The Corona and Heliosphere Section (C&H)

The corona and heliosphere section of HAO conducts observations of the magnetic field and the dynamic evolution of the lower solar corona through the development and operation of a suite of coronal observing instruments, and in parallel, carries out observational analyses, and theoretical and numerical modeling to study the structure, energetics, and dynamics of the corona and the solar wind, and the initiation and properties of eruptive events such as flares and coronal mass ejections (CMEs).

Mauna Loa Solar Observatory (MLSO):

MLSO
The Mauna Loa Solar Observatory (MLSO) provides unique observations of the solar photosphere, chromosphere and low corona that are designed to advance our understanding of the Sun's continuous and dynamic release of magnetized plasma and energy into interplanetary space. MLSO data are used to study solar activity, such as Coronal Mass Ejections (CMEs), prominence eruptions, flares and MHD waves as well as the long term evolution of the solar atmosphere occurring over solar cycle (11-year) time scales. MLSO is located on the island of Hawaii ('Big Island') at 11,200 feet. The site is ideal for coronal observations due to the dark skies, very low water vapor, few cloudy days and total lack of vegetation. All observations acquired at Mauna Loa since 1980 are available to the community from the Mauna Loa web page.


Coronal Solar Magnetism Observatory (COSMO):

MLSO
Driven by society's need to understand the origins of space weather, NCAR scientists at the High Altitude Observatory, along with colleagues at the University of Hawaii and the University of Michigan, plan to build the Coronal Solar Magnetism Observatory (COSMO). The facility will take continuous synoptic measurements of the entire corona in order to understand solar eruptive events that drive space weather and to investigate long-term and solar-cycle phenomena. The primary instrument will consist of a 1.5-m coronagraph with two detector systems: a narrow-band filter polarimeter and a spectropolarimeter. Supporting instruments are a white-light coronagraph to record the evolution of the electron scattered corona (K-corona) and a chromosphere and prominence magnetometer. This new facility will replace the current NCAR Mauna Loa Solar Observatory which has been collecting synoptic coronal data for over 40 years in support of the solar and heliospheric community. More information about COSMO can be found at: http://www.cosmo.ucar.edu/


 

Prominence Magnetometry:

The measurement of the vector magnetic field in solar prominences and filaments has become a priority for coronal physics. The long-term stability of quiescent prominences (from several days to several weeks) suggests that these structures of the solar atmosphere are associated with a highly ordered topology of the magnetic field, right at the interface between the solar corona and the lower solar atmosphere. This long-term stability is not easily disrupted, despite the fact that the visible structure of quiescent prominences appears to be continually affected by highly dynamical events, like rising large-scale voids, and ascending and descending small-scale plumes. This is rather strong evidence that the stability of solar prominences - and its sudden disruption, when a quiescent prominence eventually erupts, leading to a coronal mass ejection - must somehow involve the magnetic topology of a much larger volume of the solar atmosphere than the actual visible structure, extending also to the prominence cavity and the corona above. That is why a concerted effort for measuring the magnetic field vector in prominences and in the solar corona is fundamental for the ultimate goal of understanding the manifestation of energetic events in the heliosphere, which are the main driver of space weather.


Coronal Observational Studies (website):

MLSO

Coronal observational studies at HAO take the unique data of MLSO as their starting point, but connect to a wide range of data from space satellites and ground-based observatories around the world. Coronal mass ejections (CMEs) are an area of particular emphasis, and the MLSO observations in the low corona are well-suited to probe the origins and early evolution of CMEs. Examples of current observational CME/precursor-related topics under study include dark bubbles rising through prominences, coronal prominence cavities, and acceleration of coronal mass ejection/prominences in the low corona. How the corona has varied over the past few cycles is another area of emphasis, and a study is underway to determine the variation of coronal brightness on solar cycle time scales. We are also deeply involved in a series of international campaigns designed to characterize the three-dimensional interconnected solar-heliospheric-planetary system at solar minimum, and to examine how it varies from cycle to cycle. All of these studies are part of our overall goal to understand the structure and dynamics of the three-dimensional solar corona, in the context of the broader heliosphere.


MHD theory and numerical modeling:

MLSO
The theoretical studies and numerical modeling carried out at the C&H section of HAO aim to understand the fundamental physical processes involved in the heating of the solar corona, the acceleration of the solar wind, the initiation and properties of solar eruptive events such as flares and CMEs. Major topics of current research include:

 


Heliospheric modeling:

Understanding how disturbances such as coronal mass ejections (CMEs) propagate from the Sun to the Earth through the heliosphere is an essential component of space weather. To foster such understanding, HAO scientists have been developing a three-dimensional numerical model of the heliosphere based on the FLASH code created and distributed by the University of Chicago.