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FRIDAY THE 13TH METEOR SHOWER: Earth is passing through a stream of debris from rock comet 3200 Phaethon, source of the annual Geminid meteor shower. This is an unlucky year for Geminids, because the shower's peak on Dec. 13-14 coincides with a nearly-full Moon. Lunar glare tonight will reduce visible meteor rates 5-fold or more. Next year will be better. [Photo gallery]

COSMIC RAY UPDATE: Something ironic is happening in Earth's atmosphere. Solar activity is low--very low. Yet atmospheric radiation is heading in the opposite direction. Cosmic rays percolating through the air around us are at a 5 year high.

Take a look at these data gathered by cosmic ray balloons launched by Spaceweather.com and the students of Earth to Sky Calculus almost weekly since March 2015:

Radiation levels have been increasing almost non-stop since the monitoring program began, with recent flights registering the highest levels of all.

What's happening? The answer is "Solar Minimum"--the low point of the 11-year solar cycle. During Solar Minimum (underway now) the sun's magnetic field weakens and allows energetic particles from deep space to penetrate the Solar System. As solar activity goes down, cosmic rays go up; yin-yang.

When cosmic rays hit the top of Earth's atmosphere, they produce a spray of secondary particles and photons that rain down on Earth's surface. This is what our balloons measure--the secondary spray. We use X-ray and gamma-ray detectors sensitive to energies in the range 10 keV to 20 MeV. This type of radiation, which you can also find in medical X-ray machines and airport security scanners, has increased more than 20% in the stratosphere.

Another way to measure cosmic rays is using a neutron monitor. Neutrons are an important type of secondary cosmic ray. They reach Earth's surface with relative ease and are biologically effective. Neutron monitors at the Sodankyla Geophysical Observatory in Oulu, Finland, are getting results similar to ours. Oulu data show that cosmic rays have been increasing for the past 5 years and, moreover, are within percentage points of the Space Age record.

The Space Age record for cosmic rays isn't very old. It was was set in late 2009-early 2010 near the end of a very deep Solar Minimum much like the one we're experiencing now. As 2019 comes to a close, neutron counts at Oulu are approaching those same levels. Indeed, a new record could be just weeks or months away.

Who cares? Anyone who steps on an airplane. Cosmic rays penetrate commercial jets, delivering whole-body dosages equal to one or more dental X-rays even on regular flights across the USA. Cosmic rays pose an even greater hazard to astronauts, of course. Cosmic rays can also alter the electro-chemistry of Earth's upper atmosphere and are thought to play some role in sparking lightning. Stay tuned for updates.

A sharable version of this story is available here.

Realtime Spaceweather Photo Gallery
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CHRISTMAS GIFTS FROM THE EDGE OF SPACE: So far in 2019, the students of Earth to Sky Calculus have launched 41 space weather balloons to the stratosphere, measuring cosmic rays over 2 continents and 6 different US states. You can help them pay their helium bill by purchasing a Christmas gift from the edge of space:

Every item in the Earth to Sky Store has flown to the stratosphere alongside an array of cosmic ray sensors. Carried aloft by giant helium balloons, these unique gifts travel above 99.7% of Earth's atmosphere, experiencing space-like blasts of cosmic rays, extreme cold, and a wild ride parachuting back to Earth after the balloon explodes. Even Amazon doesn't carry items this far out.

Don't forget to enter coupon code "XMASRAYS" at checkout for a 10% holiday discount.

Far Out Gifts: Earth to Sky Store
All sales support hands-on STEM education

Realtime Aurora Photo Gallery
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On Dec. 13, 2019, the network reported 56 fireballs.
(29 Geminids, 21 sporadics, 4 sigma Hydrids, 1 Dec. Monocerotid, 1 Puppid-Velid)

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]

Recent & Upcoming Earth-asteroid encounters:

