Are there moths on the way to the sun right now going, "It's gonna be worth it!"
Bill Hicks
From the time when men stood tall on the savanna until 3, 2, 1, lift off at Cape Canaveral on February 11th, 2010 the Sun has been a subject of awe and wonder for all of humanity. On that day in February mankind focused millenia of wonder into one astounding device. The Solar Dynamics Observatory is the most advanced instrument devoted to study of the Sun ever created.
We've learned a bit since those days long ago on the Sun drenched and dusty plains of Africa. We no longer consider the Sun a god to be worshipped though we understand, just as they may have, that it is the engine of life. Though we've moved beyond the mystical stories of our ancestors, we still imagine stories to explain the world only now these tales are based on observation of real phenomena.
This the final diary of a series dedicated to the Solar Dynamics Observatory. Sun er Tuesday Science Videos Solar Dynamics Observatory introduced the observatory, it's launch and first light observations. In Sunday Science Videos #8 -- Living With A Star discussed NASA's Living With A Star the Solar Dynamics Observatory's parent program. In today's final episode we describe SDO's instruments and experiments...
Solar Dynamics Observatory
As we've mentioned, the Solar Dynamics Observatory is the first mission of the Living With A Star initiative. This incredible satellite contains 3 separate instrument packages in order to observe various solar phenomena. The Helioseismic and Magnetic Imager (HMI), Extreme Ultraviolet Variability Experiment (EVE), and the Atmospheric Imaging Assembly (AIA).
Here we have a funny introduction to the Solar Dynamics Observatory from the SDOmission2009 YouTube site
The Experiments
Helioseismic and Magnetic Imager (HMI)
The HMI was designed to gather data on solar wave propagation, turbulance, and the magnetic fields on the surface of the sun. Principal Investigator for the HMI is Dr. Phil Scherrer of Stanford University.
To get an idea of what helioseismology is here is a definition from Wikipedia...
Helioseismology is the study of the propagation of wave oscillations, particularly acoustic pressure waves, in the Sun. Unlike seismic waves on Earth, solar waves have practically no shear component (s-waves). Solar pressure waves are believed to be generated by the turbulence in the convection zone near the surface of the sun.[1] Certain frequencies are amplified by constructive interference. In other words, the turbulence "rings" the sun like a bell. The acoustic waves are transmitted to the outer photosphere of the sun, which is where the light generated through absorption of radiant energy from nuclear fusion at the centre of the sun, leaves the surface. These oscillations are detectable on almost any time series of solar images, but are best observed by measuring the Doppler shift of photospheric absorption lines. Changes in the propagation of oscillation waves through the Sun reveal inner structures and allow astrophysicists to develop extremely detailed profiles of the interior conditions of the Sun.Wiki
By studying solar seismic waves scientists can deduce what is happening inside the Sun.
We use the wave data to study the inside of the Sun. As the waves travel through the Sun they are influenced by conditions inside the Sun. The speed of sound increases where solar material is hotter, so the speed and angle at which the wave is generated determine how far it will penetrate into the solar inte- rior. The shallower the angle, the shallower the pen- etration; the steeper the angle, the deeper the wave will travel. It takes about 2 hours for a sound wave to propagate through the Sun’s interior. The frequency and spatial pattern the waves make on the surface indicate where the waves have traveled. Scientists learn about the temperature, chemical makeup, pressure, density, and motions of material throughout the Sun by analyzing the detailed properties of these waves.SDO Guide
Extreme Ultraviolet Variability Experiment (EVE)
The Extreme Ultraviolet Variability Experiment is an instrument designed to measure fluctuations in extreme ultraviolet solar radiation. EUV plays an important role in the Earth's upper atmosphere and understanding when the Sun is active in this range of electromagnetic radiation makes it possible to discern the reasons for various the effects observed in the upper atmosphere. EVE's principal investigator is Dr. Tom Woods of the the University of Colorodo's Laboratory for Atmospheric and Space Physics.
