Space Flight Center. "Each observatory is shaped like a giant hockey puck, about 12 feet in diameter and 4 feet in height," says Karen Halterman, MMS Project Manager at Goddard.
The mission's sensors for monitoring electromagnetic fields and charged particles are being built at a number of universities and laboratories around the country, led by the Southwest Research Institute. When the instruments are done, they will be integrated into the spacecraft frames at Goddard. Launch is scheduled for 2014 onboard an Atlas V rocket.
Any new physics MMS learns could ultimately help alleviate the energy crisis on Earth.
"For many years, researchers have looked to fusion as a clean and abundant source of energy for our planet," says Burch. "One approach, magnetic confinement fusion, has yielded very promising results with devices such as tokamaks. But there have been problems keeping the plasma (hot ionized gas) contained in the chamber."
"One of the main problems is magnetic reconnection," he continues. "A spectacular and even dangerous result of reconnection is known as the sawtooth crash. As the heat in the tokamak builds up, the electron temperature reaches a peak and then 'crashes' to a lower value, and some of the hot plasma escapes. This is caused by reconnection of the containment field."
In light of this, you might suppose that tokamaks would be a good place to study reconnection. But no, says Burch. Reconnection in a tokamak happens in such a tiny volume, only a few millimeters wide, that it is very difficult to study. It is practically impossible to build sensors small enough to probe the reconnection zone.
Earth's magnetosphere is much better. In the expansive magnetic bubble that surrounds our planet, the process plays out over volumes as large as tens of kilometers across. "We can fly spacecraft in and around it and get a good look at what's going on," he says.
That is what MMS will do: fly directly into the reconnection zone. The spacecraft are sturdy enough to withstand the energetics of reconnection events known to occur in Earth's magnetosphere, so there is nothing standing in the way of a full two year mission of discovery.