Asteroid	Date(UT)	Miss Distance	Velocity (km/s)	Diameter (m)
2019 VH5	2019-Dec-08	18 LD	9.8	76
2019 XY	2019-Dec-09	3.2 LD	13.1	9
2019 XB	2019-Dec-09	17.4 LD	7.9	68
2019 WT3	2019-Dec-09	9.8 LD	11	43
2019 WO2	2019-Dec-09	4.8 LD	7.6	32
2019 XW	2019-Dec-10	10.8 LD	15.6	60
2019 XO1	2019-Dec-13	7.9 LD	7.9	44
2019 WP6	2019-Dec-14	6.4 LD	4.4	22
2019 XF	2019-Dec-18	9.3 LD	24.1	76
216258	2019-Dec-20	15.3 LD	11.8	324
2013 XY20	2019-Dec-21	18.3 LD	1.9	28
2017 XQ60	2019-Dec-22	11 LD	15.6	47
310442	2019-Dec-26	19 LD	12.3	372
2019 WR4	2019-Dec-31	11.7 LD	4.2	21
2019 AE3	2020-Jan-02	4.9 LD	8.2	13
2019 UO	2020-Jan-10	11.8 LD	9.4	351
2019 WC5	2020-Jan-11	6.3 LD	13	108
2011 EP51	2020-Jan-15	19.6 LD	7.1	32
2017 RZ15	2020-Jan-15	12.1 LD	7.4	14
2009 BH2	2020-Jan-18	14.6 LD	17.9	118
2013 DU	2020-Jan-20	15.3 LD	6.4	59
2019 TF2	2020-Jan-23	16.2 LD	1.6	18
2018 BM5	2020-Jan-23	13.1 LD	8.6	12
2018 AL12	2020-Jan-30	18.2 LD	17.7	39
2018 BU1	2020-Feb-02	19.4 LD	10	41

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

SOMETHING NEW! We have developed a new predictive model of aviation radiation. It's called E-RAD--short for Empirical RADiation model. We are constantly flying radiation sensors onboard airplanes over the US and and around the world, so far collecting more than 22,000 gps-tagged radiation measurements. Using this unique dataset, we can predict the dosage on any flight over the USA with an error no worse than 15%.

E-RAD lets us do something new: Every day we monitor approximately 1400 flights criss-crossing the 10 busiest routes in the continental USA. Typically, this includes more than 80,000 passengers per day. E-RAD calculates the radiation exposure for every single flight.

The Hot Flights Table is a daily summary of these calculations. It shows the 5 charter flights with the highest dose rates; the 5 commercial flights with the highest dose rates; 5 commercial flights with near-average dose rates; and the 5 commercial flights with the lowest dose rates. Passengers typically experience dose rates that are 20 to 70 times higher than natural radiation at sea level.

To measure radiation on airplanes, we use the same sensors we fly to the stratosphere onboard Earth to Sky Calculus cosmic ray balloons: neutron bubble chambers and X-ray/gamma-ray Geiger tubes sensitive to energies between 10 keV and 20 MeV. These energies span the range of medical X-ray machines and airport security scanners.

Column definitions: (1) The flight number; (2) The maximum dose rate during the flight, expressed in units of natural radiation at sea level; (3) The maximum altitude of the plane in feet above sea level; (4) Departure city; (5) Arrival city; (6) Duration of the flight.

SPACE WEATHER BALLOON DATA: 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 18% since 2015:

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.

En route to the stratosphere, our sensors also pass through aviation altitudes:

In this plot, 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.

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.

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.

Essential web links

NOAA Space Weather Prediction Center

The official U.S. government space weather bureau

Atmospheric Optics

The first place to look for information about sundogs, pillars, rainbows and related phenomena.

Solar Dynamics Observatory

Researchers call it a "Hubble for the sun." SDO is the most advanced solar observatory ever.

STEREO

3D views of the sun from NASA's Solar and Terrestrial Relations Observatory

Solar and Heliospheric Observatory

Realtime and archival images of the Sun from SOHO.

Daily Sunspot Summaries

from the NOAA Space Environment Center

NOAA 27-Day Space Weather Forecasts

fun to read, but should be taken with a grain of salt! Forecasts looking ahead more than a few days are often wrong.

Aurora 30 min forecast

from the NOAA Space Environment Center

Heliophysics

the underlying science of space weather

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