* Astronomy

Members Login
Username 
 
Password 
    Remember Me  
Home -> Astronomy News -> Solar System -> The Sun
Post Info
TOPIC: The Sun
Blobrana


L

Posts: 131433
Date:
RE: The Sun
Permalink  
 

Data from the ESA/NASA spacecraft SOHO shows clearly that powerful starquakes ripple around the Sun in the wake of mighty solar flares that explode above its surface. The observations give solar physicists new insight into a long-running solar mystery and may even provide a way of studying other stars.
 The outermost quarter of the Suns interior is a constantly churning maelstrom of hot gas. Turbulence in this region causes ripples that criss-cross the solar surface, making it heave up and down in a patchwork pattern of peaks and troughs.
The joint ESA-NASA Solar and Heliospheric Observatory (SOHO) has proved to be an exceptional spacecraft for studying this phenomenon. Discovering how the ripples move around the Sun has provided valuable information about the Suns interior conditions. A class of oscillations called the 5-minute oscillations with a frequency of around 3 millihertz have proven particularly useful.

Read more

__________________
Blobrana


L

Posts: 131433
Date:
Permalink  
 

Tsunami on Sun



__________________
Blobrana


L

Posts: 131433
Date:
Permalink  
 

Title: Tomography of the Solar Interior
Authors: L. Gizon

Solar oscillations consist of a rich spectrum of internal acoustic waves and surface gravity waves, stochastically excited by turbulent convection. They have been monitored almost continuously over the last ten years with high-precision Doppler images of the solar surface. The purpose of helioseismology is to retrieve information about the structure and the dynamics of the solar interior from the frequencies, phases, and amplitudes of solar waves. Methods of analysis are being developed to make three-dimensional images of subsurface motions and temperature inhomogeneities in order to study convective structures and regions of magnetic activity, like sunspots.

Read more (1957kb, PDF)

__________________
Blobrana


L

Posts: 131433
Date:
Permalink  
 

Astrophysicists are having a heated debate over the wave structure of the Suns Corona - a debate which may one day influence solar weather forecasting and the theory behind fusion reactors.
 The Suns core is about 6000 degrees C, but its outer layer, the Corona, which is filled with a strong magnetic field, is 200 to 300 times hotter.
Last year American scientists thought they had cracked this paradox with research showing how high-energy Alfvén wave structures could super-heat the Corona.
The astrophysicists said they could detect Alfvén waves within the Corona waves that have a corkscrew motion along the magnetic field at supersonic speed.
They published their results in prestigious journal Science.
However, scientists at the University of Warwick say these are well known and earlier discovered magneto-acoustic kink waves. These, they say, are a better fit for the complex magnetic fields of the Suns outer layer.
Theyve published their results today in the Astrophysical Journal Letters.

We interpret the data differently. They think theyre looking at an Alfvén wave, but in fact they are looking at Kink wave. Kink waves are a bending of the magnetic field, much alike the bending of the string, when playing the guitar. Moreover, because the scientists from Boulder Colorado identified the wrong kind of wave all of their subsequent calculations are out. And, sadly, it means the question of why the Corona is hot remains unanswered - Dr Tom Van Doorsselaere, Warwick astrophysicist .

Source: University of Warwick

__________________
Blobrana


L

Posts: 131433
Date:
Permalink  
 

SST July 14



__________________
Blobrana


L

Posts: 131433
Date:
Permalink  
 

Our Star in pictures

photosphere coronasunspot chromospheresunspot photospheresunspotsolar jetmercury sun

