Space Weather Update: 10/02/2016
By Spaceweather.com, 10/02/2016
SUNSET SKY SHOW: When the sun goes down tonight, step outside and look west. An exquisitely slender crescent Moon is shining about 10 degrees to the right of Venus. A clear view of the horizon is essential, as both are hanging low.
NO SUNSPOTS. WHAT DOES IT MEAN? It’s happening again: The sunspot number has dropped to zero. Yesterday, sunspot group AR2597 vanished, leaving the face of the sun blank. There are no significant dark cores in today’s image of the sun from NASA’s Solar Dynamics Observatory:
What does this mean? Blank suns herald the coming of Solar Minimum.
The sunspot cycle is like a pendulum, swinging back and forth with a period of 11 or 12 years. Right now the pendulum is swinging toward low sunspot numbers. Forecasters expect the the cycle to hit rock bottom in 2019-2020. Between now and then, there will be lots of spotless suns. At first, the blank stretches will be measured in days; later in weeks and months. The current blank spell is the 4th such interval of 2016, so far.
Because solar flares subside during Solar Minimum, many people think space weather goes away during this time. Not so. Solar Minimum brings many interesting changes. For instance, as the extreme ultraviolet output of the sun decreases, the upper atmosphere of Earth cools and collapses. This allows space junk to accumulate around our planet. Also, the heliosphere shrinks, bringing interstellar space closer to Earth. Galactic cosmic rays penetrate the inner solar system with relative ease. Indeed, there is already evidence of increasing radiationin Earth’s atmosphere–a matter of keen interest to air travelers and possible space tourists.
NEW MAPS OF THE SOUTH ATLANTIC ANOMALY: Researchers have long known that one of the van Allen Radiation Belts dips down toward Earth over South America, creating a zone of high radiation called “The South Atlantic Anomaly” (SAA). Since its discovery in 1958, the SAA has been shape-shifting, growing larger and intensifying. A map published just last week in the American Geophysical Union’s journal Space Weather Quarterly outlines the anomaly with new precision:
When a spacecraft in low-Earth orbit passes through the anomaly, “the radiation causes faults in spacecraft electronics and can induce false instrument readings,” explains Bob Schaefer of the Johns Hopkins University Applied Physics Lab, lead author of the paper reporting the results. “We actually used these spurious signals to map out the radiation environment at an altitude of 850 km.”
Specifically, they looked at pulses of noise in an ultraviolet photometer carried aboard many polar orbiting Defense Meteorological Satellite Program (DMSP) satellites. When high-energy protons in the SAA pass through these sensors, theyproduce spurious signals–or, in the case of this study, valuable data. By monitoring the rate of spurious UV pulses, the researchers were able to trace the outlines of the anomaly and monitor its evolution over a period of years.
They found that the anomaly is slowly drifting north and west at rates of 0.16 deg/yr and 0.36 deg/yr, respectively. Currently, it is most intense over a broad region centered on Sao Paulo, Brazil, including much of Paraguay, Uruguay, and northern Argentina. They also detected a seasonal variation: On average, the SAA is most intense in February and again in September-October. In this plot, yearly average counts have been subtracted to reveal the double-peaked pattern:
One maximum coincides with an equinox, but the other does not. The authors were not able to explain the origin of this unexpected pattern.
The solar cycle matters, too, as the data revealed a yin-yang anti-correlation with sunspots. “During years of high solar activity, the radiation intensity is lower, while during solar quiet years the radiation intensity is higher,” writes Schaefer.
According to orthodox thinking, the SAA reaches down from space to within about 200 km of Earth’s surface. Below that altitude, its effects should be mitigated by the shielding of Earth’s atmosphere and geomagnetic field. To test this idea, Spaceweather.com and Earth to Sky Calculus have undertaken a program to map the SAA from below using weather balloons equipped with radiation sensors. Next week we will share the results of our first flight from a launch site in Chile. Stay tuned!
SPRINGTIME IN ANTARCTICA: Spring has begun in Antarctica, and the skies are turning green. No wonder overwintering researchers are taking off their parkas and going outside. B. Sudarsan Patro took this picture onOctober 1st from the Bharati Indian Base Station in the Larsemann Hills:
“The view was absolutely amazing,”says Patro. “The auroras were so bright and colorful. They brought joy to our celebration of Navaratri.”
Navaratri is a festival dedicated to the worship of the Hindu deity Durga. Technically, it begins on Oct. 2nd, but Patro and colleagues got an early start. The festival lasts 9 days. Earth is passing through an unusually broad stream of solar wind, so a fair fraction of the celebration could be attended by Southern Lights.
As October begins, the solar wind around Earth is blowing almost 600 km/s (1.3 million mph). This could spark auroras around both poles this weekend. Monitor the gallery for sightings:
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.
All Sky Fireball Network
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. 2, 2016, the network reported 22 fireballs.
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 October 2, 2016 there were 1731 potentially hazardous asteroids.
Recent & Upcoming Earth-asteroid encounters:Asteroid
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.
speed: 541.3 km/sec
density: 2.8 protons/cm3
explanation | more data
Updated: Today at 1835 UTX-ray Solar Flares
6-hr max: B3 1633 UT Oct02
24-hr: B4 0459 UT Oct02
explanation | more data
Updated: Today at: 1800 UTDaily Sun: 02 Oct 16The sun is blank-no sunspots. SOlar flare activity is very low. Credit: SDO/HMI
Sunspot number: 0
What is the sunspot number?
Updated 01 Oct 2016
Current Stretch: 1 days
2016 total: 21 days (8%)
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 02 Oct 2016
Current Auroral Oval:
Switch to: Europe, USA, New Zealand, Antarctica
Credit: NOAA/OvationPlanetary K-index
Now: Kp= 2 quiet
24-hr max: Kp= 4 unsettled
explanation | more data
Interplanetary Mag. Field
Btotal: 5.6 nT
Bz: 4.2 nT south
explanation | more data
Updated: Today at 1836 UTCoronal Holes: 02 Oct 16
Earth is inside a stream of solar wind flowing from the indicated coronal hole. Credit: NASA/SDO.Noctilucent Clouds NASA’s AIM spacecraft has suffered an anomaly, and a software patch is required to fix it. As a result, current noctilucent cloud images will not return until late September 2016.
Switch view: Europe, USA, Asia, PolarUpdated at: 08-06-2016 16:55:02
Updated at: 2016 Oct 01 2200 UTC
Probabilities for significant disturbances in Earth’s magnetic field are given for three activity levels: active, minor storm, severe stormUpdated at: 2016 Oct 01 2200 UTCMid-latitudes