Archive for category Science
You may have heard of Comet ISON, a comet discovered last year that is currently approaching the Sun. It is expected to be visible in the SOHO-LASCO C2 and C3: from SOHO’s viewpoint the comet enters from the lower right early on November 27 and exits towards the top near the end of November 30 this year.
It will also be visible from the COR1 and COR2 instruments on board both STEREO spacecraft. The SOHO Hotshot webpage for Comet ISON has many more links to more details on the path of the comet as seen from SOHO and STEREO. At the moment it looks like this, as seen by the Hubble Space Telescope. It might be a spectacular sight from Earth. The appearance of comets from Earth is hard to predict because how it looks when it gets closer to the Sun depends on the details of its composition. We’ll have to wait and see!
As the movie progresses, you see a small eruption take place. As the eruption starts, you can clearly see the southern base of the loop displace. The loop appears to be released in some way, which shakes the whole loop along its entire length. This event is a great example of a transverse coronal loop oscillation. These were first observed by the Transition Region and Coronal Explorer (TRACE) in 1998. Since these initial observations, many more examples have been observed, by both TRACE and AIA. The mechanism of the excitation of these waves remains hidden, but it can be connected with a blast wave generated in a flare epicentre. For scale, the Earth is roughly the same size as the Helioviewer logo in the bottom right hand corner of the movie.
although it is much more difficult to see in the AIA 193 Angstrom channel compared to the AIA 171 Angstrom channedl(the dark wavy material you see are motions in a prominence, not the same as the coronal loop oscillation).
Observations of coronal loop oscillations, coupled with a theoretical understanding of how these oscillations behave in the coronal plasma has lead to a new field of study called coronal seismology. Coronal seismology is analogous to seismology on Earth. Seismology is the study of earthquakes and the propagation of waves arising from earthquakes, and can be used to infer properties of the structure of the Earth. Similarly, coronal seismology is used to measure properties of the Sun’s coronal plasma. Using coronal seismology, we can derive the density and magnetic field of the coronal plasma, measurements that are difficult make in other ways.
Sometimes, instruments that are not specifically designed to observe the Sun can see something from the Sun. This was the case with Fermi, a gamma ray telescope operated by NASA. Its primary mission is to study the most energetic features and events in the Universe, such as supermassive black holes and the merging of neutron stars. Sometimes, however, the Sun makes an appearance in Fermi data. The following GOES X-class flare on March 7th, 2012
was an intense source of gamma-rays. SDO-AIA is not designed to observe gamma-rays. However, Fermi saw the gamma rays from this event. For a great explanation of what Fermi saw from the Sun, check out the following video.
A new version of JHelioviewer is available for download. What’s new? This update release contains improved movie export functionality, an updated LASCO C2 coronagraph mask, the new SDO Cutout Service plug-in plus various bug fixes.
The new movie export menu makes it easier to set the exact scaling of the area you are interested in, and the processing itself is now performed on the graphics card using OpenGL:
The SDO Cutout Service plug-in allows you to request science-quality image data from the SDO/AIA and HMI instruments for the region of interest and time range selected in JHelioviewer:
Why does the orbit have this shape? It’s because SDO takes so many large images that it has to have its own ground station to receive all that data (around 1.5 TB/day). In order to keep the flow of data running off the spacecraft, its geosynchronous orbit was designed to maintain contact with the ground station. For more detail, please go to http://sdo.gsfc.nasa.gov/mission/project/specs.php.
What happened? Well, there was an eruption on the back side of the Sun, that caused a propagating disturbance in the solar atmosphere. that appears to have triggered a prominence lift-off on the front-side of the Sun. This is a great example of how the high cadence, continuous observations from Solar Dynamics Observatory give us a much better view of how distant parts of the Sun can physically influence each other. We liked this event so much we made and uploaded some movies of our own. The lower cadence of these movies allows you to see the swaying of coronal material in response to the disturbance from the initial eruption.
A colleague who works with LASCO data yesterday found this lovely spiralling eruption close to the south pole.
It’s a great example of how the magnetic field can influence the dynamics of erupting plasma. The eruption starts around 00:13 in the above video.
YouTube and Helioviewer.org user sedge2002 found another coronal cavity. This one was on the Sun late 2011 to early 2012. It appears towards the end of this movie, at around 30-45 degrees clockwise from the north pole of Sun, above the limb:
Thanks to sedge2002 for making this movie and sharing it with other users of Helioviewer.org. As the movie demonstrates, coronal cavities do occur, and so the one you may have earlier in the week, whilst a great example of a coronal cavity, is definitely not unique. What is a coronal cavity? Let Dr. Alex Young of the The Sun Today tell you:
The material travels in to the field of view from its launch location, which can be seen in STEREO-B EUVI images. If you go to STEREO latest image selector and select ‘Behind EUVI 195’, pick a resolution of 512 x 512, type in a start and end date of 20120202, and select ‘Slideshow’, you get an animation of the event as seen from STEREO-B. There is a filament eruption on the upper left of the disk (it is hard to spot) which is the same material seen in the AIA 304 movie above:
Thanks to goggog67 for spotting this event and sharing it with us!
The coronal mass ejection associated with the flare event of 23 January 2012 has just been spotted by the Advanced Composition Explorer (ACE) spacecraft. ACE orbits the L1 libration point which is a point of Earth-Sun gravitational equilibrium about 1.5 million km from Earth and 148.5 million km from the Sun. From its location at L1 ACE has a prime view of the solar wind, interplanetary magnetic field and higher energy particles accelerated by the Sun, as well as particles accelerated in the heliosphere and the galactic regions beyond.
