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The decay phase of AR 9393 (April 26, 2001) (a) the photospheric magnetic field and the horizontal velocity field at a depth of 2 Mm (b) the vertical (the grayscale map positive -upflows, negative - downflows) and horizontal velocity fields at the depth of 2 Mm (c) the vertical and horizontal velocities at the depth of 6.4 Mm. Figure 7. Sound-speed variations (vertical cuts) associated with developing active region NOAA 10488 (October 2003) (a) emergence of the active region in the...

Potential Field Source Surface PFSS Models

PFSS models are perhaps the most useful Sun-heliosphere connection models to date and have many applications (Arge et al., 2002 Luhmann et al., 2002 DeRosa and Schrijver, 2002). They use the potential field assumption mentioned above and hence decouple the coronal heating problem and the open-flux connection problem by making the inner corona exclusively magnetically dominated and time-independent. For a given choice of source surface radius, rs , the magnetic field potential then can be...

Space Weather Challenges

As pointed out above, the planned return of astronauts to the Moon has led to increased concern about our ability to predict the onset and evolution of large SEP events. The discussion above highlights several questions that need to be answered 10 27 2003 11 6 2003 11 16 2003 11 26 2003 Figure 8. Example showing the creation and disappearance of a new radiation belt coinciding with the occurrence of two SEP events with associated geomagnetic storms. The top trace shows the 1 MeV nuc Fe...

Why Are There Shock Waves

Shock waves arise whenever information about an obstacle in a flow needs to be communicated to that flow faster than a characteristic information or wave speed (i.e., the sound speed in a simple fluid, the fast magnetosonic speed in an MHD plasma, etc.). The ratio of this required communication speed to the linear wave speed is known as the Mach number, M, and is a key parameter of shock physics. The medium must support some nonlinear steepening or compression, which can be balanced by either...

Inner Magnetospheric Convection

Dayside Magnetopause Reconnection (DMR) During times of geomagnetic disturbance, sunward plasma convection (or advection), plays a crucial role in plasmaspheric dynamics. Perhaps the most fundamental cause of inner magnetospheric convection is dayside magnetopause reconnection (DMR). The magnetopause is the boundary between the geomagnetic field and the interplanetary magnetic field (IMF), nominally found at subsolar distance 10 Re. When the IMF at the magnetopause is oriented opposite...

The Low Speed Solar Wind at High Solar Activity LSA and its Sources

The slow solar wind filling most of the heliosphere during high solar activity has to be considered a separate category. It emerges above active regions distributed over large parts of the Sun, probably far from any heliospheric current sheet. In fact, even at high latitudes there is now always slow wind prevailing, in sharp contrast to Figure 5. Polar plots of solar wind speed as a function of latitude of Ulysses' first two orbits. Sunspot number (bottom panel) shows that the first orbit...

Ionospheric Convection

The coupling between the solar wind and magnetosphere is dominated mainly by magnetic reconnection at the dayside magnetopause between the IMF and the geomagnetic field, and was first described for southward IMF by Dungey (1961) and for northward IMF by Dungey (1963). The scenario for southward IMF is illustrated in Figure 1 in which a cross section in the noon-midnight plane of the magnetosphere is presented. Reconnection occurs at the sub-solar point of the magnetopause, resulting in newly...

Magnetohydrodynamic MHD Models

The PFSS models have now been surpassed by MHD models that have more capability to address the important connection between coronal heating and the field and plasma ranging into the heliosphere (Linker etal., 1999 Riley etal., 2002 Roussev etal., 2003,2004). These computations solve all MHD equations, typically using a simple energy equation with additional a priori assumptions about heating profiles or boundary conditions. MHD models have important advantages over PFSS models because they can...

Particle Acceleration in Secondary Flare Loops

The quadrupolar configuration (Figure 1, right-hand side) involves magnetic reconnection between two closed magnetic field lines, which relaxes into an alternative quadrupolar connection with switched polarities. This basic (3D) quadrupolar reconnection process has also been dubbed as a flaring process between two interacting loops and was physically interpreted as a magnetic flux transfer between two current-carrying loops (Melrose, 1997). Observational evidence for this type of reconnection...

Basic Properties and Structure of the Ring Current

Cyclotron motion (gyration) and bounce motion of a charged particle along a geomagnetic field line. Figure 1. Cyclotron motion (gyration) and bounce motion of a charged particle along a geomagnetic field line. consists of two components, a bounce motion back and forth along the field line between mirror points and a slow drift motion around the Earth. The large difference in the respective time scales of these motions makes a mathematical separation possible and leads to the...

Collisionless or as it is Often Called Anomalous Resistivity

Current energy dissipation due to wave-particle interaction is the normal dissipation mode in collisionless plasmas. By historical reasons it is often called anomalous in contrast to dissipation due to binary particle collisions, important in plasmas with a small plasma parameter Np nX3D > 1. Here n is the number density and XD vt wpe the Debye length, vt JkT me is the electron thermal velocity, wpe yne2 eome the electron plasma frequency, me, e the electron's mass and charge, respectively....

Oe

UT 4 00 5 00 6 00 7 00 8 00 9 00 10 00 MLT 1100 1200 1300 1400 1500 1600 1700 Figure 2. (a-d) Top row EUV plasmasphere images from a typical erosion event on 18 June 2001 (Goldstein and Sandel, 2005). The format is similar to that of Figure 1b the Sun is to the right and Earth is the half-shaded circle in the center. Dotted circles are drawn at L 2,4, and 6 the solid circle indicates geosynchronous orbit. Bottom row Extracted plasmapause points from the images directly above. During the erosion...

References

Anastasiadis, A., and Vlahos, L. 1991, Astron. Astrophys. 245, 271. Arzner, K., and Vlahos, L. 2004, Astrophys. J. 605, L69. Buchlin, E., Aletti, V., Galtier, S., Velli, M., Einaudi, G., and Vial, J.-C. 2003, Astron. Astrophys. 406, 1061. Dmitruk, P., Matthaeus, W. H., Seenu, N., and Brown, M. R. 2003, Astrophys. J. 597, L81. Dmitruk, P., Matthaeus, W. H., and Seenu, N. 2004, Astrophys. J. 617, 667. Fragos, T., Rantsiou, E., and Vlahos, L. 2004, Astron. Astrophys. 420, 719. Galsgaard, K. 2002,...

Statistical Properties

To see the ICME as disturbances superposed on the solar wind, we first show the distributions of magnetic field strength, speed, density and temperature of the solar wind obtained from Omniweb for a time period 1996-2003 (see Figure 3). Note that the solar wind parameters obtained from Omniweb correspond to a heliocentric distance of 1 AU and may have different values at other distances. The number of hours with missing data was only a small fraction (< 8 ). The distributions with and without...