New advances in solar monitoring

Launched in February, data from sensors from devices on NASA's Solar Dynamics Observatory reshaped what we knew about the processes of the Sun and the causes of cosmic weather, Alan Title said.

The most beautiful sun is when it is most dangerous. That beauty is visible from the Earth in the form of northern and southern light, which occurs when charged particles from the Sun strike the Earth's upper atmosphere. But beyond space, the consequences of 'cosmic weather' are caused by the unfavorable Sun: X-rays and gamma rays that the Sun emits can damage sensitive electronic devices, destroying computers. and there are dangerous (even fatal) effects on astronauts.

Live the same star.

Most of the time, the Earth's atmosphere and magnetic fields protect us from harmful situations that occur in the Sun's atmosphere, such as explosions near the surface of the Sun (known as fire Sun) or cases that erupt giant gas bubbles from inside the Sun (called mass corona liberation, or CMEs). However, when charged particles from the Sun hit the Earth's magnetic field, the field is distorted and compressed. As a result, changes in the density of charged particles in the Earth's upper atmosphere can produce significant impacts. Radio communications can be interrupted, and sometimes, can cause damaging streams in long wires, underground cables and oil pipelines. These giant flames even destroy transformers and cut off the entire electrical network.

However, like the aurora appearance, the Sun's processes that cause cosmic weather are also great scenes. The images above show a ring-shaped protrusion that erupts from the surface of the Sun, sending out masses of plasma pulses rushing outside at speeds of about 300 km / sec. Before the eruption, this prominence existed as a relatively cool long tube, magnetically containing visible surface materials. It is then destabilized by a mechanism that we cannot grasp. Such mechanisms are important because they produce CMES, which can eject up to 10 billion tons of hot plasma into the heliosphere - with extremely serious consequences for objects and people, and it is happening before our eyes.

One of the main goals of NASA's Solar Dynamics Agency (SDO) is to understand instability mechanisms. To learn more about them, and the phenomena that are born, we need to observe the events that are currently taking place on the Sun. This is not an easy thing. Intense flares and CMES can happen almost anywhere at all times, so we need a system to observe the entire surface of the Sun continuously. Furthermore, very fast solar explosions - at a rate of 1000 km / s are not uncommon - so images must be at a certain level and with exposure periods to be captured. Get instantaneous developments of complex events. Sending data from many images to Earth, sorting and moving to scientists is also a difficult thing. Finally, common problems arise when working in space: you only have one 'transmitter', so if the device doesn't work, then you can't fix it, all devices must Be as neat as possible for all worth up to £ 200,000 per sign just to launch an experiment, and the device must have an extremely sensitive sensor, and the computer must be able to withstand time Severe cosmic details that they have the task of studying, without the protection of the Earth's magnetic field.

The fire ears exploded at the surface of the Sun.

All of these factors pose a challenge for each of us who are responsible for designing devices for SDO. As the first mission of NASA's 'Living with a Star' program, SOD's aim is to help us get more information about the events of the Sun, such as the emergent arc area. shown in Figure 1, the effects on heliosphere and in particular, how they cause cosmic weather. In this way, SDO is designed based on previous missions such as SOHO or STEREO, launched in 1995 and 2006 respectively. These two missions are still in operation, adding to our knowledge base of The event takes place on the Sun by collecting additional data based on the outer halo, while STEREO, providing additional observations of the Sun's explosions. Similarly, TRACE, launched in 1996 and ending its next December mission, provides high-resolution images of predetermined areas of the Sun's atmosphere.

The results from previous missions provide a concrete view of how the Sun moves. However, this new mission will give us more about the Sun that previous missions have not done. All previous images of the Sun aura were degraded by three major limitations. One is that they cannot combine high-resolution spatial photography with observations covering the entire Sun disk. Secondly, devices cannot interrupt images (called "high-speed" operations) because data limits can be sent to Earth. And finally, because previous devices couldn't capture images on a range of different wavelengths, and at a rate comparable to the development of aura, it couldn't distinguish whether the event recorded Received is due to hot porcelain, coldness or density changes.

The trio observes the Sun.