You can check here for recent observations of the distribution of the aurora borealis from space, courtesy of the NOAA Polar Operational Environmental Satellite. NOAA also have a test data product and webpage that shows the output of a model that predicts the probability of seeing the aurora. You can keep informed on the latest space weather activity at NOAA Space Weather Prediction Center and the Integrated Space Weather Laboratory.
Here are some more movies of the original event shared by our users – thanks to everyone!
YouTube and Helioviewer.org user losyziemi shared this video of the eruption and the consequent view in LASCO C2 and C3. Those streaks and dots are due to particles accelerated by the event impacting the detectors of LASCO C2 and C3
YouTube and Helioviewer.org user otraLoly shared this video of the eruption, concentrating on AIA 171 and LASCO C2.
As you will already know since you are reading this, Helioviewer Project services have now returned to nominal operations earlier than anticipated. Thanks to all those concerned for their work and for keeping the downtime to a minimum!
Just before our scheduled outage, many of our users caught sight of a flaring active region (videos below). Well, since then the Solar Weather Prediction Center
“has issued a Geomagnetic Storm Watch with G2 level storming likely and G3 level storming possible, with the storm continuing into Wednesday, Jan 25. All of this activity is related to a moderate (R2) Radio Blackout x-ray flare that erupted Sunday night (11pm EST).”
which the self-same flaring event spotted by our users. This is a developing story – please consult the Solar Weather Prediction Center for more updates on the progress of the storm. There is great animation of the predicted progress of the coronal mass ejection through interplanetary space as it comes towards Earth here. Geomagnetic storms are temporary disturbances in the Earth’s magnetic field; this one is predicted to be moderate, possibly strong. On average, there are a few of these every year; the good news is that if you haven’t noticed one before, you’re probably not going to notice this one.
I’ve included some videos of the flaring event below, made by Helioviewer users and shared with Helioviewer and YouTube users – thanks everyone!
YouTube user Idontwannastopat6
Nice close-up of the flare in SDO/AIA 304 ansgtrom from YouTube user 666redwater.
YouTube user 666redwater also made a zoomed-out video of this event using the SDO/AIA 131 filter. In this filter you see very different structures compared to SDO/AIA 304 and 171. There are a total of 10 filters of AIA, each of them telling us something different about the structure of the sun’s atmosphere.
Comet Lovejoy will be passing close to the Sun in the next couple of days. SDO will be taking special observations of the comet beginning 22:59 UT on 2011/12/15 (5.59pm 2011/12/15, Eastern Time), and lasting for a couple of hours. The comet will pass behind the solar limb at around 00:07 UT 2011/12/16 (7:07pm 2011/12/15, Eastern Time). There is a chance the comet will survive its encounter with the Sun.
SDO/AIA will take special observations to view the comet; AIA will change its pointing and point slightly away from the center of the Sun in order to try to get more observations of the comet as it gets close to the disk of the Sun.
Why are these observations being taken? Well, we are looking for something like we saw on 2011/07/05 this year. On that day a comet fell in to the Sun. These kinds of comets have been seen before in LASCO-C3 and LASCO-C2 images. What was new about this observation was that for the first time the comet was seen against the disk of the Sun. The video below gives a description of what was seen.
SDO/AIA detects different wavelengths of light. So in order for us to see it, the comet must have been emitting at those different wavelengths, and the comet must have disintegrated in to a big enough cloud of ionized gas for us to see it. So the big scientific question about seeing this comet against the disk of the Sun is explaining both how it came to be emitting at wavelengths that SDO/AIA could see, and figuring out how it could have disintegrated. This is an active area of research, with presentations on this subject given last week at the American Geophysical Union‘s Fall Meeting, and a paper set to appear in Science.
We hope you enjoy tracking Comet Lovejoy as it gets closer to the Sun. Please let us know if you have any further questions about the Helioviewer Project and Comet Lovejoy.
The filament is the large dark straggly line of material in the upper left of the movie. Click here to see the movie in helioviewer.org.
Filaments are cool strands of material about 100 times cooler than the surrounding plasma, and are supported by magnetic fields. They can lie suspended but cool in the hot solar atmosphere for weeks, and then erupt in a matter of minutes, causing coronal mass ejections. It should be rotating into the SDO field of view in the next couple of days. If you are on Facebook, The Sun Today has a great post about this filament. Let’s see what happens!
NASA astrophysicist James Klimchuk recently gave a talk to the American Geophysical Union on the connection between the Sun, space weather and the Earth.
Dr. Klimchuk gives a great description of the chain of physics that leads from the Sun to the Earth, and it is well worth a look for those who want to get an overview of how events on the Sun can affect the Earth. For example at this time Dr. Klimchuk talks about the solar prominences and how we create artificial eclipses to see coronal mass ejections. From here Dr. Klimchuk talks about the production of the aurora and other effects that Earth-directed coronal mass ejections can produce.
If you are interested in learning more about the AGU’s science, please go to their YouTube channel to see more.
The filament(1) is the narrow dark moving thread in the middle of the field of view. As the movie progresses the filament evolves and eventually erupts out in to space, causing a coronal mass ejection. The material underneath the filament darkens, indicating an evacuation of plasma, that is, the plasma is draining away from that part of the solar atmosphere. These kinds of events happen a lot, and will happen more as solar activity ramps up. Thank you, muriealdurian, for uploading a good example of a filament eruption.
(1) Prominences are filaments seen over the limb of the Sun – prominences and filaments are the same thing, but have different names for historical reasons. Prominences and filaments were first observed in different wavelengths, and so acquired different names. Later, we realized that they were the same thing, but the two names have stuck around in the literature.