Alfven waves

From Portal
Jump to: navigation, search



Eurekalert.org

Scientists find solution to solar puzzle

The study, which has been published in the illustrious Science journal, has discovered evidence for the existence of a new breed of solar wave, called the Alfvén wave, which transports energy to heat the Sun's corona. This phenomenon was first proposed by Hannes Alfvén in 1942, but despite winning a Nobel Prize for his pioneering work in this field, hard evidence for the wave has not been found until now in the solar atmosphere.
Often, waves can be visualized by the rippling of water when a stone is dropped into a pond, or by the motions of a guitar string when plucked. However, Alfvén waves cannot be seen so easily. In fact, they are completely invisible to the naked eye. Only by examining the motions of structures and their corresponding velocities in the Sun's turbulent atmosphere could we find, for the first time, the presence of these elusive Alfvén waves.
More: http://www.eurekalert.org/pub_releases/2009-03/uos-sfs032009.php


Hinode mission delves into solar mysteries

Several research teams report evidence of Alfvén waves, which could potentially heat the corona to extreme temperatures by releasing energy as they travel outward from the Sun along magnetic field lines. These findings may help solve the so-called “corona problem,” which refers to the fact that the sun’s surface, the photosphere, is only about 6,000 Kelvin, while the corona is at least 1 million Kelvin.
More: http://www.eurekalert.org/pub_releases/2007-12/aaft-hmd113007.php

Current Research of Cynthia Cattell, Professor/Associate Head (Physics), Univ. of Minnesota

Energization and Loss of Relativistic Electrons in Van Allen Belts

We are using plasma wave and energetic particle data obtained during the 4 perigee passes of the NASA STEREO spacecraft to examine dynamics of the radiation belts. Using observations from STEREO and results of a particle tracing code run on MSI supercomputers, we have shown that electrons can be accelerated by the order of MeV within less than .1s, showing that electron energization can be coherent and rapid rather than stochastic and slow (10s of hours). Studies of electron energization and loss utilizing STEREO and SAMPEX data and development of improved simulations are ongoing.
Waves associated with interplanetary shocks and solar wind electrons
Utilizing particle and waves data from the WIND and STEREO satellites, we are examining dissipation at collisionless shocks. We are also studying a number of wave-particle interaction processes in the solar wind.
Particle acceleration in the aurora
Using in situ particle and fields data from the NASA FAST and Polar satellites and auroral images from IMAGE and TIMED, we are addressing a number of questions associated with the acceleration of electrons and ions in the Earth's auroral regions.
Microphysics of reconnection
Reconnection is a ubiquitous process in magnetized plasmas, converting magnetic field energy to particle energy. Using data from the Polar and Cluster satellites, we are studying microphysics of reconnection, including the role of solitary waves, whistlers and lower hybrid waves.
More at the profile of Prof. Cyntia Cattell, School of Physics and Astronomy, University of Minnesota