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INCOMING HALO CME: An M1.2-class solar flare from sunspot 4028 on March 21st appears to have hurled a CME toward Earth. SOHO coronagraphs have detected a faint expanding halo; this is usually indicative of an incoming CME. Stay tuned for an estimated arrival time. CME impact alerts: SMS Text.
NEW EVIDENCE THAT COSMIC RAYS SPARK LIGHTNING: Every second, almost 50 bolts of lightning zig-zag across the skies of Earth. Despite centuries of study, however, researchers still aren't sure how the bolts get started. Electric fields in thunderclouds are often too weak to ignite a powerful discharge.
A lightning bolt over Brazil. Photo credit: Sergio Mazzi
A new study just published in the Journal of Geophysical Research may have solved the mystery.
"We believe that most lightning flashes in thunderstorms are ignited by cosmic ray showers," says the study's lead author Xuan-Min Shao, a senior scientist at the Los Alamos National Laboratory in New Mexico.
To investigate the earliest moments of lightning formation, Shao and colleagues built a radio interferometer named "BIMAP-3D." Consisting of an array of 8 antennas in Los Alamos, BIMAP-3D can make three dimensional images of lightning and pinpoint the bolts inside thunderclouds. Here's an example:
Caption: Colors in the image represent time. Blue traces the earliest moments of the bolt, while red denotes the end.
This is a lightning bolt from a massive thunderstorm that passed by Los Alamos on July 30, 2022. BIMAP-3D imaged more than 300 bolts during the 90-minute storm. It was a treasure trove of data.
The experimenters realized that some of the bolts they observed happened in parts of the storm where electric fields were too weak to cause the "Initial Breakdown Event" (IBE)--the initial spark that sets the lightning in motion. Modern theories of relativistic electron avalanche couldn't explain what they saw. Their suspicions soon focused on cosmic rays.
Cosmic rays are high energy particles that come from distant supernova explosions and other violent events across the cosmos. They strike Earth's atmosphere all the time, creating a secondary spray of particles called "cosmic ray showers." Regular readers are familiar with these showers because we routinely monitor them using Earth to Sky cosmic ray balloons over California.
One of the important things about cosmic ray showers is that they contain antimatter--positrons as well as ordinary electrons. The Los Alamos 3D lightning maps contained strong evidence for positrons. Electrons and positrons are bent in opposite directions by Earth's magnetic field, so they leave opposite imprints on the lightning's polarization, which BIMAP-3D also measured.
"It took me a while to figure this out," admits Shao. "I started with electrons only at the beginning, but could not explain the observations. With both electrons and positrons involved, all the observations can be consistently explained."
Positrons clinched the case for cosmic rays. "The fact that a cosmic ray shower provides an ionized path in the cloud that otherwise lacks free electrons strongly favor the inference that most lightning flashes are ignited by cosmic rays," the authors wrote.
In fact, it's still unclear how much of Earth's lightning is sparked by cosmic rays. Many more storms need to be studied with this method to improve the statistics. "This will require a lot of long-term and good quality lightning data," Shao says.
Stay tuned! And meanwhile, read the original research here.
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ROSE QUARTZ TREE OF LIFE PENDANT: You cannot buy this on Amazon. Only the Earth to Sky Store has the Rose Quartz Tree of Life Space Pendant. This one flew to the stratosphere March 4th onboard a cosmic ray research balloon:
You can have it for $129.95. The pendant's rose quartz gemstone is surrounded by a hand-wrapped stainless steel tree of life. During its 3-hour flight, it experienced temperatures as low as -63 C and air pressures less than 0.3% of sea level--truly, an out-of-this world gift!
The students are selling space jewelry to pay the helium bill for their high altitude ballooning program. Each pendant comes with a greeting card showing the item in flight and telling the story of its journey to the stratosphere and back again.
Far Out Gifts: Earth to Sky Store
All sales support hands-on STEM education
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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 Mar 21, 2025, the network reported 2 fireballs.
(2 sporadics)
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]
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 March 21, 2025 there were 2349 potentially hazardous asteroids.
