Archive for February, 2011
The latest JHelioviewer update adds support for SDO/HMI data and features a new contrast filter, as well as an improved plugin to access the Heliophysics Event Knowledgebase (HEK).
Today we are making available images from the Helioseismic Magnetic Imager (HMI), an instrument on board the Solar Dynamics Observatory. HMI is designed to study oscillations and the magnetic field at the solar surface, or photosphere. We are providing line-of-sight magnetograms and continuum images* based on HMI science data. A line-of-sight magnetogram measures the flux of magnetic field as seen along the line of sight from HMI to the Sun. A continuum image is formed by filtering portions of the visible light part of the spectrum.
The line-of-sight magnetograms shows blobs of dark emission, and blobs of brighter emission. These correspond to opposite polarity magnetic fields breaking through the Sun’s photosphere. The magnetic field is important as it is related to the activity seen in layers of the Sun’s atmosphere such as the corona (which is observed by AIA). The continuum images allow us to track the evolution of sunspots. These images are important as they allow us to better understand the dynamic nature of the solar atmosphere.
The primary goal of the Helioseismic and Magnetic Imager (HMI) investigation is to study the origin of solar variability and to characterize and understand the Sun’s interior and the various components of magnetic activity. HMI makes measurements of the motion of the solar photosphere to study solar oscillations and measurements of the polarization in a specific spectral line to study all three spatial components of the photospheric magnetic field. HMI produces data to determine the interior sources and mechanisms of solar variability and how the physical processes inside the Sun are related to surface magnetic field and activity. It also produces data to enable estimates of the coronal magnetic field for studies of variability in the extended solar atmosphere, which is where the Earth is. Solar variability that affects the Earth is called “space weather”. HMI observations will help establish the relationships between internal dynamics and magnetic activity. In turn this will lead to better understanding of solar variability and its effects.
For much more information on HMI, please visit http://hmi.stanford.edu/. For more information on SDO, please visit http://sdo.gsfc.nasa.gov.
* HMI is a successor to the Michelson Doppler Imager (MDI) on the Solar and Heliospheric Observatory (SOHO). The Helioviewer Project has MDI line-of-sight magnetogram and continuum images going back to early 1996.
We recently changed the process of how we convert SDO-AIA science data into JPEG2000 images for use with the Helioviewer Project. The new process is now based on the scaling algorithms used to provide images for the Goddard Spaceflight Center’s SDO webpage. Images with the new scaling start from about 2011/01/31 02:00 – 04:00 UT onwards, depending on the measurement. The SDO-AIA 171 waveband shows the least difference between old and new scaling algorithms. All other wavebands show significant changes. We changed the scaling algorithms we use so that users are better able to see the structure and detail in these images without having to do any extra image processing themselves. We think the new images are a definite improvement, and we hope you like them too. Thanks to Leila Mays and Barbara Thompson of the SDO mission for their help in implementing the new scaling algorithms.