| Asteroid | Date(UT) | Miss Distance | Velocity (km/s) | Diameter (m) |
| 2020 OA5 | 2020-Jul-27 | 16.8 LD | 10.2 | 15 |
| 2020 OO1 | 2020-Jul-27 | 1.7 LD | 7.3 | 18 |
| 2020 NZ | 2020-Jul-28 | 8.2 LD | 7.8 | 31 |
| 2020 OE2 | 2020-Jul-28 | 4.5 LD | 2.9 | 14 |
| 2020 OY4 | 2020-Jul-28 | 0.1 LD | 12.4 | 3 |
| 2020 OR4 | 2020-Jul-28 | 1.2 LD | 22.9 | 27 |
| 2020 OU5 | 2020-Jul-29 | 9.3 LD | 11.2 | 39 |
| 2020 MX3 | 2020-Jul-29 | 9.4 LD | 8.5 | 62 |
| 2020 OM4 | 2020-Jul-30 | 8 LD | 15.3 | 73 |
| 2018 PY7 | 2020-Jul-31 | 8.9 LD | 9.5 | 16 |
| 2007 RF1 | 2020-Jul-31 | 10.7 LD | 5 | 21 |
| 2020 OC1 | 2020-Jul-31 | 9.6 LD | 4 | 19 |
| 2020 OT4 | 2020-Jul-31 | 12 LD | 4.3 | 18 |
| 2020 OX5 | 2020-Jul-31 | 6.8 LD | 9.2 | 14 |
| 2020 OO2 | 2020-Aug-01 | 14.9 LD | 7.8 | 30 |
| 2018 BD | 2020-Aug-03 | 7.6 LD | 9.4 | 3 |
| 2020 OA6 | 2020-Aug-04 | 6.4 LD | 10.4 | 22 |
| 2020 OG3 | 2020-Aug-04 | 7.1 LD | 6 | 16 |
| 2009 PQ1 | 2020-Aug-05 | 10.8 LD | 13.5 | 112 |
| 2020 OL4 | 2020-Aug-08 | 9.5 LD | 10.8 | 38 |
| 2020 FA1 | 2020-Aug-23 | 18.4 LD | 1.9 | 20 |
| 2016 AH164 | 2020-Aug-26 | 15.7 LD | 5.6 | 4 |
| 2011 ES4 | 2020-Sep-01 | 0.3 LD | 8.2 | 30 |
| 465824 | 2020-Sep-06 | 19.4 LD | 14 | 162 |
| 2012 RM15 | 2020-Sep-12 | 14.9 LD | 9.8 | 45 |
| 2017 US | 2020-Sep-13 | 17.3 LD | 5.9 | 21 |
| 2014 QJ33 | 2020-Sep-18 | 11.5 LD | 8.3 | 65 |
| 2017 SL16 | 2020-Sep-20 | 8.9 LD | 6.4 | 25 |
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 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 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.
| | The official U.S. government space weather bureau |
| | The first place to look for information about sundogs, pillars, rainbows and related phenomena. |
| | Researchers call it a "Hubble for the sun." SDO is the most advanced solar observatory ever. |
| | 3D views of the sun from NASA's Solar and Terrestrial Relations Observatory |
| | Realtime and archival images of the Sun from SOHO. |
| | from the NOAA Space Environment Center |
| | fun to read, but should be taken with a grain of salt! Forecasts looking ahead more than a few days are often wrong. |
| | from the NOAA Space Environment Center |
| | the underlying science of space weather |
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