Special Offer: SAVE 600nok per person. Book a combo aurora borealis chase and scenic day tour during the months of September, October or November 2019 for the special price of 1800 kr. Check Marianne's webpage for details!

SOLAR MINIMUM CONDITIONS ARE IN EFFECT: The sun has been blank (no sunspots) for 54 of the past 60 days. This is a sign that Solar Minimum is underway. During this phase of the solar cycle, sunspots and solar flares are rare, but we get plenty of holes in the sun's atmosphere and lots of extra cosmic rays. Solar Minimum conditions are expected to continue mostly uninterrupted for the remainder of 2019. Aurora alerts: SMS Text.

A GREEN FLASH AT SUNSET: For seaside photographers, nothing beats a green flash--that sudden pulse of verdant light at sunset as the sun vanishes beneath the ocean waves. Earlier this week, James W. Young was vacationing in Seaside, Oregon, so naturally he tried to catch the elusive flash. "Got it!" he says.

"At sunset from Ecola Park on the north coast of Oregon, a substantial green flash developed as the sun set into the Pacific Ocean," says Young. "I caught it just beyond the Tillamook Rock Lighthouse using a telephoto lens and my Canon 1Dx Mark II camera."

The Oregon coast is a good place to find green flashes at this time of year. Warm summer air overlying cold ocean water creates a temperature gradient in the coastal atmosphere. This gradient can have a magnifying effect on the usual prismatic action of the atmosphere, amplifying the green component of the sun's rays into an eye-catching flash.

EARLY PERSEID METEORS (WITH SOUND): Every summer, sky watchers around the northern hemisphere look forward to the Perseid meteor shower--the only major meteor shower of the year that occurs on warm, comfortable nights. News flash: It's begun. Frankie Lucena of Cabo Rojo, Puerto Rico, video recorded two Perseid meteors on July 22nd:

Turn up the volume and play it again. "The audio ping was obtained using a 500 foot long telephone wire connected to my PC sound card," explains Lucena. "This setup allows me to capture very low frequency radio emissions, which are caused by the temporary ionization of the atmosphere in a meteor's trail."

Perseid meteors are dusty debris from giant Comet Swift-Tuttle. Every year in late July and early August, Earth passes through the comet's debris zone, causing meteoroids to strike the atmosphere at speeds exceeding 133,000 mph, disintegrating in luminous streaks.

The Perseids Lucena saw are just the first of many to come. The shower's peak is expected on August 12th and 13th, when Earth passes through the densest part of the debris stream. Dozens of meteors per hour streaking across northern skies make those dates a great time to camp out under the stars.

Realtime Space Weather Photo Gallery
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STERLING SILVER MOONSTONE PENDANT: Are you looking for a far-out gift? Nothing says "I love you" like a moonstone from the edge of space. On Jan 27th, the students of Earth to Sky Calculus flew this moonstone wrapped in a hand-crafted sterling silver Celtic love knot 35.1 km (115,158 feet) above Earth's surface:

You can have it for $179.95. The students are selling these pendants to support their cosmic ray ballooning program. Each one comes with a greeting card showing the item in flight and telling the story of its journey to the edge of space. All sales support the Earth to Sky Calculus cosmic ray ballooning program and hands-on STEM research.

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

Realtime Aurora Photo Gallery
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On Jul. 23, 2019, the network reported 76 fireballs.
(73 sporadics, 2 alpha Capricornids, 1 July Pegasid)

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 NJ2	2019-Jul-19	13.4 LD	13.5	38
2015 HM10	2019-Jul-24	12.2 LD	9.5	68
2019 OD	2019-Jul-24	0.9 LD	19.2	69
2019 OE	2019-Jul-24	2.5 LD	9	31
2010 PK9	2019-Jul-26	8.2 LD	16.5	155
2019 NT1	2019-Jul-27	19 LD	3.7	14
2019 NN4	2019-Jul-29	6.6 LD	3.8	26
2006 QQ23	2019-Aug-10	19.4 LD	4.7	339
454094	2019-Aug-12	17 LD	8.2	148
2018 PN22	2019-Aug-17	17.1 LD	2.3	11
2016 PD1	2019-Aug-26	11.4 LD	5.9	65
2002 JR100	2019-Aug-27	19.4 LD	8.4	49
2018 DE1	2019-Sep-03	12.7 LD	6.6	28
2019 GT3	2019-Sep-06	19.5 LD	13.6	227
2010 RM82	2019-Sep-13	18.2 LD	14.6	23
2013 CV83	2019-Sep-13	15.7 LD	13.1	62
504800	2019-Sep-14	13.9 LD	14.4	155
467317	2019-Sep-14	13.9 LD	6.4	389
2019 JF1	2019-Sep-16	11.2 LD	4.3	61
2018 FU1	2019-Sep-16	18.4 LD	4.7	16

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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