Observables Processing for the Helioseismic and Magnetic Imager Instrument on the Solar Dynamics Observatory

Couvidat, S.; Schou, J.; Hoeksema, J. T.; Bogart, R. S.; Bush, R. I.; Duvall, T. L.; Liu, Y.; Norton, A. A.; Scherrer, P. H.

doi:10.1007/s11207-016-0957-3

Cited by 135 publications

(137 citation statements)

References 33 publications

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“…Data calibration procedures for HMI data are described in Couvidat et al (2016). SHARP data is available in either unprojected (in plate coordinates) form or as Lambert cylindrical equal area (CEA) projected data, see Thompson (2006) and Snyder (1987) for detailed reviews of common solar coordinate systems and cartography.…”

Section: Data and Analysismentioning

confidence: 99%

Magnetic Flux Emergence and Decay Rates for Preceder and Follower Sunspots Observed with HMI

Norton

Jones

Linton

et al. 2017

ApJ

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We quantify the emergence and decay rates of preceder (p) and follower (f) sunspots within ten active regions from 2010-2014 using Space-weather Helioseismic Magnetic Imager Active Region Patch data. The sunspots are small-to mid-sized regions and contain a signed flux within a single polarity sunspot of (1.1 − 6.5) × 10 21 Mx. The net unsigned flux within the regions, including plage, ranges from (5.1 − 20) × 10 21 Mx. Rates are calculated with and without intensity contours to differentiate between sunspot formation and flux emergence. Signed flux emergence rates, calculated with intensity contours, for the p (f) spots average 6.8 (4.9) ×1019 Mx h −1 , while decay rates are −1.9(−3.4) × 10 19Mx h −1 . The mean, signed flux emergence rate of the regions, including plage, is 7.1 × 10 19 Mx h −1 for a mean peak flux of 5.9 × 10 21 Mx. Using a synthesis of these results and others reported previously, there is a clear trend for larger flux regions to emerge faster than smaller ones. Observed emergence rates (dφ/dt, Mx h −1 ) scale with total signed peak flux,φ max , as a power law with an exponent of 0.36, i.e., dφ/dt = Aφ 0.36 max . The observed rates may assist in constraining the boundary and initial conditions in simulations which already demonstrate increased rates for flux tubes with higher buoyancy and twist, or in the presence of a strong upflow. Overall, the observed emergence rates are smaller than those in simulations, which may indicate a slower rise of the flux in the interior than captured in simulations.

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Section: Data and Analysismentioning

confidence: 99%

Magnetic Flux Emergence and Decay Rates for Preceder and Follower Sunspots Observed with HMI

Norton

Jones

Linton

et al. 2017

ApJ

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“…A close factor of 1.35 was also found by Svalgaard and Sun (2016). The differences between the measurements from MDI and HMI data can be due to their different calibration and a number of other factors (see Riley et al, 2014;Watson, Penn, and Livingston, 2014;Couvidat et al, 2016). Thus, in the transition from SOHO to SDO data, the relation Φ MDI = 1.4Φ HMI should be used.…”

Section: Comparison Of Erupted Magnetic Fluxesmentioning

confidence: 81%

An Early Diagnostics of the Geoeffectiveness of Solar Eruptions from Photospheric Magnetic Flux Observations: The Transition from SOHO to SDO

2017

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In our previous articles (Chertok et al.: 2013, Solar Phys. 282, 175, and 2015, Solar Phys. 290, 627), we presented a preliminary tool for the early diagnostics of the geoeffectiveness of solar eruptions based on the estimate of the total unsigned line-of-sight photospheric magnetic flux in accompanying extreme ultraviolet (EUV) arcades and dimmings. This tool was based on the analysis of eruptions observed during 1996 -2005 with the Extreme-ultraviolet Imaging Telescope (EIT) and the Michelson Doppler Imager (MDI) on board the Solar and Heliospheric Observatory (SOHO). Empirical relationships were obtained to estimate the probable importance of upcoming space weather disturbances caused by an eruption, which just occurred, without data on the associated coronal mass ejections. In particular, it was possible to estimate the intensity of a non-recurrent geomagnetic storm (GMS) and Forbush decrease (FD), as well as their onset and peak times. After 2010 -2011, data on solar eruptions are obtained with the Atmospheric Imaging Assembly (AIA) and the Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO). We use relatively short intervals of overlapping EIT -AIA and MDI -HMI detailed observations and, additionally, a number of large eruptions over the next five years with the 12-hour cadence EIT images to adapt the SOHO diagnostic tool to SDO data. We show that the adopted brightness thresholds select from the EIT 195Å and AIA 193Å image practically the same areas of arcades and dimmings with a cross-calibration factor of 3. 6 -5.8 (5.0 -8.2) for the AIA exposure time of 2.0 s (2.9 s). We also find that for the same photospheric areas, the MDI line-of-sight magnetic flux systematically exceeds the HMI flux by a factor of 1.4. Based on these results, the empirical diagnostic relationships obtained from SOHO data are adjusted to SDO instruments. Examples of a postdiagnostics based on SDO data are presented. As before, the tool is applicable

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“…This can be corrected by a fitting (e.g., see Hoeksema et al (2014) and Couvidat et al (2016)) that we do not apply here.…”

Section: Discussionmentioning

confidence: 99%

A New Method to Quantify and Reduce the Net Projection Error in Whole-Solar-Active-Region Parameters Measured From Vector Magnetograms

Falconer

Tiwari

Moore

et al. 2016

ApJL

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Abstract:Projection error limits the use of vector magnetograms of active regions (ARs) far from disk center. In this Letter, for ARs observed up to 60 o from disk center, we demonstrate a method of measuring and reducing the projection error in the magnitude of any whole-AR parameter derived from a vector magnetogram that has been deprojected to disk center. The method assumes that the center-to-limb curve of the average of the parameter's absolute values measured from the disk passage of a large number of ARs and normalized to each AR's absolute value of the parameter at central meridian, gives the average fractional projection error at each radial distance from disk center. To demonstrate the method, we use a large set of large-flux ARs and apply the method to a whole-AR parameter that is among the simplest to measure: whole-AR magnetic flux. We measure 30,845 SDO/HMI vector magnetograms covering the disk passage of 272 large-flux ARs, each having whole-AR flux >10 22 Mx. We obtain the center-to-limb radial-distance run of the average projection error in measured whole-AR flux from a Chebyshev fit to the radial-distance plot of the 30,845 normalized measured values. The average projection error in the measured whole-AR flux of an AR at a given radial distance is removed by multiplying the measured flux by the correction factor given by the fit. The correction is important for both the study of evolution of ARs and for improving the accuracy of forecasting an AR's major flare/CME productivity.

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Observables Processing for the Helioseismic and Magnetic Imager Instrument on the Solar Dynamics Observatory

Cited by 135 publications

References 33 publications

Magnetic Flux Emergence and Decay Rates for Preceder and Follower Sunspots Observed with HMI

Magnetic Flux Emergence and Decay Rates for Preceder and Follower Sunspots Observed with HMI

An Early Diagnostics of the Geoeffectiveness of Solar Eruptions from Photospheric Magnetic Flux Observations: The Transition from SOHO to SDO

A New Method to Quantify and Reduce the Net Projection Error in Whole-Solar-Active-Region Parameters Measured From Vector Magnetograms

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