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Middle Latitude Auroral Activity Watch - April 20 & 21, 2014


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Solar Activity and Geophysical Activity Summary

On April 18, around 13:00 UTC, sunspot region 2036 produced a strong M7.3 (R2-moderate) solar flare. It was a long duration solar flare located at 18 degrees south and 34 degrees west. Sunspot region 2036 was at the time in a good position for any eruptions to be earth-directed. The solar flare produced an asymmetrical full halo Coronal Mass Ejection (short: CME) with the bulk of the ejecta heading south, away from Earth. A good portion of the cloud is however Earth-directed. It is estimated that the CME left the Sun with a speed of about 1.000km/s which is moderately fast for a CME. A S1 space radiation storm developed right after the solar flare and it the storm will likely remain at the S1 level until the CME arrives. Before the CME arrives we might see a new rise in protons but it is unlikely to reach the S2 level. For a complete overview of all the events we recommend you read >this topic.

 

https://www.youtube.com/watch?v=F_RH6_K0zVY

The CME as seen by SOHO/LASCO C3:

 

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Expected geomagnetic activity

We expect the CME to arrive around 21:00UTC on April 20 with a plus/minus of 6 hours. G1 geomagnetic storm conditions will likely develop in the hours after the CME impact with possible periods of G2 geomagnetic storming conditions. North America will benefit the most of this CME impact considering the expected arrival time but an early arrival could give European sky watchers at the upper middle latitudes a chance as well on evening of April 20 and the night of April 21. CME effects will likely persist throughout April 21 so also southern hemisphere sky watchers from Tasmania and southern New Zealand should be alert for auroral displays when they approach magnetic midnight.

 

Note that it will only be possible to really determine what kind of geomagnetic conditions are to be expected once an impact has been detected and we know what the solar wind and IMF values are, so keep following our updates in this topic and on our social media channels for the most up-to-date and accurate information, this is a preliminary forecast.

 

Low Latitudes: 1% chance

Lower Middle Latitudes: 20% chance

Upper Middle Latitudes: 55% chance

High Latitudes: 95% chance

 

Moon

The moon will be illuminated for 54% and rise a few hours after local midnight. Once it rises it might be harder to see weak aurora but it should not be too much of a problem. More information

 

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The locations below will have a reasonable chance to see aurorae during a G1 geomagnetic storm provided local viewing conditions are good. This includes but is not limited to: a clear sight towards the northern or southern horizon, no clouds, no light pollution and complete darkness.

  

 

North America:

Seattle (WA, USA) Chicago (IL, USA) Toronto (ON, Canada) Halifax (NS, Canada)

Europe:

Edinburgh (Scotland) Gothenburg (Sweden) Riga (Latvia)

Southern Hemisphere:

Hobart (Australia) Invercargill (New Zealand)

More info

 

The locations below will have a reasonable chance to see aurorae during a G2 geomagnetic storm provided local viewing conditions are good. This includes but is not limited to: a clear sight towards the northern or southern horizon, no clouds, no light pollution and complete darkness.

 

North America:

Portland (OR, USA) Boise (ID, USA) Casper (WY, USA) Lincoln (NE, USA) Indianapolis (IN, USA) Columbus (OH, USA) New York City (NY, USA)

Europe:

Dublin (Ireland) Manchester (England) Hamburg (Germany) Gdańsk (Poland) Vilnius (Lithuania) Moscow (Russia)

Southern Hemisphere:

Devonport (Australia) Christchurch (New Zealand)

More info

 

We will continue to monitor the activity and post updates on the forum, Facebook, and Google+. Keep following us for the latest information. Got questions, comments, or maybe you have a different opinion? Then feel free to post in this topic and we will do our best to help you out! We also have an email alert system and Twitter account which informs you of strong solar flares, Coronal Mass Ejection impacts and much more.

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Reminder: A Middle Latitude Auroral Activity Watch is in effect for April 20 and 21, 2014 thanks to the M7 solar flare of April 18. Our initial analyses stands: G2 geomagnetic storming (Kp6) is possible. The NOAA SWPC have issued a G2 storm watch today as well just like the Belgian SIDC.

