Search Publications
Did the Sun Change Its Behaviour During the Decline of Cycle 23 and Into Cycle 24?
Tapping, K. F.; Valdés, J. J.
The activity minimum between the end of cycle 23 and the beginning of cycle 24 was the longest and deepest since at least the beginning of the 20th century. This has led to speculation that the Sun is changing its behaviour. The sunspot number and 10.7-cm solar radio flux indices have traditionally been highly correlated, so a change in the relati…
Linking Remote-Sensing and In Situ Observations of Coronal Mass Ejections Using STEREO
Mierla, M.; Zhukov, A. N.; Rodriguez, L. +2 more
The twin STEREO spacecraft have been observing the Sun since 2006. Even though STEREO has only been active during solar minimum conditions so far, an important number of coronal mass ejections (CMEs) and their interplanetary counterparts (ICMEs) have been observed. Many of the ICMEs can be linked back to the corresponding CMEs on the Sun through t…
Constructing Semi-Empirical Sunspot Models for Helioseismology
Gizon, L.; Schunker, H.; Pietarila, A. +1 more
One goal of helioseismology is to determine the subsurface structure of sunspots. In order to do so, it is important to understand first the near-surface effects of sunspots on solar waves, which are dominant. Here we construct simplified, cylindrically-symmetric sunspot models that are designed to capture the magnetic and thermodynamics effects c…
Signatures of Emerging Subsurface Structures in Acoustic Power Maps of the Sun
Kosovichev, A. G.; Zhao, J.; Hartlep, T. +1 more
We show that under certain conditions, subsurface structures in the solar interior can alter the average acoustic power observed at the photosphere above them. By using numerical simulations of wave propagation, we show that this effect is large enough for it to be potentially used for detecting emerging active regions before they appear on the su…
Large-Scale Variation of Solar Wind Electron Properties from Quasi-Thermal Noise Spectroscopy: Ulysses Measurements
Issautier, K.; Meyer-Vernet, N.; Hoang, S. +1 more
The transport of energy in space plasmas, especially in the solar wind, is far from being understood. Measuring the temperature of the electrons and their non-thermal properties is essential to understand the transport properties in collisionless plasmas. Quasi-thermal noise spectroscopy is a reliable tool for measuring the electron temperature ac…
Understanding the Behavior of the Heliospheric Magnetic Field and the Solar Wind During the Unusual Solar Minimum Between Cycles 23 and 24
Zhao, L.; Fisk, L.
The properties of the heliospheric magnetic field and the solar wind were substantially different in the unusual solar minimum between Cycles 23 and 24: the magnetic-field strength was substantially reduced, as were the flow properties of the solar wind, such as the mass flux. Explanations for these changes are offered that do not require any subs…
Relation Between the 3D-Geometry of the Coronal Wave and Associated CME During the 26 April 2008 Event
Temmer, M.; Veronig, A. M.; Gopalswamy, N. +1 more
We study the kinematical characteristics and 3D geometry of a large-scale coronal wave that occurred in association with the 26 April 2008 flare-CME event. The wave was observed with the EUVI instruments aboard both STEREO spacecraft (STEREO-A and STEREO-B) with a mean speed of ∼ 240 km s−1. The wave is more pronounced in the eastern pr…
Failed Eruption of a Filament as a Driver for Vertical Oscillations of Coronal Loops
Mrozek, T.
We present observations of a failed eruption of a magnetic flux rope recorded during the M6.2 flare of 14 July 2004. The observations were mainly made with TRACE 171 Å and 1600 Å filters. The flare was accompanied by a destabilization of a magnetic structure observed as a filament eruption. After an initial acceleration, the eruption slowed down a…
Multiwavelength Observations of a Failed Flux Rope in the Eruption and Associated M-Class Flare from NOAA AR 11045
Filippov, B.; Erdélyi, R.; Kumar, Pankaj +2 more
We present the multiwavelength observations of a flux rope that was trying to erupt from NOAA AR 11045 and the associated M-class solar flare on 12 February 2010 using space-based and ground-based observations from TRACE, STEREO, SOHO/MDI, Hinode/XRT, and BBSO. While the flux rope was rising from the active region, an M1.1/2F class flare was trigg…
Streamer Wave Events Observed in Solar Cycle 23
Feng, S. W.; Chen, Y.; Li, B. +4 more
In this paper we conduct a data survey searching for well-defined streamer wave events observed by the Large Angle and Spectrometric Coronagraph (LASCO) on-board the Solar and Heliospheric Observatory (SOHO) throughout Solar Cycle 23. As a result, eight candidate events are found and presented here. We compare different events and find that in mos…