SDO was launched in the Kennedy Center on February 11 and put into a static orbit of 36,000 km above Earth with the Atlas V. rocket Three devices on board are designed to support each other. The heliocentric and magnetic observation (HMI) developed by Stanford University researchers and Lockeed Martin Space Astrophysics Laboratory (LMSAL), will study how magnetic fields work at the surface. Sun face. To do this, every 30 seconds the HMI creates maps of matter flowing on the surface of the Sun. It also maps the 'linear' field every 45 seconds and the magnetic field every 15 minutes. Surface flow maps let us infer some of the things that are happening below the surface of the Sun, because the shapes of surface flow can reveal the movement of magnetic fields, even before they appear on the visible hemisphere. The vector field maps, meanwhile, show the direction and magnitude of the magnetic field that appears across the surface of the Sun. For linear maps, they show magnetic flux toward Earth. Vector fields provide more information, but linear measurements are more accurate.

Photographic equipment

The second device on SDO is the atmospheric imaging complex (AIA), also developed at LMSAL (Figure 2). Its task is to study how the solar aura responds to the magnetic fields that the HMI observes near the surface of the Sun. Four AIA telescopes (see frame) send light to CCD cameras, recording images of the Sun's atmosphere at wavelengths corresponding to the ionization state of iron and helium, as well as three optical ranges spectrum in the ultraviolet region of the spectrum. Data from iron spectral lines allow us to chart the halo temperature in a range of 700,000–20 × 106 K, while data for helium record temperatures of 30,000–100,000 K.

The last device on the SDO ship is the Instrument measuring the varied variation of ultraviolet rays (EVE). Developed by a team of staff at Colorado University's Atmospheric and Space Physics Laboratory, EVE includes a series of spectrometers to measure solar radiation on a total number of wavelengths between 0.1-105 nm. Because EVE and AIA fly together, it can also be changed to combine changes in solar radiation with solar events, by comparing the time of changes in EVE measurements. with spectral sequence data among AIA images.

Manage the data collected.

The requirements for high-speed imaging, quality spatial resolution and the need for clear spectra led to the design of three devices, as well as the characteristics and trajectories of spacecraft carrying them. The trajectory of the observatory, for example, provides two important advantages in studying the Sun. First, that orbit is high enough on Earth, the only planet shading the Sun for one hour per day maximum - and even then two hours, two weeks per year, in September and March. Second thing , the province means that the SDO ship is always on the same latitude, so it can transmit data and receive continuous commands from a single control station gradually White Sands, New Mexico.

Keeping in touch with the checkpoint is very important for SDO, thanks to the sheer volume of data generated. There are a total of six CCD cameras on the SDO - two on the HMI and six on the AIA - and almost every second takes a 4096 x 4096 pixel image (16 megapixels) from each of the following read and read to the Left. Land. The actual pixel level is large compared to the standard CCD commercial camera (13 × 13 μm).

Because the number of photons detected in the single exposure is proportional to the pixel size, the CCDs on the AIA have a large range and are mobile - from 1 to 10,000. (The luster is designed and manufactured by scientists at Rutherford Appelon Laboratory near Didcot, while the CCD detector is made by e2v, also in the UK). This is great that can cover a wide range of intensity on the Sun, but this also means a 'heavy' picture of a quarter of terabit of data. Indeed, the total data sent from AIA and HMI to the checkpoint in New Mexico is about 18 terabytes per day, or 67 megabits per second. To get an idea of ​​the scale of the relevant data, considering each photo, it will fill 6.25 DVDs, so it will need 540,000 DVDs to contain all the photos taken in a day.

This high-speed data has a significant impact on the design of the General Operational Science Center on HMI and AIA (EVE has much smaller data transfer rates, has its own data center), system data distribution and the rest of the scientific community used to access data. The final feature is especially important, whereby if you ask a data scientist he wants the car, the first answer is usually 'All that.' Unfortunately, this terrible truth is that once the photos are compressed, AIA unilaterally generates about 3.5 terabytes of data every day - equivalent to downloading 700,000 quality MP3 audio files.

To make it easier for solar scientists, a number of utilities have been developed that allow us to store distributed SDO data into specific scientific goals. For example, some questions that scientists are trying to find whether the included flame solutions are associated with CMEs, what kind of fire is associated with specific features in the EVE spectrum, and the termites Any statistical correlation between the wire explosion and the shape of the magnetic field. We produce a data viewer, allowing scientists to view archives with compressed data. This greatly reduces the amount of data that must be collected before accurate scientific assessments can begin. The data processing tools include the 'Sun Today' homepage (www.Imsal.com) that shows sample images slowly from the AIA and HMI spectrum, updated every 5 minutes, as well as every day video clips of variables Trying on the Sun.

