Search Publications
Velocity Structure and Temperature Dependence of an Extreme-Ultraviolet Jet Observed by Hinode
Imada, S.; Kawai, T.; Kanda, N.
The acceleration mechanism of EUV and X-ray jets is still unclear. In general, there are two candidates for the mechanism. One is magnetic reconnection, and the other is chromospheric evaporation. We observed a relatively compact X-ray jet that occurred between 10:50 - 11:10 UT on 18 February 2011 by using the Solar Dynamics Observatory/Atmospheri…
Transient Dimming of the Bright Fe XIV Emission Region in the Solar Corona of the 21 August 2017 Total Solar Eclipse
Liebenberg, D. H.
During the 21 August 2017 total solar eclipse the corona was observed through a narrowband filter centered at the Fe XIV green emission line at a cadence of 30 frames/s. A bright region on the east limb was observed to dim during the 2 m 35 s totality. Details of the temporal behavior of this region are reported. The likely association of the dimm…
Quiet-Sun EUV He II (30.4 nm) Spatial Power Ratios and Network Dissipation Trend for 2010 - 2018
Didkovsky, Leonid
We explore a significant change of the trend of the transition region network scale variation that occurred around of 2016 when a series of spotless days in 2018, with similar radiative characteristics, were added to previously analyzed days in 2017. We find that a mean per six-year spatial power ratio for 2016 vs. 2010 shows a 29% yearly increase…
Global-Mode Analysis of Full-Disk Data from the Michelson Doppler Imager and the Helioseismic and Magnetic Imager
Schou, Jesper; Larson, Timothy P.
Building upon our previous work, in which we analyzed smoothed and subsampled velocity data from the Michelson Doppler Imager (MDI), we extend our analysis to unsmoothed, full-resolution MDI data. We also present results from the Helioseismic and Magnetic Imager (HMI), in both full resolution and processed to be a proxy for the low-resolution MDI …
First Analysis of Ground-Level Enhancement (GLE) 72 on 10 September 2017: Spectral and Anisotropy Characteristics
Usoskin, I.; Vainio, R.; Valtonen, E. +4 more
Using data obtained with neutron monitors and space-borne instruments, we analyzed the second ground-level enhancement (GLE) of Solar Cycle 24, namely the event of 10 September 2017 (GLE 72), and derived the spectral and angular characteristics of associated GLE particles. We employed a new neutron-monitor yield function and a recently proposed mo…
The Instruments and Capabilities of the Miniature X-Ray Solar Spectrometer (MinXSS) CubeSats
Chamberlin, Phillip C.; Woods, Thomas N.; Caspi, Amir +6 more
The Miniature X-ray Solar Spectrometer (MinXSS) CubeSat is the first solar science oriented CubeSat mission flown for the NASA Science Mission Directorate, with the main objective of measuring the solar soft X-ray (SXR) flux and a science goal of determining its influence on Earth's ionosphere and thermosphere. These observations can also be used …
Instrument Calibration of the Interface Region Imaging Spectrograph (IRIS) Mission
De Pontieu, B.; Bryans, P.; Liu, W. +15 more
The Interface Region Imaging Spectrograph (IRIS) is a NASA small explorer mission that provides high-resolution spectra and images of the Sun in the 133 - 141 nm and 278 - 283 nm wavelength bands. The IRIS data are archived in calibrated form and made available to the public within seven days of observing. The calibrations applied to the data incl…
CMEs in the Heliosphere: I. A Statistical Analysis of the Observational Properties of CMEs Detected in the Heliosphere from 2007 to 2017 by STEREO/HI-1
Rodriguez, L.; Möstl, C.; Kilpua, E. K. J. +10 more
We present a statistical analysis of coronal mass ejections (CMEs) imaged by the Heliospheric Imager (HI) instruments on board NASA's twin-spacecraft STEREO mission between April 2007 and August 2017 for STEREO-A and between April 2007 and September 2014 for STEREO-B. The analysis exploits a catalogue that was generated within the FP7 HELCATS proj…
Detection of Quasi-Periodic Pulsations in Solar EUV Time Series
Zhukov, A. N.; Dolla, L.; Lapenta, G. +2 more
Quasi-periodic pulsations (QPPs) are intrinsically connected to the mechanism of solar flares. They are regularly observed in the impulsive phase of flares since the 1970s. In the past years, the studies of QPPs regained interest with the advent of a new generation of soft X-ray/extreme ultraviolet radiometers that pave the way for statistical sur…
Subsurface Zonal and Meridional Flow During Cycles 23 and 24
Howe, R.; Komm, R.; Hill, F.
We study the solar-cycle variation of subsurface flows from the surface to a depth of 16 Mm. We have used ring-diagram analysis to analyze Dopplergrams obtained with the Michelson Doppler Imager (MDI) Dynamics Program, the Global Oscillation Network Group (GONG), and the Helioseismic and Magnetic Imager (HMI) instrument. We combined the zonal and …