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The Mauna Loa Solar Observatory

The Mauna Loa Solar Observatory. Operated by the High Altitude Observatory A Division of the National Center for Atmospheric Research. October 2001.

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The Mauna Loa Solar Observatory

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  1. The Mauna Loa Solar Observatory Operated by the High Altitude Observatory A Division of the National Center for Atmospheric Research October 2001

  2. A major goal of HAO’s solar atmospheric and heliospheric program is to observe and understand the Sun's continuous release of gas and magnetic field energy into interplanetary space. To support this goal, HAO operates the Mauna Loa Solar Observatory (MLSO) on the island of Hawaii. Scientific Goals MLSO Mark-4 K-coronameter image from June 9, 2000

  3. The Mauna Loa Observatory contains instruments to record images of the solar disk and atmosphere many times each day. These observations are used as the basis for determining the physical behaviors of the Sun and determining its variability over both short (hours) and long (years) time scales. Mauna Loa Observer Eric Yasukawa with the CHIP Helium-I Imager Mauna Loa Solar Observatory October 2001

  4. When we speak of solar variability, we refer to the observable effects of the magnetic cycle of the Sun. The solar magnetic cycle is a 22 year variation in the appearance and disappearance of sunspots as well as changes in the solar output of electromagnetic radiation, and magnetized gas (or plasma). Mauna Loa Ha solar disk images. Image on left is from January 14, 1996 during solar minimum, and the image on the right from January 3, 2001 is during solar maximum. Mauna Loa Solar Observatory October 2001

  5. The sun’s outer atmosphere, or corona, expands outward to form a solar wind that fills interplanetary space. The solar wind consists of steady flows of particles and magnetized plasmas as well as highly time-dependent events, such as coronal mass ejections, (CMEs), that are a primary cause for “space weather” at Earth. The solar wind continually strikes the upper atmosphere of the Earth, changing the relatively thin envelope surrounding our planet in ways very important to us. Mauna Loa Solar Observatory October 2001

  6. History of the Mauna Loa Solar Observatory At left: Climax Observatory. The large observing dome at Chalk Mountain was completed at Climax in 1954 and housed a 26’ spar. As more was learned about the Sun and space weather, it became apparent that systematic measurements of the corona were needed. Approximately thirty years after Bernard Lyot invented the coronagraph to detect the corona in lieu of a total solar eclipse, HAO built the Mark-1 K-coronameter to provide the first routine observations of the white light corona. This instrument was first tested in Boulder, Colorado in 1956 and deployed at Climax, Colorado in 1957. Mauna Loa Solar Observatory October 2001

  7. The Mauna Loa Solar Observatory was completed in 1965. It is located at 3400 meters (11,000 feet) on the active volcano of Mauna Loa on the island of Hawaii. Atmospheric conditions at Climax were good but not ideal for coronal observations. Using meteorological data from the Weather Bureau’s station on Mauna Loa, it was determined that Mauna Loa possesses the ideal sky conditions for the K-coronameter. In 1964 the K-coronameter was temporarily moved to the Mees Solar Observatory on Haleakala and then to its current location in 1965 with the completion of the Mauna Loa Solar Observatory. Mauna Loa Solar Observatory October 2001

  8. In 1968 a second coronameter, the Mark-2 was added. Then in 1980, a major breakthrough in ground based coronal observations began with the installation of the Mark-3 coronameter. Mark-3 generated 2-dimensional images, providing a snapshot of the entire low corona every few minutes, in contrast to Mark-1 and -2 that recorded coronal intensities at just two heights. The highly successful Mark-3 instrument operated until September 1999, supporting 4 different space-based coronagraphs and providing the longest single, continuous set of white light coronal observations. Mauna Loa Solar Observatory October 2001

  9. The newest K-coronameter, the Mark-4, began operation in October 1998. The state-of- the-art electronics and improved optics provide increased signal to noise, larger field of view, and higher spatial resolution than the Mark-3. Mark-4 image from June 9, 2000. Mauna Loa Solar Observatory October 2001

