Planes were grounded at some of Sweden's busiest airports on Wednesday afternoon because of a "solar storm" interfering with air traffic control radar systems, authorities said. Planes "disappeared from radar". http://www.thelocal.se/20151104/solar-storm-grounds-swedish-air-traffic
This ACE plot shows the energy impact of the flare. The spacecraft is located 1 million miles closer to the sun. Sweden at the time of the event was not on DST (UT +1 hour). The interruption occurred at about 15:30 Stockholm LT (04:30 UT) 10-29-15.<if I did the math correctly>
Fascinating report -- I wonder if the far northern latitude might have contributed? In my 45+ years with the FAA, I've never seen solar activity cause a complete surveillance disruption. Some communications problems, radar ducting, etc., but never that severe.
Vic, First time in my book with radar the same as you. I could guess all day, but a few things jump out so far: 1. No other reports have surfaced to date. I received this link from FEMA directly. Usually people send me reports like this and say "figure this one out". 2. I can imagine others had the usual radio problems and wrote it off as "another solar storm". 3. Intense geomagnetic fields and ground current disturbances can be isolated to a confined region during a solar storm. It could turn out this was a "hot spot" based on time and magnitude of the event. 4. Sweden is preparing a huge batch of King Gustav Glogg for the Christmas Holidays and the batch was too hot. I am sure that many groups are taking a look at this. If I hear any updates, I will post them here (as well as anyone else, please). 73's Keith
Thats a bit misleading. What happens is the clutter goes up so high that the planes dont have enough snr on the reflection backscatter. 73 Chip W1YW
It was not interference to primary radar, PSR, which is quite sparingly used in northern Europe, that caused the problems. Instead it was secondary radar,SSR, that was affected. Normally, the link budgets for SSR would be good enough that external noise should not have any influence. In this instance, several factors were contributing; Extreme tropo ducting Heavy air traffic A solar flare at just before sunset where the spectral peak was at 1000 MHz which is near the middle of the SSR downlink range. Even before the flare, the radar extractors were heavily loaded, and the noise energy from the flare generated signals that looked like thousands of false transponder returns which saturated the correlators and the following signal processing creating an "avalanche" of unrelated targets. These false targets masked the "legitimate" aircraft returns for the ATC controllers and the ATC authorities then decided that the airspace integrity and capacity in many sectors had become severely compromised. After sunset, this saturation condition in the signal processing chain vanished and the situation went back to normal. This is an extremely uncommon occurrence in modern ATC radar and information systems, less than one per decade have been recorded previously. 73/ Karl-Arne SM0AOM
Great explanation, Karl-Arne. On several occasions, we've seen ECM during military coastal training exercises, in the 1030/1090 MHz range, that temporarily overloaded both the primary and secondary systems, but they were almost always of a very short duration and usually just a wedge. I can't recall a total system overload to the NAS due to a solar event anytime during my years in the ATC system. I'm not sure our MODE- S systems are robust enough to handle the situation you describe. ECM is a local event...the solar event you describe could have a severe wide-spread impact on the highly congested NAS here in the USA, were it to occur. Interesting stuff... 73, Vic
Special thanks to Karl-Arne SMoAOM for his report. Special thanks to Vic KB7GL for his insight from his experience. Special thanks to Torny Avell from SMHI. This event could turn into a major project for a researcher with some extra time off. I made an inquiry to the Swedish Meteorological and Hydrological Institute (SMHI) regarding the weather radar network. Torny Avell responded with the following: 1. Of the 14 weather radar sites in Sweden, 7 had no data from 1515 to 1525 LT. These sites operated normally before and after this time period. 2. The 4 sites that were still reporting data: Karlskrona, Leksand, Ornskoldsvik, and Lulea. 3. They cannot be certain that the "solstormen" was the cause. It could have been a system problem. In looking at data from the Space Weather Prediction Center (SWPC) I found the following: 1. Two regions on the sun seem to have created most of the radio bursts on 10-29-15. 2. Region 2437 was located on the extreme western edge about 22 degrees south of the equator. 3. Region 2443 was located on the extreme eastern edge about 6 degrees north of the equator. 4. Between 0200 and 0330 UT: 3 type II, 3 type III, and 1 type IV radio bursts. 5. At 0341 UT region 2443 created a Type IV radio burst that lasted almost 7 hours (end 1016 UT). 6. The frequencies for each flare and radio burst are listed in a data file. They seem to match Karl-Arne's observations. I have posted a PDF file of this data at: http://www.sweoc.org/SWPC_Reports_11-16-17.pdf 7. The ACE data plot matches imaging from SDO and GOES SXI. Bottom line: It seems only a few minutes (8 to 15) for this event to travel from the Sun to Earth. Sweden during the time period, was at a 90 degree angle to the sun. Indeed a very rare set of conditions leading up to the outages. Solar storms are like snowflakes, no two seem to be the same.
