A Perfect Storm of Cosmic Rays

April 23, 2019: Ten years ago, NASA reported a “perfect storm of cosmic rays.” During the year 2009, radiation peppering Earth from deep space reached a 50-year high, registering levels never before seen during the Space Age.

It’s about to happen again.

Ground-based neutron monitors and high-altitude cosmic ray balloons are registering a new increase in cosmic rays. The Oulu neutron monitor in Finland, which has been making measurements since 1964, reports levels in April 2019 only percentage points below the Space Age maximum of 2009:


Source: The Sodankyla Geophysical Observatory in Oulu, Finland.

What’s going on? The answer is “Solar Minimum.” During the low phase of the 11-year solar cycle, the sun’s magnetic field and solar wind weaken. Cosmic rays find it easier to penetrate the inner solar system. In 2009, the sun experienced the deepest solar minimum in a century. Cosmic rays reaching Earth naturally surged.

Ten years later, solar minimum is back with renewed weakening of the sun’s magnetic field and the solar wind. Again, it’s a “perfect storm.” A panel of experts led by NOAA and NASA recently predicted that the current minimum would reach a nadir in late 2019 or 2020, likely matching the record-setting minimum of 2009. If they’re right, cosmic rays will continue to increase, with a new record possible in the near future.


Four years of overlapping data from neutron monitors and cosmic ray balloons agree that atmospheric radiation is increasing again.

Cosmic rays cause “air showers” of secondary particles when they hit Earth’s atmosphere. Indeed, this is what neutron monitors and cosmic ray balloons are measuring–the secondary spray of cosmic rays that rains down on Earth.

This spray is of special interest to air travelers. Secondary cosmic rays penetrate the hulls of commercial aircraft, dosing passengers with the whole body equivalent of a dental X-ray even on ordinary mid-latitude flights across the USA. International travelers receive even greater doses.

The International Commission on Radiological Protection has classified pilots as occupational radiation workers because of accumulated cosmic ray doses they receive while flying. Moreover, a recent study by researchers at the Harvard School of Public Health shows that flight attendants face an elevated risk of cancer compared to members of the general population. They listed cosmic rays as one of several risk factors.

Stay tuned for updates as solar minimum deepens.

Neutron Radiation over the USA

April 17, 2019: Want to experience space weather? Just step onboard an airplane. At typical cruising altitudes, cosmic rays from deep space penetrate the hulls of commercial jetliners, dosing passengers with levels of radiation comparable to dental X-rays. To measure this radiation, Spaceweather.com and the students of Earth to Sky Calculus have been flying cosmic ray sensors onboard airplanes over 5 continents. Our latest results show something potentially interesting about the continental USA.

Above: Neutrons detected during a flight from Portland to DC on April 9,2019.

On April 9th and 11th we flew neutron bubble chambers from Portland, Oregon, to Washington DC and back again. In the photo, above, each bubble was created by a cosmic ray neutron. Why measure neutrons? Studies show that neutrons can be ten times more effective at causing biological damage compared to X-rays and gamma-rays in the same energy range. Neutrons are so effective, they are used for cancer therapy, killing tumors better than other forms of radiation.

During these flights, we measured more than 20 uGy of neutron radiation–the whole body equivalent of two panoramic dental X-rays. That’s significant, but no worse than a trip to the dentist’s office.

The interesting thing is how these values compare to other places we’ve flown. Our neutron chambers have traveled more than 40,000 miles on 14 flights over North America, South America, Asia, Europe, and Africa, all with typical altitudes near 35,000 feet. So far, neutron dose rates have been highest in one place: the continental USA (CONUS).

In this histogram, flights over CONUS are color-coded red. Other parts of the world are blue. The distribution’s red tail shows the tendency of US flights to “out-neutron” international flights. This may be a result of small-number statistics. If so, the anomaly could disappear as more data are added. Our neutron survey is continuing, so stay tuned.

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Big Sunspot Produces “Ocean Surf” Sounds

April 15, 2019: If you have a shortwave radio, you might have heard some unusual sounds this weekend. Big sunspot AR2738 is producing strong bursts of radio static. “They sound like ocean surf,” says Thomas Ashcraft, who recorded this specimen on April 13th using an amateur radio telescope in New Mexico:

These radio sounds are caused by beams of electrons–in this case, accelerated by B-class explosions in the sunspot’s magnetic canopy. As the electrons slice through the sun’s atmosphere, they generate a ripple of plasma waves and radio emissions detectable on Earth 93 million miles away. Astronomers classify solar radio bursts into five types; Ashcraft’s recording captured a Type III.

“There have been a lot of these sounds over the past week, and they appear to be intensifying now that the sunspot is  directly facing Earth,” says Ashcraft.

Readers, if you would like to detect solar radio bursts in your own backyard, order a radio telescope kit from NASA’s RadioJOVE project.

