NLN Aurora Briefs – February 24, 2015

Share Button

Sunspot activity has decreased. The main feature impacting Earth’s space weather has shifted from solar flares to coronal holes over the last month or so. Once again this week, we are seeing elevated solar winds as the result of a coronal hole high speed stream.

Solar winds picked up mid-yesterday and have been slowly increasing from 440km/s yesterday to over 500km/s as of this writing. There was a brief peak of winds over 550km/s. Two days ago, this small coronal hole was pointed directly at Earth:

AIA 211 image of coronal hole
Coronal Hole from 2/21/2015 influences Earth’s space weather on Feb 23, 2015

High solar winds make our geomagnetosphere more susceptible to the impacts of solar disturbances. Any high proton flux or high density have the potential to activate aurora as reflected by higher KP. Late on the 23rd, and so far early on the 24th, KP values have already increased to 4. If Bz stays south for an extended period of time, the wing-KP model will likely register higher values.

Even without sunspots, we’ll take the Aurora activity. Here’s a great Aurora shot in today’s featured tweet, shared by Sun Viewer @SunViewer (who does an awesome job curating really nice Aurora photos!):

CMEs, Comet Captured in SOHO/LASCO Imagery 2/20/2015

Share Button

The Earth-facing solar disk has been relatively quiet for the last week. Yesterday, however, SOHO LASCO instruments imaged a pair of CMEs. Concurrent with those CMEs, a comet was visible looping around the Sun in the same images. In this post, we’ll take a look at a time lapse of LASCO imagery and guide you through what is going on. Here’s the video:

Where the images come from: SOHO is the Solar and Heliospheric Observatory. It is a spacecraft run jointly by NASA and ESA (European Space Agency) that orbits near L1 – that’s the same stable place DSCOVR is headed. It’s primary missing is to image the Sun and Solar atmosphere. It has several cameras aboard, one of those is LASCO.

LASCO stands for Large Angle and Specrometric Cornograph. Effectively, It is a camera pointed at the Sun that is focused such that the Sun is in the center and it is a wide enough angle that it captures an image of space up to 8 sun-diameters in each direction (32 radii total). In order to actually capture the atmosphere of the sun, an arm holds a circular disk in front of the lens to block the Sun itself. In the video, you can see the result – a narrow blocked bar (the arm) from bottom left to center, and the dark circle in the middle. This leaves just the Corona, stars behind, and planets behind the Sun visible.

Lasco is particularly useful for spotting plasma eruptions (CMEs) from the Sun. As the ejecta lifts off the surface of the Sun it becomes visible as bright plumes around the blocked disk. Scientists can measure how large, how wide, and how fast the ejections are moving by studying their signature on the coronagraph.

In this video, the first CME is visible in the Northeast limb between :09 and :12. This is a fairly narrow CME, and given the timelapse, it lasted about 4 hours. The Second CME is much more impressive and launches from the Southwest limb. It is brighter, and it is much wider, appearing to emerge from almost 90 degree of the disk. The second CME can be seen starting around :38 and continuing to the end of the sequence.

Finally, and arguably most interesting, if you watch carefully, you will see a comet looping around the Sun in this image. It is small. The easiest way to see it is by watching the left side of the screen towards the end of the video, you will see it and it’s small tail moving from right to left and slightly up. Now, watch the video again, and see if you can watch it swing from the upper right down around behind the larger CME, and emerge to the South of the sun, then progress behind the Arm, and emerge again.

We’ve taken a screen grab and circled the comet below:

Comet SOHO 2875 in LASCO
ScreenGrab from LASCO timelapse with Comet 2875 identified

Happy Hunting!

NLN Aurora Briefs – February 17, 2015

Share Button

Activity really picked up from the continued influence of the CH HSS (Coronal Hole High Speed Stream). Solar wind became enhanced with speeds reaching about 450 km/sec, and the Bz component having periods of sustained negative readings, the KP reached 5.33. As a result, aurora pictures from Norway, Finland, Northern England, Iceland, Canada, Alaska and New Zealand flooded our social media feeds .

Geomagnetic activity is expected to trail off today and then be quiet for the next several days. The coronal hole has left the Earth-Sun line, so solar winds should subside. The next chance for solar activity appears to be the return of active region 2268. Once it rotates into view and is renumbered the flare threat level will be adjusted to reflect it’s potential.

So many great tweets to pick from for today’s featured tweet. This one from Paul Le Comte really captured the magic:

Happy hunting!