  10. Though the Mauna Loa Solar Observatory was originally built to house the K-coronameters for coronal studies, it became apparent that acquiring additional types of solar data would expedite the development of a comprehensive understanding of the physical processes that shape and alter the corona and help relate these processes to the larger physical system created by the solar dynamo. Mauna Loa Solar Observatory October 2001

  11. Current Mauna Loa Solar Observatory Instruments Mark-4 K-Coronameter White Light Corona 1.09 to 2.79 solar radii PICS Ha Limb/Disk Chromosphere ~ 1600 km CHIP Helium-I Imager Chromosphere ~ 2000 km and coronal holes PSPT Photosphere (surface) and the chromosphere ~ 400 km Echo Solar Oscillations from the Solar Interior Mauna Loa Solar Observatory October 2001

  12. Ha (Hydrogen-alpha) In 1980, a camera was installed at Mauna Loa to record full disk and limb images of the solar chromosphere, the colder, thin layer of the atmosphere below the corona, in a neutral emission line of hydrogen known as Ha. Ha is ideal for viewing prominences, cool condensations of partially ionized plasma, which are large- scale structures often seen to erupt in conjunction with coronal mass ejections. Prominences are the bright features visible over the solar limb and the large dark features on the disk. In 1994 a digital Ha camera was installed at Mauna Loa. Mauna Loa Solar Observatory October 2001

  13. Helium-I In 1996 the Chromospheric Helium-I Imaging Photometer (CHIP) was installed providing the highest available time cadence of the chromosphere in the Helium-I 1083.0 nm line. The Helium-I images provide views of chromospheric activity such as prominence eruptions and changes in boundaries between open and closed magnetic structures. Open structures, known as coronal holes, are regions from which solar wind emanates. Mauna Loa Solar Observatory October 2001

  14. Precision Solar Photometric Telescope The Mauna Loa Observatory was expanded in 1997 with the installation of a new dome to house the Precision Solar Photometric Telescope (PSPT). This telescope is the centerpiece of the National Science Foundation’s Radiative Inputs from Sun to Earth (RISE) program. The aim of RISE is to measure and understand the variability in solar radiative output. The PSPT provides full disk digital images of the photosphere at unprecedented 0.1% photometric precision per pixel. Designed and built by the National Solar Observatory (NSO), PSPT instruments operate at NSO, Mauna Loa and Rome Astronomical Observatory. Mauna Loa Solar Observatory October 2001

  15. Experiment for Coordinated Helioseismic Observations (ECHO) The ECHO instrument, originally named Low-L, was installed at Mauna Loa in 1994 to measure solar oscillations. ECHO observes solar acoustic oscillations as seen in variations of the radial velocity over the solar surface. Since these oscillations are global in nature, their observed properties can be used to diagnose the structure and rotation of the solar interior. The ECHO instrument is specifically optimized to observe modes of low degree, which probe deepest into the solar interior. A second ECHO instrument is now operating in Tenerife, in the Canary Islands. Mauna Loa Solar Observatory October 2001

  16. Scientific Research at Mauna Loa Above left: the corona at solar maximum (1980). Above right: the corona at solar minimum (1986). Magnetic forces generally dominate in the corona, shaping the large scale plasma density structures and changing the shape of the corona over the sunspot cycle. Both the total brightness and average temperature of the corona vary over the cycle. The corona is, on average, brighter and hotter around solar maximum. Brighter regions are believed to be areas of closed magnetic fields, where the atmospheric plasma is confined. Closed regions are locations of Coronal Mass Ejections (CMEs). Mauna Loa Solar Observatory October 2001

  17. Coronal Mass Ejections A major goal of coronal studies is to understand transient events known as coronal mass ejections (CMEs) since these are widely believed to be the major cause of non-recurring geomagnetic storms. The energy responsible for producing CMEs is magnetic in nature. There is no general agreement on the exact physical processes that are responsible for CMEs. Two broad types of theories to explain CMEs are systems that are directly driven by magnetic energy or systems that store magnetic energy for later release. Mauna Loa Solar Observatory October 2001