EVE measures the solar extreme ultraviolet (EUV) irradiance with unprecedented spectral resolution, temporal cadence, accuracy, and precision. Furthermore, the EVE program will incorporate physics-based models of the solar EUV irradiance to advance the understanding of the solar EUV irradiance variations based on the activity of the solar magnetic features.EVE Website
Again from the EVE Website
EVE Primary Science Objectives
1) |
Specify the solar EUV spectral irradiance and its variability on multiple time scales
|
2) |
Advance current understanding of how and why the solar EUV spectral irradiance varies
|
3) |
Improve the capability to predict the EUV spectral irradiance variability
|
4) |
Understand the response of the geospace environment to variations in the solar EUV spectral irradiance and the impact on human endeavors
|
Atmospheric Imaging Assembly (AIA)
The AIA is an array of 4 telescopes capable of imaging the Sun in 8 out of 10 possible wavelengths every 10 seconds. The telescopic arrary is sensitive in 9 ultraviolet or extreme ultraviolet wavelenghths with the tenth sensistive to visible light. The AIA experiment is lead by Dr. Alan Title of Lockheed Martin's Solar and Astrophysics Lab
The Atmospheric Imaging Assembly (AIA) for the Solar Dynamics Observatory (SDO) is designed to provide an unprecedented view of the solar corona, taking images that span at least 1.3 solar diameters in multiple wavelengths nearly simultaneously, at a resolution of about 1 arcsec and at a cadence of 10 seconds or better. The primary goal of the AIA Science Investigation is to use these data, together with data from other SDO instruments and from other observatories, to significantly improve our understanding of the physics behind the activity displayed by the Sun's atmosphere, which drives space weather in the heliosphere and in planetary environments. The AIA will produce data required for quantitative studies of the evolving coronal magnetic field, and the plasma that it holds, both in quiescent phases and during flares and eruptions. The AIA science investigation aims to utilize these data in a comprehensive research program to provide new understanding of the observed processes and, ultimately, to guide development of advanced forecasting tools needed by the user community of the Living With a Star (LWS) program.AIA Website
Each of the bands of light that the AIA telescopes are sensitive to can be related to a temperature range. Each temperature range can be associated with a highly ionized atom of either helium or iron. The Wikipedia article describes how extreme ultraviolet radiation is generated...
Neutral atoms or condensed matter cannot emit EUV radiation. Ionization must take place first. EUV light can only be emitted by electrons which are bound to multicharged positive ions; for example, to remove an electron from a +3 charged carbon ion (three electrons already removed) requires about 65 eV. Such electrons are more tightly bound than typical valence electrons. The existence of multicharged positive ions is only possible in a hot dense plasma.
Here are some illustrations of each telescope's region of sensitivity and the associated form of ionic iron associated with that wavelength
The table below shows the regions where the AIA telescopes are active. The higher temperatures correspond to higher excitations of ionized iron.
Wikipedia table displaying the AIA band and temperature sensitivity.
Below are two videos of the June 7th solar flare in the ultraviolet ranges of 171 Å and 211 Å.
171 Å video of the June 7th solar flare.
211 Å video of the June 7th solar flare.
As you can imagine, the SDO generates quite a bit of data. Transmitting data back to the research institutes are a pair of high-gain antennas transmitting in the Ka-band at a frequency of about 26GHz. Telemetry is transmitted over a pair of s-band omni-directional antennas. Communications is routed through two redundant 18-meter dishes at the White Sands Missle Range in New Mexico. Data is transmitted at approximately 150Mbits per second which is about 1.5 terabytes of data per day.
I wish my internet had that kind of bandwidth :) The SDO needs such a high data transmission rate because its instruments are very quick. Previous solar telescopes were able to image the sun at frequencies of minutes. The SDO can take an image of the Sun every 10 seconds at a resolution several times greater than HDTV. Evidence of that can be seen in the various videos included in these diaries.
The scientific importance of the ability to image the Sun so quickly is described in the SDO Guide (pdf)
Because such fast cadences with multiple telescopes have never been attempted before by an orbiting solar observatory, the potential for discovery is significant. In particular, researchers hope to learn how storms get started near the sun’s surface and how they propagate upward through the sun’s atmosphere toward Earth and elsewhere in the solar system. Scientists will also use AIA data to help them understand how the Sun’s changing magnetic fields release the energy that heats the corona and creates solar flares.SDO Press Kit
Links
AIA - Atmospheric Imaging Assembly
Atmospheric Imaging Assembly for the Solar Dynamics Observatory
Helioseismology - Wikipedia, the free encyclopedia
Smithsonian Astrophysical Observatory - Wikipedia, the free encyclopedia
Solar Dynamics Observatory - Wikipedia, the free encyclopedia
White Sands Missile Range - Wikipedia, the free encyclopedia
SDO - EVE-Extreme ultraviolet Variability Experiment
Laboratory for Atmospheric and Space Physics
LWS – Living With a Star Program
Living With a Star Program Details
Living With a Star Targeted Research & Technology Program
Radiation Belt Storm Probes (RBSP) Web Site
Home Page - Heliophysics Science Division - 670
SDO | Solar Dynamics Observatory
Solar and Heliospheric Observatory Homepage
Camilla Corona SDO- Stanford Solar Center
SolarIMG - Solar and Terrestrial images and data
ARTIS @ SolarIMG
HEA Research: Sun
Balloon Array for RBSP Relativistic Electron Losses
Dartmouth College - Space Physics - Balloon Group
Helioviewer - Solar and heliospheric image visualization tool
SolarSoft Latest Events
NASA - Living With a Star Program
NASA - The Sun-Earth Connection: Heliophysics News
'Spectacular' First Images from New Solar Observatory Released | Space.com
YouTube - LittleSDOHMI's Channel
YouTube - NASAedge's Channel
YouTube - SDOEVE's Channel
YouTube - SDOmission2009's Channel
Guide to SDO Data Analysis
As always I look forward to your comments, critiques and questions. I hope I've entertained and informed you a bit with this little diary. If you've learned anything or cracked a smile then I am content.
palantir