__________________
Blobrana


L

Posts: 131433
Date:
Permalink  
 

Solar eclipse seen by NASA's STEREO spacecraft



__________________
Blobrana


L

Posts: 131433
Date:
Solar cycles
Permalink  
 

Title: Are solar cycles predictable?
Authors: Manfred Schuessler

Various methods (or recipes) have been proposed to predict future solar activity levels - with mixed success. Among these, some precursor methods based upon quantities determined around or a few years before solar minimum have provided rather high correlations with the strength of the following cycles. Recently, data assimilation with an advection-dominated (flux-transport) dynamo model has been proposed as a predictive tool, yielding remarkably high correlation coefficients. After discussing the potential implications of these results and the criticism that has been raised, we study the possible physical origin(s) of the predictive skill provided by precursor and other methods. It is found that the combination of the overlap of solar cycles and their amplitude-dependent rise time (Waldmeier's rule) introduces correlations in the sunspot number (or area) record, which account for the predictive skill of many precursor methods. This explanation requires no direct physical relation between the precursor quantity and the dynamo mechanism (in the sense of the Bab****-Leighton scheme or otherwise).

Read more (84kb, PDF)

__________________
Blobrana


L

Posts: 131433
Date:
RE: The Sun
Permalink  
 

Title: The Sun in Time: Activity and Environment
Authors: M. Guedel

The Sun's magnetic activity has steadily declined during its main-sequence life. While the solar photospheric luminosity was about 30% lower 4.6 Gyr ago when the Sun arrived on the main sequence compared to present-day levels, its faster rotation generated enhanced magnetic activity; magnetic heating processes in the chromosphere, the transition region, and the corona induced ultraviolet, extreme-ultraviolet, and X-ray emission about 10, 100, and 1000 times, respectively, the present-day levels, as inferred from young solar-analogue stars. Also, the production rate of accelerated, high-energy particles was orders of magnitude higher than in present-day solar flares, and a much stronger wind escaped from the Sun, permeating the entire solar system. The consequences of the enhanced radiation and particle fluxes from the young Sun were potentially severe for the evolution of solar-system planets and moons. Interactions of high-energy radiation and the solar wind with upper planetary atmospheres may have led to the escape of important amounts of atmospheric constituents. The present dry atmosphere of Venus and the thin atmosphere of Mars may be a product of early irradiation and heating by solar high-energy radiation. High levels of magnetic activity are also inferred for the pre-main sequence Sun. At those stages, interactions of high-energy radiation and particles with the circumsolar disk in which planets eventually formed were important. Traces left in meteorites by energetic particles and anomalous isotopic abundance ratios in meteoritic inclusions may provide evidence for a highly active pre-main sequence Sun. The present article reviews these various issues related to the magnetic activity of the young Sun and the consequent interactions with its environment.

Read more (905kb, PDF)

__________________
Blobrana


L

Posts: 131433
Date:
Heliopause
Permalink  
 

The Voyager 2 spacecraft's Plasma Science instrument, developed at MIT in the 1970s, has turned up surprising revelations about the boundary zone that marks the edge of the sun's influence in space.
The unexpected findings emerged in the last few weeks as the spacecraft traversed the termination shockwave formed when the flow of particles constantly streaming out from the sun--the solar wind--slams into the surrounding thin gas that fills the space between stars.
Heliopause


The first surprise is that there is an unexpectedly strong magnetic field in that surrounding interstellar region, generated by currents in that incredibly tenuous gas. This magnetic field is squashing the bubble of outflowing gas from the sun, distorting it from the uniform spherical shape space physicists had expected to find.
A second surprise also emerged from Voyager 2's passage through the solar system's outer edge: Just outside that boundary the temperature, although hotter than inside, was ten times cooler than expected. Theorists had to scramble to come up with an explanation for the unanticipated chilling effect.

voyager-still-enlarged.jpg
Voyager 2 (and its twin, Voyager 1) carried a wide array of instruments to take pictures, measure magnetism and a variety of other properties, and communicate with Earth. The Plasma Instrument, developed 30 years ago at MIT and run by MIT researchers ever since, is the small yellow triangle located on top of the boom at right.
Photo / John Belcher and Mark Bessette, MIT
Voyager's passage


Source

__________________
«First  <  1 … 9 10 11 12 13 … 15  >  Last»  | Page of 15  sorted by
Quick Reply

Please log in to post quick replies.
Home -> Astronomy News -> Solar System -> The Sun


Create your own FREE Forum
Report Abuse 		Powered by ActiveBoard