  18. CMEs continued Most of the material in CMEs originates in the corona, though a few events have contained a large fraction of cooler prominence material. The speeds, accelerations and masses of CMEs can vary greatly, and the rate of CME production varies with the solar cycle. Mauna Loa K-coronameter data have been combined with space-based observations of the outer corona to provide a more complete picture of coronal mass ejection formation and propagation. Low coronal data are essential for observing the formation and initial acceleration of CMEs. Mauna Loa Solar Observatory October 2001

  19. Prominence Eruptions Erupting prominences are the most common type of solar activity associated with coronal mass ejections and as such they are closely monitored over the solar limb and across the solar disk. Prominences may play a fundamental role in the formation of coronal mass ejections. MLSO combined disk and limb Ha images. Mauna Loa Solar Observatory October 2001

  20. Solar Variability In addition to the changes in the solar magnetic field, the total radiative output of the sun also varies with the sunspot cycle. The exact cause is not known but it is correlated with visible changes in the area of plagues, the bright regions seen around sunspots. The goal of the MLSO PSPT Red continuum data PSPT project is to provide uniform, long-term, high-precision photometric data sets that can be used to address many of the important questions regarding the physics of solar irradiance and luminosity variability on timescales from hours to years and the effects this variability has on the Earth. Mauna Loa Solar Observatory October 2001

  21. Solar Convection PSPT CaK (calcium-K) data are used to study solar convection and supergranular cells. These data are being used to measure temperature contrasts associated with supergranular convection. Analysis of PSPT data has shown that the supergranule centers are found to be dimmer than the mean MLSO PSPT CaK data quiet Sun continuum. Understanding this in terms of the radiative transport of magnetic flux tubes in the network may lead to a deeper understanding of the supergranule phenomenon and its scale. Mauna Loa Solar Observatory October 2001

  22. Solar Oscillations The colored disk at the far left shows contours of solar interior rotation rates from Sun center to the surface. The colored disk at right indicates the errors in the rotation rate estimates (largest errors are at sun center). Sound waves generated in the Sun can be seen as oscillations at the solar surface and are used to infer the conditions in the solar interior. Data from ECHO are used to determine how solar rotation varies with depth inside the sun. ECHO data are currently used to study the tachocline, the thin layer deep in the Sun between the radiative and convective zones, where the solar dynamo generates the Sun’s magnetic field. Mauna Loa Solar Observatory October 2001

  23. Benefits of Solar Research Understanding our Sun and its variable nature has led to an improved understanding of the variations in the Earth’s atmosphere. The Earth is subjected to a continuous bombardment of high energy particles from the sun. Earth-directed solar eruptions can cause numerous hazards for communication systems, satellites and humans working in space. In addition, the proximity of our Sun allows us to collect the wealth of information needed to study a star in detail in order to fully understand the complex and dynamic behavior that stars possess. Mauna Loa Solar Observatory October 2001

  24. Future Experiments It is known that the magnetic field in the corona is responsible for its changing appearance from day to day and through the solar cycle and provides the source of energy for solar activity and in particular for coronal mass ejections. Despite the central role played by the magnetic field in coronal physics, there are no routine measurements of the coronal magnetic field. The methods used to measure magnetic fields near the solar surface become very difficult to employ in the million degree corona. NCAR scientists and collaborators are working on the development of a new instrument, a coronal magnetometer, to obtain routine coronal magnetic field measurements. The goal is to deploy the instrument at Mauna Loa to be used in conjunction with K-coronameter images. Mauna Loa Solar Observatory October 2001

  25. Mauna Loa Solar Observatory on the web HAO observer Darryl Koon operates the solar instruments at the Mauna Loa Solar Observatory. Contact us or to find out more about the Mauna Loa Solar Observatory: stanger@ucar.edu iguana@ucar.edu Mauna Loa Solar Observatory October 2001

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