Listed here are links to a variety of MPEG and animated GIF
files that are used to elucidate predictions and discussions in the course.
The list has been split into four parts, each of which contains those files
that are relevant to that section.
Section 1. The Visible Surface
This animated GIF shows the visible photosphere of the Sun (courtesy of D. Hathaway, MSFC/NASA). There are several things to notice about the image.
The surface is homogeneous in appearance. However, one can also see the rotation of the Sun sweeping sunspots across the visible disc. As we shall see in the final section of the course, these spots show where strong bundles of magnetic flux erupt through the photosphere. You should also note that the spot groups appear in preferred bands of latitude (again, more on this in the final section of the module).
The edge, or limb, of the disc appears slightly darker (i.e., cooler)
than the disc centre: this phenomenon is called limb
darkening. Remember, when we observe a particular
location on the photosphere we see radiation emerging from an optical depth
of unity. At the limb, this corresponds to a physical location that is
higher in the atmosphere where the temperature is lower.
Visit the NASA
Marshall Space Flight Centre (MSFC) Solar Physics website
Section 2. The Convection
Zone
This MPEG file (238Kb) shows the results of complex simulations of convection made by Nic Brummel (University of Colorado) and colleagues. The salient points to notice here are the brighter cells (or granules) that contain hotter, rising material and the cooler intergranular lanes that contain sinking, cooler material. The vertical velocities associated with the upward and downard flows reach magnitudes of a few kilometers per second at the top of the convection zone.
As the simulation progresses the structure of the granules evolves,
i.e., they have characteristic life times of the order of 15 minutes
on average.
Section 3. The Picture From
Helioseismology
These MPEGS (courtesy of TAC/Aarhus Copyright 1997) show the internal
ray paths followed by sound waves with different spatial horizontal wavelengths.
These figures are effecitvely a cut through the centre of the Sun. Remember
that the horizontal wavelength is quantized in terms of the angular degree,
l.
The smaller l, the larger the physical separation between the locations
of successive reflections at the top of the bounded cavity in which the
wave is trapped, i.e., the larger the spatial scale.
The following displays the Doppler-shift pattern that the trapped
standing sound waves give rise to over the solar surface. The still images
below are snapshots in time an l=1 (left-hand panel) and l=36
mode (right-hand panel), indicating those regions that are red and blue
shifted. The strongest modes have periods of about 5 minutes, so a complete
cycle of one oscillation will cycle through from red to blue to red again
in this time.
The l=1 mode has a much simpler spatial pattern associated with it; the l=36 mode pattern has a much smaller characteristic spatial scale (i.e., a smaller separation between adjacent nodes and antinodes over the solar surface).
The following MPEG is an animation (once more courtesy of TAC/Aarhus Copyright 1997) of the pulsation patterns arising from an l=8 mode:
Section 4. The Dynamic
Sun
Here, I present some of the colourful, still images included in Sections
4.1 and 4.2 of the Lecture Notes (description above
each image). Included also are links to some solar movies showing these
dramatic, energetic phenomena.
4.1 Phenomenology of the Active Sun
Figure 4.01: This is the
image at the top of this page, which shows sunspots swept across the visible
surface by the rotation of the Sun.
Figure 4.04: The lower solar corona, showing active regions and loops, as observed by EIT on SOHO (courtesy of the EIT/SOHO consortium. SOHO is a project of international cooperation between ESA and NASA).
Figure 4.05: Prominences in the solar corona (courtesy of the EIT/SOHO consortium. SOHO is a project of international cooperation between ESA and NASA).
Figure 4.06: A CME observed by the LASCO instrument on board SOHO (courtesy of the LASCO/SOHO consortium. SOHO is a project of international cooperation between ESA and NASA).
Take a look at these two coronal-mass-ejection
movies, made using LASCO data (again, both courtesy of the LASCO/SOHO
consortium). Both movies also show Sun-grazing comets passing through the
frame.
Figure 4.07: A large solar flare observed by the EIT instrument on board SOHO (courtesy of the EIT/SOHO consortium. SOHO is a project of international cooperation between ESA and NASA).
Take a look at the movie of this flare (2.0 MB)
4.2 The Solar Activity Cycle
Figure 4.10: Magnetograms of the solar surface showing regions of magnetic activity. The left-hand panel in February 1996 and the right-hand panel in March 2000 (images courtesy of Kitt Peak Vacuum Telescope, the National Solar Observatory).
Figure 4.11: The hot solar corona, revealed by observations made by the EIT instrument on board SOHO (courtesy of the EIT/SOHO consortium. SOHO is a project of international cooperation between ESA and NASA).
Figure 4.12: The polarity of sunspots over the solar surface during subsequent cycles (courtesy of D. Hathaway, MSFC/NASA). The plot shows the visible hemisphere projected onto latitute and longitude coordinates; the spots are indicated by the presence of strong concentrations of magnetic field, as shown by the blue (negative) and yellow (positive polarity) regions.
Figure 4.13: The angle of tilt of sunspot pairs with respect to the solar equator (courtesy of D. Hathaway, MSFC/NASA).
Last modified: 2001 Aug 24
