Lights Over Lapland is excited to announce that our aurora webcam will be up and running 365 days per year! You can now enjoy watching the Midnight Sun and all of the other drama in the sky above Abisko National Park, Sweden here.

INCOMING SOLAR WIND STREAM: A stream of solar wind is approaching Earth and it could graze our planet's magnetic field on April 26th. The gaseous material is flowing from a northern hole in the sun's atmosphere. The stream won't hit our planet head on, but sometimes grazing impacts produce interesting effects--for instance, making Earth's magnetosphere ring like a bell. Free: Aurora Alerts

THE MYSTERY OF LAST FRIDAY'S AURORAS: Before sunrise on Friday, April 20th, Northern Lights spilled across the Canadian border into almost a dozen US states. The unexpected display was seen from Washington to Maine, with sightings as far south as Illinois and Indiana. "The lights danced from sunrise to sunset," reports eyewitness Thomas Spence, who sends this picture from the Superior National Forest  in the Arrowhead Region of Minnesota:

The display was sparked by an interplanetary shock wave that hit Earth's magnetic field during the waning minutes of April 19th. Interplanetary shock waves are supersonic disturbances in the solar wind, causing sudden discontinuities in the speed, temperature, and density of gaseous material blowing around our planet. During periods of high solar activity, these shocks are routinely delivered to Earth by coronal mass ejections (CMEs)--that is, big explosions on the sun.

And therein lies the mystery.

There was no big explosion on the sun last week. So what caused the shock wave? No one knows. Despite the fact that there are multiple satellites keeping an eye on the sun 24/7, we missed something. The stealthy disturbance left the surface of the sun and traveled across the sun-Earth divide, unseen and undetected for several days, before it hit, sparking a moderately strong G2-class geomagnetic storm attended by strangely colored, widespread auroras. Surprises are still possible in space weather, after all.

Realtime Aurora Photo Gallery

NOW THAT'S A HOMER: No one has ever hit a Red Sox baseball this far before. On Apr. 22, 2018, the students of Earth to Sky Calculus launched one to the edge of space on board a cosmic ray balloon. Riding alongside an array of radiation sensors, the commemorative baseball sailed 33.4 km (109,580 feet) above Earth's surface:

You can have it for $139.95. The students are selling space baseballs as a fund-raiser for their cosmic ray monitoring program. All proceeds support atmospheric radiation measurements and hands-on STEM education.

Are you a fan of a different team? The payload also carried commemorative baseballs for the Royals, Dodgers, Cubs, Yankees, Padres, and Giants. During checkout, enter your preferred team in the COMMENTS section. We will send you the corresponding baseball. If your home team is not on the list, let us know and we will fly it for you on an upcoming flight.

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

VOLCANIC SUNDOGS: Sundogs are common. The rainbow-colored splashes of light frequently appear on either side of the sun when sunbeams lance through icy cirrus clouds. On April 20th, Daryl Peterson of Anchorage, Alaska, witnessed an uncommon type of sundog. "They were volcanic," he says. Take a look at his photo, then scroll down for an explanation:

"From my location in Anchorage, I can easily see three active volcanoes in the ring of fire group that begins just 90 miles from here, across the Cook Inlet," says Pederson. "On April 20th I was scouting locations that would make great foregrounds for Northern Lights photography. For the first time in a long time I could see activity from all three volcanoes. Just before sunset an intense sundog formed from the steam that had been pumping out of the Mount Spurr stratovolcano."

The steamy exhaust was freezing in the cold Alaska air, forming the ice crystals required for sundog formation. "These rare sundogs were made even more impressive by their reflection on the water," says Pederson.

Realtime Space Weather Photo Gallery

On Apr. 24, 2018, the network reported 26 fireballs.
(18 sporadics, 8 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]

Recent & Upcoming Earth-asteroid encounters:

Asteroid	Date(UT)	Miss Distance	Velocity (km/s)	Diameter (m)
2018 HU	2018-Apr-18	8 LD	9.7	27
2018 HC1	2018-Apr-19	1.2 LD	15.5	16
2018 HS	2018-Apr-20	5.1 LD	18.9	35
2018 GS3	2018-Apr-20	8.5 LD	19.8	24
2016 JP	2018-Apr-20	12 LD	12.7	214
2018 HT	2018-Apr-21	7.1 LD	7.6	15
2018 GR1	2018-Apr-21	18.3 LD	16.4	52
2018 HN	2018-Apr-21	8 LD	9.8	37
2018 HV	2018-Apr-22	0.4 LD	16	6
2018 GG4	2018-Apr-23	9.8 LD	14.9	20
2012 XL16	2018-Apr-23	15.8 LD	6.1	28
2018 GH	2018-Apr-25	14.6 LD	10.7	89
2018 HP	2018-Apr-26	11.6 LD	10.3	20
2018 GH5	2018-Apr-27	12.2 LD	12.7	32
2018 GB2	2018-Apr-27	17.1 LD	14.6	92
2013 US3	2018-Apr-29	10.1 LD	7.7	214
2018 GO4	2018-Apr-29	11.8 LD	8.6	46
2018 GY1	2018-Apr-29	13.2 LD	16.7	141
2018 FV4	2018-Apr-29	17.7 LD	6.5	59
2002 JR100	2018-Apr-29	10.8 LD	7.7	49
2018 HB1	2018-May-02	10.2 LD	9.2	39
1999 FN19	2018-May-07	9.7 LD	5.7	118
2016 JQ5	2018-May-08	6.3 LD	10.4	9
388945	2018-May-09	6.5 LD	9	295
2018 GR2	2018-May-11	13.4 LD	9.8	109
1999 LK1	2018-May-15	13.3 LD	10	141
2018 GL1	2018-May-18	14.3 LD	5.2	67
68347	2018-May-29	9.5 LD	13.3	389
2013 LE7	2018-May-31	17.8 LD	1.7	12
2018 EJ4	2018-Jun-10	5.6 LD	6.2	195
2015 DP155	2018-Jun-11	9 LD	4.4	170
2017 YE5	2018-Jun-21	15.6 LD	15.5	513

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

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 13% 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.

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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