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MOTHER’S DAY IS LESS THAN ONE MONTH AWAY: Tell Mom how much you love her — to the Moon and Back! On March 5th, the students of Earth to Sky Calculus launched an array of cosmic ray sensors to the edge of space onboard a helium balloon. This Mother’s Day pendant went along for the ride:

The silvery crescent declares “I love you to the Moon and Back” and surrounds a 14K gold plated heart labeled “Mom.”

You can have it for $99.95. 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. 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

Experts Predict a Long, Deep Solar Minimum

April 10, 2019:  If you like solar minimum, good news: It could last for years. That was one of the predictions issued last week by an international panel of experts who gathered at NOAA’s annual Space Weather Workshop to forecast the next solar cycle. If the panel is correct, already-low sunspot counts will reach a nadir sometime between July 2019 and Sept 2020, followed by a slow recovery toward a new Solar Maximum in 2023-2026.

“We expect Solar Cycle 25 will be very similar to Cycle 24: another fairly weak maximum, preceded by a long, deep minimum,” says panel co-chair Lisa Upton, a solar physicist with Space Systems Research Corp.


The solar cycle is like a pendulum, swinging back and forth between periods of high and low sunspot number every 11 years or so. Researchers have been tracking the cycle since it was discovered in the 19th century. Not all cycles are alike. Some are intense, with lots of sunspots and explosive solar flares; the Space Age began with a big booming solar maximum. Others are weak, such as the most recent, Solar Cycle 24, which peaked in 2012-2014 with relatively little action.

Researchers are still learning to predict the ebb and flow of solar activity. Forecasting techniques range from physical models of the sun’s inner magnetic dynamo to statistical methods akin to those used by stock market analysts.

“We assessed ~61 predictions in the following categories: Climatology, Dynamo, Machine Learning/Neural Networks, Precursor Methods, Spectral/Statistical Methods, Surface Flux Transport, and Other,” says Upton. “The majority agreed that Solar Cycle 25 would be very similar to Solar Cycle 24.”

“Here,” she says, “is a figure showing the last minimum and where we are with the current minimum.”


“As you can see – we haven’t quite reached the lowest levels of the last cycle – where we experienced several consecutive months with no sunspots. However, the panel expects that we should reach those levels [between now and the end of 2020].”

In recent years, the Internet has buzzed with the idea that a super-deep solar minimum such as the 70-year Maunder Minimum of the 17th century might cool the Earth, saving us from climate change. That’s not what the panel is saying, however.

“There is no indication that we are currently approaching a Maunder-type minimum in solar activity,” says Upton. Solar minimum will be deep, but not that deep.

The panel predicts a “fairly weak” Solar Cycle 25. What does that mean? Saying that a solar cycle is “weak” is a bit like saying hurricane season will be “weak.” In other words, there may be fewer storms, but when a storm comes, you’d better batten down the hatches. “Weak” Solar Cycle 24 produced a number of intense X-class solar flares, strong geomagnetic storms, and even a Ground Level Event (GLE) when solar energetic particles reached Earth’s surface. An equally “weak” Solar Cycle 25 could do the same 3 or 4 years hence.


Meanwhile, we have solar minimum. This is a widely misunderstood phase of the solar cycle. Many people think it brings a period of dull quiet. In fact, space weather changes in interesting ways. For instance, as the sun’s magnetic field weakens, holes open in the sun’s atmosphere. Emerging streams of solar wind buffet Earth’s magnetic field, sustaining auroras even without solar flares and sunspots. Some observers believe that Solar Minimum auroras have a distinctive palette, pinker than during other phases of the solar cycle.

The sun’s weakening magnetic field also allows cosmic rays to enter the solar system. Energetic particles from deep space penetrate Earth’s atmosphere with a myriad of possible effects ranging from changes in upper atmospheric electricity to extra doses of radiation for people on airplanes.

Finally, the sun dims, especially at extreme ultraviolet wavelengths. This, in turn, causes the upper atmosphere to cool and contract. Aerodynamic drag that would normally cause satellites to decay is reduced; space junk accumulates. This effect makes solar minimum a terrible time to blow up satellites–although people do it anyway.

The Solar Cycle Prediction Panel is comprised of scientists representing NOAA, NASA, the International Space Environment Services, and other U.S. and international scientists. Their April 5th prediction was preliminary, and they plan to issue a refined forecast by the end of 2019. Stay tuned.

Blue Squids over Norway — Crazy Artificial Auroras

April 7, 2019: On April 5th in northern Norway, scientists at the Andøya Space Center launched two sounding rockets into an ongoing display of Northern Lights. When they dumped their payloads of chemical powders, the sky went wild with strangely-colored shapes. Frank Olsen photographed squid-like figures dancing over a beach near Andenes, Norway:

“Often canceled and rescheduled, this rocket launch has been planned for a year,” says Olsen. “How lucky we were to be there at the right time.”

