Search Publications
On the Collective Magnetic Field Strength and Vector Structure of Dark Umbral Cores Measured by the Hinode Spectropolarimeter
Schad, T. A.
We study 7530 sunspot umbrae and pores measured by the Hinode Spectropolarimeter (SP) between November 2006 and November 2012. We primarily seek confirmation of the long term secular decrease in the mean magnetic field strength of sunspot umbrae found by Penn and Livingston (IAU Symp.273, 126, 2011) between 1998 and 2011. The excellent SP photomet…
A Challenging Solar Eruptive Event of 18 November 2003 and the Causes of the 20 November Geomagnetic Superstorm. II. CMEs, Shock Waves, and Drifting Radio Bursts
Temmer, M.; Grechnev, V. V.; Fainshtein, V. G. +7 more
We continue our study (Grechnev et al., 2013, doi:10.1007/s11207-013-0316-6; Paper I) on the 18 November 2003 geoffective event. To understand possible impact on geospace of coronal transients observed on that day, we investigated their properties from solar near-surface manifestations in extreme ultraviolet, LASCO white-light images, and dynamic …
Transit Time of Coronal Mass Ejections under Different Ambient Solar Wind Conditions
Shanmugaraju, A.; Vršnak, Bojan
The speed [v(R)] of coronal mass ejections (CMEs) at various distances from the Sun is modeled (as proposed by Vršnak and Gopalswamy in J. Geophys. Res. 107, 2002, doi:10.1029/2001/JA000120) by using the equation of motion adrag=γ(v−w) and its quadratic form adrag=γ(v−w)|v−w|, where v and w are the speeds of the CME and solar…
Influence of the Solar Global Magnetic-Field Structure Evolution on CMEs
Bilenko, Irina A.
We consider the influence of the solar global magnetic-field structure (GMFS) cycle evolution on the occurrence rate and parameters of coronal mass ejections (CMEs) in Solar Cycles 23 - 24. It has been shown that, over solar cycles, CMEs are not distributed randomly, but they are regulated by evolutionary changes in the GMFS. It is proposed that t…
Kinematic Properties of Slow ICMEs and an Interpretation of a Modified Drag Equation for Fast and Moderate ICMEs
Tokumaru, M.; Fujiki, K.; Iju, T.
We report kinematic properties of slow interplanetary coronal mass ejections (ICMEs) identified by SOHO/LASCO, interplanetary scintillation, and in situ observations and propose a modified equation for the ICME motion. We identified seven ICMEs between 2010 and 2011 and compared them with 39 events reported in our previous work. We examined 15 fas…
Long-Period Oscillations of Sunspots Observed by SOHO/MDI
Solov'ev, A. A.; Efremov, V. I.; Parfinenko, L. D. +1 more
We processed magnetograms that were obtained with the Michaelson Doppler Imager onboard the Solar and Heliospheric Observatory (SOHO/MDI). The results confirm the basic properties of long-period oscillations of sunspots that have previously been established and also reveal new properties. We show that the limiting (lowest) eigenmode of low-frequen…
Quiescent Reconnection Rate Between Emerging Active Regions and Preexisting Field, with Associated Heating: NOAA AR 11112
Longcope, Dana W.; McKenzie, David E.; Yoshimura, Keiji +1 more
When magnetic flux emerges from beneath the photosphere, it displaces the preexisting field in the corona, and a current sheet generally forms at the boundary between the old and new magnetic domains. Reconnection in the current sheet relaxes this highly stressed configuration to a lower energy state. This scenario is most familiar and most often …
A Challenging Solar Eruptive Event of 18 November 2003 and the Causes of the 20 November Geomagnetic Superstorm. I. Unusual History of an Eruptive Filament
Temmer, M.; Grechnev, V. V.; Chertok, I. M. +4 more
This is the first of four companion papers, which comprehensively analyze a complex eruptive event of 18 November 2003 in active region (AR) 10501 and the causes of the largest Solar Cycle 23 geomagnetic storm on 20 November 2003. Analysis of a complete data set, not considered before, reveals a chain of eruptions to which hard X-ray and microwave…
Elemental Abundances in the Solar Corona as Measured by the X-ray Solar Monitor Onboard Chandrayaan-1
Alha, L.; Huovelin, J.; Narendranath, S. +3 more
The X-ray Solar Monitor (XSM) on the Indian lunar mission Chandrayaan-1 was flown to complement lunar elemental abundance studies by the X-ray fluorescence experiment C1XS. XSM measured the ≈ 1.8 - 20 keV solar X-ray spectrum during its nine months of operation in lunar orbit. The soft X-ray spectra can be used to estimate absolute coronal abundan…
Different Periodicities in the Sunspot Area and the Occurrence of Solar Flares and Coronal Mass Ejections in Solar Cycle 23 - 24
Norris, M.; Lawrence, J. K.; Cadavid, A. C. +1 more
In order to investigate the relationship between magnetic-flux emergence, solar flares, and coronal mass ejections (CMEs), we study the periodicity in the time series of these quantities. It has been known that solar flares, sunspot area, and photospheric magnetic flux have a dominant periodicity of about 155 days, which is confined to a part of t…