 |
Recent & Upcoming Earth-asteroid encounters: | Asteroid | Date(UT) | Miss Distance | Velocity (km/s) | Diameter (m) |
| 2025 EC1 | 2025-Mar-16 | 8.6 LD | 6.5 | 19 |
| 2025 FN | 2025-Mar-17 | 5.7 LD | 13.3 | 10 |
| 2025 FD | 2025-Mar-18 | 5.1 LD | 24.5 | 60 |
| 2025 FP | 2025-Mar-18 | 2.1 LD | 8.9 | 13 |
| 2025 DU25 | 2025-Mar-18 | 2.9 LD | 5.3 | 13 |
| 2025 FC | 2025-Mar-18 | 0.2 LD | 17.2 | 6 |
| 2025 EQ2 | 2025-Mar-19 | 5.2 LD | 6.2 | 15 |
| 2025 FF | 2025-Mar-20 | 10.3 LD | 6.3 | 17 |
| 2025 FL | 2025-Mar-20 | 1.2 LD | 9 | 19 |
| 2025 FG | 2025-Mar-20 | 7.3 LD | 5.5 | 13 |
| 2025 FE | 2025-Mar-21 | 7.9 LD | 15 | 41 |
| 2025 FJ | 2025-Mar-21 | 2.4 LD | 11 | 9 |
| 2021 FH1 | 2025-Mar-21 | 3.9 LD | 13.8 | 31 |
| 2025 FK | 2025-Mar-21 | 19.8 LD | 12 | 35 |
| 2025 DA15 | 2025-Mar-23 | 16.9 LD | 7.8 | 36 |
| 2025 FS | 2025-Mar-24 | 3.1 LD | 13.6 | 23 |
| 2025 FT | 2025-Mar-25 | 5.1 LD | 9 | 13 |
| 2014 TN17 | 2025-Mar-26 | 13.3 LD | 21.5 | 174 |
| 2025 DW5 | 2025-Mar-26 | 16.5 LD | 5.6 | 42 |
| 2025 DV22 | 2025-Mar-27 | 16.5 LD | 12.2 | 57 |
| 2020 VA4 | 2025-Mar-30 | 11.6 LD | 5.6 | 12 |
| 2022 FR3 | 2025-Apr-01 | 6.6 LD | 7.4 | 105 |
| 2020 XT2 | 2025-Apr-04 | 13.6 LD | 6.2 | 41 |
| 2023 GC2 | 2025-Apr-04 | 17.3 LD | 6.3 | 12 |
| 2020 FH4 | 2025-Apr-04 | 12.8 LD | 3 | 7 |
| 2025 BC10 | 2025-Apr-05 | 9.7 LD | 22.9 | 479 |
| 2007 SQ6 | 2025-Apr-05 | 10.9 LD | 6.6 | 129 |
| 2025 DV40 | 2025-Apr-06 | 16.8 LD | 13.1 | 109 |
| 2003 GQ22 | 2025-Apr-07 | 19.6 LD | 8.9 | 180 |
| 2025 DL28 | 2025-Apr-08 | 16.2 LD | 5.6 | 38 |
| 2023 HG | 2025-Apr-11 | 3.7 LD | 8.6 | 14 |
| 2023 KU | 2025-Apr-11 | 2.8 LD | 18 | 119 |
| 2023 RX1 | 2025-Apr-13 | 18.1 LD | 1.4 | 3 |
| 2023 UH | 2025-Apr-15 | 8.8 LD | 11 | 21 |
| 2022 UO | 2025-Apr-15 | 19.8 LD | 16.2 | 18 |
| 2025 DC36 | 2025-Apr-15 | 14.2 LD | 4.9 | 58 |
| 2017 RN16 | 2025-Apr-17 | 10.9 LD | 8.7 | 6 |
| 2014 HS124 | 2025-Apr-22 | 10.9 LD | 8.9 | 93 |
| 2019 FY2 | 2025-Apr-24 | 12.8 LD | 5.3 | 12 |
| 462959 | 2025-Apr-25 | 12.9 LD | 9.5 | 213 |
| 2024 BF | 2025-May-01 | 9.5 LD | 4.6 | 47 |
| 2024 JM2 | 2025-May-03 | 7.2 LD | 11.3 | 62 |
| 2021 JN1 | 2025-May-06 | 18.3 LD | 16.3 | 39 |
| 2021 HZ | 2025-May-08 | 20 LD | 10.2 | 30 |
| 612356 | 2025-May-09 | 11 LD | 5.1 | 305 |
| 2021 KH | 2025-May-10 | 18.3 LD | 7.2 | 19 |
| 2011 HJ7 | 2025-May-12 | 6.6 LD | 15.8 | 118 |
| 2011 YU74 | 2025-May-13 | 11.4 LD | 5 | 90 |
| 2025 DT50 | 2025-May-14 | 16 LD | 6.4 | 101 |
Notes: LD means "Lunar Distance." 1 LD = 384,401 km, the distance between Earth and the Moon. 1 LD also equals 0.00256 AU. | | Cosmic Rays in the Atmosphere |
SPACE WEATHER BALLOON DATA: Almost 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 sensors that detect secondary cosmic rays, a form of radiation from space that can penetrate all the way down to Earth's surface. Our monitoring program has been underway without interruption for 10 years, resulting in a unique dataset of in situ atmospheric measurements.
Latest results (Nov. 2024): Atmospheric radiation is decreasing in 2024. Our latest measurements in November registered a 10-year low:
What's going on? Ironically, the radiation drop is caused by increasing solar activity. Solar Cycle 25 has roared to life faster than forecasters expected. The sun's strengthening and increasingly tangled magnetic field repels cosmic rays from deep space. In addition, solar coronal mass ejections (CMEs) sweep aside cosmic rays, causing sharp reductions called "Forbush Decreases." The two effects blend together to bring daily radiation levels down.
.Who cares? Cosmic rays are a surprisingly "down to Earth" form of space weather. They can alter the chemistry of the atmosphere, trigger lightning, and penetrate commercial airplanes. According to a study from the Harvard T.H. Chan school of public health, crews of aircraft have higher rates of cancer than the general population. The researchers listed cosmic rays, irregular sleep habits, and chemical contaminants as leading risk factors. A number of controversial studies (#1, #2, #3, #4) go even further, linking cosmic rays with cardiac arrhythmias and sudden cardiac death.
Technical notes: 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.
Data points in the graph labeled "Stratospheric Radiation" correspond to the peak of the Regener-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 Regener and Georg Pfotzer discovered the maximum using balloons in the 1930s and it is what we are measuring today.
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