The name of the rocket mission is AZURE–short for Auroral Zone Upwelling Rocket Experiment. Its goal is to measure winds and currents in the ionosphere, a electrically-charged layer of the Earth’s atmosphere where auroras appear. Specifically, mission scientist are interested in discovering how auroral energy might percolate down toward Earth to influence the lower atmosphere.

At the Alomar Observatory in northern Norway, space scientist Jason Ahrns used video cameras to track the motions of the clouds:

“I’m one of the scientists working with this launch, so we knew exactly when to expect it,” says Ahrns. “Even so, we were all stunned by how spectacular the display was, as it unfolded.”

The twin rockets deployed two chemical tracers: trimethyl aluminum (TMA) and a barium/strontium mixture. These mixtures create colorful clouds that allow researchers to visually track the flow of neutral and charged particles, respectively. According to NASA, which funded the mission, the chemicals pose no hazard to residents in the region.

Realtime Aurora Photo Gallery

Space Weather Probes Shatter GPS Record

April 5, 2019: NASA’s MMS probes, which use GPS signals to orbit Earth in tight formation, have just shattered the record for long-distance GPS navigation. The four probes recently located themselves 116,300 miles above Earth’s surface, surprising experts who once thought that GPS could function no higher than about 22,000 miles.

“When we began the mission, we had no idea high-altitude GPS would be such a robust capability,” says Trevor Williams, the MMS flight dynamics lead at NASA’s Goddard Space Flight Center.

Above: an artist’s concept of the 4 MMS spacecraft

MMS, short for “Magnetospheric Multiscale,” is a constellation of 4 spacecraft launched in 2015. They are on a mission to study magnetic explosions in our planet’s magnetosphere. High above Earth where the magnetic field is buffeted by solar wind, magnetic lines of force criss-cross, reconnect and—Bang! Magnetic energy is unleashed, with charged-particles flying off near the speed of light. The process is called “magnetic reconnection, and it serves as a power source for geomagnetic storms.

To study the inner physics of reconnection, the MMS probes must fly in precise formation, as close as 10 km apart, so that they can sample particles and fields inside the tight reconnection zone. With the aid of GPS, the fleet maintain formation with an accuracy of only 100 meters, which is crucial to their measurements.

GPS satellites are not designed to assist spacecraft. They focus their radio energy on Earth where we use the signals for terrestrial navigation. So how do the MMS probes do it? The answer is “side lobes.” This diagram shows a simplified but typical GPS antenna pattern:

All GPS antennas allow a little bit of radio energy to leak out in unwanted directions through side lobes. Receivers on the MMS probes tap into the leaked signal and use it to locate themselves. The first time MMS attempted navigation at the extremes of its orbit, the satellites had as many as 12 GPS fixes, each requiring signals from four GPS satellites. Not bad for a “leak.”

This type of navigation could reach all the way to the Moon. NASA analysts have run simulations suggesting that all six international GPS-like constellations (collectively known as GNSS) when working together could guide spacecraft in lunar orbit 238,000 miles from Earth. NASA is even considering adding GPS navigation to its Gateway outpost, a proposed space station for the Moon.

Solar Minimum is a Terrible Time to Blow Up a Satellite

April 3, 2019: Note to space powers: If you’re going to blow a satellite to bits, solar minimum is a terrible time to do it. India is grappling with this important truth today as debris from their March 27th anti-satellite weapons test spreads through space. As many as 6,500 pieces of the Microsat-R Earth observation satellite are now circling Earth, according to a simulation created by Analytical Graphics Inc.:

During solar minimum–happening now!–Earth’s upper atmosphere cools and contracts, sharply reducing aerodynamic drag that causes satellites to decay. Indeed, in 2019 the temperature of the thermosphere is close to a Space Age record low. This could double or triple the time required for fragments of the shattered satellite to sink into the atmosphere and disintegrate. Small fragments in high orbits may remain aloft for years, circling the planet like tiny bullets traveling 17,000 mph.

This event brings to mind a Chinese ASAT test in 2007, which also occurred near solar minimum and created a significant debris field of more than 35,000 pieces. That test occured at an altitude of 865 km, with particles ultimately spreading between 200 km and 4000 km. At least one Russian satellite was unintentionally damaged by the debris.

India’s test at 300 km altitude has created an upward spray of debris that could threaten the International Space Station only 100 km overhead, according to statements made by NASA Administrator Jim Bridenstine during an April 1st town hall meeting in Washington DC.

“That is a terrible, terrible thing, to create an event that sends debris in an apogee that goes above the International Space Station,” he told NASA employees.

Officials say there are 60 trackable fragments of Microsat-R measuring 10 cm across or larger. Of that total, 24 ended up in orbits with high points, or apogees, above the 400 km altitude of the ISS. Low solar activity, which could last for years as the solar cycle ponderously swings through its minimum phase, will help keep these fragments aloft, prolonging their threat to other satellites.

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