Search Publications
Characterizing and predicting the magnetic environment leading to solar eruptions
Amari, Tahar; Canou, Aurélien; Aly, Jean-Jacques
The physical mechanism responsible for coronal mass ejections has been uncertain for many years, in large part because of the difficulty of knowing the three-dimensional magnetic field in the low corona. Two possible models have emerged. In the first, a twisted flux rope moves out of equilibrium or becomes unstable, and the subsequent reconnection…
Variations in solar luminosity and their effect on the Earth's climate
Fröhlich, C.; Foukal, P.; Spruit, H. +1 more
Variations in the Sun's total energy output (luminosity) are caused by changing dark (sunspot) and bright structures on the solar disk during the 11-year sunspot cycle. The variations measured from spacecraft since 1978 are too small to have contributed appreciably to accelerated global warming over the past 30 years. In this Review, we show that …
Solar chromospheric spicules from the leakage of photospheric oscillations and flows
De Pontieu, Bart; Erdélyi, Robert; James, Stewart P.
Spicules are dynamic jets propelled upwards (at speeds of ~20kms-1) from the solar `surface' (photosphere) into the magnetized low atmosphere of the Sun. They carry a mass flux of 100 times that of the solar wind into the low solar corona. With diameters close to observational limits (< 500km), spicules have been largely unexplained …
An interplanetary shock traced by planetary auroral storms from the Sun to Saturn
Vourlidas, Angelos; Hansen, Kenneth C.; Prangé, Renée +4 more
A relationship between solar activity and aurorae on Earth was postulated long before space probes directly detected plasma propagating outwards from the Sun. Violent solar eruption events trigger interplanetary shocks that compress Earth's magnetosphere, leading to increased energetic particle precipitation into the ionosphere and subsequent auro…
Rossby waves on the Sun as revealed by solar `hills'
Kuhn, J. R.; Bush, R. I.; Scherrer, P. +1 more
It is a long-standing puzzle that the Sun's photosphere-its visible surface-rotates differentially, with the equatorial regions rotating faster than the poles. It has been suggested that waves analogous to terrestrial Rossby waves, and known as r-mode oscillations, could explain the Sun's differential rotation: Rossby waves are seen in the oceans …
Discovery of a comet by its Lyman-α emission
Bertaux, Jean-Loup; Laakso, Harri; Lallement, Rosine +6 more
Several searches for near-Earth objects have recently been initiated, as a result of increased awareness of the hazard of impacts on the Earth. These programs mainly search for asteroids, so amateur astronomers can still contribute to the discovery of comets, especially out of the orbital plane of the Solar System. An ideal way to search for comet…
X-ray flare sparks quake inside Sun
Kosovichev, A. G.; Zharkova, V. V.
Solar flares involve a release of the Sun's magnetic energy as X-radiation, particle beams and high-speed plasma flows. But we have discovered, using data from the Solar and Heliospheric Observatory (SOHO), that these flares also affect the Sun's interior, generating seismic waves similar to earthquakes. For example, a three-kilometre-high seismic…
Large-scale coronal heating by the small-scale magnetic field of the Sun
Schrijver, C. J.; Tarbell, T. D.; Shine, R. A. +6 more
Magnetic fields play a crucial role in heating the outer atmospheres of the Sun and Sun-like stars, but the mechanisms by which magnetic energy in the photosphere is converted to thermal energy in the corona remain unclear. Observations show that magnetic fields emerge onto the solar surface as bipolar regions with a broad range of length scales. …
The sun's shape and brightness
Kuhn, J. R.; Bush, R. I.; Scherrer, P. +1 more
We present satellite data that show that the sun's shape and temperature vary with latitude in an unexpectedly complex way. Although the solar oblateness shows no evidence of varying with the solar cycle, we find a significant hexadecapole shape term which may vary. We also see a variation of about 1.5 K in the surface temperature with latitude. B…
Long-lived giant cells detected at the surface of the Sun
Scherrer, P. H.; Duvall, T. L.; Beck, J. G.
Giant convective cells have been predicted to exist in the Sun. Such cells should span the entire zone unstable to convective motions - now known to cover the outer 29 per cent of the Sun's radius - and could be dredging up the magnetic flux that is thought to be the source of solar activity (sunspots). Several studies have failed to detect these …