Through mimicking observations in high-latitude areas, we find that the foreshortening affects the time-distance measured mean travel-times, but is not accountable for the center-to-limb effect in travel-time differences.
We have generated a dataset of emerging active regions (EARs) observed by SDO/HMI that is specifically suitable for helioseismic analysis. Using this dataset we show that, on average the bipoles have a symmetric the east-west velocity relative to differential rotation.
HMI now routinely produces vector magnetic field synoptic charts. This Nugget describes the data reduction procedures and the method chosen to resolve the 180-degree ambiguity in azimuth.
Using a combination of the magnetograms, we find signs of the beginning of the 25th cycle from both HMI and WSO by calculating the inclination angles determined from the variation in line of sight field during a disk passage.
Large-scale inflows form around emerging solar active regions in the near-surface layer and alter the global meridional flow patterns.
The HMI data-collection scheme was changed on 13 April 2016 to reduce noise in the vector magnetic field measurement. Starting at 19:24, the Stokes data series hmi.S_720s has been computed by combining filtergrams from both HMI cameras.
HMI and MDI both captured the Mercury transit in May 2016. We have created composite images showing the transit in its entirety.
A realistic MHD simulation driven directly by SDO/HMI vector magnetograms reproduced a solar eruption in a non-potential flux-emerging active region.
An atypical X-shaped-ribbon flare provides evidence for 3D magnetic reconnection at a separator.
The F10.7 microwave flux shows remarkabke agreement with the unsigned magnetic flux from MDI and HMI over the past 20 years, attesting to the accuracy and significance of both.