Additional analyses suggest we could see a slightly earlier impact then we first expected. The ACE EPAM plot is climbing nicely indicating the approaching CME is coming closer and with the elevated background solar wind (near 500km/s) it is possible that CME does not slow down as much as we initially thought. It is vital to be alert all day tomorrow as an impact during the European afternoon could signal auroral chances for the European middle latitudes on the evening of April 20 and the night of April 21.

For CME impact alerts: follow us on Twitter or sign up for our email alerts: http://www.spaceweatherlive.com/en/aurora-alertmail

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Guest Steve Brooks

heading South from Perth Western Australia this afternoon for the Southern Parts.

Fingers Crossed for a show tonight

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Our alert system was very awake and detected the impact:

Weak CME impact

Currently we see the effects of the arrival of a Coronal Mass Ejection (CME) at the ACE satellite. The solar wind speed rose with 81.51km/sec to 598.3km/sec. The plasma cloud will reach the Earth in 42 minutes.

The strength of the interplanetary magnetic field (IMF) at impact is also weak (14.9nT). With a direction that is currently north (10.9nT), chances for geomagnetic storm are very low.

  • Solar wind speed 598.3km/sec & density 3.8p/cm3
  • IMF Bt (strength): 14.9nT - Bz: 10.9nT

The IMF gained some strength after the initial impact, going up to 18.2nT which is moderate. But the direction of the IMF is still north. We will follow it closely and will update if necessary.

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Here is a look at the current stats as measured by ACE. The solar wind speed lies around 700km/s which is fast and the strength of the IMF (Bt) hovers around 20nT, a moderate value. These are good values for a geomagnetic storm to develop. The direction of the IMF (Bz) is however a crucial element and it is not cooperating. The direction is pointing northward which is not good for a geomagnetic storm to develop. With the current stats it will be hard for a geomagnetic storm to develop but should the direction of the IMF (Bz) swing south for a few hours then we could easily see the development of a G1 or G2 geomagnetic storm.

A sudden impulse was detected a few minutes ago by magnetometers on Earth indicating the CME has arrived at Earth.

 

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Guest Keith Woodard

Neutron counts fell significantly to 4200 counts/hour/100 according to the Thule AB, monitoring station. Although the data is skewed, the fall in equivalent CGRs began on the 19th and reset the baseline for reporting. I have not observed this before.

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Yesterday's CME impact never made it to the predicted G2 (moderate) level but we did see a period of G1 (minor) storming. Nice aurora shows were reported from the high latitudes like Canada, Scandinavia, Scotland and Tasmania. The IMF and solar wind stats are slowly falling back to background levels currently and no more geomagnetic storming is to be expected. This event had the potential for G2 levels but the orientation of the interplanetary magnetic field wasn't on our side. The direction of the IMF was mostly north which suppressed geomagnetic activity.

Solar activity is currently low, only C-class flares have occurred in the past 24 hours. None of the regions on the earth-facing disk are very interesting at the moment. C-class flares are likely with only a very slight chance for an M-class event. Sunspot region 2038 (location: S11W16) is as I write this producing a long duration C5 solar flare. Should it be of interest (read: launch a CME) then we will get back on it.

 

The anticipated G2 storm did not make it. But then the G1 did and the conditions were just goog enough to have some weak photographic polar light in the Northern parts of the Netherlands.

Invisible to the naked eye, this image is from April 21st,00:08 UTC when Kiruna made its strongest dip.

Congratulations Vincent, do you have more images or was it just visible for a few minutes?

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Guest Keith Woodard

I remember a day in my teens when I used to draw out sunspots using my 60 mm refractor's projection screen and report my results to the solar division of NOAA. There were many times, too many sunsponts to count. I remember one day there was a sunspot so large that you could see it with the unaided eye, protected of course. Maybe this influx of solar activity brought us out of our cold snap in the 1970s and lead to the hottest years on record, 1988.

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