What are we studying:

At the end of March, we opened the wings of the AIA telescope for the first time. The first images are gorgeous. The sophisticated filters on the front of the telescopes are safe after the launch and all devices work perfectly. After a few days we started taking data, the Sun rewarded us with a big explosion to the east of it - a great start to the five-year mission.

Since then, we have been watching the Sun almost continuously, only taking a break as planned. During this time, the Sun has been shown through a number of CMEs, rope spikes, small flames and even quite a few times. As a result, we began to assess how much of the Sun is affected by a rearrangement of the magnetic field in a very adjacent area. For example, the area without dark spots can create disorders that affect 30-60% of the visible surface.

Taking high-speed photos brings a great prize. At the beginning of wire or CME operations, some features occur at speeds of 100–600 km / sec. At the beginning of an intense burst of fire, there are sometimes 'plasma' moves that travel at 1000–2000 km / sec. When such fluctuations occur, part of their diffuse surface is caused by motion blur; a typical 3s exposure image taken by the AIA, for example, blurs the image of a 2000 km / s structure by 4-8 pixels. A typical 30s exposure image of the previous spacecraft would lose five times or more strokes and make the image blur 25 times - very blurry, in fact, this event is hard to detect. We also see wave patterns moving along magnetic field lines at 1000–2000 km / s as in the case of fire tracks.
These fast waves have never been seen before and we do not know the mechanism by which they are created or their role in explosive processes.

The sun was shining brilliantly.

Although some of this data is better in terms of numerical interpretation, complex temperature images taken by AIA can also be combined with some types of wrong color heat maps, as shown in Figure 3. Videos of color maps also allow scientists to study the sun to find out how patterns of temperature develop when the Sun is static, as well as when it moves. The videos provide visual images between the events of the events on the Sun that are quite far apart. For decades there have been scientific debates about whether string eruptions or explosions are also available to cause a subsequent event at a distance. Now, after only a few months of observation, the AIA footage has established a clear cause for the distances of the solar diameter and more. Although we are experiencing the deepest minimum of the Sun's activities more than a whole century, the Sun still has quite a lot to say to us.

AIA telescopes: a four-fold challenge:

NASA's Solar Dynamics Observatory carries three instruments, one of which is the Atmospheric Imaging Complex (AIA). Its four telescopes design shows four major challenges, one of which is caused by sunlight itself. The amount of light reaching a typical ultraviolet (EUV) channel is one billion times weaker than the sunlight that hits the front of the telescope. In order to eliminate visible light, the front of each EUV channel is covered with a metal filter of only 150n thick, or about 0.2% glass of human hair - thick enough to block visible light, but also thin enough to shine EUV morning pass.

Producing such filters is a big challenge, but designing them together is even harder. Mounting must be strong enough to withstand vibrations or pressure changes that they must resist during launch, but they cannot block a large part of EUV light. The image shows one of the many filters that failed during the test to determine which models were able to tolerate the ejection environment perfectly.

AIA telescope filter.

The second method is to ensure that EUV light is reflected from the telescope mirrors. EUV light will not reflect from a single silver or aluminum coating for mirrors of visible light telescopes, so instead we have to cover the mirror with layers of silicon and molybdenum substitutes. This coating cannot peel, so if there is an error in the coating process the mirror will not be used. Mirrors must also have the right shape, and because the wavelength of EUV light is very short, they must be extremely smooth, with vibrations in each absolute square at about 0.3 nm.

The third challenge is that EUV light can be easily absorbed by contaminants such as silicon and hydrocarbon compounds used to hold AIA glasses together. A dirty coating that is only 50 nm thick is enough to reduce the glass transfer rate by 50%, and the AIA glasses keep on 11 different surfaces where such dirty areas can be solved, including many filters and prisms. level and secondary of the telescope, and the main surface of the CCD camera. This means less than 5 nm of contaminants are allowed on any surface, either during fabrication or from the exhaust of star components when AIA enters orbit.

CCD cameras sample light from a cone about 0.6 seconds wide, corresponding to about 730 km from the center of the Sun's disk. In order to create a sharp image, the motion caused by the spacecraft must be limited to about 0.02 second angle, or about 14 km above the Sun's surface. This requires a stable operating system, where the signals generated by the telescopes themselves are used to control the corners of the secondary mirror mounted on the piezoelectric actuator. The result is very stable like keeping a laser pointing to a target circle of 1mm diameter at a distance of 10km. For golf fans, this is equivalent to a person hitting a hole on the Old Course in St Andrews while standing at Piccadilly Circus.