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Evolving Submerged Meridional Circulation Cells within the Upper Convection Zone Revealed by Ring-Diagram Analysis
Hill, Frank; Toomre, Juri; Bogart, Richard S. +3 more
Using the local helioseismic technique of ring-diagram analysis applied to Michelson Doppler Imager (MDI) Dynamics Program data from the Solar and Heliospheric Observatory, we have discovered that the meridional flow within the upper convection zone can develop additional circulation cells whose boundaries wander in latitude and depth as the solar…
Evidence of EIT and Moreton Waves in Numerical Simulations
Wu, S. T.; Chen, P. F.; Shibata, K. +1 more
Solar coronal mass ejections (CMEs) are associated with many dynamical phenomena, among which EIT waves have always been a puzzle. In this Letter MHD processes of CME-induced wave phenomena are numerically simulated. It is shown that as the flux rope rises, a piston-driven shock is formed along the envelope of the expanding CME, which sweeps the s…
Interacting Coronal Mass Ejections and Solar Energetic Particles
Kaiser, M. L.; Howard, R. A.; Gopalswamy, N. +5 more
We studied the association between solar energetic particle (SEP) events and coronal mass ejections (CMEs) and found that CME interaction is an important aspect of SEP production. Each SEP event was associated with a primary CME that is faster and wider than average CMEs and originated from west of E45°. For most of the SEP events, the primary CME…
Hot Coronal Loop Oscillations Observed by SUMER: Slow Magnetosonic Wave Damping by Thermal Conduction
Ofman, L.; Wang, Tongjiang
Recently, strongly damped Doppler shift oscillations of hot (T>6 MK) coronal loops were observed with the Solar Ultraviolet Measurement of Emitted Radiation (SUMER) spectrometer on board the Solar and Heliospheric Observatory. The oscillations are interpreted as signatures of slow-mode magnetosonic waves excited impulsively in the loops. Using …
Solar Phenomena Associated with ``EIT Waves''
Thompson, B. J.; Biesecker, D. A.; Vourlidas, A. +2 more
In an effort to understand what an ``EIT wave'' is and what its causes are, we have looked for correlations between the initiation of EIT waves and the occurrence of other solar phenomena. An EIT wave is a coronal disturbance, typically appearing as a diffuse brightening propagating across the Sun. A catalog of EIT waves, covering the period from …
Measurement of Magnetic Helicity Injection and Free Energy Loading into the Solar Corona
Kusano, K.; Sakurai, T.; Yokoyama, T. +1 more
We develop a new methodology that can determine magnetic helicity flux as well as Poynting flux across the photosphere based on magnetograph observation. By applying this method, we study the injection mechanism of magnetic helicity and magnetic free energy into the solar corona. In order to derive the helicity and energy fluxes, first the velocit…
Coronal Holes and the High-Speed Solar Wind
Cranmer, Steven R.
Coronal holes are the lowest density plasma components of the Sun's outer atmosphere, and are associated with rapidly expanding magnetic fields and the acceleration of the high-speed solar wind. Spectroscopic and polarimetric observations of the extended corona, coupled with interplanetary particle and radio sounding measurements going back severa…
Doppler Shift Oscillations of Hot Solar Coronal Plasma Seen by SUMER: A Signature of Loop Oscillations?
Solanki, S. K.; Curdt, W.; Innes, D. E. +2 more
We report observations of strongly damped Doppler shift oscillations detected in a flare line, Fe XIX, with the Solar Ultraviolet Measurement of Emitted Radiation spectrometer. Spectra were recorded above an active region at the western limb of the Sun, from lines with formation temperatures ranging from 0.01 to 10 MK. However, the oscillations we…
Reducing heliospheric magnetic flux from coronal mass ejections without disconnection
Crooker, N. U.; Gosling, J. T.; Kahler, S. W.
Until 1995, disconnection at the Sun was thought to be the only solution to the problem of balancing the magnetic flux coronal mass ejections (CMEs) added to the heliosphere, in spite of the fact that the expected solar wind signature of disconnection was rare. Disconnection was pictured as merging between open field lines to create completely dis…
What is the source of the magnetic helicity shed by CMEs? The long-term helicity budget of AR 7978
Thompson, B. J.; Mandrini, C. H.; van Driel-Gesztelyi, L. +5 more
An isolated active region (AR) was observed on the Sun during seven rotations, starting from its birth in July 1996 to its full dispersion in December 1996. We analyse the long-term budget of the AR relative magnetic helicity. Firstly, we calculate the helicity injected by differential rotation at the photospheric level using MDI/SoHO magnetograms…