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.